Add migration that drops offers table.

Add adaptive icon for API 26+ and Play Store icon

Closes #1456

See merge request briar/briar!1293

.idea/codeStyles/Project.xml

@@ -28,6 +28,11 @@
       <option name="JD_ALIGN_EXCEPTION_COMMENTS" value="false" />
     </JavaCodeStyleSettings>
     <JetCodeStyleSettings>
+      <option name="PACKAGES_TO_USE_STAR_IMPORTS">
+        <value />
+      </option>
+      <option name="NAME_COUNT_TO_USE_STAR_IMPORT" value="2147483647" />
+      <option name="NAME_COUNT_TO_USE_STAR_IMPORT_FOR_MEMBERS" value="2147483647" />
       <option name="CODE_STYLE_DEFAULTS" value="KOTLIN_OFFICIAL" />
     </JetCodeStyleSettings>
     <XML>

bramble-android/.gitignore

@@ -3,3 +3,4 @@ gen
 build
 .settings
 src/main/res/raw/*.zip
+src/main/jniLibs

bramble-android/build.gradle

@@ -5,14 +5,14 @@ apply plugin: 'witness'
 apply from: 'witness.gradle'
 
 android {
-	compileSdkVersion 29
-	buildToolsVersion '29.0.2'
+	compileSdkVersion rootProject.ext.compileSdkVersion
+	buildToolsVersion rootProject.ext.buildToolsVersion
 
 	defaultConfig {
-		minSdkVersion 16
-		targetSdkVersion 28
-		versionCode 10209
-		versionName "1.2.9"
+		minSdkVersion rootProject.ext.minSdkVersion
+		targetSdkVersion rootProject.ext.targetSdkVersion
+		versionCode rootProject.ext.versionCode
+		versionName rootProject.ext.versionName
 		consumerProguardFiles 'proguard-rules.txt'
 
 		testInstrumentationRunner "androidx.test.runner.AndroidJUnitRunner"
@@ -53,10 +53,12 @@ dependencies {
 }
 
 def torBinariesDir = 'src/main/res/raw'
+def torLibsDir = 'src/main/jniLibs'
 
 task cleanTorBinaries {
 	doLast {
 		delete fileTree(torBinariesDir) { include '*.zip' }
+		delete fileTree(torLibsDir) { include '**/*.so' }
 	}
 }
 
@@ -67,8 +69,36 @@ task unpackTorBinaries {
 		copy {
 			from configurations.tor.collect { zipTree(it) }
 			into torBinariesDir
-			// TODO: Remove after next Tor upgrade, which won't include non-PIE binaries
-			include 'geoip.zip', '*_pie.zip'
+			include 'geoip.zip'
+		}
+		configurations.tor.each { outer ->
+			zipTree(outer).each { inner ->
+				if (inner.name.endsWith('_arm_pie.zip')) {
+					copy {
+						from zipTree(inner)
+						into torLibsDir
+						rename '(.*)', 'armeabi-v7a/lib$1.so'
+					}
+				} else if (inner.name.endsWith('_arm64_pie.zip')) {
+					copy {
+						from zipTree(inner)
+						into torLibsDir
+						rename '(.*)', 'arm64-v8a/lib$1.so'
+					}
+				} else if (inner.name.endsWith('_x86_pie.zip')) {
+					copy {
+						from zipTree(inner)
+						into torLibsDir
+						rename '(.*)', 'x86/lib$1.so'
+					}
+				} else if (inner.name.endsWith('_x86_64_pie.zip')) {
+					copy {
+						from zipTree(inner)
+						into torLibsDir
+						rename '(.*)', 'x86_64/lib$1.so'
+					}
+				}
+			}
 		}
 	}
 	dependsOn cleanTorBinaries
@@ -76,5 +106,6 @@ task unpackTorBinaries {
 
 tasks.withType(MergeResources) {
 	inputs.dir torBinariesDir
+	inputs.dir torLibsDir
 	dependsOn unpackTorBinaries
 }

bramble-android/src/main/java/org/briarproject/bramble/plugin/bluetooth/AndroidBluetoothPlugin.java

@@ -71,7 +71,6 @@ class AndroidBluetoothPlugin
 	private final Application app;
 	private final Clock clock;
 
-	private volatile boolean wasEnabledByUs = false;
 	private volatile BluetoothStateReceiver receiver = null;
 
 	// Non-null if the plugin started successfully
@@ -133,41 +132,10 @@ class AndroidBluetoothPlugin
 		return adapter != null && adapter.isEnabled();
 	}
 
-	@Override
-	void enableAdapter() {
-		if (adapter != null && !adapter.isEnabled()) {
-			if (adapter.enable()) {
-				LOG.info("Enabling Bluetooth");
-				wasEnabledByUs = true;
-			} else {
-				LOG.info("Could not enable Bluetooth");
-			}
-		}
-	}
-
-	@Override
-	void disableAdapterIfEnabledByUs() {
-		if (isAdapterEnabled() && wasEnabledByUs) {
-			if (adapter.disable()) LOG.info("Disabling Bluetooth");
-			else LOG.info("Could not disable Bluetooth");
-			wasEnabledByUs = false;
-		}
-	}
-
-	@Override
-	void setEnabledByUs() {
-		wasEnabledByUs = true;
-	}
-
-	@Override
-	void onAdapterDisabled() {
-		super.onAdapterDisabled();
-		wasEnabledByUs = false;
-	}
-
 	@Override
 	@Nullable
 	String getBluetoothAddress() {
+		if (adapter == null) return null;
 		String address = AndroidUtils.getBluetoothAddress(app, adapter);
 		return address.isEmpty() ? null : address;
 	}

bramble-android/src/main/java/org/briarproject/bramble/plugin/tor/AndroidTorPlugin.java

@@ -16,19 +16,42 @@ import org.briarproject.bramble.api.system.AndroidWakeLockManager;
 import org.briarproject.bramble.api.system.Clock;
 import org.briarproject.bramble.api.system.LocationUtils;
 import org.briarproject.bramble.api.system.ResourceProvider;
+import org.briarproject.bramble.util.AndroidUtils;
 
 import java.io.File;
+import java.io.FileInputStream;
+import java.io.FileNotFoundException;
 import java.io.IOException;
+import java.util.ArrayList;
+import java.util.List;
 import java.util.concurrent.Executor;
+import java.util.logging.Logger;
+import java.util.zip.ZipEntry;
+import java.util.zip.ZipInputStream;
 
 import javax.net.SocketFactory;
 
+import static android.os.Build.VERSION.SDK_INT;
+import static java.util.Arrays.asList;
+import static java.util.logging.Level.INFO;
+import static java.util.logging.Logger.getLogger;
+
 @MethodsNotNullByDefault
 @ParametersNotNullByDefault
 class AndroidTorPlugin extends TorPlugin {
 
+	private static final List<String> LIBRARY_ARCHITECTURES =
+			asList("armeabi-v7a", "arm64-v8a", "x86", "x86_64");
+
+	private static final String TOR_LIB_NAME = "libtor.so";
+	private static final String OBFS4_LIB_NAME = "libobfs4proxy.so";
+
+	private static final Logger LOG =
+			getLogger(AndroidTorPlugin.class.getName());
+
 	private final Application app;
 	private final AndroidWakeLock wakeLock;
+	private final File torLib, obfs4Lib;
 
 	AndroidTorPlugin(Executor ioExecutor,
 			Executor wakefulIoExecutor,
@@ -55,6 +78,9 @@ class AndroidTorPlugin extends TorPlugin {
 				maxIdleTime, torDirectory);
 		this.app = app;
 		wakeLock = wakeLockManager.createWakeLock("TorPlugin");
+		String nativeLibDir = app.getApplicationInfo().nativeLibraryDir;
+		torLib = new File(nativeLibDir, TOR_LIB_NAME);
+		obfs4Lib = new File(nativeLibDir, OBFS4_LIB_NAME);
 	}
 
 	@Override
@@ -85,4 +111,112 @@ class AndroidTorPlugin extends TorPlugin {
 		super.stop();
 		wakeLock.release();
 	}
+
+	@Override
+	protected File getTorExecutableFile() {
+		return torLib.exists() ? torLib : super.getTorExecutableFile();
+	}
+
+	@Override
+	protected File getObfs4ExecutableFile() {
+		return obfs4Lib.exists() ? obfs4Lib : super.getObfs4ExecutableFile();
+	}
+
+	@Override
+	protected void installTorExecutable() throws IOException {
+		File extracted = super.getTorExecutableFile();
+		if (torLib.exists()) {
+			// If an older version left behind a Tor binary, delete it
+			if (extracted.exists()) {
+				if (extracted.delete()) LOG.info("Deleted Tor binary");
+				else LOG.info("Failed to delete Tor binary");
+			}
+		} else if (SDK_INT < 29) {
+			// The binary wasn't extracted at install time. Try to extract it
+			extractLibraryFromApk(TOR_LIB_NAME, extracted);
+		} else {
+			// No point extracting the binary, we won't be allowed to execute it
+			throw new FileNotFoundException(torLib.getAbsolutePath());
+		}
+	}
+
+	@Override
+	protected void installObfs4Executable() throws IOException {
+		File extracted = super.getObfs4ExecutableFile();
+		if (obfs4Lib.exists()) {
+			// If an older version left behind an obfs4 binary, delete it
+			if (extracted.exists()) {
+				if (extracted.delete()) LOG.info("Deleted obfs4 binary");
+				else LOG.info("Failed to delete obfs4 binary");
+			}
+		} else if (SDK_INT < 29) {
+			// The binary wasn't extracted at install time. Try to extract it
+			extractLibraryFromApk(OBFS4_LIB_NAME, extracted);
+		} else {
+			// No point extracting the binary, we won't be allowed to execute it
+			throw new FileNotFoundException(obfs4Lib.getAbsolutePath());
+		}
+	}
+
+	private void extractLibraryFromApk(String libName, File dest)
+			throws IOException {
+		File sourceDir = new File(app.getApplicationInfo().sourceDir);
+		if (sourceDir.isFile()) {
+			// Look for other APK files in the same directory, if we're allowed
+			File parent = sourceDir.getParentFile();
+			if (parent != null) sourceDir = parent;
+		}
+		List<String> libPaths = getSupportedLibraryPaths(libName);
+		for (File apk : findApkFiles(sourceDir)) {
+			ZipInputStream zin = new ZipInputStream(new FileInputStream(apk));
+			for (ZipEntry e = zin.getNextEntry(); e != null;
+					e = zin.getNextEntry()) {
+				if (libPaths.contains(e.getName())) {
+					if (LOG.isLoggable(INFO)) {
+						LOG.info("Extracting " + e.getName()
+								+ " from " + apk.getAbsolutePath());
+					}
+					extract(zin, dest); // Zip input stream will be closed
+					return;
+				}
+			}
+			zin.close();
+		}
+		throw new FileNotFoundException(libName);
+	}
+
+	/**
+	 * Returns all files with the extension .apk or .APK under the given root.
+	 */
+	private List<File> findApkFiles(File root) {
+		List<File> files = new ArrayList<>();
+		findApkFiles(root, files);
+		return files;
+	}
+
+	private void findApkFiles(File f, List<File> files) {
+		if (f.isFile() && f.getName().toLowerCase().endsWith(".apk")) {
+			files.add(f);
+		} else if (f.isDirectory()) {
+			File[] children = f.listFiles();
+			if (children != null) {
+				for (File child : children) findApkFiles(child, files);
+			}
+		}
+	}
+
+	/**
+	 * Returns the paths at which libraries with the given name would be found
+	 * inside an APK file, for all architectures supported by the device, in
+	 * order of preference.
+	 */
+	private List<String> getSupportedLibraryPaths(String libName) {
+		List<String> architectures = new ArrayList<>();
+		for (String abi : AndroidUtils.getSupportedArchitectures()) {
+			if (LIBRARY_ARCHITECTURES.contains(abi)) {
+				architectures.add("lib/" + abi + "/" + libName);
+			}
+		}
+		return architectures;
+	}
 }

bramble-api/src/main/java/org/briarproject/bramble/api/Consumable.java

@@ -0,0 +1,25 @@
+package org.briarproject.bramble.api;
+
+import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
+
+import java.util.concurrent.atomic.AtomicReference;
+
+import javax.annotation.Nullable;
+
+/**
+ * An item that can be consumed once.
+ */
+@NotNullByDefault
+public class Consumable<T> {
+
+	private final AtomicReference<T> reference;
+
+	public Consumable(T item) {
+		reference = new AtomicReference<>(item);
+	}
+
+	@Nullable
+	public T consume() {
+		return reference.getAndSet(null);
+	}
+}

bramble-api/src/main/java/org/briarproject/bramble/api/client/ClientHelper.java

@@ -35,24 +35,24 @@ public interface ClientHelper {
 
 	Message createMessageForStoringMetadata(GroupId g);
 
-	Message getMessage(MessageId m) throws DbException;
+	Message getSmallMessage(MessageId m) throws DbException;
 
-	Message getMessage(Transaction txn, MessageId m) throws DbException;
+	Message getSmallMessage(Transaction txn, MessageId m) throws DbException;
 
-	BdfList getMessageAsList(MessageId m) throws DbException, FormatException;
+	BdfList getSmallMessageAsList(MessageId m)
+			throws DbException, FormatException;
 
-	BdfList getMessageAsList(Transaction txn, MessageId m) throws DbException,
-			FormatException;
+	BdfList getSmallMessageAsList(Transaction txn, MessageId m)
+			throws DbException, FormatException;
 
-	BdfDictionary getGroupMetadataAsDictionary(GroupId g) throws DbException,
-			FormatException;
+	BdfDictionary getGroupMetadataAsDictionary(GroupId g)
+			throws DbException, FormatException;
 
 	BdfDictionary getGroupMetadataAsDictionary(Transaction txn, GroupId g)
 			throws DbException, FormatException;
 
 	BdfDictionary getMessageMetadataAsDictionary(MessageId m)
-			throws DbException,
-			FormatException;
+			throws DbException, FormatException;
 
 	BdfDictionary getMessageMetadataAsDictionary(Transaction txn, MessageId m)
 			throws DbException, FormatException;
@@ -67,8 +67,8 @@ public interface ClientHelper {
 			BdfDictionary query) throws DbException, FormatException;
 
 	Map<MessageId, BdfDictionary> getMessageMetadataAsDictionary(
-			Transaction txn, GroupId g, BdfDictionary query) throws DbException,
-			FormatException;
+			Transaction txn, GroupId g, BdfDictionary query)
+			throws DbException, FormatException;
 
 	void mergeGroupMetadata(GroupId g, BdfDictionary metadata)
 			throws DbException, FormatException;

bramble-api/src/main/java/org/briarproject/bramble/api/crypto/KeyStrengthener.java

@@ -5,9 +5,6 @@ import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
 /**
  * Interface for strengthening a password-based key, for example by using a
  * key stored in a key management service or hardware security module.
- *
- * TODO: Remove after a reasonable migration period unless we can work around
- * Android keymaster bugs. Added 2020-02-24
  */
 @NotNullByDefault
 public interface KeyStrengthener {

bramble-api/src/main/java/org/briarproject/bramble/api/db/DatabaseComponent.java

@@ -163,27 +163,23 @@ public interface DatabaseComponent extends TransactionManager {
 	 * less than or equal to the given length, for transmission over a
 	 * transport with the given maximum latency. Returns null if there are no
 	 * sendable messages that fit in the given length.
+	 *
+	 * @param small True if only single-block messages should be sent
 	 */
 	@Nullable
 	Collection<Message> generateBatch(Transaction txn, ContactId c,
-			int maxLength, int maxLatency) throws DbException;
+			int maxLength, int maxLatency, boolean small) throws DbException;
 
 	/**
 	 * Returns an offer for the given contact for transmission over a
 	 * transport with the given maximum latency, or null if there are no
 	 * messages to offer.
+	 *
+	 * @param small True if only single-block messages should be offered
 	 */
 	@Nullable
 	Offer generateOffer(Transaction txn, ContactId c, int maxMessages,
-			int maxLatency) throws DbException;
-
-	/**
-	 * Returns a request for the given contact, or null if there are no
-	 * messages to request.
-	 */
-	@Nullable
-	Request generateRequest(Transaction txn, ContactId c, int maxMessages)
-			throws DbException;
+			int maxLatency, boolean small) throws DbException;
 
 	/**
 	 * Returns a batch of messages for the given contact, with a total length
@@ -272,13 +268,14 @@ public interface DatabaseComponent extends TransactionManager {
 	Collection<Identity> getIdentities(Transaction txn) throws DbException;
 
 	/**
-	 * Returns the message with the given ID.
+	 * Returns the single-block message with the given ID.
 	 * <p/>
 	 * Read-only.
 	 *
 	 * @throws MessageDeletedException if the message has been deleted
+	 * @throws MessageTooLargeException if the message has more than one block
 	 */
-	Message getMessage(Transaction txn, MessageId m) throws DbException;
+	Message getSmallMessage(Transaction txn, MessageId m) throws DbException;
 
 	/**
 	 * Returns the IDs of all delivered messages in the given group.

bramble-api/src/main/java/org/briarproject/bramble/api/db/MessageTooLargeException.java

@@ -0,0 +1,8 @@
+package org.briarproject.bramble.api.db;
+
+/**
+ * Thrown when a multi-block message is requested from the database via a
+ * method that is only suitable for requesting single-block messages.
+ */
+public class MessageTooLargeException extends DbException {
+}

bramble-api/src/main/java/org/briarproject/bramble/api/plugin/event/BluetoothEnabledEvent.java

@@ -1,15 +0,0 @@
-package org.briarproject.bramble.api.plugin.event;
-
-import org.briarproject.bramble.api.event.Event;
-import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
-
-import javax.annotation.concurrent.Immutable;
-
-/**
- * An event that informs the Bluetooth plugin that we have enabled the
- * Bluetooth adapter.
- */
-@Immutable
-@NotNullByDefault
-public class BluetoothEnabledEvent extends Event {
-}

bramble-api/src/main/java/org/briarproject/bramble/api/plugin/event/DisableBluetoothEvent.java

@@ -1,15 +0,0 @@
-package org.briarproject.bramble.api.plugin.event;
-
-import org.briarproject.bramble.api.event.Event;
-import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
-
-import javax.annotation.concurrent.Immutable;
-
-/**
- * An event that asks the Bluetooth plugin to disable the Bluetooth adapter if
- * we previously enabled it.
- */
-@Immutable
-@NotNullByDefault
-public class DisableBluetoothEvent extends Event {
-}

bramble-api/src/main/java/org/briarproject/bramble/api/plugin/event/EnableBluetoothEvent.java

@@ -1,14 +0,0 @@
-package org.briarproject.bramble.api.plugin.event;
-
-import org.briarproject.bramble.api.event.Event;
-import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
-
-import javax.annotation.concurrent.Immutable;
-
-/**
- * An event that asks the Bluetooth plugin to enable the Bluetooth adapter.
- */
-@Immutable
-@NotNullByDefault
-public class EnableBluetoothEvent extends Event {
-}

bramble-api/src/main/java/org/briarproject/bramble/api/sync/SyncConstants.java

@@ -29,10 +29,15 @@ public interface SyncConstants {
 	 */
 	int MESSAGE_HEADER_LENGTH = UniqueId.LENGTH + 8;
 
+	/**
+	 * The maximum length of a block in bytes.
+	 */
+	int MAX_BLOCK_LENGTH = 32 * 1024; // 32 KiB
+
 	/**
 	 * The maximum length of a message body in bytes.
 	 */
-	int MAX_MESSAGE_BODY_LENGTH = 32 * 1024; // 32 KiB
+	int MAX_MESSAGE_BODY_LENGTH = MAX_BLOCK_LENGTH;
 
 	/**
 	 * The maximum length of a message in bytes.

bramble-api/src/main/java/org/briarproject/bramble/api/sync/event/MessageToAckEvent.java

@@ -1,26 +0,0 @@
-package org.briarproject.bramble.api.sync.event;
-
-import org.briarproject.bramble.api.contact.ContactId;
-import org.briarproject.bramble.api.event.Event;
-import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
-
-import javax.annotation.concurrent.Immutable;
-
-/**
- * An event that is broadcast when a message is received from, or offered by, a
- * contact and needs to be acknowledged.
- */
-@Immutable
-@NotNullByDefault
-public class MessageToAckEvent extends Event {
-
-	private final ContactId contactId;
-
-	public MessageToAckEvent(ContactId contactId) {
-		this.contactId = contactId;
-	}
-
-	public ContactId getContactId() {
-		return contactId;
-	}
-}

bramble-api/src/main/java/org/briarproject/bramble/api/sync/event/MessagesToAckEvent.java

@@ -7,16 +7,16 @@ import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
 import javax.annotation.concurrent.Immutable;
 
 /**
- * An event that is broadcast when a message is offered by a contact and needs
- * to be requested.
+ * An event that is broadcast when one or more messages are received from, or
+ * offered by, a contact and need to be acknowledged.
  */
 @Immutable
 @NotNullByDefault
-public class MessageToRequestEvent extends Event {
+public class MessagesToAckEvent extends Event {
 
 	private final ContactId contactId;
 
-	public MessageToRequestEvent(ContactId contactId) {
+	public MessagesToAckEvent(ContactId contactId) {
 		this.contactId = contactId;
 	}
 

bramble-api/src/main/java/org/briarproject/bramble/api/sync/event/MessagesToRequestEvent.java

@@ -0,0 +1,39 @@
+package org.briarproject.bramble.api.sync.event;
+
+import org.briarproject.bramble.api.Consumable;
+import org.briarproject.bramble.api.contact.ContactId;
+import org.briarproject.bramble.api.event.Event;
+import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
+import org.briarproject.bramble.api.sync.MessageId;
+
+import java.util.Collection;
+
+import javax.annotation.Nullable;
+import javax.annotation.concurrent.Immutable;
+
+/**
+ * An event that is broadcast when one or more messages are offered by a
+ * contact and need to be requested.
+ */
+@Immutable
+@NotNullByDefault
+public class MessagesToRequestEvent extends Event {
+
+	private final ContactId contactId;
+	private final Consumable<Collection<MessageId>> ids;
+
+	public MessagesToRequestEvent(ContactId contactId,
+			Collection<MessageId> ids) {
+		this.contactId = contactId;
+		this.ids = new Consumable<>(ids);
+	}
+
+	public ContactId getContactId() {
+		return contactId;
+	}
+
+	@Nullable
+	public Collection<MessageId> consumeIds() {
+		return ids.consume();
+	}
+}

bramble-core/src/main/java/org/briarproject/bramble/account/AccountManagerImpl.java

@@ -179,9 +179,8 @@ class AccountManagerImpl implements AccountManager {
 	@GuardedBy("stateChangeLock")
 	private boolean encryptAndStoreDatabaseKey(SecretKey key, String password) {
 		byte[] plaintext = key.getBytes();
-		// Don't use a key strengthener as the Android keymaster isn't reliable
-		byte[] ciphertext =
-				crypto.encryptWithPassword(plaintext, password, null);
+		byte[] ciphertext = crypto.encryptWithPassword(plaintext, password,
+				databaseConfig.getKeyStrengthener());
 		return storeEncryptedDatabaseKey(toHexString(ciphertext));
 	}
 
@@ -198,13 +197,13 @@ class AccountManagerImpl implements AccountManager {
 	@Override
 	public void signIn(String password) throws DecryptionException {
 		synchronized (stateChangeLock) {
-			databaseKey = loadAndDecryptDatabaseKey(password, false);
+			databaseKey = loadAndDecryptDatabaseKey(password);
 		}
 	}
 
 	@GuardedBy("stateChangeLock")
-	private SecretKey loadAndDecryptDatabaseKey(String password,
-			boolean changing) throws DecryptionException {
+	private SecretKey loadAndDecryptDatabaseKey(String password)
+			throws DecryptionException {
 		String hex = loadEncryptedDatabaseKey();
 		if (hex == null) {
 			LOG.warning("Failed to load encrypted database key");
@@ -215,11 +214,11 @@ class AccountManagerImpl implements AccountManager {
 		byte[] plaintext = crypto.decryptWithPassword(ciphertext, password,
 				keyStrengthener);
 		SecretKey key = new SecretKey(plaintext);
-		// If the DB key was encrypted with a hardware-backed key, re-encrypt
-		// it without the hardware-backed key so keymaster bugs don't delete
-		// the user's account
-		if (!changing && crypto.isEncryptedWithStrengthenedKey(ciphertext)) {
-			LOG.info("Re-encrypting database key without strengthened key");
+		// If the DB key was encrypted with a weak key and a key strengthener
+		// is now available, re-encrypt the DB key with a strengthened key
+		if (keyStrengthener != null &&
+				!crypto.isEncryptedWithStrengthenedKey(ciphertext)) {
+			LOG.info("Re-encrypting database key with strengthened key");
 			encryptAndStoreDatabaseKey(key, password);
 		}
 		return key;
@@ -229,7 +228,7 @@ class AccountManagerImpl implements AccountManager {
 	public void changePassword(String oldPassword, String newPassword)
 			throws DecryptionException {
 		synchronized (stateChangeLock) {
-			SecretKey key = loadAndDecryptDatabaseKey(oldPassword, true);
+			SecretKey key = loadAndDecryptDatabaseKey(oldPassword);
 			encryptAndStoreDatabaseKey(key, newPassword);
 		}
 	}

bramble-core/src/main/java/org/briarproject/bramble/client/ClientHelperImpl.java

@@ -116,25 +116,27 @@ class ClientHelperImpl implements ClientHelper {
 	}
 
 	@Override
-	public Message getMessage(MessageId m) throws DbException {
-		return db.transactionWithResult(true, txn -> getMessage(txn, m));
+	public Message getSmallMessage(MessageId m) throws DbException {
+		return db.transactionWithResult(true, txn -> getSmallMessage(txn, m));
 	}
 
 	@Override
-	public Message getMessage(Transaction txn, MessageId m) throws DbException {
-		return db.getMessage(txn, m);
+	public Message getSmallMessage(Transaction txn, MessageId m)
+			throws DbException {
+		return db.getSmallMessage(txn, m);
 	}
 
 	@Override
-	public BdfList getMessageAsList(MessageId m) throws DbException,
-			FormatException {
-		return db.transactionWithResult(true, txn -> getMessageAsList(txn, m));
-	}
-
-	@Override
-	public BdfList getMessageAsList(Transaction txn, MessageId m)
+	public BdfList getSmallMessageAsList(MessageId m)
 			throws DbException, FormatException {
-		return toList(db.getMessage(txn, m).getBody());
+		return db.transactionWithResult(true, txn ->
+				getSmallMessageAsList(txn, m));
+	}
+
+	@Override
+	public BdfList getSmallMessageAsList(Transaction txn, MessageId m)
+			throws DbException, FormatException {
+		return toList(db.getSmallMessage(txn, m).getBody());
 	}
 
 	@Override

bramble-core/src/main/java/org/briarproject/bramble/db/Database.java

@@ -12,6 +12,7 @@ import org.briarproject.bramble.api.db.DataTooOldException;
 import org.briarproject.bramble.api.db.DatabaseComponent;
 import org.briarproject.bramble.api.db.DbException;
 import org.briarproject.bramble.api.db.MessageDeletedException;
+import org.briarproject.bramble.api.db.MessageTooLargeException;
 import org.briarproject.bramble.api.db.Metadata;
 import org.briarproject.bramble.api.db.MigrationListener;
 import org.briarproject.bramble.api.identity.Author;
@@ -125,11 +126,6 @@ interface Database<T> {
 	void addMessageDependency(T txn, Message dependent, MessageId dependency,
 			MessageState dependentState) throws DbException;
 
-	/**
-	 * Records that a message has been offered by the given contact.
-	 */
-	void addOfferedMessage(T txn, ContactId c, MessageId m) throws DbException;
-
 	/**
 	 * Stores a pending contact.
 	 */
@@ -218,13 +214,6 @@ interface Database<T> {
 	boolean containsVisibleMessage(T txn, ContactId c, MessageId m)
 			throws DbException;
 
-	/**
-	 * Returns the number of messages offered by the given contact.
-	 * <p/>
-	 * Read-only.
-	 */
-	int countOfferedMessages(T txn, ContactId c) throws DbException;
-
 	/**
 	 * Deletes the message with the given ID. Unlike
 	 * {@link #removeMessage(Object, MessageId)}, the message ID and any other
@@ -332,13 +321,14 @@ interface Database<T> {
 	Collection<Identity> getIdentities(T txn) throws DbException;
 
 	/**
-	 * Returns the message with the given ID.
+	 * Returns the single-block message with the given ID.
 	 * <p/>
 	 * Read-only.
 	 *
 	 * @throws MessageDeletedException if the message has been deleted
+	 * @throws MessageTooLargeException if the message has more than one block
 	 */
-	Message getMessage(T txn, MessageId m) throws DbException;
+	Message getSmallMessage(T txn, MessageId m) throws DbException;
 
 	/**
 	 * Returns the IDs and states of all dependencies of the given message.
@@ -457,13 +447,13 @@ interface Database<T> {
 			int maxMessages, int maxLatency) throws DbException;
 
 	/**
-	 * Returns the IDs of some messages that are eligible to be requested from
-	 * the given contact, up to the given number of messages.
+	 * Returns the IDs of some single-block messages that are eligible to be
+	 * offered to the given contact, up to the given number of messages.
 	 * <p/>
 	 * Read-only.
 	 */
-	Collection<MessageId> getMessagesToRequest(T txn, ContactId c,
-			int maxMessages) throws DbException;
+	Collection<MessageId> getSmallMessagesToOffer(T txn, ContactId c,
+			int maxMessages, int maxLatency) throws DbException;
 
 	/**
 	 * Returns the IDs of some messages that are eligible to be sent to the
@@ -474,6 +464,15 @@ interface Database<T> {
 	Collection<MessageId> getMessagesToSend(T txn, ContactId c, int maxLength,
 			int maxLatency) throws DbException;
 
+	/**
+	 * Returns the IDs of some single-block messages that are eligible to be
+	 * sent to the given contact, up to the given total length.
+	 * <p/>
+	 * Read-only.
+	 */
+	Collection<MessageId> getSmallMessagesToSend(T txn, ContactId c,
+			int maxLength, int maxLatency) throws DbException;
+
 	/**
 	 * Returns the IDs of any messages that need to be validated.
 	 * <p/>
@@ -636,13 +635,6 @@ interface Database<T> {
 	 */
 	void removeMessage(T txn, MessageId m) throws DbException;
 
-	/**
-	 * Removes the given offered messages that were offered by the given
-	 * contact.
-	 */
-	void removeOfferedMessages(T txn, ContactId c,
-			Collection<MessageId> requested) throws DbException;
-
 	/**
 	 * Removes a pending contact (and all associated state) from the database.
 	 */

bramble-core/src/main/java/org/briarproject/bramble/db/DatabaseComponentImpl.java

@@ -61,10 +61,10 @@ import org.briarproject.bramble.api.sync.event.MessageAddedEvent;
 import org.briarproject.bramble.api.sync.event.MessageRequestedEvent;
 import org.briarproject.bramble.api.sync.event.MessageSharedEvent;
 import org.briarproject.bramble.api.sync.event.MessageStateChangedEvent;
-import org.briarproject.bramble.api.sync.event.MessageToAckEvent;
-import org.briarproject.bramble.api.sync.event.MessageToRequestEvent;
 import org.briarproject.bramble.api.sync.event.MessagesAckedEvent;
 import org.briarproject.bramble.api.sync.event.MessagesSentEvent;
+import org.briarproject.bramble.api.sync.event.MessagesToAckEvent;
+import org.briarproject.bramble.api.sync.event.MessagesToRequestEvent;
 import org.briarproject.bramble.api.sync.event.SyncVersionsUpdatedEvent;
 import org.briarproject.bramble.api.sync.validation.MessageState;
 import org.briarproject.bramble.api.transport.KeySetId;
@@ -91,7 +91,6 @@ import static org.briarproject.bramble.api.sync.Group.Visibility.INVISIBLE;
 import static org.briarproject.bramble.api.sync.Group.Visibility.SHARED;
 import static org.briarproject.bramble.api.sync.validation.MessageState.DELIVERED;
 import static org.briarproject.bramble.api.sync.validation.MessageState.UNKNOWN;
-import static org.briarproject.bramble.db.DatabaseConstants.MAX_OFFERED_MESSAGES;
 import static org.briarproject.bramble.util.LogUtils.logDuration;
 import static org.briarproject.bramble.util.LogUtils.logException;
 import static org.briarproject.bramble.util.LogUtils.now;
@@ -406,19 +405,22 @@ class DatabaseComponentImpl<T> implements DatabaseComponent {
 	@Nullable
 	@Override
 	public Collection<Message> generateBatch(Transaction transaction,
-			ContactId c, int maxLength, int maxLatency) throws DbException {
+			ContactId c, int maxLength, int maxLatency, boolean small)
+			throws DbException {
 		if (transaction.isReadOnly()) throw new IllegalArgumentException();
 		T txn = unbox(transaction);
 		if (!db.containsContact(txn, c))
 			throw new NoSuchContactException();
-		Collection<MessageId> ids =
-				db.getMessagesToSend(txn, c, maxLength, maxLatency);
+		Collection<MessageId> ids;
+		if (small)
+			ids = db.getSmallMessagesToSend(txn, c, maxLength, maxLatency);
+		else ids = db.getMessagesToSend(txn, c, maxLength, maxLatency);
+		if (ids.isEmpty()) return null;
 		List<Message> messages = new ArrayList<>(ids.size());
 		for (MessageId m : ids) {
-			messages.add(db.getMessage(txn, m));
+			messages.add(db.getSmallMessage(txn, m));
 			db.updateExpiryTimeAndEta(txn, c, m, maxLatency);
 		}
-		if (ids.isEmpty()) return null;
 		db.lowerRequestedFlag(txn, c, ids);
 		transaction.attach(new MessagesSentEvent(c, ids));
 		return messages;
@@ -427,34 +429,21 @@ class DatabaseComponentImpl<T> implements DatabaseComponent {
 	@Nullable
 	@Override
 	public Offer generateOffer(Transaction transaction, ContactId c,
-			int maxMessages, int maxLatency) throws DbException {
+			int maxMessages, int maxLatency, boolean small) throws DbException {
 		if (transaction.isReadOnly()) throw new IllegalArgumentException();
 		T txn = unbox(transaction);
 		if (!db.containsContact(txn, c))
 			throw new NoSuchContactException();
-		Collection<MessageId> ids =
-				db.getMessagesToOffer(txn, c, maxMessages, maxLatency);
+		Collection<MessageId> ids;
+		if (small)
+			ids = db.getSmallMessagesToOffer(txn, c, maxMessages, maxLatency);
+		else ids = db.getMessagesToOffer(txn, c, maxMessages, maxLatency);
 		if (ids.isEmpty()) return null;
 		for (MessageId m : ids)
 			db.updateExpiryTimeAndEta(txn, c, m, maxLatency);
 		return new Offer(ids);
 	}
 
-	@Nullable
-	@Override
-	public Request generateRequest(Transaction transaction, ContactId c,
-			int maxMessages) throws DbException {
-		if (transaction.isReadOnly()) throw new IllegalArgumentException();
-		T txn = unbox(transaction);
-		if (!db.containsContact(txn, c))
-			throw new NoSuchContactException();
-		Collection<MessageId> ids = db.getMessagesToRequest(txn, c,
-				maxMessages);
-		if (ids.isEmpty()) return null;
-		db.removeOfferedMessages(txn, c, ids);
-		return new Request(ids);
-	}
-
 	@Nullable
 	@Override
 	public Collection<Message> generateRequestedBatch(Transaction transaction,
@@ -465,12 +454,12 @@ class DatabaseComponentImpl<T> implements DatabaseComponent {
 			throw new NoSuchContactException();
 		Collection<MessageId> ids =
 				db.getRequestedMessagesToSend(txn, c, maxLength, maxLatency);
+		if (ids.isEmpty()) return null;
 		List<Message> messages = new ArrayList<>(ids.size());
 		for (MessageId m : ids) {
-			messages.add(db.getMessage(txn, m));
+			messages.add(db.getSmallMessage(txn, m));
 			db.updateExpiryTimeAndEta(txn, c, m, maxLatency);
 		}
-		if (ids.isEmpty()) return null;
 		db.lowerRequestedFlag(txn, c, ids);
 		transaction.attach(new MessagesSentEvent(c, ids));
 		return messages;
@@ -559,12 +548,12 @@ class DatabaseComponentImpl<T> implements DatabaseComponent {
 	}
 
 	@Override
-	public Message getMessage(Transaction transaction, MessageId m)
+	public Message getSmallMessage(Transaction transaction, MessageId m)
 			throws DbException {
 		T txn = unbox(transaction);
 		if (!db.containsMessage(txn, m))
 			throw new NoSuchMessageException();
-		return db.getMessage(txn, m);
+		return db.getSmallMessage(txn, m);
 	}
 
 	@Override
@@ -819,7 +808,7 @@ class DatabaseComponentImpl<T> implements DatabaseComponent {
 				db.addMessage(txn, m, UNKNOWN, false, false, c);
 				transaction.attach(new MessageAddedEvent(m, c));
 			}
-			transaction.attach(new MessageToAckEvent(c));
+			transaction.attach(new MessagesToAckEvent(c));
 		}
 	}
 
@@ -830,21 +819,20 @@ class DatabaseComponentImpl<T> implements DatabaseComponent {
 		T txn = unbox(transaction);
 		if (!db.containsContact(txn, c))
 			throw new NoSuchContactException();
-		boolean ack = false, request = false;
-		int count = db.countOfferedMessages(txn, c);
+		boolean ack = false;
+		List<MessageId> request = new ArrayList<>(o.getMessageIds().size());
 		for (MessageId m : o.getMessageIds()) {
 			if (db.containsVisibleMessage(txn, c, m)) {
 				db.raiseSeenFlag(txn, c, m);
 				db.raiseAckFlag(txn, c, m);
 				ack = true;
-			} else if (count < MAX_OFFERED_MESSAGES) {
-				db.addOfferedMessage(txn, c, m);
-				request = true;
-				count++;
+			} else {
+				request.add(m);
 			}
 		}
-		if (ack) transaction.attach(new MessageToAckEvent(c));
-		if (request) transaction.attach(new MessageToRequestEvent(c));
+		if (ack) transaction.attach(new MessagesToAckEvent(c));
+		if (!request.isEmpty())
+			transaction.attach(new MessagesToRequestEvent(c, request));
 	}
 
 	@Override

bramble-core/src/main/java/org/briarproject/bramble/db/DatabaseConstants.java

@@ -6,13 +6,6 @@ import static java.util.concurrent.TimeUnit.DAYS;
 
 interface DatabaseConstants {
 
-	/**
-	 * The maximum number of offered messages from each contact that will be
-	 * stored. If offers arrive more quickly than requests can be sent and this
-	 * limit is reached, additional offers will not be stored.
-	 */
-	int MAX_OFFERED_MESSAGES = 1000;
-
 	/**
 	 * The namespace of the {@link Settings} where the database schema version
 	 * is stored.

bramble-core/src/main/java/org/briarproject/bramble/db/DatabaseModule.java

@@ -6,7 +6,6 @@ import org.briarproject.bramble.api.db.TransactionManager;
 import org.briarproject.bramble.api.event.EventBus;
 import org.briarproject.bramble.api.event.EventExecutor;
 import org.briarproject.bramble.api.lifecycle.ShutdownManager;
-import org.briarproject.bramble.api.sync.MessageFactory;
 import org.briarproject.bramble.api.system.Clock;
 
 import java.sql.Connection;
@@ -22,9 +21,8 @@ public class DatabaseModule {
 
 	@Provides
 	@Singleton
-	Database<Connection> provideDatabase(DatabaseConfig config,
-			MessageFactory messageFactory, Clock clock) {
-		return new H2Database(config, messageFactory, clock);
+	Database<Connection> provideDatabase(DatabaseConfig config, Clock clock) {
+		return new H2Database(config, clock);
 	}
 
 	@Provides

bramble-core/src/main/java/org/briarproject/bramble/db/H2Database.java

@@ -6,7 +6,6 @@ import org.briarproject.bramble.api.db.DbClosedException;
 import org.briarproject.bramble.api.db.DbException;
 import org.briarproject.bramble.api.db.MigrationListener;
 import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
-import org.briarproject.bramble.api.sync.MessageFactory;
 import org.briarproject.bramble.api.system.Clock;
 import org.briarproject.bramble.util.StringUtils;
 
@@ -51,9 +50,8 @@ class H2Database extends JdbcDatabase {
 	private volatile SecretKey key = null;
 
 	@Inject
-	H2Database(DatabaseConfig config, MessageFactory messageFactory,
-			Clock clock) {
-		super(dbTypes, messageFactory, clock);
+	H2Database(DatabaseConfig config, Clock clock) {
+		super(dbTypes, clock);
 		this.config = config;
 		File dir = config.getDatabaseDirectory();
 		String path = new File(dir, "db").getAbsolutePath();

bramble-core/src/main/java/org/briarproject/bramble/db/HyperSqlDatabase.java

@@ -6,7 +6,6 @@ import org.briarproject.bramble.api.db.DbClosedException;
 import org.briarproject.bramble.api.db.DbException;
 import org.briarproject.bramble.api.db.MigrationListener;
 import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
-import org.briarproject.bramble.api.sync.MessageFactory;
 import org.briarproject.bramble.api.system.Clock;
 import org.briarproject.bramble.util.StringUtils;
 
@@ -51,9 +50,8 @@ class HyperSqlDatabase extends JdbcDatabase {
 	private volatile SecretKey key = null;
 
 	@Inject
-	HyperSqlDatabase(DatabaseConfig config, MessageFactory messageFactory,
-			Clock clock) {
-		super(dbTypes, messageFactory, clock);
+	HyperSqlDatabase(DatabaseConfig config, Clock clock) {
+		super(dbTypes, clock);
 		this.config = config;
 		File dir = config.getDatabaseDirectory();
 		String path = new File(dir, "db").getAbsolutePath();

bramble-core/src/main/java/org/briarproject/bramble/db/JdbcDatabase.java

@@ -16,6 +16,7 @@ import org.briarproject.bramble.api.db.DataTooOldException;
 import org.briarproject.bramble.api.db.DbClosedException;
 import org.briarproject.bramble.api.db.DbException;
 import org.briarproject.bramble.api.db.MessageDeletedException;
+import org.briarproject.bramble.api.db.MessageTooLargeException;
 import org.briarproject.bramble.api.db.Metadata;
 import org.briarproject.bramble.api.db.MigrationListener;
 import org.briarproject.bramble.api.identity.Author;
@@ -30,7 +31,6 @@ import org.briarproject.bramble.api.sync.Group;
 import org.briarproject.bramble.api.sync.Group.Visibility;
 import org.briarproject.bramble.api.sync.GroupId;
 import org.briarproject.bramble.api.sync.Message;
-import org.briarproject.bramble.api.sync.MessageFactory;
 import org.briarproject.bramble.api.sync.MessageId;
 import org.briarproject.bramble.api.sync.MessageStatus;
 import org.briarproject.bramble.api.sync.validation.MessageState;
@@ -76,6 +76,7 @@ import static org.briarproject.bramble.api.db.Metadata.REMOVE;
 import static org.briarproject.bramble.api.sync.Group.Visibility.INVISIBLE;
 import static org.briarproject.bramble.api.sync.Group.Visibility.SHARED;
 import static org.briarproject.bramble.api.sync.Group.Visibility.VISIBLE;
+import static org.briarproject.bramble.api.sync.SyncConstants.MAX_BLOCK_LENGTH;
 import static org.briarproject.bramble.api.sync.SyncConstants.MESSAGE_HEADER_LENGTH;
 import static org.briarproject.bramble.api.sync.validation.MessageState.DELIVERED;
 import static org.briarproject.bramble.api.sync.validation.MessageState.PENDING;
@@ -98,7 +99,7 @@ import static org.briarproject.bramble.util.LogUtils.now;
 abstract class JdbcDatabase implements Database<Connection> {
 
 	// Package access for testing
-	static final int CODE_SCHEMA_VERSION = 47;
+	static final int CODE_SCHEMA_VERSION = 49;
 
 	// Time period offsets for incoming transport keys
 	private static final int OFFSET_PREV = -1;
@@ -180,8 +181,9 @@ abstract class JdbcDatabase implements Database<Connection> {
 					+ " state INT NOT NULL,"
 					+ " shared BOOLEAN NOT NULL,"
 					+ " temporary BOOLEAN NOT NULL,"
-					+ " length INT NOT NULL,"
-					+ " raw BLOB," // Null if message has been deleted
+					+ " length INT NOT NULL," // Includes message header
+					+ " deleted BOOLEAN NOT NULL,"
+					+ " blockCount INT NOT NULL,"
 					+ " PRIMARY KEY (messageId),"
 					+ " FOREIGN KEY (groupId)"
 					+ " REFERENCES groups (groupId)"
@@ -218,13 +220,15 @@ abstract class JdbcDatabase implements Database<Connection> {
 					+ " REFERENCES messages (messageId)"
 					+ " ON DELETE CASCADE)";
 
-	private static final String CREATE_OFFERS =
-			"CREATE TABLE offers"
-					+ " (messageId _HASH NOT NULL," // Not a foreign key
-					+ " contactId INT NOT NULL,"
-					+ " PRIMARY KEY (messageId, contactId),"
-					+ " FOREIGN KEY (contactId)"
-					+ " REFERENCES contacts (contactId)"
+	private static final String CREATE_BLOCKS =
+			"CREATE TABLE blocks"
+					+ " (messageId _HASH NOT NULL,"
+					+ " blockNumber INT NOT NULL,"
+					+ " blockLength INT NOT NULL," // Excludes block header
+					+ " data BLOB," // Null if message has been deleted
+					+ " PRIMARY KEY (messageId, blockNumber),"
+					+ " FOREIGN KEY (messageId)"
+					+ " REFERENCES messages (messageId)"
 					+ " ON DELETE CASCADE)";
 
 	private static final String CREATE_STATUSES =
@@ -339,7 +343,6 @@ abstract class JdbcDatabase implements Database<Connection> {
 	private static final Logger LOG =
 			getLogger(JdbcDatabase.class.getName());
 
-	private final MessageFactory messageFactory;
 	private final Clock clock;
 	private final DatabaseTypes dbTypes;
 
@@ -359,10 +362,8 @@ abstract class JdbcDatabase implements Database<Connection> {
 
 	protected abstract void compactAndClose() throws DbException;
 
-	JdbcDatabase(DatabaseTypes databaseTypes, MessageFactory messageFactory,
-			Clock clock) {
+	JdbcDatabase(DatabaseTypes databaseTypes, Clock clock) {
 		this.dbTypes = databaseTypes;
-		this.messageFactory = messageFactory;
 		this.clock = clock;
 	}
 
@@ -440,10 +441,12 @@ abstract class JdbcDatabase implements Database<Connection> {
 				if (LOG.isLoggable(INFO))
 					LOG.info("Migrating from schema " + start + " to " + end);
 				if (listener != null) listener.onDatabaseMigration();
+				long startTime = now();
 				// Apply the migration
 				m.migrate(txn);
 				// Store the new schema version
 				storeSchemaVersion(txn, end);
+				logDuration(LOG, "Migration", startTime);
 				dataSchemaVersion = end;
 			}
 		}
@@ -463,7 +466,9 @@ abstract class JdbcDatabase implements Database<Connection> {
 				new Migration43_44(dbTypes),
 				new Migration44_45(),
 				new Migration45_46(),
-				new Migration46_47(dbTypes)
+				new Migration46_47(dbTypes),
+				new Migration47_48(dbTypes),
+				new Migration48_49()
 		);
 	}
 
@@ -508,7 +513,7 @@ abstract class JdbcDatabase implements Database<Connection> {
 			s.executeUpdate(dbTypes.replaceTypes(CREATE_MESSAGES));
 			s.executeUpdate(dbTypes.replaceTypes(CREATE_MESSAGE_METADATA));
 			s.executeUpdate(dbTypes.replaceTypes(CREATE_MESSAGE_DEPENDENCIES));
-			s.executeUpdate(dbTypes.replaceTypes(CREATE_OFFERS));
+			s.executeUpdate(dbTypes.replaceTypes(CREATE_BLOCKS));
 			s.executeUpdate(dbTypes.replaceTypes(CREATE_STATUSES));
 			s.executeUpdate(dbTypes.replaceTypes(CREATE_TRANSPORTS));
 			s.executeUpdate(dbTypes.replaceTypes(CREATE_PENDING_CONTACTS));
@@ -726,7 +731,7 @@ abstract class JdbcDatabase implements Database<Connection> {
 		ResultSet rs = null;
 		try {
 			String sql = "SELECT messageId, timestamp, state, shared,"
-					+ " length, raw IS NULL"
+					+ " length, deleted"
 					+ " FROM messages"
 					+ " WHERE groupId = ?";
 			ps = txn.prepareStatement(sql);
@@ -739,9 +744,8 @@ abstract class JdbcDatabase implements Database<Connection> {
 				boolean messageShared = rs.getBoolean(4);
 				int length = rs.getInt(5);
 				boolean deleted = rs.getBoolean(6);
-				boolean seen = removeOfferedMessage(txn, c, id);
 				addStatus(txn, id, c, g, timestamp, length, state, groupShared,
-						messageShared, deleted, seen);
+						messageShared, deleted, false);
 			}
 			rs.close();
 			ps.close();
@@ -788,8 +792,8 @@ abstract class JdbcDatabase implements Database<Connection> {
 		PreparedStatement ps = null;
 		try {
 			String sql = "INSERT INTO messages (messageId, groupId, timestamp,"
-					+ " state, shared, temporary, length, raw)"
-					+ " VALUES (?, ?, ?, ?, ?, ?, ?, ?)";
+					+ " state, shared, temporary, length, deleted, blockCount)"
+					+ " VALUES (?, ?, ?, ?, ?, ?, ?, FALSE, 1)";
 			ps = txn.prepareStatement(sql);
 			ps.setBytes(1, m.getId().getBytes());
 			ps.setBytes(2, m.getGroupId().getBytes());
@@ -797,21 +801,29 @@ abstract class JdbcDatabase implements Database<Connection> {
 			ps.setInt(4, state.getValue());
 			ps.setBoolean(5, shared);
 			ps.setBoolean(6, temporary);
-			byte[] raw = messageFactory.getRawMessage(m);
-			ps.setInt(7, raw.length);
-			ps.setBytes(8, raw);
+			ps.setInt(7, m.getRawLength());
 			int affected = ps.executeUpdate();
 			if (affected != 1) throw new DbStateException();
 			ps.close();
+			sql = "INSERT INTO blocks (messageId, blockNumber, blockLength,"
+					+ " data)"
+					+ " VALUES (?, 0, ?, ?)";
+			ps = txn.prepareStatement(sql);
+			ps.setBytes(1, m.getId().getBytes());
+			ps.setInt(2, m.getBody().length);
+			ps.setBytes(3, m.getBody());
+			affected = ps.executeUpdate();
+			if (affected != 1) throw new DbStateException();
+			ps.close();
 			// Create a status row for each contact that can see the group
 			Map<ContactId, Boolean> visibility =
 					getGroupVisibility(txn, m.getGroupId());
 			for (Entry<ContactId, Boolean> e : visibility.entrySet()) {
 				ContactId c = e.getKey();
-				boolean offered = removeOfferedMessage(txn, c, m.getId());
-				boolean seen = offered || c.equals(sender);
+				boolean seen = c.equals(sender);
 				addStatus(txn, m.getId(), c, m.getGroupId(), m.getTimestamp(),
-						raw.length, state, e.getValue(), shared, false, seen);
+						m.getRawLength(), state, e.getValue(), shared, false,
+						seen);
 			}
 			// Update denormalised column in messageDependencies if dependency
 			// is in same group as dependent
@@ -830,37 +842,6 @@ abstract class JdbcDatabase implements Database<Connection> {
 		}
 	}
 
-	@Override
-	public void addOfferedMessage(Connection txn, ContactId c, MessageId m)
-			throws DbException {
-		PreparedStatement ps = null;
-		ResultSet rs = null;
-		try {
-			String sql = "SELECT NULL FROM offers"
-					+ " WHERE messageId = ? AND contactId = ?";
-			ps = txn.prepareStatement(sql);
-			ps.setBytes(1, m.getBytes());
-			ps.setInt(2, c.getInt());
-			rs = ps.executeQuery();
-			boolean found = rs.next();
-			if (rs.next()) throw new DbStateException();
-			rs.close();
-			ps.close();
-			if (found) return;
-			sql = "INSERT INTO offers (messageId, contactId) VALUES (?, ?)";
-			ps = txn.prepareStatement(sql);
-			ps.setBytes(1, m.getBytes());
-			ps.setInt(2, c.getInt());
-			int affected = ps.executeUpdate();
-			if (affected != 1) throw new DbStateException();
-			ps.close();
-		} catch (SQLException e) {
-			tryToClose(rs, LOG, WARNING);
-			tryToClose(ps, LOG, WARNING);
-			throw new DbException(e);
-		}
-	}
-
 	private void addStatus(Connection txn, MessageId m, ContactId c, GroupId g,
 			long timestamp, int length, MessageState state, boolean groupShared,
 			boolean messageShared, boolean deleted, boolean seen)
@@ -1262,40 +1243,22 @@ abstract class JdbcDatabase implements Database<Connection> {
 		}
 	}
 
-	@Override
-	public int countOfferedMessages(Connection txn, ContactId c)
-			throws DbException {
-		PreparedStatement ps = null;
-		ResultSet rs = null;
-		try {
-			String sql = "SELECT COUNT (messageId) FROM offers "
-					+ " WHERE contactId = ?";
-			ps = txn.prepareStatement(sql);
-			ps.setInt(1, c.getInt());
-			rs = ps.executeQuery();
-			if (!rs.next()) throw new DbException();
-			int count = rs.getInt(1);
-			if (rs.next()) throw new DbException();
-			rs.close();
-			ps.close();
-			return count;
-		} catch (SQLException e) {
-			tryToClose(rs, LOG, WARNING);
-			tryToClose(ps, LOG, WARNING);
-			throw new DbException(e);
-		}
-	}
-
 	@Override
 	public void deleteMessage(Connection txn, MessageId m) throws DbException {
 		PreparedStatement ps = null;
 		try {
-			String sql = "UPDATE messages SET raw = NULL WHERE messageId = ?";
+			String sql = "UPDATE messages SET deleted = TRUE"
+					+ " WHERE messageId = ?";
 			ps = txn.prepareStatement(sql);
 			ps.setBytes(1, m.getBytes());
 			int affected = ps.executeUpdate();
+			if (affected < 0 || affected > 1) throw new DbStateException();
+			ps.close();
+			sql = "UPDATE blocks SET data = NULL WHERE messageId = ?";
+			ps = txn.prepareStatement(sql);
+			ps.setBytes(1, m.getBytes());
+			affected = ps.executeUpdate();
 			if (affected < 0) throw new DbStateException();
-			if (affected > 1) throw new DbStateException();
 			ps.close();
 			// Update denormalised column in statuses
 			sql = "UPDATE statuses SET deleted = TRUE WHERE messageId = ?";
@@ -1688,11 +1651,13 @@ abstract class JdbcDatabase implements Database<Connection> {
 	}
 
 	@Override
-	public Message getMessage(Connection txn, MessageId m) throws DbException {
+	public Message getSmallMessage(Connection txn, MessageId m)
+			throws DbException {
 		PreparedStatement ps = null;
 		ResultSet rs = null;
 		try {
-			String sql = "SELECT groupId, timestamp, raw FROM messages"
+			String sql = "SELECT groupId, timestamp, deleted, blockCount"
+					+ " FROM messages"
 					+ " WHERE messageId = ?";
 			ps = txn.prepareStatement(sql);
 			ps.setBytes(1, m.getBytes());
@@ -1700,15 +1665,25 @@ abstract class JdbcDatabase implements Database<Connection> {
 			if (!rs.next()) throw new DbStateException();
 			GroupId g = new GroupId(rs.getBytes(1));
 			long timestamp = rs.getLong(2);
-			byte[] raw = rs.getBytes(3);
+			boolean deleted = rs.getBoolean(3);
+			int blockCount = rs.getInt(4);
 			if (rs.next()) throw new DbStateException();
 			rs.close();
 			ps.close();
-			if (raw == null) throw new MessageDeletedException();
-			if (raw.length <= MESSAGE_HEADER_LENGTH) throw new AssertionError();
-			byte[] body = new byte[raw.length - MESSAGE_HEADER_LENGTH];
-			System.arraycopy(raw, MESSAGE_HEADER_LENGTH, body, 0, body.length);
-			return new Message(m, g, timestamp, body);
+			if (deleted) throw new MessageDeletedException();
+			if (blockCount > 1) throw new MessageTooLargeException();
+			sql = "SELECT data FROM blocks"
+					+ " WHERE messageId = ? AND blockNumber = 0";
+			ps = txn.prepareStatement(sql);
+			ps.setBytes(1, m.getBytes());
+			rs = ps.executeQuery();
+			if (!rs.next()) throw new DbStateException();
+			byte[] data = rs.getBytes(1);
+			if (data == null) throw new DbStateException();
+			if (rs.next()) throw new DbStateException();
+			rs.close();
+			ps.close();
+			return new Message(m, g, timestamp, data);
 		} catch (SQLException e) {
 			tryToClose(rs, LOG, WARNING);
 			tryToClose(ps, LOG, WARNING);
@@ -2101,17 +2076,28 @@ abstract class JdbcDatabase implements Database<Connection> {
 	}
 
 	@Override
-	public Collection<MessageId> getMessagesToRequest(Connection txn,
-			ContactId c, int maxMessages) throws DbException {
+	public Collection<MessageId> getSmallMessagesToOffer(Connection txn,
+			ContactId c, int maxMessages, int maxLatency) throws DbException {
+		long now = clock.currentTimeMillis();
+		long eta = now + maxLatency;
 		PreparedStatement ps = null;
 		ResultSet rs = null;
 		try {
-			String sql = "SELECT messageId FROM offers"
-					+ " WHERE contactId = ?"
-					+ " LIMIT ?";
+			String sql = "SELECT messageId FROM statuses"
+					+ " WHERE contactId = ? AND state = ?"
+					+ " AND length <= ?"
+					+ " AND groupShared = TRUE AND messageShared = TRUE"
+					+ " AND deleted = FALSE"
+					+ " AND seen = FALSE AND requested = FALSE"
+					+ " AND (expiry <= ? OR eta > ?)"
+					+ " ORDER BY timestamp LIMIT ?";
 			ps = txn.prepareStatement(sql);
 			ps.setInt(1, c.getInt());
-			ps.setInt(2, maxMessages);
+			ps.setInt(2, DELIVERED.getValue());
+			ps.setInt(3, MESSAGE_HEADER_LENGTH + MAX_BLOCK_LENGTH);
+			ps.setLong(4, now);
+			ps.setLong(5, eta);
+			ps.setInt(6, maxMessages);
 			rs = ps.executeQuery();
 			List<MessageId> ids = new ArrayList<>();
 			while (rs.next()) ids.add(new MessageId(rs.getBytes(1)));
@@ -2164,6 +2150,47 @@ abstract class JdbcDatabase implements Database<Connection> {
 		}
 	}
 
+	@Override
+	public Collection<MessageId> getSmallMessagesToSend(Connection txn,
+			ContactId c, int maxLength, int maxLatency) throws DbException {
+		long now = clock.currentTimeMillis();
+		long eta = now + maxLatency;
+		PreparedStatement ps = null;
+		ResultSet rs = null;
+		try {
+			String sql = "SELECT length, messageId FROM statuses"
+					+ " WHERE contactId = ? AND state = ?"
+					+ " AND length <= ?"
+					+ " AND groupShared = TRUE AND messageShared = TRUE"
+					+ " AND deleted = FALSE"
+					+ " AND seen = FALSE"
+					+ " AND (expiry <= ? OR eta > ?)"
+					+ " ORDER BY timestamp";
+			ps = txn.prepareStatement(sql);
+			ps.setInt(1, c.getInt());
+			ps.setInt(2, DELIVERED.getValue());
+			ps.setInt(3, MESSAGE_HEADER_LENGTH + MAX_BLOCK_LENGTH);
+			ps.setLong(4, now);
+			ps.setLong(5, eta);
+			rs = ps.executeQuery();
+			List<MessageId> ids = new ArrayList<>();
+			int total = 0;
+			while (rs.next()) {
+				int length = rs.getInt(1);
+				if (total + length > maxLength) break;
+				ids.add(new MessageId(rs.getBytes(2)));
+				total += length;
+			}
+			rs.close();
+			ps.close();
+			return ids;
+		} catch (SQLException e) {
+			tryToClose(rs, LOG, WARNING);
+			tryToClose(ps, LOG, WARNING);
+			throw new DbException(e);
+		}
+	}
+
 	@Override
 	public Collection<MessageId> getMessagesToValidate(Connection txn)
 			throws DbException {
@@ -2182,7 +2209,7 @@ abstract class JdbcDatabase implements Database<Connection> {
 		ResultSet rs = null;
 		try {
 			String sql = "SELECT messageId FROM messages"
-					+ " WHERE state = ? AND raw IS NOT NULL";
+					+ " WHERE state = ? AND deleted = FALSE";
 			ps = txn.prepareStatement(sql);
 			ps.setInt(1, state.getValue());
 			rs = ps.executeQuery();
@@ -2887,50 +2914,6 @@ abstract class JdbcDatabase implements Database<Connection> {
 		}
 	}
 
-	private boolean removeOfferedMessage(Connection txn, ContactId c,
-			MessageId m) throws DbException {
-		PreparedStatement ps = null;
-		try {
-			String sql = "DELETE FROM offers"
-					+ " WHERE contactId = ? AND messageId = ?";
-			ps = txn.prepareStatement(sql);
-			ps.setInt(1, c.getInt());
-			ps.setBytes(2, m.getBytes());
-			int affected = ps.executeUpdate();
-			if (affected < 0 || affected > 1) throw new DbStateException();
-			ps.close();
-			return affected == 1;
-		} catch (SQLException e) {
-			tryToClose(ps, LOG, WARNING);
-			throw new DbException(e);
-		}
-	}
-
-	@Override
-	public void removeOfferedMessages(Connection txn, ContactId c,
-			Collection<MessageId> requested) throws DbException {
-		PreparedStatement ps = null;
-		try {
-			String sql = "DELETE FROM offers"
-					+ " WHERE contactId = ? AND messageId = ?";
-			ps = txn.prepareStatement(sql);
-			ps.setInt(1, c.getInt());
-			for (MessageId m : requested) {
-				ps.setBytes(2, m.getBytes());
-				ps.addBatch();
-			}
-			int[] batchAffected = ps.executeBatch();
-			if (batchAffected.length != requested.size())
-				throw new DbStateException();
-			for (int rows : batchAffected)
-				if (rows != 1) throw new DbStateException();
-			ps.close();
-		} catch (SQLException e) {
-			tryToClose(ps, LOG, WARNING);
-			throw new DbException(e);
-		}
-	}
-
 	@Override
 	public void removePendingContact(Connection txn, PendingContactId p)
 			throws DbException {

bramble-core/src/main/java/org/briarproject/bramble/db/Migration38_39.java

@@ -37,6 +37,7 @@ class Migration38_39 implements Migration<Connection> {
 			s.execute("ALTER TABLE incomingKeys"
 					+ " ALTER COLUMN contactId"
 					+ " SET NOT NULL");
+			s.close();
 		} catch (SQLException e) {
 			tryToClose(s, LOG, WARNING);
 			throw new DbException(e);

bramble-core/src/main/java/org/briarproject/bramble/db/Migration39_40.java

@@ -36,6 +36,7 @@ class Migration39_40 implements Migration<Connection> {
 			s.execute("ALTER TABLE statuses"
 					+ " ALTER COLUMN eta"
 					+ " SET NOT NULL");
+			s.close();
 		} catch (SQLException e) {
 			tryToClose(s, LOG, WARNING);
 			throw new DbException(e);

bramble-core/src/main/java/org/briarproject/bramble/db/Migration40_41.java

@@ -38,6 +38,7 @@ class Migration40_41 implements Migration<Connection> {
 			s = txn.createStatement();
 			s.execute("ALTER TABLE contacts"
 					+ dbTypes.replaceTypes(" ADD alias _STRING"));
+			s.close();
 		} catch (SQLException e) {
 			tryToClose(s, LOG, WARNING);
 			throw new DbException(e);

bramble-core/src/main/java/org/briarproject/bramble/db/Migration41_42.java

@@ -89,6 +89,7 @@ class Migration41_42 implements Migration<Connection> {
 					+ " FOREIGN KEY (keySetId)"
 					+ " REFERENCES outgoingHandshakeKeys (keySetId)"
 					+ " ON DELETE CASCADE)"));
+			s.close();
 		} catch (SQLException e) {
 			tryToClose(s, LOG, WARNING);
 			throw new DbException(e);

bramble-core/src/main/java/org/briarproject/bramble/db/Migration42_43.java

@@ -44,6 +44,7 @@ class Migration42_43 implements Migration<Connection> {
 					+ " ADD COLUMN handshakePublicKey _BINARY"));
 			s.execute("ALTER TABLE contacts"
 					+ " DROP COLUMN active");
+			s.close();
 		} catch (SQLException e) {
 			tryToClose(s, LOG, WARNING);
 			throw new DbException(e);

bramble-core/src/main/java/org/briarproject/bramble/db/Migration43_44.java

@@ -50,6 +50,7 @@ class Migration43_44 implements Migration<Connection> {
 					+ " ADD COLUMN rootKey _SECRET"));
 			s.execute("ALTER TABLE outgoingKeys"
 					+ " ADD COLUMN alice BOOLEAN");
+			s.close();
 		} catch (SQLException e) {
 			tryToClose(s, LOG, WARNING);
 			throw new DbException(e);

bramble-core/src/main/java/org/briarproject/bramble/db/Migration44_45.java

@@ -31,6 +31,7 @@ class Migration44_45 implements Migration<Connection> {
 		try {
 			s = txn.createStatement();
 			s.execute("ALTER TABLE pendingContacts DROP COLUMN state");
+			s.close();
 		} catch (SQLException e) {
 			tryToClose(s, LOG, WARNING);
 			throw new DbException(e);

bramble-core/src/main/java/org/briarproject/bramble/db/Migration45_46.java

@@ -32,6 +32,7 @@ class Migration45_46 implements Migration<Connection> {
 			s = txn.createStatement();
 			s.execute("ALTER TABLE messages"
 					+ " ADD COLUMN temporary BOOLEAN DEFAULT FALSE NOT NULL");
+			s.close();
 		} catch (SQLException e) {
 			tryToClose(s, LOG, WARNING);
 			throw new DbException(e);

bramble-core/src/main/java/org/briarproject/bramble/db/Migration46_47.java

@@ -39,6 +39,7 @@ class Migration46_47 implements Migration<Connection> {
 			s.execute(dbTypes.replaceTypes("ALTER TABLE contacts"
 					+ " ADD COLUMN syncVersions"
 					+ " _BINARY DEFAULT '00' NOT NULL"));
+			s.close();
 		} catch (SQLException e) {
 			tryToClose(s, LOG, WARNING);
 			throw new DbException(e);

bramble-core/src/main/java/org/briarproject/bramble/db/Migration47_48.java

@@ -0,0 +1,95 @@
+package org.briarproject.bramble.db;
+
+import org.briarproject.bramble.api.db.DbException;
+
+import java.sql.Connection;
+import java.sql.PreparedStatement;
+import java.sql.ResultSet;
+import java.sql.SQLException;
+import java.sql.Statement;
+import java.util.logging.Logger;
+
+import static java.lang.System.arraycopy;
+import static java.sql.Types.BINARY;
+import static java.util.logging.Level.INFO;
+import static java.util.logging.Level.WARNING;
+import static java.util.logging.Logger.getLogger;
+import static org.briarproject.bramble.api.sync.SyncConstants.MESSAGE_HEADER_LENGTH;
+import static org.briarproject.bramble.db.JdbcUtils.tryToClose;
+
+class Migration47_48 implements Migration<Connection> {
+
+	private static final Logger LOG = getLogger(Migration47_48.class.getName());
+
+	private final DatabaseTypes dbTypes;
+
+	Migration47_48(DatabaseTypes dbTypes) {
+		this.dbTypes = dbTypes;
+	}
+
+	@Override
+	public int getStartVersion() {
+		return 47;
+	}
+
+	@Override
+	public int getEndVersion() {
+		return 48;
+	}
+
+	@Override
+	public void migrate(Connection txn) throws DbException {
+		Statement s = null;
+		ResultSet rs = null;
+		PreparedStatement ps = null;
+		try {
+			s = txn.createStatement();
+			s.execute("ALTER TABLE messages"
+					+ " ADD COLUMN deleted BOOLEAN DEFAULT FALSE NOT NULL");
+			s.execute("UPDATE messages SET deleted = TRUE WHERE raw IS NULL");
+			s.execute("ALTER TABLE messages"
+					+ " ADD COLUMN blockCount INT DEFAULT 1 NOT NULL");
+			s.execute(dbTypes.replaceTypes("CREATE TABLE blocks"
+					+ " (messageId _HASH NOT NULL,"
+					+ " blockNumber INT NOT NULL,"
+					+ " blockLength INT NOT NULL," // Excludes block header
+					+ " data BLOB," // Null if message has been deleted
+					+ " PRIMARY KEY (messageId, blockNumber),"
+					+ " FOREIGN KEY (messageId)"
+					+ " REFERENCES messages (messageId)"
+					+ " ON DELETE CASCADE)"));
+			rs = s.executeQuery("SELECT messageId, length, raw FROM messages");
+			ps = txn.prepareStatement("INSERT INTO blocks"
+					+ " (messageId, blockNumber, blockLength, data)"
+					+ " VALUES (?, 0, ?, ?)");
+			int migrated = 0;
+			while (rs.next()) {
+				byte[] id = rs.getBytes(1);
+				int length = rs.getInt(2);
+				byte[] raw = rs.getBytes(3);
+				ps.setBytes(1, id);
+				ps.setInt(2, length - MESSAGE_HEADER_LENGTH);
+				if (raw == null) {
+					ps.setNull(3, BINARY);
+				} else {
+					byte[] data = new byte[raw.length - MESSAGE_HEADER_LENGTH];
+					arraycopy(raw, MESSAGE_HEADER_LENGTH, data, 0, data.length);
+					ps.setBytes(3, data);
+				}
+				if (ps.executeUpdate() != 1) throw new DbStateException();
+				migrated++;
+			}
+			ps.close();
+			rs.close();
+			s.execute("ALTER TABLE messages DROP COLUMN raw");
+			s.close();
+			if (LOG.isLoggable(INFO))
+				LOG.info("Migrated " + migrated + " messages");
+		} catch (SQLException e) {
+			tryToClose(ps, LOG, WARNING);
+			tryToClose(rs, LOG, WARNING);
+			tryToClose(s, LOG, WARNING);
+			throw new DbException(e);
+		}
+	}
+}

bramble-core/src/main/java/org/briarproject/bramble/db/Migration48_49.java

@@ -0,0 +1,40 @@
+package org.briarproject.bramble.db;
+
+import org.briarproject.bramble.api.db.DbException;
+
+import java.sql.Connection;
+import java.sql.SQLException;
+import java.sql.Statement;
+import java.util.logging.Logger;
+
+import static java.util.logging.Level.WARNING;
+import static java.util.logging.Logger.getLogger;
+import static org.briarproject.bramble.db.JdbcUtils.tryToClose;
+
+class Migration48_49 implements Migration<Connection> {
+
+	private static final Logger LOG = getLogger(Migration48_49.class.getName());
+
+	@Override
+	public int getStartVersion() {
+		return 48;
+	}
+
+	@Override
+	public int getEndVersion() {
+		return 49;
+	}
+
+	@Override
+	public void migrate(Connection txn) throws DbException {
+		Statement s = null;
+		try {
+			s = txn.createStatement();
+			s.execute("DROP TABLE offers");
+			s.close();
+		} catch (SQLException e) {
+			tryToClose(s, LOG, WARNING);
+			throw new DbException(e);
+		}
+	}
+}

bramble-core/src/main/java/org/briarproject/bramble/keyagreement/KeyAgreementConnector.java

@@ -1,5 +1,6 @@
 package org.briarproject.bramble.keyagreement;
 
+import org.briarproject.bramble.api.Pair;
 import org.briarproject.bramble.api.crypto.KeyAgreementCrypto;
 import org.briarproject.bramble.api.crypto.KeyPair;
 import org.briarproject.bramble.api.data.BdfList;
@@ -8,6 +9,8 @@ import org.briarproject.bramble.api.keyagreement.KeyAgreementListener;
 import org.briarproject.bramble.api.keyagreement.Payload;
 import org.briarproject.bramble.api.keyagreement.TransportDescriptor;
 import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
+import org.briarproject.bramble.api.plugin.BluetoothConstants;
+import org.briarproject.bramble.api.plugin.LanTcpConstants;
 import org.briarproject.bramble.api.plugin.Plugin;
 import org.briarproject.bramble.api.plugin.PluginManager;
 import org.briarproject.bramble.api.plugin.TransportId;
@@ -19,7 +22,9 @@ import org.briarproject.bramble.api.record.RecordWriterFactory;
 import java.io.IOException;
 import java.io.InputStream;
 import java.util.ArrayList;
+import java.util.HashMap;
 import java.util.List;
+import java.util.Map;
 import java.util.concurrent.Callable;
 import java.util.concurrent.CopyOnWriteArrayList;
 import java.util.concurrent.CountDownLatch;
@@ -28,8 +33,10 @@ import java.util.logging.Logger;
 
 import javax.annotation.Nullable;
 
+import static java.util.Arrays.asList;
 import static java.util.logging.Level.INFO;
 import static java.util.logging.Level.WARNING;
+import static java.util.logging.Logger.getLogger;
 import static org.briarproject.bramble.api.keyagreement.KeyAgreementConstants.CONNECTION_TIMEOUT;
 import static org.briarproject.bramble.util.LogUtils.logException;
 
@@ -41,7 +48,10 @@ class KeyAgreementConnector {
 	}
 
 	private static final Logger LOG =
-			Logger.getLogger(KeyAgreementConnector.class.getName());
+			getLogger(KeyAgreementConnector.class.getName());
+
+	private static final List<TransportId> PREFERRED_TRANSPORTS =
+			asList(BluetoothConstants.ID, LanTcpConstants.ID);
 
 	private final Callbacks callbacks;
 	private final KeyAgreementCrypto keyAgreementCrypto;
@@ -105,24 +115,35 @@ class KeyAgreementConnector {
 		this.alice = alice;
 		aliceLatch.countDown();
 
-		// Start connecting over supported transports
+		// Start connecting over supported transports in order of preference
 		if (LOG.isLoggable(INFO)) {
 			LOG.info("Starting outgoing BQP connections as "
 					+ (alice ? "Alice" : "Bob"));
 		}
+		Map<TransportId, TransportDescriptor> descriptors = new HashMap<>();
 		for (TransportDescriptor d : remotePayload.getTransportDescriptors()) {
-			Plugin p = pluginManager.getPlugin(d.getId());
-			if (p instanceof DuplexPlugin) {
+			descriptors.put(d.getId(), d);
+		}
+		List<Pair<DuplexPlugin, BdfList>> transports = new ArrayList<>();
+		for (TransportId id : PREFERRED_TRANSPORTS) {
+			TransportDescriptor d = descriptors.get(id);
+			Plugin p = pluginManager.getPlugin(id);
+			if (d != null && p instanceof DuplexPlugin) {
 				if (LOG.isLoggable(INFO))
-					LOG.info("Connecting via " + d.getId());
-				DuplexPlugin plugin = (DuplexPlugin) p;
-				byte[] commitment = remotePayload.getCommitment();
-				BdfList descriptor = d.getDescriptor();
-				connectionChooser.submit(new ReadableTask(
-						new ConnectorTask(plugin, commitment, descriptor)));
+					LOG.info("Connecting via " + id);
+				transports.add(new Pair<>((DuplexPlugin) p, d.getDescriptor()));
 			}
 		}
 
+		// TODO: If we don't have any transports in common with the peer,
+		//  warn the user and give up (#1224)
+
+		if (!transports.isEmpty()) {
+			byte[] commitment = remotePayload.getCommitment();
+			connectionChooser.submit(new ReadableTask(new ConnectorTask(
+					transports, commitment)));
+		}
+
 		// Get chosen connection
 		try {
 			KeyAgreementConnection chosen =
@@ -148,15 +169,13 @@ class KeyAgreementConnector {
 
 	private class ConnectorTask implements Callable<KeyAgreementConnection> {
 
+		private final List<Pair<DuplexPlugin, BdfList>> transports;
 		private final byte[] commitment;
-		private final BdfList descriptor;
-		private final DuplexPlugin plugin;
 
-		private ConnectorTask(DuplexPlugin plugin, byte[] commitment,
-				BdfList descriptor) {
-			this.plugin = plugin;
+		private ConnectorTask(List<Pair<DuplexPlugin, BdfList>> transports,
+				byte[] commitment) {
+			this.transports = transports;
 			this.commitment = commitment;
-			this.descriptor = descriptor;
 		}
 
 		@Nullable
@@ -164,13 +183,18 @@ class KeyAgreementConnector {
 		public KeyAgreementConnection call() throws Exception {
 			// Repeat attempts until we connect, get stopped, or get interrupted
 			while (!stopped) {
-				DuplexTransportConnection conn =
-						plugin.createKeyAgreementConnection(commitment,
-								descriptor);
-				if (conn != null) {
-					if (LOG.isLoggable(INFO))
-						LOG.info(plugin.getId() + ": Outgoing connection");
-					return new KeyAgreementConnection(conn, plugin.getId());
+				for (Pair<DuplexPlugin, BdfList> pair : transports) {
+					if (stopped) return null;
+					DuplexPlugin plugin = pair.getFirst();
+					BdfList descriptor = pair.getSecond();
+					DuplexTransportConnection conn =
+							plugin.createKeyAgreementConnection(commitment,
+									descriptor);
+					if (conn != null) {
+						if (LOG.isLoggable(INFO))
+							LOG.info(plugin.getId() + ": Outgoing connection");
+						return new KeyAgreementConnection(conn, plugin.getId());
+					}
 				}
 				// Wait 2s before retry (to circumvent transient failures)
 				Thread.sleep(2000);

bramble-core/src/main/java/org/briarproject/bramble/plugin/PluginManagerImpl.java

@@ -53,6 +53,7 @@ import static java.util.logging.Level.WARNING;
 import static java.util.logging.Logger.getLogger;
 import static org.briarproject.bramble.api.plugin.Plugin.PREF_PLUGIN_ENABLE;
 import static org.briarproject.bramble.api.plugin.Plugin.State.ACTIVE;
+import static org.briarproject.bramble.api.plugin.Plugin.State.DISABLED;
 import static org.briarproject.bramble.api.plugin.Plugin.State.STARTING_STOPPING;
 import static org.briarproject.bramble.util.LogUtils.logDuration;
 import static org.briarproject.bramble.util.LogUtils.logException;
@@ -354,6 +355,10 @@ class PluginManagerImpl implements PluginManager, Service {
 				} else if (oldState == ACTIVE) {
 					eventBus.broadcast(new TransportInactiveEvent(id));
 				}
+			} else if (newState == DISABLED) {
+				// Broadcast an event even though the state hasn't changed, as
+				// the reasons for the plugin being disabled may have changed
+				eventBus.broadcast(new TransportStateEvent(id, newState));
 			}
 		}
 

bramble-core/src/main/java/org/briarproject/bramble/plugin/bluetooth/BluetoothPlugin.java

@@ -21,9 +21,6 @@ import org.briarproject.bramble.api.plugin.PluginException;
 import org.briarproject.bramble.api.plugin.TransportId;
 import org.briarproject.bramble.api.plugin.duplex.DuplexPlugin;
 import org.briarproject.bramble.api.plugin.duplex.DuplexTransportConnection;
-import org.briarproject.bramble.api.plugin.event.BluetoothEnabledEvent;
-import org.briarproject.bramble.api.plugin.event.DisableBluetoothEvent;
-import org.briarproject.bramble.api.plugin.event.EnableBluetoothEvent;
 import org.briarproject.bramble.api.properties.TransportProperties;
 import org.briarproject.bramble.api.properties.event.RemoteTransportPropertiesUpdatedEvent;
 import org.briarproject.bramble.api.rendezvous.KeyMaterialSource;
@@ -93,12 +90,6 @@ abstract class BluetoothPlugin<S, SS> implements DuplexPlugin, EventListener {
 
 	abstract boolean isAdapterEnabled();
 
-	abstract void enableAdapter();
-
-	abstract void disableAdapterIfEnabledByUs();
-
-	abstract void setEnabledByUs();
-
 	/**
 	 * Returns the local Bluetooth address, or null if no valid address can
 	 * be found.
@@ -189,10 +180,7 @@ abstract class BluetoothPlugin<S, SS> implements DuplexPlugin, EventListener {
 			throw new PluginException(e);
 		}
 		updateProperties();
-		if (enabledByUser) {
-			if (isAdapterEnabled()) bind();
-			else enableAdapter();
-		}
+		if (enabledByUser && isAdapterEnabled()) bind();
 	}
 
 	private void bind() {
@@ -319,7 +307,6 @@ abstract class BluetoothPlugin<S, SS> implements DuplexPlugin, EventListener {
 	public void stop() {
 		SS ss = state.setStopped();
 		tryToClose(ss);
-		disableAdapterIfEnabledByUs();
 	}
 
 	@Override
@@ -449,8 +436,10 @@ abstract class BluetoothPlugin<S, SS> implements DuplexPlugin, EventListener {
 		String uuid = UUID.nameUUIDFromBytes(commitment).toString();
 		DuplexTransportConnection conn;
 		if (descriptor.size() == 1) {
-			if (LOG.isLoggable(INFO))
-				LOG.info("Discovering address for key agreement UUID " + uuid);
+			if (LOG.isLoggable(INFO)) {
+				LOG.info("Discovering address for key agreement UUID " +
+						uuid);
+			}
 			conn = discoverAndConnect(uuid);
 		} else {
 			String address;
@@ -490,13 +479,7 @@ abstract class BluetoothPlugin<S, SS> implements DuplexPlugin, EventListener {
 
 	@Override
 	public void eventOccurred(Event e) {
-		if (e instanceof EnableBluetoothEvent) {
-			ioExecutor.execute(this::enableAdapter);
-		} else if (e instanceof DisableBluetoothEvent) {
-			ioExecutor.execute(this::disableAdapterIfEnabledByUs);
-		} else if (e instanceof BluetoothEnabledEvent) {
-			setEnabledByUs();
-		} else if (e instanceof SettingsUpdatedEvent) {
+		if (e instanceof SettingsUpdatedEvent) {
 			SettingsUpdatedEvent s = (SettingsUpdatedEvent) e;
 			if (s.getNamespace().equals(ID.getString()))
 				ioExecutor.execute(() -> onSettingsUpdated(s.getSettings()));
@@ -522,11 +505,13 @@ abstract class BluetoothPlugin<S, SS> implements DuplexPlugin, EventListener {
 		if (ss != null) {
 			LOG.info("Disabled by user, closing server socket");
 			tryToClose(ss);
-			disableAdapterIfEnabledByUs();
 		} else if (s == INACTIVE) {
-			LOG.info("Enabled by user, opening server socket");
-			if (isAdapterEnabled()) bind();
-			else enableAdapter();
+			if (isAdapterEnabled()) {
+				LOG.info("Enabled by user, opening server socket");
+				bind();
+			} else {
+				LOG.info("Enabled by user but adapter is disabled");
+			}
 		}
 	}
 

bramble-core/src/main/java/org/briarproject/bramble/plugin/tor/TorPlugin.java

@@ -132,7 +132,7 @@ abstract class TorPlugin implements DuplexPlugin, EventHandler, EventListener {
 	private final CircumventionProvider circumventionProvider;
 	private final ResourceProvider resourceProvider;
 	private final int maxLatency, maxIdleTime, socketTimeout;
-	private final File torDirectory, torFile, geoIpFile, obfs4File, configFile;
+	private final File torDirectory, geoIpFile, configFile;
 	private final File doneFile, cookieFile;
 	private final AtomicBoolean used = new AtomicBoolean(false);
 
@@ -181,9 +181,7 @@ abstract class TorPlugin implements DuplexPlugin, EventHandler, EventListener {
 			socketTimeout = Integer.MAX_VALUE;
 		else socketTimeout = maxIdleTime * 2;
 		this.torDirectory = torDirectory;
-		torFile = new File(torDirectory, "tor");
 		geoIpFile = new File(torDirectory, "geoip");
-		obfs4File = new File(torDirectory, "obfs4proxy");
 		configFile = new File(torDirectory, "torrc");
 		doneFile = new File(torDirectory, "done");
 		cookieFile = new File(torDirectory, ".tor/control_auth_cookie");
@@ -192,6 +190,14 @@ abstract class TorPlugin implements DuplexPlugin, EventHandler, EventListener {
 				new PoliteExecutor("TorPlugin", ioExecutor, 1);
 	}
 
+	protected File getTorExecutableFile() {
+		return new File(torDirectory, "tor");
+	}
+
+	protected File getObfs4ExecutableFile() {
+		return new File(torDirectory, "obfs4proxy");
+	}
+
 	@Override
 	public TransportId getId() {
 		return TorConstants.ID;
@@ -224,6 +230,7 @@ abstract class TorPlugin implements DuplexPlugin, EventHandler, EventListener {
 			LOG.warning("Old auth cookie not deleted");
 		// Start a new Tor process
 		LOG.info("Starting Tor");
+		File torFile = getTorExecutableFile();
 		String torPath = torFile.getAbsolutePath();
 		String configPath = configFile.getAbsolutePath();
 		String pid = String.valueOf(getProcessId());
@@ -322,44 +329,43 @@ abstract class TorPlugin implements DuplexPlugin, EventHandler, EventListener {
 	}
 
 	private void installAssets() throws PluginException {
-		InputStream in = null;
-		OutputStream out = null;
 		try {
 			// The done file may already exist from a previous installation
 			//noinspection ResultOfMethodCallIgnored
 			doneFile.delete();
-			// Unzip the Tor binary to the filesystem
-			in = getTorInputStream();
-			out = new FileOutputStream(torFile);
-			copyAndClose(in, out);
-			// Make the Tor binary executable
-			if (!torFile.setExecutable(true, true)) throw new IOException();
-			// Unzip the GeoIP database to the filesystem
-			in = getGeoIpInputStream();
-			out = new FileOutputStream(geoIpFile);
-			copyAndClose(in, out);
-			// Unzip the Obfs4 proxy to the filesystem
-			in = getObfs4InputStream();
-			out = new FileOutputStream(obfs4File);
-			copyAndClose(in, out);
-			// Make the Obfs4 proxy executable
-			if (!obfs4File.setExecutable(true, true)) throw new IOException();
-			// Copy the config file to the filesystem
-			in = getConfigInputStream();
-			out = new FileOutputStream(configFile);
-			copyAndClose(in, out);
+			installTorExecutable();
+			installObfs4Executable();
+			extract(getGeoIpInputStream(), geoIpFile);
+			extract(getConfigInputStream(), configFile);
 			if (!doneFile.createNewFile())
 				LOG.warning("Failed to create done file");
 		} catch (IOException e) {
-			tryToClose(in, LOG, WARNING);
-			tryToClose(out, LOG, WARNING);
 			throw new PluginException(e);
 		}
 	}
 
-	private InputStream getTorInputStream() throws IOException {
+	protected void extract(InputStream in, File dest) throws IOException {
+		OutputStream out = new FileOutputStream(dest);
+		copyAndClose(in, out);
+	}
+
+	protected void installTorExecutable() throws IOException {
 		if (LOG.isLoggable(INFO))
 			LOG.info("Installing Tor binary for " + architecture);
+		File torFile = getTorExecutableFile();
+		extract(getTorInputStream(), torFile);
+		if (!torFile.setExecutable(true, true)) throw new IOException();
+	}
+
+	protected void installObfs4Executable() throws IOException {
+		if (LOG.isLoggable(INFO))
+			LOG.info("Installing obfs4proxy binary for " + architecture);
+		File obfs4File = getObfs4ExecutableFile();
+		extract(getObfs4InputStream(), obfs4File);
+		if (!obfs4File.setExecutable(true, true)) throw new IOException();
+	}
+
+	private InputStream getTorInputStream() throws IOException {
 		InputStream in = resourceProvider
 				.getResourceInputStream("tor_" + architecture, ".zip");
 		ZipInputStream zin = new ZipInputStream(in);
@@ -376,8 +382,6 @@ abstract class TorPlugin implements DuplexPlugin, EventHandler, EventListener {
 	}
 
 	private InputStream getObfs4InputStream() throws IOException {
-		if (LOG.isLoggable(INFO))
-			LOG.info("Installing obfs4proxy binary for " + architecture);
 		InputStream in = resourceProvider
 				.getResourceInputStream("obfs4proxy_" + architecture, ".zip");
 		ZipInputStream zin = new ZipInputStream(in);
@@ -569,6 +573,7 @@ abstract class TorPlugin implements DuplexPlugin, EventHandler, EventListener {
 		if (enable) {
 			Collection<String> conf = new ArrayList<>();
 			conf.add("UseBridges 1");
+			File obfs4File = getObfs4ExecutableFile();
 			if (needsMeek) {
 				conf.add("ClientTransportPlugin meek_lite exec " +
 						obfs4File.getAbsolutePath());

bramble-core/src/main/java/org/briarproject/bramble/properties/TransportPropertyManagerImpl.java

@@ -199,7 +199,7 @@ class TransportPropertyManagerImpl implements TransportPropertyManager,
 			Map<TransportId, LatestUpdate> latest = findLatestLocal(txn);
 			// Retrieve and parse the latest local properties
 			for (Entry<TransportId, LatestUpdate> e : latest.entrySet()) {
-				BdfList message = clientHelper.getMessageAsList(txn,
+				BdfList message = clientHelper.getSmallMessageAsList(txn,
 						e.getValue().messageId);
 				local.put(e.getKey(), parseProperties(message));
 			}
@@ -220,7 +220,7 @@ class TransportPropertyManagerImpl implements TransportPropertyManager,
 						true);
 				if (latest != null) {
 					// Retrieve and parse the latest local properties
-					BdfList message = clientHelper.getMessageAsList(txn,
+					BdfList message = clientHelper.getSmallMessageAsList(txn,
 							latest.messageId);
 					p = parseProperties(message);
 				}
@@ -250,7 +250,7 @@ class TransportPropertyManagerImpl implements TransportPropertyManager,
 			if (latest == null) {
 				local = new TransportProperties();
 			} else {
-				BdfList message = clientHelper.getMessageAsList(txn,
+				BdfList message = clientHelper.getSmallMessageAsList(txn,
 						latest.messageId);
 				local = parseProperties(message);
 			}
@@ -271,8 +271,8 @@ class TransportPropertyManagerImpl implements TransportPropertyManager,
 				remote = new TransportProperties();
 			} else {
 				// Retrieve and parse the latest remote properties
-				BdfList message =
-						clientHelper.getMessageAsList(txn, latest.messageId);
+				BdfList message = clientHelper.getSmallMessageAsList(txn,
+						latest.messageId);
 				remote = parseProperties(message);
 			}
 			// Merge in any discovered properties
@@ -315,7 +315,7 @@ class TransportPropertyManagerImpl implements TransportPropertyManager,
 					}
 					changed = true;
 				} else {
-					BdfList message = clientHelper.getMessageAsList(txn,
+					BdfList message = clientHelper.getSmallMessageAsList(txn,
 							latest.messageId);
 					TransportProperties old = parseProperties(message);
 					merged = new TransportProperties(old);

bramble-core/src/main/java/org/briarproject/bramble/rendezvous/RendezvousPollerImpl.java

@@ -42,6 +42,7 @@ import org.briarproject.bramble.api.rendezvous.event.RendezvousConnectionOpenedE
 import org.briarproject.bramble.api.rendezvous.event.RendezvousPollEvent;
 import org.briarproject.bramble.api.system.Clock;
 import org.briarproject.bramble.api.system.TaskScheduler;
+import org.briarproject.bramble.api.system.TaskScheduler.Cancellable;
 import org.briarproject.bramble.api.system.Wakeful;
 
 import java.security.GeneralSecurityException;
@@ -68,6 +69,7 @@ import static org.briarproject.bramble.api.contact.PendingContactState.ADDING_CO
 import static org.briarproject.bramble.api.contact.PendingContactState.FAILED;
 import static org.briarproject.bramble.api.contact.PendingContactState.OFFLINE;
 import static org.briarproject.bramble.api.contact.PendingContactState.WAITING_FOR_CONNECTION;
+import static org.briarproject.bramble.api.nullsafety.NullSafety.requireNonNull;
 import static org.briarproject.bramble.api.nullsafety.NullSafety.requireNull;
 import static org.briarproject.bramble.rendezvous.RendezvousConstants.POLLING_INTERVAL_MS;
 import static org.briarproject.bramble.rendezvous.RendezvousConstants.RENDEZVOUS_TIMEOUT_MS;
@@ -102,6 +104,8 @@ class RendezvousPollerImpl implements RendezvousPoller, Service, EventListener {
 			new HashMap<>();
 	@Nullable
 	private KeyPair handshakeKeyPair = null;
+	@Nullable
+	private Cancellable pollTask = null;
 
 	@Inject
 	RendezvousPollerImpl(@IoExecutor Executor ioExecutor,
@@ -144,8 +148,6 @@ class RendezvousPollerImpl implements RendezvousPoller, Service, EventListener {
 		} catch (DbException e) {
 			throw new ServiceException(e);
 		}
-		scheduler.scheduleWithFixedDelay(this::poll, worker,
-				POLLING_INTERVAL_MS, POLLING_INTERVAL_MS, MILLISECONDS);
 	}
 
 	@EventExecutor
@@ -186,6 +188,12 @@ class RendezvousPollerImpl implements RendezvousPoller, Service, EventListener {
 			}
 			if (cs.numEndpoints == 0) broadcastState(p.getId(), OFFLINE);
 			else broadcastState(p.getId(), WAITING_FOR_CONNECTION);
+			if (cryptoStates.size() == 1) {
+				LOG.info("Starting poller");
+				requireNull(pollTask);
+				pollTask = scheduler.scheduleWithFixedDelay(this::poll, worker,
+						POLLING_INTERVAL_MS, POLLING_INTERVAL_MS, MILLISECONDS);
+			}
 		} catch (DbException | GeneralSecurityException e) {
 			logException(LOG, WARNING, e);
 		}
@@ -208,6 +216,7 @@ class RendezvousPollerImpl implements RendezvousPoller, Service, EventListener {
 	// Worker
 	@Wakeful
 	private void poll() {
+		LOG.info("Polling");
 		removeExpiredPendingContacts();
 		for (PluginState ps : pluginStates.values()) poll(ps);
 	}
@@ -234,6 +243,11 @@ class RendezvousPollerImpl implements RendezvousPoller, Service, EventListener {
 			RendezvousEndpoint endpoint = ps.endpoints.remove(p);
 			if (endpoint != null) tryToClose(endpoint, LOG, INFO);
 		}
+		if (cryptoStates.isEmpty()) {
+			LOG.info("Stopping poller");
+			requireNonNull(pollTask).cancel();
+			pollTask = null;
+		}
 	}
 
 	// Worker

bramble-core/src/main/java/org/briarproject/bramble/sync/DuplexOutgoingSession.java

@@ -15,6 +15,7 @@ import org.briarproject.bramble.api.plugin.TransportId;
 import org.briarproject.bramble.api.plugin.event.TransportInactiveEvent;
 import org.briarproject.bramble.api.sync.Ack;
 import org.briarproject.bramble.api.sync.Message;
+import org.briarproject.bramble.api.sync.MessageId;
 import org.briarproject.bramble.api.sync.Offer;
 import org.briarproject.bramble.api.sync.Priority;
 import org.briarproject.bramble.api.sync.Request;
@@ -25,8 +26,8 @@ import org.briarproject.bramble.api.sync.event.CloseSyncConnectionsEvent;
 import org.briarproject.bramble.api.sync.event.GroupVisibilityUpdatedEvent;
 import org.briarproject.bramble.api.sync.event.MessageRequestedEvent;
 import org.briarproject.bramble.api.sync.event.MessageSharedEvent;
-import org.briarproject.bramble.api.sync.event.MessageToAckEvent;
-import org.briarproject.bramble.api.sync.event.MessageToRequestEvent;
+import org.briarproject.bramble.api.sync.event.MessagesToAckEvent;
+import org.briarproject.bramble.api.sync.event.MessagesToRequestEvent;
 import org.briarproject.bramble.api.system.Clock;
 import org.briarproject.bramble.api.transport.StreamWriter;
 
@@ -87,8 +88,6 @@ class DuplexOutgoingSession implements SyncSession, EventListener {
 	private final AtomicBoolean generateAckQueued = new AtomicBoolean(false);
 	private final AtomicBoolean generateBatchQueued = new AtomicBoolean(false);
 	private final AtomicBoolean generateOfferQueued = new AtomicBoolean(false);
-	private final AtomicBoolean generateRequestQueued =
-			new AtomicBoolean(false);
 	private final AtomicLong nextSendTime = new AtomicLong(Long.MAX_VALUE);
 
 	private volatile boolean interrupted = false;
@@ -125,7 +124,6 @@ class DuplexOutgoingSession implements SyncSession, EventListener {
 			generateAck();
 			generateBatch();
 			generateOffer();
-			generateRequest();
 			long now = clock.currentTimeMillis();
 			long nextKeepalive = now + maxIdleTime;
 			boolean dataToFlush = true;
@@ -197,11 +195,6 @@ class DuplexOutgoingSession implements SyncSession, EventListener {
 			dbExecutor.execute(new GenerateOffer());
 	}
 
-	private void generateRequest() {
-		if (generateRequestQueued.compareAndSet(false, true))
-			dbExecutor.execute(new GenerateRequest());
-	}
-
 	private void setNextSendTime(long time) {
 		long old = nextSendTime.getAndSet(time);
 		if (time < old) writerTasks.add(NEXT_SEND_TIME_DECREASED);
@@ -227,12 +220,16 @@ class DuplexOutgoingSession implements SyncSession, EventListener {
 		} else if (e instanceof MessageRequestedEvent) {
 			if (((MessageRequestedEvent) e).getContactId().equals(contactId))
 				generateBatch();
-		} else if (e instanceof MessageToAckEvent) {
-			if (((MessageToAckEvent) e).getContactId().equals(contactId))
+		} else if (e instanceof MessagesToAckEvent) {
+			if (((MessagesToAckEvent) e).getContactId().equals(contactId))
 				generateAck();
-		} else if (e instanceof MessageToRequestEvent) {
-			if (((MessageToRequestEvent) e).getContactId().equals(contactId))
-				generateRequest();
+		} else if (e instanceof MessagesToRequestEvent) {
+			MessagesToRequestEvent m = (MessagesToRequestEvent) e;
+			if (m.getContactId().equals(contactId)) {
+				Collection<MessageId> ids = m.consumeIds();
+				if (ids != null)
+					writerTasks.add(new WriteRequest(new Request(ids)));
+			}
 		} else if (e instanceof LifecycleEvent) {
 			LifecycleEvent l = (LifecycleEvent) e;
 			if (l.getLifecycleState() == STOPPING) interrupt();
@@ -340,7 +337,7 @@ class DuplexOutgoingSession implements SyncSession, EventListener {
 			try {
 				Offer o = db.transactionWithNullableResult(false, txn -> {
 					Offer offer = db.generateOffer(txn, contactId,
-							MAX_MESSAGE_IDS, maxLatency);
+							MAX_MESSAGE_IDS, maxLatency, true);
 					setNextSendTime(db.getNextSendTime(txn, contactId));
 					return offer;
 				});
@@ -372,27 +369,6 @@ class DuplexOutgoingSession implements SyncSession, EventListener {
 		}
 	}
 
-	private class GenerateRequest implements Runnable {
-
-		@DatabaseExecutor
-		@Override
-		public void run() {
-			if (interrupted) return;
-			if (!generateRequestQueued.getAndSet(false))
-				throw new AssertionError();
-			try {
-				Request r = db.transactionWithNullableResult(false, txn ->
-						db.generateRequest(txn, contactId, MAX_MESSAGE_IDS));
-				if (LOG.isLoggable(INFO))
-					LOG.info("Generated request: " + (r != null));
-				if (r != null) writerTasks.add(new WriteRequest(r));
-			} catch (DbException e) {
-				logException(LOG, WARNING, e);
-				interrupt();
-			}
-		}
-	}
-
 	private class WriteRequest implements ThrowingRunnable<IOException> {
 
 		private final Request request;
@@ -407,7 +383,6 @@ class DuplexOutgoingSession implements SyncSession, EventListener {
 			if (interrupted) return;
 			recordWriter.writeRequest(request);
 			LOG.info("Sent request");
-			generateRequest();
 		}
 	}
 }

bramble-core/src/main/java/org/briarproject/bramble/sync/SimplexOutgoingSession.java

@@ -186,7 +186,8 @@ class SimplexOutgoingSession implements SyncSession, EventListener {
 				Collection<Message> b =
 						db.transactionWithNullableResult(false, txn ->
 								db.generateBatch(txn, contactId,
-										MAX_RECORD_PAYLOAD_BYTES, maxLatency));
+										MAX_RECORD_PAYLOAD_BYTES, maxLatency,
+										true));
 				if (LOG.isLoggable(INFO))
 					LOG.info("Generated batch: " + (b != null));
 				if (b == null) decrementOutstandingQueries();

bramble-core/src/main/java/org/briarproject/bramble/sync/validation/ValidationManagerImpl.java

@@ -120,7 +120,7 @@ class ValidationManagerImpl implements ValidationManager, Service,
 			Pair<Message, Group> mg = db.transactionWithResult(true, txn -> {
 				MessageId id = unvalidated.poll();
 				if (id == null) throw new AssertionError();
-				Message m = db.getMessage(txn, id);
+				Message m = db.getSmallMessage(txn, id);
 				Group g = db.getGroup(txn, m.getGroupId());
 				return new Pair<>(m, g);
 			});
@@ -179,7 +179,7 @@ class ValidationManagerImpl implements ValidationManager, Service,
 						invalidateMessage(txn, id);
 						addDependentsToInvalidate(txn, id, invalidate);
 					} else if (allDelivered) {
-						Message m = db.getMessage(txn, id);
+						Message m = db.getSmallMessage(txn, id);
 						Group g = db.getGroup(txn, m.getGroupId());
 						ClientId c = g.getClientId();
 						int majorVersion = g.getMajorVersion();

bramble-core/src/main/java/org/briarproject/bramble/versioning/ClientVersioningManagerImpl.java

@@ -298,7 +298,8 @@ class ClientVersioningManagerImpl implements ClientVersioningManager,
 	private List<ClientVersion> loadClientVersions(Transaction txn,
 			MessageId m) throws DbException {
 		try {
-			return parseClientVersions(clientHelper.getMessageAsList(txn, m));
+			return parseClientVersions(
+					clientHelper.getSmallMessageAsList(txn, m));
 		} catch (FormatException e) {
 			throw new DbException(e);
 		}
@@ -391,7 +392,7 @@ class ClientVersioningManagerImpl implements ClientVersioningManager,
 
 	private Update loadUpdate(Transaction txn, MessageId m) throws DbException {
 		try {
-			return parseUpdate(clientHelper.getMessageAsList(txn, m));
+			return parseUpdate(clientHelper.getSmallMessageAsList(txn, m));
 		} catch (FormatException e) {
 			throw new DbException(e);
 		}

bramble-core/src/test/java/org/briarproject/bramble/account/AccountManagerImplTest.java

@@ -134,7 +134,7 @@ public class AccountManagerImplTest extends BrambleMockTestCase {
 					keyStrengthener);
 			will(returnValue(key.getBytes()));
 			oneOf(crypto).isEncryptedWithStrengthenedKey(encryptedKey);
-			will(returnValue(false));
+			will(returnValue(true));
 		}});
 
 		storeDatabaseKey(keyFile, encryptedKeyHex);
@@ -160,8 +160,9 @@ public class AccountManagerImplTest extends BrambleMockTestCase {
 					keyStrengthener);
 			will(returnValue(key.getBytes()));
 			oneOf(crypto).isEncryptedWithStrengthenedKey(encryptedKey);
-			will(returnValue(true));
-			oneOf(crypto).encryptWithPassword(key.getBytes(), password, null);
+			will(returnValue(false));
+			oneOf(crypto).encryptWithPassword(key.getBytes(), password,
+					keyStrengthener);
 			will(returnValue(newEncryptedKey));
 		}});
 
@@ -261,7 +262,8 @@ public class AccountManagerImplTest extends BrambleMockTestCase {
 			oneOf(identityManager).registerIdentity(identity);
 			oneOf(crypto).generateSecretKey();
 			will(returnValue(key));
-			oneOf(crypto).encryptWithPassword(key.getBytes(), password, null);
+			oneOf(crypto).encryptWithPassword(key.getBytes(), password,
+					keyStrengthener);
 			will(returnValue(encryptedKey));
 		}});
 
@@ -321,8 +323,10 @@ public class AccountManagerImplTest extends BrambleMockTestCase {
 			oneOf(crypto).decryptWithPassword(encryptedKey, password,
 					keyStrengthener);
 			will(returnValue(key.getBytes()));
+			oneOf(crypto).isEncryptedWithStrengthenedKey(encryptedKey);
+			will(returnValue(true));
 			oneOf(crypto).encryptWithPassword(key.getBytes(), newPassword,
-					null);
+					keyStrengthener);
 			will(returnValue(newEncryptedKey));
 		}});
 

bramble-core/src/test/java/org/briarproject/bramble/client/ClientHelperImplTest.java

@@ -122,11 +122,11 @@ public class ClientHelperImplTest extends BrambleTestCase {
 		expectToList(true);
 		context.checking(new DbExpectations() {{
 			oneOf(db).transactionWithResult(with(true), withDbCallable(txn));
-			oneOf(db).getMessage(txn, messageId);
+			oneOf(db).getSmallMessage(txn, messageId);
 			will(returnValue(message));
 		}});
 
-		clientHelper.getMessageAsList(messageId);
+		clientHelper.getSmallMessageAsList(messageId);
 		context.assertIsSatisfied();
 	}
 

bramble-core/src/test/java/org/briarproject/bramble/db/DatabaseComponentImplTest.java

@@ -44,10 +44,10 @@ import org.briarproject.bramble.api.sync.event.MessageAddedEvent;
 import org.briarproject.bramble.api.sync.event.MessageRequestedEvent;
 import org.briarproject.bramble.api.sync.event.MessageSharedEvent;
 import org.briarproject.bramble.api.sync.event.MessageStateChangedEvent;
-import org.briarproject.bramble.api.sync.event.MessageToAckEvent;
-import org.briarproject.bramble.api.sync.event.MessageToRequestEvent;
 import org.briarproject.bramble.api.sync.event.MessagesAckedEvent;
 import org.briarproject.bramble.api.sync.event.MessagesSentEvent;
+import org.briarproject.bramble.api.sync.event.MessagesToAckEvent;
+import org.briarproject.bramble.api.sync.event.MessagesToRequestEvent;
 import org.briarproject.bramble.api.transport.IncomingKeys;
 import org.briarproject.bramble.api.transport.KeySetId;
 import org.briarproject.bramble.api.transport.OutgoingKeys;
@@ -76,7 +76,6 @@ import static org.briarproject.bramble.api.sync.SyncConstants.MAX_MESSAGE_LENGTH
 import static org.briarproject.bramble.api.sync.validation.MessageState.DELIVERED;
 import static org.briarproject.bramble.api.sync.validation.MessageState.UNKNOWN;
 import static org.briarproject.bramble.api.transport.TransportConstants.REORDERING_WINDOW_SIZE;
-import static org.briarproject.bramble.db.DatabaseConstants.MAX_OFFERED_MESSAGES;
 import static org.briarproject.bramble.test.TestUtils.getAgreementPrivateKey;
 import static org.briarproject.bramble.test.TestUtils.getAgreementPublicKey;
 import static org.briarproject.bramble.test.TestUtils.getAuthor;
@@ -295,11 +294,11 @@ public class DatabaseComponentImplTest extends BrambleMockTestCase {
 			throws Exception {
 		context.checking(new Expectations() {{
 			// Check whether the contact is in the DB (which it's not)
-			exactly(18).of(database).startTransaction();
+			exactly(17).of(database).startTransaction();
 			will(returnValue(txn));
-			exactly(18).of(database).containsContact(txn, contactId);
+			exactly(17).of(database).containsContact(txn, contactId);
 			will(returnValue(false));
-			exactly(18).of(database).abortTransaction(txn);
+			exactly(17).of(database).abortTransaction(txn);
 		}});
 		DatabaseComponent db = createDatabaseComponent(database, eventBus,
 				eventExecutor, shutdownManager);
@@ -323,7 +322,7 @@ public class DatabaseComponentImplTest extends BrambleMockTestCase {
 
 		try {
 			db.transaction(false, transaction ->
-					db.generateBatch(transaction, contactId, 123, 456));
+					db.generateBatch(transaction, contactId, 123, 456, true));
 			fail();
 		} catch (NoSuchContactException expected) {
 			// Expected
@@ -331,15 +330,7 @@ public class DatabaseComponentImplTest extends BrambleMockTestCase {
 
 		try {
 			db.transaction(false, transaction ->
-					db.generateOffer(transaction, contactId, 123, 456));
-			fail();
-		} catch (NoSuchContactException expected) {
-			// Expected
-		}
-
-		try {
-			db.transaction(false, transaction ->
-					db.generateRequest(transaction, contactId, 123));
+					db.generateOffer(transaction, contactId, 123, 456, true));
 			fail();
 		} catch (NoSuchContactException expected) {
 			// Expected
@@ -624,7 +615,7 @@ public class DatabaseComponentImplTest extends BrambleMockTestCase {
 
 		try {
 			db.transaction(false, transaction ->
-					db.getMessage(transaction, messageId));
+					db.getSmallMessage(transaction, messageId));
 			fail();
 		} catch (NoSuchMessageException expected) {
 			// Expected
@@ -865,14 +856,14 @@ public class DatabaseComponentImplTest extends BrambleMockTestCase {
 			will(returnValue(txn));
 			oneOf(database).containsContact(txn, contactId);
 			will(returnValue(true));
-			oneOf(database).getMessagesToSend(txn, contactId,
+			oneOf(database).getSmallMessagesToSend(txn, contactId,
 					MAX_MESSAGE_LENGTH * 2, maxLatency);
 			will(returnValue(ids));
-			oneOf(database).getMessage(txn, messageId);
+			oneOf(database).getSmallMessage(txn, messageId);
 			will(returnValue(message));
 			oneOf(database).updateExpiryTimeAndEta(txn, contactId, messageId,
 					maxLatency);
-			oneOf(database).getMessage(txn, messageId1);
+			oneOf(database).getSmallMessage(txn, messageId1);
 			will(returnValue(message1));
 			oneOf(database).updateExpiryTimeAndEta(txn, contactId, messageId1,
 					maxLatency);
@@ -885,7 +876,7 @@ public class DatabaseComponentImplTest extends BrambleMockTestCase {
 
 		db.transaction(false, transaction ->
 				assertEquals(messages, db.generateBatch(transaction, contactId,
-						MAX_MESSAGE_LENGTH * 2, maxLatency)));
+						MAX_MESSAGE_LENGTH * 2, maxLatency, true)));
 	}
 
 	@Test
@@ -897,7 +888,8 @@ public class DatabaseComponentImplTest extends BrambleMockTestCase {
 			will(returnValue(txn));
 			oneOf(database).containsContact(txn, contactId);
 			will(returnValue(true));
-			oneOf(database).getMessagesToOffer(txn, contactId, 123, maxLatency);
+			oneOf(database).getSmallMessagesToOffer(txn, contactId, 123,
+					maxLatency);
 			will(returnValue(ids));
 			oneOf(database).updateExpiryTimeAndEta(txn, contactId, messageId,
 					maxLatency);
@@ -909,36 +901,13 @@ public class DatabaseComponentImplTest extends BrambleMockTestCase {
 				eventExecutor, shutdownManager);
 
 		db.transaction(false, transaction -> {
-			Offer o = db.generateOffer(transaction, contactId, 123, maxLatency);
+			Offer o = db.generateOffer(transaction, contactId, 123, maxLatency,
+					true);
 			assertNotNull(o);
 			assertEquals(ids, o.getMessageIds());
 		});
 	}
 
-	@Test
-	public void testGenerateRequest() throws Exception {
-		MessageId messageId1 = new MessageId(getRandomId());
-		Collection<MessageId> ids = asList(messageId, messageId1);
-		context.checking(new Expectations() {{
-			oneOf(database).startTransaction();
-			will(returnValue(txn));
-			oneOf(database).containsContact(txn, contactId);
-			will(returnValue(true));
-			oneOf(database).getMessagesToRequest(txn, contactId, 123);
-			will(returnValue(ids));
-			oneOf(database).removeOfferedMessages(txn, contactId, ids);
-			oneOf(database).commitTransaction(txn);
-		}});
-		DatabaseComponent db = createDatabaseComponent(database, eventBus,
-				eventExecutor, shutdownManager);
-
-		db.transaction(false, transaction -> {
-			Request r = db.generateRequest(transaction, contactId, 123);
-			assertNotNull(r);
-			assertEquals(ids, r.getMessageIds());
-		});
-	}
-
 	@Test
 	public void testGenerateRequestedBatch() throws Exception {
 		Collection<MessageId> ids = asList(messageId, messageId1);
@@ -951,11 +920,11 @@ public class DatabaseComponentImplTest extends BrambleMockTestCase {
 			oneOf(database).getRequestedMessagesToSend(txn, contactId,
 					MAX_MESSAGE_LENGTH * 2, maxLatency);
 			will(returnValue(ids));
-			oneOf(database).getMessage(txn, messageId);
+			oneOf(database).getSmallMessage(txn, messageId);
 			will(returnValue(message));
 			oneOf(database).updateExpiryTimeAndEta(txn, contactId, messageId,
 					maxLatency);
-			oneOf(database).getMessage(txn, messageId1);
+			oneOf(database).getSmallMessage(txn, messageId1);
 			will(returnValue(message1));
 			oneOf(database).updateExpiryTimeAndEta(txn, contactId, messageId1,
 					maxLatency);
@@ -1018,10 +987,10 @@ public class DatabaseComponentImplTest extends BrambleMockTestCase {
 			oneOf(database).raiseAckFlag(txn, contactId, messageId);
 			oneOf(database).commitTransaction(txn);
 			// First time: the message was received and added
-			oneOf(eventBus).broadcast(with(any(MessageToAckEvent.class)));
+			oneOf(eventBus).broadcast(with(any(MessagesToAckEvent.class)));
 			oneOf(eventBus).broadcast(with(any(MessageAddedEvent.class)));
 			// Second time: the message needs to be acked
-			oneOf(eventBus).broadcast(with(any(MessageToAckEvent.class)));
+			oneOf(eventBus).broadcast(with(any(MessagesToAckEvent.class)));
 		}});
 		DatabaseComponent db = createDatabaseComponent(database, eventBus,
 				eventExecutor, shutdownManager);
@@ -1049,7 +1018,7 @@ public class DatabaseComponentImplTest extends BrambleMockTestCase {
 			oneOf(database).raiseAckFlag(txn, contactId, messageId);
 			oneOf(database).commitTransaction(txn);
 			// The message was received but not added
-			oneOf(eventBus).broadcast(with(any(MessageToAckEvent.class)));
+			oneOf(eventBus).broadcast(with(any(MessagesToAckEvent.class)));
 		}});
 		DatabaseComponent db = createDatabaseComponent(database, eventBus,
 				eventExecutor, shutdownManager);
@@ -1080,19 +1049,15 @@ public class DatabaseComponentImplTest extends BrambleMockTestCase {
 	public void testReceiveOffer() throws Exception {
 		MessageId messageId1 = new MessageId(getRandomId());
 		MessageId messageId2 = new MessageId(getRandomId());
-		MessageId messageId3 = new MessageId(getRandomId());
+
 		context.checking(new Expectations() {{
 			oneOf(database).startTransaction();
 			will(returnValue(txn));
 			oneOf(database).containsContact(txn, contactId);
 			will(returnValue(true));
-			// There's room for two more offered messages
-			oneOf(database).countOfferedMessages(txn, contactId);
-			will(returnValue(MAX_OFFERED_MESSAGES - 2));
 			// The first message isn't visible - request it
 			oneOf(database).containsVisibleMessage(txn, contactId, messageId);
 			will(returnValue(false));
-			oneOf(database).addOfferedMessage(txn, contactId, messageId);
 			// The second message is visible - ack it
 			oneOf(database).containsVisibleMessage(txn, contactId, messageId1);
 			will(returnValue(true));
@@ -1101,19 +1066,14 @@ public class DatabaseComponentImplTest extends BrambleMockTestCase {
 			// The third message isn't visible - request it
 			oneOf(database).containsVisibleMessage(txn, contactId, messageId2);
 			will(returnValue(false));
-			oneOf(database).addOfferedMessage(txn, contactId, messageId2);
-			// The fourth message isn't visible, but there's no room to store it
-			oneOf(database).containsVisibleMessage(txn, contactId, messageId3);
-			will(returnValue(false));
 			oneOf(database).commitTransaction(txn);
-			oneOf(eventBus).broadcast(with(any(MessageToAckEvent.class)));
-			oneOf(eventBus).broadcast(with(any(MessageToRequestEvent.class)));
+			oneOf(eventBus).broadcast(with(any(MessagesToAckEvent.class)));
+			oneOf(eventBus).broadcast(with(any(MessagesToRequestEvent.class)));
 		}});
 		DatabaseComponent db = createDatabaseComponent(database, eventBus,
 				eventExecutor, shutdownManager);
 
-		Offer o = new Offer(asList(messageId, messageId1,
-				messageId2, messageId3));
+		Offer o = new Offer(asList(messageId, messageId1, messageId2));
 		db.transaction(false, transaction ->
 				db.receiveOffer(transaction, contactId, o));
 	}

bramble-core/src/test/java/org/briarproject/bramble/db/DatabasePerformanceComparisonTest.java

@@ -3,11 +3,9 @@ package org.briarproject.bramble.db;
 import org.briarproject.bramble.api.crypto.SecretKey;
 import org.briarproject.bramble.api.db.DatabaseConfig;
 import org.briarproject.bramble.api.db.DbException;
-import org.briarproject.bramble.api.sync.MessageFactory;
 import org.briarproject.bramble.api.system.Clock;
 import org.briarproject.bramble.system.SystemClock;
 import org.briarproject.bramble.test.TestDatabaseConfig;
-import org.briarproject.bramble.test.TestMessageFactory;
 import org.briarproject.bramble.test.UTest;
 
 import java.io.IOException;
@@ -32,8 +30,7 @@ public abstract class DatabasePerformanceComparisonTest
 	private SecretKey databaseKey = getSecretKey();
 
 	abstract Database<Connection> createDatabase(boolean conditionA,
-			DatabaseConfig databaseConfig, MessageFactory messageFactory,
-			Clock clock);
+			DatabaseConfig databaseConfig, Clock clock);
 
 	@Override
 	protected void benchmark(String name,
@@ -76,8 +73,7 @@ public abstract class DatabasePerformanceComparisonTest
 	private Database<Connection> openDatabase(boolean conditionA)
 			throws DbException {
 		Database<Connection> db = createDatabase(conditionA,
-				new TestDatabaseConfig(testDir), new TestMessageFactory(),
-				new SystemClock());
+				new TestDatabaseConfig(testDir), new SystemClock());
 		db.open(databaseKey, null);
 		return db;
 	}

bramble-core/src/test/java/org/briarproject/bramble/db/DatabasePerformanceTest.java

@@ -41,7 +41,6 @@ import static org.briarproject.bramble.test.TestUtils.getGroup;
 import static org.briarproject.bramble.test.TestUtils.getIdentity;
 import static org.briarproject.bramble.test.TestUtils.getMessage;
 import static org.briarproject.bramble.test.TestUtils.getRandomBytes;
-import static org.briarproject.bramble.test.TestUtils.getRandomId;
 import static org.briarproject.bramble.test.TestUtils.getTestDirectory;
 import static org.briarproject.bramble.test.UTest.Result.INCONCLUSIVE;
 import static org.briarproject.bramble.test.UTest.Z_CRITICAL_0_1;
@@ -81,7 +80,6 @@ public abstract class DatabasePerformanceTest extends BrambleTestCase {
 	private static final int METADATA_KEYS_PER_MESSAGE = 5;
 	private static final int METADATA_KEY_LENGTH = 10;
 	private static final int METADATA_VALUE_LENGTH = 100;
-	private static final int OFFERED_MESSAGES_PER_CONTACT = 100;
 
 	/**
 	 * How many benchmark iterations to run in each block.
@@ -192,16 +190,6 @@ public abstract class DatabasePerformanceTest extends BrambleTestCase {
 		});
 	}
 
-	@Test
-	public void testCountOfferedMessages() throws Exception {
-		String name = "countOfferedMessages(T, ContactId)";
-		benchmark(name, db -> {
-			Connection txn = db.startTransaction();
-			db.countOfferedMessages(txn, pickRandom(contacts).getId());
-			db.commitTransaction(txn);
-		});
-	}
-
 	@Test
 	public void testGetContact() throws Exception {
 		String name = "getContact(T, ContactId)";
@@ -454,17 +442,6 @@ public abstract class DatabasePerformanceTest extends BrambleTestCase {
 		});
 	}
 
-	@Test
-	public void testGetMessagesToRequest() throws Exception {
-		String name = "getMessagesToRequest(T, ContactId, int)";
-		benchmark(name, db -> {
-			Connection txn = db.startTransaction();
-			db.getMessagesToRequest(txn, pickRandom(contacts).getId(),
-					MAX_MESSAGE_IDS);
-			db.commitTransaction(txn);
-		});
-	}
-
 	@Test
 	public void testGetMessagesToSend() throws Exception {
 		String name = "getMessagesToSend(T, ContactId, int)";
@@ -507,11 +484,11 @@ public abstract class DatabasePerformanceTest extends BrambleTestCase {
 	}
 
 	@Test
-	public void testGetMessage() throws Exception {
-		String name = "getMessage(T, MessageId)";
+	public void testGetSmallMessage() throws Exception {
+		String name = "getSmallMessage(T, MessageId)";
 		benchmark(name, db -> {
 			Connection txn = db.startTransaction();
-			db.getMessage(txn, pickRandom(messages).getId());
+			db.getSmallMessage(txn, pickRandom(messages).getId());
 			db.commitTransaction(txn);
 		});
 	}
@@ -583,9 +560,6 @@ public abstract class DatabasePerformanceTest extends BrambleTestCase {
 					groupMessages.get(g.getId()).add(m.getId());
 				}
 			}
-			for (int j = 0; j < OFFERED_MESSAGES_PER_CONTACT; j++) {
-				db.addOfferedMessage(txn, c, new MessageId(getRandomId()));
-			}
 		}
 		for (int i = 0; i < LOCAL_GROUPS; i++) {
 			Group g = getGroup(clientIds.get(i % CLIENTS), 123);

bramble-core/src/test/java/org/briarproject/bramble/db/DatabaseTraceTest.java

@@ -3,11 +3,9 @@ package org.briarproject.bramble.db;
 import org.briarproject.bramble.api.crypto.SecretKey;
 import org.briarproject.bramble.api.db.DatabaseConfig;
 import org.briarproject.bramble.api.db.DbException;
-import org.briarproject.bramble.api.sync.MessageFactory;
 import org.briarproject.bramble.api.system.Clock;
 import org.briarproject.bramble.system.SystemClock;
 import org.briarproject.bramble.test.TestDatabaseConfig;
-import org.briarproject.bramble.test.TestMessageFactory;
 import org.briarproject.bramble.util.IoUtils;
 
 import java.io.File;
@@ -26,7 +24,7 @@ public abstract class DatabaseTraceTest extends DatabasePerformanceTest {
 	private SecretKey databaseKey = getSecretKey();
 
 	abstract Database<Connection> createDatabase(DatabaseConfig databaseConfig,
-			MessageFactory messageFactory, Clock clock);
+			Clock clock);
 
 	@Nullable
 	protected abstract File getTraceFile();
@@ -48,8 +46,7 @@ public abstract class DatabaseTraceTest extends DatabasePerformanceTest {
 
 	private Database<Connection> openDatabase() throws DbException {
 		Database<Connection> db = createDatabase(
-				new TestDatabaseConfig(testDir), new TestMessageFactory(),
-				new SystemClock());
+				new TestDatabaseConfig(testDir), new SystemClock());
 		db.open(databaseKey, null);
 		return db;
 	}

bramble-core/src/test/java/org/briarproject/bramble/db/H2DatabasePerformanceTest.java

@@ -16,6 +16,6 @@ public class H2DatabasePerformanceTest extends SingleDatabasePerformanceTest {
 	@Override
 	protected JdbcDatabase createDatabase(DatabaseConfig config,
 			MessageFactory messageFactory, Clock clock) {
-		return new H2Database(config, messageFactory, clock);
+		return new H2Database(config, clock);
 	}
 }

bramble-core/src/test/java/org/briarproject/bramble/db/H2DatabaseTest.java

@@ -9,6 +9,6 @@ public class H2DatabaseTest extends JdbcDatabaseTest {
 	@Override
 	protected JdbcDatabase createDatabase(DatabaseConfig config,
 			MessageFactory messageFactory, Clock clock) {
-		return new H2Database(config, messageFactory, clock);
+		return new H2Database(config, clock);
 	}
 }

bramble-core/src/test/java/org/briarproject/bramble/db/H2DatabaseTraceTest.java

@@ -1,7 +1,6 @@
 package org.briarproject.bramble.db;
 
 import org.briarproject.bramble.api.db.DatabaseConfig;
-import org.briarproject.bramble.api.sync.MessageFactory;
 import org.briarproject.bramble.api.system.Clock;
 import org.junit.Ignore;
 
@@ -15,8 +14,8 @@ public class H2DatabaseTraceTest extends DatabaseTraceTest {
 
 	@Override
 	Database<Connection> createDatabase(DatabaseConfig databaseConfig,
-			MessageFactory messageFactory, Clock clock) {
-		return new H2Database(databaseConfig, messageFactory, clock) {
+			Clock clock) {
+		return new H2Database(databaseConfig, clock) {
 			@Override
 			@Nonnull
 			String getUrl() {

bramble-core/src/test/java/org/briarproject/bramble/db/H2HyperSqlDatabasePerformanceComparisonTest.java

@@ -1,7 +1,6 @@
 package org.briarproject.bramble.db;
 
 import org.briarproject.bramble.api.db.DatabaseConfig;
-import org.briarproject.bramble.api.sync.MessageFactory;
 import org.briarproject.bramble.api.system.Clock;
 import org.junit.Ignore;
 
@@ -13,11 +12,11 @@ public class H2HyperSqlDatabasePerformanceComparisonTest
 
 	@Override
 	Database<Connection> createDatabase(boolean conditionA,
-			DatabaseConfig databaseConfig, MessageFactory messageFactory,
+			DatabaseConfig databaseConfig,
 			Clock clock) {
 		if (conditionA)
-			return new H2Database(databaseConfig, messageFactory, clock);
-		else return new HyperSqlDatabase(databaseConfig, messageFactory, clock);
+			return new H2Database(databaseConfig, clock);
+		else return new HyperSqlDatabase(databaseConfig, clock);
 	}
 
 	@Override

bramble-core/src/test/java/org/briarproject/bramble/db/H2MigrationTest.java

@@ -11,7 +11,7 @@ public class H2MigrationTest extends DatabaseMigrationTest {
 	@Override
 	Database<Connection> createDatabase(
 			List<Migration<Connection>> migrations) {
-		return new H2Database(config, messageFactory, clock) {
+		return new H2Database(config, clock) {
 			@Override
 			List<Migration<Connection>> getMigrations() {
 				return migrations;

bramble-core/src/test/java/org/briarproject/bramble/db/H2SelfDatabasePerformanceComparisonTest.java

@@ -1,7 +1,6 @@
 package org.briarproject.bramble.db;
 
 import org.briarproject.bramble.api.db.DatabaseConfig;
-import org.briarproject.bramble.api.sync.MessageFactory;
 import org.briarproject.bramble.api.system.Clock;
 import org.junit.Ignore;
 
@@ -18,9 +17,9 @@ public class H2SelfDatabasePerformanceComparisonTest
 
 	@Override
 	Database<Connection> createDatabase(boolean conditionA,
-			DatabaseConfig databaseConfig, MessageFactory messageFactory,
+			DatabaseConfig databaseConfig,
 			Clock clock) {
-		return new H2Database(databaseConfig, messageFactory, clock);
+		return new H2Database(databaseConfig, clock);
 	}
 
 	@Override

bramble-core/src/test/java/org/briarproject/bramble/db/H2SleepDatabasePerformanceComparisonTest.java

@@ -3,7 +3,6 @@ package org.briarproject.bramble.db;
 import org.briarproject.bramble.api.db.DatabaseConfig;
 import org.briarproject.bramble.api.db.DbException;
 import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
-import org.briarproject.bramble.api.sync.MessageFactory;
 import org.briarproject.bramble.api.system.Clock;
 import org.junit.Ignore;
 
@@ -20,12 +19,11 @@ public class H2SleepDatabasePerformanceComparisonTest
 
 	@Override
 	Database<Connection> createDatabase(boolean conditionA,
-			DatabaseConfig databaseConfig, MessageFactory messageFactory,
-			Clock clock) {
+			DatabaseConfig databaseConfig, Clock clock) {
 		if (conditionA) {
-			return new H2Database(databaseConfig, messageFactory, clock);
+			return new H2Database(databaseConfig, clock);
 		} else {
-			return new H2Database(databaseConfig, messageFactory, clock) {
+			return new H2Database(databaseConfig, clock) {
 				@Override
 				@NotNullByDefault
 				public void commitTransaction(Connection txn)

bramble-core/src/test/java/org/briarproject/bramble/db/HyperSqlDatabasePerformanceTest.java

@@ -17,6 +17,6 @@ public class HyperSqlDatabasePerformanceTest
 	@Override
 	protected JdbcDatabase createDatabase(DatabaseConfig config,
 			MessageFactory messageFactory, Clock clock) {
-		return new HyperSqlDatabase(config, messageFactory, clock);
+		return new HyperSqlDatabase(config, clock);
 	}
 }

bramble-core/src/test/java/org/briarproject/bramble/db/HyperSqlDatabaseTest.java

@@ -9,6 +9,6 @@ public class HyperSqlDatabaseTest extends JdbcDatabaseTest {
 	@Override
 	protected JdbcDatabase createDatabase(DatabaseConfig config,
 			MessageFactory messageFactory, Clock clock) {
-		return new HyperSqlDatabase(config, messageFactory ,clock);
+		return new HyperSqlDatabase(config, clock);
 	}
 }

bramble-core/src/test/java/org/briarproject/bramble/db/HyperSqlMigrationTest.java

@@ -11,7 +11,7 @@ public class HyperSqlMigrationTest extends DatabaseMigrationTest {
 	@Override
 	Database<Connection> createDatabase(
 			List<Migration<Connection>> migrations) {
-		return new HyperSqlDatabase(config, messageFactory, clock) {
+		return new HyperSqlDatabase(config, clock) {
 			@Override
 			List<Migration<Connection>> getMigrations() {
 				return migrations;

bramble-core/src/test/java/org/briarproject/bramble/db/JdbcDatabaseTest.java

@@ -41,7 +41,6 @@ import org.junit.Test;
 
 import java.io.File;
 import java.sql.Connection;
-import java.util.ArrayList;
 import java.util.Collection;
 import java.util.List;
 import java.util.Map;
@@ -166,7 +165,7 @@ public abstract class JdbcDatabaseTest extends BrambleTestCase {
 		assertTrue(db.containsGroup(txn, groupId));
 		assertTrue(db.containsMessage(txn, messageId));
 		assertArrayEquals(message.getBody(),
-				db.getMessage(txn, messageId).getBody());
+				db.getSmallMessage(txn, messageId).getBody());
 
 		// Delete the records
 		db.removeMessage(txn, messageId);
@@ -1187,35 +1186,6 @@ public abstract class JdbcDatabaseTest extends BrambleTestCase {
 		db.close();
 	}
 
-	@Test
-	public void testOfferedMessages() throws Exception {
-		Database<Connection> db = open(false);
-		Connection txn = db.startTransaction();
-
-		// Add a contact - initially there should be no offered messages
-		db.addIdentity(txn, identity);
-		assertEquals(contactId,
-				db.addContact(txn, author, localAuthor.getId(), null, true));
-		assertEquals(0, db.countOfferedMessages(txn, contactId));
-
-		// Add some offered messages and count them
-		List<MessageId> ids = new ArrayList<>();
-		for (int i = 0; i < 10; i++) {
-			MessageId m = new MessageId(getRandomId());
-			db.addOfferedMessage(txn, contactId, m);
-			ids.add(m);
-		}
-		assertEquals(10, db.countOfferedMessages(txn, contactId));
-
-		// Remove some of the offered messages and count again
-		List<MessageId> half = ids.subList(0, 5);
-		db.removeOfferedMessages(txn, contactId, half);
-		assertEquals(5, db.countOfferedMessages(txn, contactId));
-
-		db.commitTransaction(txn);
-		db.close();
-	}
-
 	@Test
 	public void testGroupMetadata() throws Exception {
 		Database<Connection> db = open(false);
@@ -1929,7 +1899,7 @@ public abstract class JdbcDatabaseTest extends BrambleTestCase {
 		assertEquals(singletonList(messageId), ids);
 
 		// The message should be available
-		Message m = db.getMessage(txn, messageId);
+		Message m = db.getSmallMessage(txn, messageId);
 		assertEquals(messageId, m.getId());
 		assertEquals(groupId, m.getGroupId());
 		assertEquals(message.getTimestamp(), m.getTimestamp());
@@ -1949,7 +1919,7 @@ public abstract class JdbcDatabaseTest extends BrambleTestCase {
 
 		// Requesting the message should throw an exception
 		try {
-			db.getMessage(txn, messageId);
+			db.getSmallMessage(txn, messageId);
 			fail();
 		} catch (MessageDeletedException expected) {
 			// Expected
@@ -2087,7 +2057,7 @@ public abstract class JdbcDatabaseTest extends BrambleTestCase {
 		Connection txn = db.startTransaction();
 		try {
 			// Ask for a nonexistent message - an exception should be thrown
-			db.getMessage(txn, messageId);
+			db.getSmallMessage(txn, messageId);
 			fail();
 		} catch (DbException expected) {
 			// It should be possible to abort the transaction without error

bramble-core/src/test/java/org/briarproject/bramble/properties/TransportPropertyManagerImplTest.java

@@ -402,7 +402,7 @@ public class TransportPropertyManagerImplTest extends BrambleMockTestCase {
 			oneOf(clientHelper).getMessageMetadataAsDictionary(txn,
 					localGroup.getId());
 			will(returnValue(messageMetadata));
-			oneOf(clientHelper).getMessageAsList(txn, fooUpdateId);
+			oneOf(clientHelper).getSmallMessageAsList(txn, fooUpdateId);
 			will(returnValue(fooUpdate));
 			oneOf(clientHelper).parseAndValidateTransportProperties(
 					fooPropertiesDict);
@@ -469,7 +469,7 @@ public class TransportPropertyManagerImplTest extends BrambleMockTestCase {
 			oneOf(clientHelper).getMessageMetadataAsDictionary(txn,
 					contactGroup2.getId());
 			will(returnValue(messageMetadata));
-			oneOf(clientHelper).getMessageAsList(txn, fooUpdateId);
+			oneOf(clientHelper).getSmallMessageAsList(txn, fooUpdateId);
 			will(returnValue(fooUpdate));
 			oneOf(clientHelper).parseAndValidateTransportProperties(
 					fooPropertiesDict);
@@ -524,7 +524,7 @@ public class TransportPropertyManagerImplTest extends BrambleMockTestCase {
 			oneOf(clientHelper).getMessageMetadataAsDictionary(txn,
 					contactGroup.getId());
 			will(returnValue(messageMetadata));
-			oneOf(clientHelper).getMessageAsList(txn, updateId);
+			oneOf(clientHelper).getSmallMessageAsList(txn, updateId);
 			will(returnValue(update));
 			oneOf(clientHelper).parseAndValidateTransportProperties(
 					fooPropertiesDict);
@@ -562,7 +562,7 @@ public class TransportPropertyManagerImplTest extends BrambleMockTestCase {
 			oneOf(clientHelper).getMessageMetadataAsDictionary(txn,
 					localGroup.getId());
 			will(returnValue(messageMetadata));
-			oneOf(clientHelper).getMessageAsList(txn, updateId);
+			oneOf(clientHelper).getSmallMessageAsList(txn, updateId);
 			will(returnValue(update));
 			oneOf(clientHelper).parseAndValidateTransportProperties(
 					fooPropertiesDict);
@@ -693,7 +693,7 @@ public class TransportPropertyManagerImplTest extends BrambleMockTestCase {
 			oneOf(clientHelper).getMessageMetadataAsDictionary(txn,
 					localGroup.getId());
 			will(returnValue(localGroupMessageMetadata));
-			oneOf(clientHelper).getMessageAsList(txn, localGroupUpdateId);
+			oneOf(clientHelper).getSmallMessageAsList(txn, localGroupUpdateId);
 			will(returnValue(oldUpdate));
 			oneOf(clientHelper).parseAndValidateTransportProperties(
 					oldPropertiesDict);
@@ -758,7 +758,7 @@ public class TransportPropertyManagerImplTest extends BrambleMockTestCase {
 			oneOf(clientHelper).getMessageMetadataAsDictionary(txn,
 					localGroup.getId());
 			will(returnValue(localGroupMessageMetadata));
-			oneOf(clientHelper).getMessageAsList(txn, localGroupUpdateId);
+			oneOf(clientHelper).getSmallMessageAsList(txn, localGroupUpdateId);
 			will(returnValue(oldUpdate));
 			oneOf(clientHelper).parseAndValidateTransportProperties(
 					oldPropertiesDict);
@@ -817,12 +817,12 @@ public class TransportPropertyManagerImplTest extends BrambleMockTestCase {
 					localGroup.getId());
 			will(returnValue(messageMetadata));
 			// Retrieve and parse the latest local properties
-			oneOf(clientHelper).getMessageAsList(txn, fooVersion999);
+			oneOf(clientHelper).getSmallMessageAsList(txn, fooVersion999);
 			will(returnValue(fooUpdate));
 			oneOf(clientHelper).parseAndValidateTransportProperties(
 					fooPropertiesDict);
 			will(returnValue(fooProperties));
-			oneOf(clientHelper).getMessageAsList(txn, barVersion3);
+			oneOf(clientHelper).getSmallMessageAsList(txn, barVersion3);
 			will(returnValue(barUpdate));
 			oneOf(clientHelper).parseAndValidateTransportProperties(
 					barPropertiesDict);

bramble-core/src/test/java/org/briarproject/bramble/rendezvous/RendezvousPollerImplTest.java

@@ -27,6 +27,7 @@ import org.briarproject.bramble.api.rendezvous.event.RendezvousConnectionOpenedE
 import org.briarproject.bramble.api.rendezvous.event.RendezvousPollEvent;
 import org.briarproject.bramble.api.system.Clock;
 import org.briarproject.bramble.api.system.TaskScheduler;
+import org.briarproject.bramble.api.system.TaskScheduler.Cancellable;
 import org.briarproject.bramble.test.BrambleMockTestCase;
 import org.briarproject.bramble.test.CaptureArgumentAction;
 import org.briarproject.bramble.test.DbExpectations;
@@ -79,6 +80,7 @@ public class RendezvousPollerImplTest extends BrambleMockTestCase {
 			context.mock(KeyMaterialSource.class);
 	private final RendezvousEndpoint rendezvousEndpoint =
 			context.mock(RendezvousEndpoint.class);
+	private final Cancellable cancellable = context.mock(Cancellable.class);
 
 	private final Executor ioExecutor = new ImmediateExecutor();
 	private final PendingContact pendingContact = getPendingContact();
@@ -107,7 +109,7 @@ public class RendezvousPollerImplTest extends BrambleMockTestCase {
 		long beforeExpiry = pendingContact.getTimestamp()
 				+ RENDEZVOUS_TIMEOUT_MS - 1000;
 		long afterExpiry = beforeExpiry + POLLING_INTERVAL_MS;
-		AtomicReference<Runnable> capturePollTask = new AtomicReference<>();
+		AtomicReference<Runnable> capturePollTask;
 
 		// Start the service
 		context.checking(new DbExpectations() {{
@@ -121,21 +123,17 @@ public class RendezvousPollerImplTest extends BrambleMockTestCase {
 			oneOf(eventBus).broadcast(with(new PredicateMatcher<>(
 					PendingContactStateChangedEvent.class, e ->
 					e.getPendingContactState() == OFFLINE)));
-			// Capture the poll task
-			oneOf(scheduler).scheduleWithFixedDelay(with(any(Runnable.class)),
-					with(any(Executor.class)), with(POLLING_INTERVAL_MS),
-					with(POLLING_INTERVAL_MS), with(MILLISECONDS));
-			will(new CaptureArgumentAction<>(capturePollTask, Runnable.class,
-					0));
 		}});
 
 		expectDeriveRendezvousKey();
+		capturePollTask = expectSchedulePolling();
 
 		rendezvousPoller.startService();
 		context.assertIsSatisfied();
 
-		// Run the poll task - pending contact expires
+		// Run the poll task - pending contact expires, polling is cancelled
 		expectPendingContactExpires(afterExpiry);
+		expectCancelPolling();
 
 		capturePollTask.get().run();
 	}
@@ -157,10 +155,6 @@ public class RendezvousPollerImplTest extends BrambleMockTestCase {
 			oneOf(eventBus).broadcast(with(new PredicateMatcher<>(
 					PendingContactStateChangedEvent.class, e ->
 					e.getPendingContactState() == FAILED)));
-			// Schedule the poll task
-			oneOf(scheduler).scheduleWithFixedDelay(with(any(Runnable.class)),
-					with(any(Executor.class)), with(POLLING_INTERVAL_MS),
-					with(POLLING_INTERVAL_MS), with(MILLISECONDS));
 		}});
 
 		rendezvousPoller.startService();
@@ -183,7 +177,8 @@ public class RendezvousPollerImplTest extends BrambleMockTestCase {
 		rendezvousPoller.eventOccurred(new TransportActiveEvent(transportId));
 		context.assertIsSatisfied();
 
-		// Add the pending contact - endpoint should be created and polled
+		// Add the pending contact - endpoint should be created and polled,
+		// polling should be scheduled
 		expectAddPendingContact(beforeExpiry, WAITING_FOR_CONNECTION);
 		expectDeriveRendezvousKey();
 		expectCreateEndpoint();
@@ -200,12 +195,16 @@ public class RendezvousPollerImplTest extends BrambleMockTestCase {
 					any(ConnectionHandler.class)))));
 		}});
 
+		expectSchedulePolling();
+
 		rendezvousPoller.eventOccurred(
 				new PendingContactAddedEvent(pendingContact));
 		context.assertIsSatisfied();
 
-		// Remove the pending contact - endpoint should be closed
+		// Remove the pending contact - endpoint should be closed,
+		// polling should be cancelled
 		expectCloseEndpoint();
+		expectCancelPolling();
 
 		rendezvousPoller.eventOccurred(
 				new PendingContactRemovedEvent(pendingContact.getId()));
@@ -221,10 +220,10 @@ public class RendezvousPollerImplTest extends BrambleMockTestCase {
 		long beforeExpiry = pendingContact.getTimestamp()
 				+ RENDEZVOUS_TIMEOUT_MS - 1000;
 		long afterExpiry = beforeExpiry + POLLING_INTERVAL_MS;
+		AtomicReference<Runnable> capturePollTask;
 
-		// Start the service, capturing the poll task
-		AtomicReference<Runnable> capturePollTask =
-				expectStartupWithNoPendingContacts();
+		// Start the service
+		expectStartupWithNoPendingContacts();
 
 		rendezvousPoller.startService();
 		context.assertIsSatisfied();
@@ -235,7 +234,8 @@ public class RendezvousPollerImplTest extends BrambleMockTestCase {
 		rendezvousPoller.eventOccurred(new TransportActiveEvent(transportId));
 		context.assertIsSatisfied();
 
-		// Add the pending contact - endpoint should be created and polled
+		// Add the pending contact - endpoint should be created and polled,
+		// polling should be scheduled
 		expectAddPendingContact(beforeExpiry, WAITING_FOR_CONNECTION);
 		expectDeriveRendezvousKey();
 		expectCreateEndpoint();
@@ -252,13 +252,17 @@ public class RendezvousPollerImplTest extends BrambleMockTestCase {
 					any(ConnectionHandler.class)))));
 		}});
 
+		capturePollTask = expectSchedulePolling();
+
 		rendezvousPoller.eventOccurred(
 				new PendingContactAddedEvent(pendingContact));
 		context.assertIsSatisfied();
 
-		// Run the poll task - pending contact expires, endpoint is closed
+		// Run the poll task - pending contact expires, endpoint is closed,
+		// polling is cancelled
 		expectPendingContactExpires(afterExpiry);
 		expectCloseEndpoint();
+		expectCancelPolling();
 
 		capturePollTask.get().run();
 		context.assertIsSatisfied();
@@ -286,6 +290,7 @@ public class RendezvousPollerImplTest extends BrambleMockTestCase {
 		// Add the pending contact - no endpoints should be created yet
 		expectAddPendingContact(beforeExpiry, OFFLINE);
 		expectDeriveRendezvousKey();
+		expectSchedulePolling();
 
 		rendezvousPoller.eventOccurred(
 				new PendingContactAddedEvent(pendingContact));
@@ -307,6 +312,8 @@ public class RendezvousPollerImplTest extends BrambleMockTestCase {
 		context.assertIsSatisfied();
 
 		// Remove the pending contact - endpoint is already closed
+		expectCancelPolling();
+
 		rendezvousPoller.eventOccurred(
 				new PendingContactRemovedEvent(pendingContact.getId()));
 	}
@@ -348,8 +355,9 @@ public class RendezvousPollerImplTest extends BrambleMockTestCase {
 		rendezvousPoller.startService();
 		context.assertIsSatisfied();
 
-		// Run the poll task - pending contact expires
+		// Run the poll task - pending contact expires, polling is cancelled
 		expectPendingContactExpires(afterExpiry);
+		expectCancelPolling();
 
 		capturePollTask.get().run();
 		context.assertIsSatisfied();
@@ -385,8 +393,9 @@ public class RendezvousPollerImplTest extends BrambleMockTestCase {
 				new RendezvousConnectionOpenedEvent(pendingContact.getId()));
 		context.assertIsSatisfied();
 
-		// Run the poll task - pending contact expires
+		// Run the poll task - pending contact expires, polling is cancelled
 		expectPendingContactExpires(afterExpiry);
+		expectCancelPolling();
 
 		capturePollTask.get().run();
 		context.assertIsSatisfied();
@@ -417,8 +426,9 @@ public class RendezvousPollerImplTest extends BrambleMockTestCase {
 				new RendezvousConnectionOpenedEvent(pendingContact.getId()));
 		context.assertIsSatisfied();
 
-		// Run the poll task - pending contact expires
+		// Run the poll task - pending contact expires, polling is cancelled
 		expectPendingContactExpires(afterExpiry);
+		expectCancelPolling();
 
 		capturePollTask.get().run();
 		context.assertIsSatisfied();
@@ -447,6 +457,8 @@ public class RendezvousPollerImplTest extends BrambleMockTestCase {
 		context.assertIsSatisfied();
 
 		// Pending contact is removed - no event should be broadcast
+		expectCancelPolling();
+
 		rendezvousPoller.eventOccurred(
 				new PendingContactRemovedEvent(pendingContact.getId()));
 		context.assertIsSatisfied();
@@ -456,25 +468,35 @@ public class RendezvousPollerImplTest extends BrambleMockTestCase {
 				pendingContact.getId(), false));
 	}
 
-	private AtomicReference<Runnable> expectStartupWithNoPendingContacts()
-			throws Exception {
-		Transaction txn = new Transaction(null, true);
+	private AtomicReference<Runnable> expectSchedulePolling() {
 		AtomicReference<Runnable> capturePollTask = new AtomicReference<>();
 
+		context.checking(new Expectations() {{
+			oneOf(scheduler).scheduleWithFixedDelay(with(any(Runnable.class)),
+					with(any(Executor.class)), with(POLLING_INTERVAL_MS),
+					with(POLLING_INTERVAL_MS), with(MILLISECONDS));
+			will(doAll(new CaptureArgumentAction<>(capturePollTask,
+					Runnable.class, 0), returnValue(cancellable)));
+		}});
+
+		return capturePollTask;
+	}
+
+	private void expectCancelPolling() {
+		context.checking(new Expectations() {{
+			oneOf(cancellable).cancel();
+		}});
+	}
+
+	private void expectStartupWithNoPendingContacts() throws Exception {
+		Transaction txn = new Transaction(null, true);
+
 		context.checking(new DbExpectations() {{
 			// Load the pending contacts
 			oneOf(db).transaction(with(true), withDbRunnable(txn));
 			oneOf(db).getPendingContacts(txn);
 			will(returnValue(emptyList()));
-			// Capture the poll task
-			oneOf(scheduler).scheduleWithFixedDelay(with(any(Runnable.class)),
-					with(any(Executor.class)), with(POLLING_INTERVAL_MS),
-					with(POLLING_INTERVAL_MS), with(MILLISECONDS));
-			will(new CaptureArgumentAction<>(capturePollTask, Runnable.class,
-					0));
 		}});
-
-		return capturePollTask;
 	}
 
 	private void expectAddPendingContact(long now,
@@ -530,7 +552,6 @@ public class RendezvousPollerImplTest extends BrambleMockTestCase {
 	private AtomicReference<Runnable> expectStartupWithPendingContact(long now)
 			throws Exception {
 		Transaction txn = new Transaction(null, true);
-		AtomicReference<Runnable> capturePollTask = new AtomicReference<>();
 
 		context.checking(new DbExpectations() {{
 			// Load the pending contacts
@@ -543,17 +564,10 @@ public class RendezvousPollerImplTest extends BrambleMockTestCase {
 			oneOf(eventBus).broadcast(with(new PredicateMatcher<>(
 					PendingContactStateChangedEvent.class, e ->
 					e.getPendingContactState() == OFFLINE)));
-			// Capture the poll task
-			oneOf(scheduler).scheduleWithFixedDelay(with(any(Runnable.class)),
-					with(any(Executor.class)), with(POLLING_INTERVAL_MS),
-					with(POLLING_INTERVAL_MS), with(MILLISECONDS));
-			will(new CaptureArgumentAction<>(capturePollTask, Runnable.class,
-					0));
 		}});
 
 		expectDeriveRendezvousKey();
-
-		return capturePollTask;
+		return expectSchedulePolling();
 	}
 
 	private void expectPendingContactExpires(long now) {

bramble-core/src/test/java/org/briarproject/bramble/sync/SimplexOutgoingSessionTest.java

@@ -64,7 +64,7 @@ public class SimplexOutgoingSessionTest extends BrambleMockTestCase {
 			oneOf(db).transactionWithNullableResult(with(false),
 					withNullableDbCallable(noMsgTxn));
 			oneOf(db).generateBatch(with(noMsgTxn), with(contactId),
-					with(any(int.class)), with(MAX_LATENCY));
+					with(any(int.class)), with(MAX_LATENCY), with(true));
 			will(returnValue(null));
 			// Send the end of stream marker
 			oneOf(streamWriter).sendEndOfStream();
@@ -101,7 +101,7 @@ public class SimplexOutgoingSessionTest extends BrambleMockTestCase {
 			oneOf(db).transactionWithNullableResult(with(false),
 					withNullableDbCallable(msgTxn));
 			oneOf(db).generateBatch(with(msgTxn), with(contactId),
-					with(any(int.class)), with(MAX_LATENCY));
+					with(any(int.class)), with(MAX_LATENCY), with(true));
 			will(returnValue(singletonList(message)));
 			oneOf(recordWriter).writeMessage(message);
 			// No more acks
@@ -113,7 +113,7 @@ public class SimplexOutgoingSessionTest extends BrambleMockTestCase {
 			oneOf(db).transactionWithNullableResult(with(false),
 					withNullableDbCallable(noMsgTxn));
 			oneOf(db).generateBatch(with(noMsgTxn), with(contactId),
-					with(any(int.class)), with(MAX_LATENCY));
+					with(any(int.class)), with(MAX_LATENCY), with(true));
 			will(returnValue(null));
 			// Send the end of stream marker
 			oneOf(streamWriter).sendEndOfStream();

bramble-core/src/test/java/org/briarproject/bramble/sync/validation/ValidationManagerImplTest.java

@@ -99,7 +99,7 @@ public class ValidationManagerImplTest extends BrambleMockTestCase {
 		context.checking(new DbExpectations() {{
 			// Load the first raw message and group
 			oneOf(db).transactionWithResult(with(true), withDbCallable(txn));
-			oneOf(db).getMessage(txn, messageId);
+			oneOf(db).getSmallMessage(txn, messageId);
 			will(returnValue(message));
 			oneOf(db).getGroup(txn, groupId);
 			will(returnValue(group));
@@ -118,7 +118,7 @@ public class ValidationManagerImplTest extends BrambleMockTestCase {
 			will(returnValue(emptyMap()));
 			// Load the second raw message and group
 			oneOf(db).transactionWithResult(with(true), withDbCallable(txn2));
-			oneOf(db).getMessage(txn2, messageId1);
+			oneOf(db).getSmallMessage(txn2, messageId1);
 			will(returnValue(message1));
 			oneOf(db).getGroup(txn2, groupId);
 			will(returnValue(group));
@@ -159,7 +159,7 @@ public class ValidationManagerImplTest extends BrambleMockTestCase {
 			oneOf(db).getMessageDependencies(txn, messageId);
 			will(returnValue(singletonMap(messageId1, DELIVERED)));
 			// Get the message and its metadata to deliver
-			oneOf(db).getMessage(txn, messageId);
+			oneOf(db).getSmallMessage(txn, messageId);
 			will(returnValue(message));
 			oneOf(db).getGroup(txn, groupId);
 			will(returnValue(group));
@@ -179,7 +179,7 @@ public class ValidationManagerImplTest extends BrambleMockTestCase {
 			oneOf(db).getMessageDependencies(txn1, messageId2);
 			will(returnValue(singletonMap(messageId1, DELIVERED)));
 			// Get the dependent and its metadata to deliver
-			oneOf(db).getMessage(txn1, messageId2);
+			oneOf(db).getSmallMessage(txn1, messageId2);
 			will(returnValue(message2));
 			oneOf(db).getGroup(txn1, groupId);
 			will(returnValue(group));
@@ -276,11 +276,11 @@ public class ValidationManagerImplTest extends BrambleMockTestCase {
 		context.checking(new DbExpectations() {{
 			// Load the first raw message - *gasp* it's gone!
 			oneOf(db).transactionWithResult(with(true), withDbCallable(txn));
-			oneOf(db).getMessage(txn, messageId);
+			oneOf(db).getSmallMessage(txn, messageId);
 			will(throwException(new NoSuchMessageException()));
 			// Load the second raw message and group
 			oneOf(db).transactionWithResult(with(true), withDbCallable(txn1));
-			oneOf(db).getMessage(txn1, messageId1);
+			oneOf(db).getSmallMessage(txn1, messageId1);
 			will(returnValue(message1));
 			oneOf(db).getGroup(txn1, groupId);
 			will(returnValue(group));
@@ -317,14 +317,14 @@ public class ValidationManagerImplTest extends BrambleMockTestCase {
 		context.checking(new DbExpectations() {{
 			// Load the first raw message
 			oneOf(db).transactionWithResult(with(true), withDbCallable(txn));
-			oneOf(db).getMessage(txn, messageId);
+			oneOf(db).getSmallMessage(txn, messageId);
 			will(returnValue(message));
 			// Load the group - *gasp* it's gone!
 			oneOf(db).getGroup(txn, groupId);
 			will(throwException(new NoSuchGroupException()));
 			// Load the second raw message and group
 			oneOf(db).transactionWithResult(with(true), withDbCallable(txn1));
-			oneOf(db).getMessage(txn1, messageId1);
+			oneOf(db).getSmallMessage(txn1, messageId1);
 			will(returnValue(message1));
 			oneOf(db).getGroup(txn1, groupId);
 			will(returnValue(group));
@@ -614,7 +614,7 @@ public class ValidationManagerImplTest extends BrambleMockTestCase {
 			oneOf(db).getMessageDependencies(txn2, messageId1);
 			will(returnValue(singletonMap(messageId, DELIVERED)));
 			// Get message 1 and its metadata
-			oneOf(db).getMessage(txn2, messageId1);
+			oneOf(db).getSmallMessage(txn2, messageId1);
 			will(returnValue(message1));
 			oneOf(db).getGroup(txn2, groupId);
 			will(returnValue(group));
@@ -634,7 +634,7 @@ public class ValidationManagerImplTest extends BrambleMockTestCase {
 			oneOf(db).getMessageDependencies(txn3, messageId2);
 			will(returnValue(singletonMap(messageId, DELIVERED)));
 			// Get message 2 and its metadata
-			oneOf(db).getMessage(txn3, messageId2);
+			oneOf(db).getSmallMessage(txn3, messageId2);
 			will(returnValue(message2));
 			oneOf(db).getGroup(txn3, groupId);
 			will(returnValue(group));
@@ -654,7 +654,7 @@ public class ValidationManagerImplTest extends BrambleMockTestCase {
 			oneOf(db).getMessageDependencies(txn4, messageId3);
 			will(returnValue(twoDependencies));
 			// Get message 3 and its metadata
-			oneOf(db).getMessage(txn4, messageId3);
+			oneOf(db).getSmallMessage(txn4, messageId3);
 			will(returnValue(message3));
 			oneOf(db).getGroup(txn4, groupId);
 			will(returnValue(group));
@@ -677,7 +677,7 @@ public class ValidationManagerImplTest extends BrambleMockTestCase {
 			oneOf(db).getMessageDependencies(txn6, messageId4);
 			will(returnValue(singletonMap(messageId3, DELIVERED)));
 			// Get message 4 and its metadata
-			oneOf(db).getMessage(txn6, messageId4);
+			oneOf(db).getSmallMessage(txn6, messageId4);
 			will(returnValue(message4));
 			oneOf(db).getGroup(txn6, groupId);
 			will(returnValue(group));

bramble-core/src/test/java/org/briarproject/bramble/versioning/ClientVersioningManagerImplTest.java

@@ -184,7 +184,7 @@ public class ClientVersioningManagerImplTest extends BrambleMockTestCase {
 					contactGroup.getId());
 			will(returnValue(singletonMap(localUpdateId, localUpdateMeta)));
 			// Load the latest local update
-			oneOf(clientHelper).getMessageAsList(txn, localUpdateId);
+			oneOf(clientHelper).getSmallMessageAsList(txn, localUpdateId);
 			will(returnValue(localUpdateBody));
 			// Latest local update is up-to-date, no visibilities have changed
 		}});
@@ -206,7 +206,7 @@ public class ClientVersioningManagerImplTest extends BrambleMockTestCase {
 			// Load the old client versions
 			oneOf(db).getMessageIds(txn, localGroup.getId());
 			will(returnValue(singletonList(localVersionsId)));
-			oneOf(clientHelper).getMessageAsList(txn, localVersionsId);
+			oneOf(clientHelper).getSmallMessageAsList(txn, localVersionsId);
 			will(returnValue(localVersionsBody));
 			// Client versions are up-to-date
 		}});
@@ -248,7 +248,7 @@ public class ClientVersioningManagerImplTest extends BrambleMockTestCase {
 			// Load the old client versions
 			oneOf(db).getMessageIds(txn, localGroup.getId());
 			will(returnValue(singletonList(oldLocalVersionsId)));
-			oneOf(clientHelper).getMessageAsList(txn, oldLocalVersionsId);
+			oneOf(clientHelper).getSmallMessageAsList(txn, oldLocalVersionsId);
 			will(returnValue(oldLocalVersionsBody));
 			// Delete the old client versions
 			oneOf(db).removeMessage(txn, oldLocalVersionsId);
@@ -272,7 +272,7 @@ public class ClientVersioningManagerImplTest extends BrambleMockTestCase {
 			will(returnValue(singletonMap(oldLocalUpdateId,
 					oldLocalUpdateMeta)));
 			// Load the latest local update
-			oneOf(clientHelper).getMessageAsList(txn, oldLocalUpdateId);
+			oneOf(clientHelper).getSmallMessageAsList(txn, oldLocalUpdateId);
 			will(returnValue(oldLocalUpdateBody));
 			// Delete the latest local update
 			oneOf(db).deleteMessage(txn, oldLocalUpdateId);
@@ -344,7 +344,7 @@ public class ClientVersioningManagerImplTest extends BrambleMockTestCase {
 			// Load the old client versions
 			oneOf(db).getMessageIds(txn, localGroup.getId());
 			will(returnValue(singletonList(oldLocalVersionsId)));
-			oneOf(clientHelper).getMessageAsList(txn, oldLocalVersionsId);
+			oneOf(clientHelper).getSmallMessageAsList(txn, oldLocalVersionsId);
 			will(returnValue(oldLocalVersionsBody));
 			// Delete the old client versions
 			oneOf(db).removeMessage(txn, oldLocalVersionsId);
@@ -367,10 +367,10 @@ public class ClientVersioningManagerImplTest extends BrambleMockTestCase {
 					contactGroup.getId());
 			will(returnValue(messageMetadata));
 			// Load the latest local update
-			oneOf(clientHelper).getMessageAsList(txn, oldLocalUpdateId);
+			oneOf(clientHelper).getSmallMessageAsList(txn, oldLocalUpdateId);
 			will(returnValue(oldLocalUpdateBody));
 			// Load the latest remote update
-			oneOf(clientHelper).getMessageAsList(txn, oldRemoteUpdateId);
+			oneOf(clientHelper).getSmallMessageAsList(txn, oldRemoteUpdateId);
 			will(returnValue(oldRemoteUpdateBody));
 			// Delete the latest local update
 			oneOf(db).deleteMessage(txn, oldLocalUpdateId);
@@ -451,10 +451,10 @@ public class ClientVersioningManagerImplTest extends BrambleMockTestCase {
 					contactGroup.getId());
 			will(returnValue(messageMetadata));
 			// Load the latest local update
-			oneOf(clientHelper).getMessageAsList(txn, oldLocalUpdateId);
+			oneOf(clientHelper).getSmallMessageAsList(txn, oldLocalUpdateId);
 			will(returnValue(oldLocalUpdateBody));
 			// Load the latest remote update
-			oneOf(clientHelper).getMessageAsList(txn, oldRemoteUpdateId);
+			oneOf(clientHelper).getSmallMessageAsList(txn, oldRemoteUpdateId);
 			will(returnValue(oldRemoteUpdateBody));
 			// Delete the old remote update
 			oneOf(db).deleteMessage(txn, oldRemoteUpdateId);
@@ -490,7 +490,7 @@ public class ClientVersioningManagerImplTest extends BrambleMockTestCase {
 			will(returnValue(singletonMap(oldLocalUpdateId,
 					oldLocalUpdateMeta)));
 			// Load the latest local update
-			oneOf(clientHelper).getMessageAsList(txn, oldLocalUpdateId);
+			oneOf(clientHelper).getSmallMessageAsList(txn, oldLocalUpdateId);
 			will(returnValue(oldLocalUpdateBody));
 			// Get client ID
 			oneOf(clientHelper).getGroupMetadataAsDictionary(txn,
@@ -557,10 +557,10 @@ public class ClientVersioningManagerImplTest extends BrambleMockTestCase {
 					contactGroup.getId());
 			will(returnValue(messageMetadata));
 			// Load the latest local update
-			oneOf(clientHelper).getMessageAsList(txn, oldLocalUpdateId);
+			oneOf(clientHelper).getSmallMessageAsList(txn, oldLocalUpdateId);
 			will(returnValue(oldLocalUpdateBody));
 			// Load the latest remote update
-			oneOf(clientHelper).getMessageAsList(txn, oldRemoteUpdateId);
+			oneOf(clientHelper).getSmallMessageAsList(txn, oldRemoteUpdateId);
 			will(returnValue(oldRemoteUpdateBody));
 			// Delete the old remote update
 			oneOf(db).deleteMessage(txn, oldRemoteUpdateId);
@@ -630,10 +630,10 @@ public class ClientVersioningManagerImplTest extends BrambleMockTestCase {
 					contactGroup.getId());
 			will(returnValue(messageMetadata));
 			// Load the latest local update
-			oneOf(clientHelper).getMessageAsList(txn, oldLocalUpdateId);
+			oneOf(clientHelper).getSmallMessageAsList(txn, oldLocalUpdateId);
 			will(returnValue(oldLocalUpdateBody));
 			// Load the latest remote update
-			oneOf(clientHelper).getMessageAsList(txn, oldRemoteUpdateId);
+			oneOf(clientHelper).getSmallMessageAsList(txn, oldRemoteUpdateId);
 			will(returnValue(oldRemoteUpdateBody));
 			// Delete the old remote update
 			oneOf(db).deleteMessage(txn, oldRemoteUpdateId);
@@ -734,9 +734,9 @@ public class ClientVersioningManagerImplTest extends BrambleMockTestCase {
 			oneOf(clientHelper).getMessageMetadataAsDictionary(txn,
 					contactGroup.getId());
 			will(returnValue(messageMetadata));
-			oneOf(clientHelper).getMessageAsList(txn, localUpdateId);
+			oneOf(clientHelper).getSmallMessageAsList(txn, localUpdateId);
 			will(returnValue(localUpdateBody));
-			oneOf(clientHelper).getMessageAsList(txn, remoteUpdateId);
+			oneOf(clientHelper).getSmallMessageAsList(txn, remoteUpdateId);
 			will(returnValue(remoteUpdateBody));
 		}});
 
@@ -769,9 +769,9 @@ public class ClientVersioningManagerImplTest extends BrambleMockTestCase {
 			oneOf(clientHelper).getMessageMetadataAsDictionary(txn,
 					contactGroup.getId());
 			will(returnValue(messageMetadata));
-			oneOf(clientHelper).getMessageAsList(txn, localUpdateId);
+			oneOf(clientHelper).getSmallMessageAsList(txn, localUpdateId);
 			will(returnValue(localUpdateBody));
-			oneOf(clientHelper).getMessageAsList(txn, remoteUpdateId);
+			oneOf(clientHelper).getSmallMessageAsList(txn, remoteUpdateId);
 			will(returnValue(remoteUpdateBody));
 		}});
 
@@ -804,9 +804,9 @@ public class ClientVersioningManagerImplTest extends BrambleMockTestCase {
 			oneOf(clientHelper).getMessageMetadataAsDictionary(txn,
 					contactGroup.getId());
 			will(returnValue(messageMetadata));
-			oneOf(clientHelper).getMessageAsList(txn, localUpdateId);
+			oneOf(clientHelper).getSmallMessageAsList(txn, localUpdateId);
 			will(returnValue(localUpdateBody));
-			oneOf(clientHelper).getMessageAsList(txn, remoteUpdateId);
+			oneOf(clientHelper).getSmallMessageAsList(txn, remoteUpdateId);
 			will(returnValue(remoteUpdateBody));
 		}});
 
@@ -839,9 +839,9 @@ public class ClientVersioningManagerImplTest extends BrambleMockTestCase {
 			oneOf(clientHelper).getMessageMetadataAsDictionary(txn,
 					contactGroup.getId());
 			will(returnValue(messageMetadata));
-			oneOf(clientHelper).getMessageAsList(txn, localUpdateId);
+			oneOf(clientHelper).getSmallMessageAsList(txn, localUpdateId);
 			will(returnValue(localUpdateBody));
-			oneOf(clientHelper).getMessageAsList(txn, remoteUpdateId);
+			oneOf(clientHelper).getSmallMessageAsList(txn, remoteUpdateId);
 			will(returnValue(remoteUpdateBody));
 		}});
 
@@ -901,7 +901,7 @@ public class ClientVersioningManagerImplTest extends BrambleMockTestCase {
 			oneOf(clientHelper).getMessageMetadataAsDictionary(txn,
 					contactGroup.getId());
 			will(returnValue(messageMetadata));
-			oneOf(clientHelper).getMessageAsList(txn, remoteUpdateId);
+			oneOf(clientHelper).getSmallMessageAsList(txn, remoteUpdateId);
 			will(returnValue(remoteUpdateBody));
 		}});
 
@@ -933,7 +933,7 @@ public class ClientVersioningManagerImplTest extends BrambleMockTestCase {
 			oneOf(clientHelper).getMessageMetadataAsDictionary(txn,
 					contactGroup.getId());
 			will(returnValue(messageMetadata));
-			oneOf(clientHelper).getMessageAsList(txn, remoteUpdateId);
+			oneOf(clientHelper).getSmallMessageAsList(txn, remoteUpdateId);
 			will(returnValue(remoteUpdateBody));
 		}});
 
@@ -965,7 +965,7 @@ public class ClientVersioningManagerImplTest extends BrambleMockTestCase {
 			oneOf(clientHelper).getMessageMetadataAsDictionary(txn,
 					contactGroup.getId());
 			will(returnValue(messageMetadata));
-			oneOf(clientHelper).getMessageAsList(txn, remoteUpdateId);
+			oneOf(clientHelper).getSmallMessageAsList(txn, remoteUpdateId);
 			will(returnValue(remoteUpdateBody));
 		}});
 

bramble-java/src/main/java/org/briarproject/bramble/plugin/bluetooth/JavaBluetoothPlugin.java

@@ -62,22 +62,6 @@ class JavaBluetoothPlugin
 		return localDevice != null && LocalDevice.isPowerOn();
 	}
 
-	@Override
-	void enableAdapter() {
-		// Nothing we can do on this platform
-		LOG.info("Could not enable Bluetooth");
-	}
-
-	@Override
-	void disableAdapterIfEnabledByUs() {
-		// We didn't enable it so we don't need to disable it
-	}
-
-	@Override
-	void setEnabledByUs() {
-		// Irrelevant on this platform
-	}
-
 	@Nullable
 	@Override
 	String getBluetoothAddress() {

briar-android/build.gradle

@@ -16,14 +16,14 @@ def getStdout = { command, defaultValue ->
 }
 
 android {
-	compileSdkVersion 29
-	buildToolsVersion '29.0.2'
+	compileSdkVersion rootProject.ext.compileSdkVersion
+	buildToolsVersion rootProject.ext.buildToolsVersion
 
 	defaultConfig {
-		minSdkVersion 16
-		targetSdkVersion 28
-		versionCode 10209
-		versionName "1.2.9"
+		minSdkVersion rootProject.ext.minSdkVersion
+		targetSdkVersion rootProject.ext.targetSdkVersion
+		versionCode rootProject.ext.versionCode
+		versionName rootProject.ext.versionName
 		applicationId "org.briarproject.briar.android"
 		buildConfigField "String", "GitHash",
 				"\"${getStdout(['git', 'rev-parse', '--short=7', 'HEAD'], 'No commit hash')}\""

briar-android/src/androidTestOfficial/java/org/briarproject/briar/android/attachment/AttachmentRetrieverIntegrationTest.java

@@ -13,8 +13,9 @@ import java.util.Random;
 import androidx.test.ext.junit.runners.AndroidJUnit4;
 
 import static androidx.test.InstrumentationRegistry.getContext;
+import static org.briarproject.briar.android.attachment.AttachmentItem.State.AVAILABLE;
+import static org.briarproject.briar.android.attachment.AttachmentItem.State.ERROR;
 import static org.junit.Assert.assertEquals;
-import static org.junit.Assert.assertFalse;
 import static org.junit.Assert.assertTrue;
 
 @RunWith(AndroidJUnit4.class)
@@ -27,7 +28,7 @@ public class AttachmentRetrieverIntegrationTest {
 
 	private final ImageHelper imageHelper = new ImageHelperImpl();
 	private final AttachmentRetriever retriever =
-			new AttachmentRetrieverImpl(null, dimensions, imageHelper,
+			new AttachmentRetrieverImpl(null, null, dimensions, imageHelper,
 					new ImageSizeCalculator(imageHelper));
 
 	@Test
@@ -35,7 +36,7 @@ public class AttachmentRetrieverIntegrationTest {
 		AttachmentHeader h = new AttachmentHeader(msgId, "image/jpeg");
 		InputStream is = getAssetInputStream("kitten_small.jpg");
 		Attachment a = new Attachment(h, is);
-		AttachmentItem item = retriever.getAttachmentItem(a, true);
+		AttachmentItem item = retriever.createAttachmentItem(a, true);
 		assertEquals(msgId, item.getMessageId());
 		assertEquals(160, item.getWidth());
 		assertEquals(240, item.getHeight());
@@ -43,7 +44,7 @@ public class AttachmentRetrieverIntegrationTest {
 		assertEquals(240, item.getThumbnailHeight());
 		assertEquals("image/jpeg", item.getMimeType());
 		assertJpgOrJpeg(item.getExtension());
-		assertFalse(item.hasError());
+		assertEquals(AVAILABLE, item.getState());
 	}
 
 	@Test
@@ -51,7 +52,7 @@ public class AttachmentRetrieverIntegrationTest {
 		AttachmentHeader h = new AttachmentHeader(msgId, "image/jpeg");
 		InputStream is = getAssetInputStream("kitten_original.jpg");
 		Attachment a = new Attachment(h, is);
-		AttachmentItem item = retriever.getAttachmentItem(a, true);
+		AttachmentItem item = retriever.createAttachmentItem(a, true);
 		assertEquals(msgId, item.getMessageId());
 		assertEquals(1728, item.getWidth());
 		assertEquals(2592, item.getHeight());
@@ -59,7 +60,7 @@ public class AttachmentRetrieverIntegrationTest {
 		assertEquals(dimensions.maxHeight, item.getThumbnailHeight());
 		assertEquals("image/jpeg", item.getMimeType());
 		assertJpgOrJpeg(item.getExtension());
-		assertFalse(item.hasError());
+		assertEquals(AVAILABLE, item.getState());
 	}
 
 	@Test
@@ -67,7 +68,7 @@ public class AttachmentRetrieverIntegrationTest {
 		AttachmentHeader h = new AttachmentHeader(msgId, "image/png");
 		InputStream is = getAssetInputStream("kitten.png");
 		Attachment a = new Attachment(h, is);
-		AttachmentItem item = retriever.getAttachmentItem(a, true);
+		AttachmentItem item = retriever.createAttachmentItem(a, true);
 		assertEquals(msgId, item.getMessageId());
 		assertEquals(737, item.getWidth());
 		assertEquals(510, item.getHeight());
@@ -75,7 +76,7 @@ public class AttachmentRetrieverIntegrationTest {
 		assertEquals(138, item.getThumbnailHeight());
 		assertEquals("image/png", item.getMimeType());
 		assertEquals("png", item.getExtension());
-		assertFalse(item.hasError());
+		assertEquals(AVAILABLE, item.getState());
 	}
 
 	@Test
@@ -83,14 +84,14 @@ public class AttachmentRetrieverIntegrationTest {
 		AttachmentHeader h = new AttachmentHeader(msgId, "image/gif");
 		InputStream is = getAssetInputStream("uber.gif");
 		Attachment a = new Attachment(h, is);
-		AttachmentItem item = retriever.getAttachmentItem(a, true);
+		AttachmentItem item = retriever.createAttachmentItem(a, true);
 		assertEquals(1, item.getWidth());
 		assertEquals(1, item.getHeight());
 		assertEquals(dimensions.minHeight, item.getThumbnailWidth());
 		assertEquals(dimensions.minHeight, item.getThumbnailHeight());
 		assertEquals("image/gif", item.getMimeType());
 		assertEquals("gif", item.getExtension());
-		assertFalse(item.hasError());
+		assertEquals(AVAILABLE, item.getState());
 	}
 
 	@Test
@@ -98,14 +99,14 @@ public class AttachmentRetrieverIntegrationTest {
 		AttachmentHeader h = new AttachmentHeader(msgId, "image/jpeg");
 		InputStream is = getAssetInputStream("lottapixel.jpg");
 		Attachment a = new Attachment(h, is);
-		AttachmentItem item = retriever.getAttachmentItem(a, true);
+		AttachmentItem item = retriever.createAttachmentItem(a, true);
 		assertEquals(64250, item.getWidth());
 		assertEquals(64250, item.getHeight());
 		assertEquals(dimensions.maxWidth, item.getThumbnailWidth());
 		assertEquals(dimensions.maxWidth, item.getThumbnailHeight());
 		assertEquals("image/jpeg", item.getMimeType());
 		assertJpgOrJpeg(item.getExtension());
-		assertFalse(item.hasError());
+		assertEquals(AVAILABLE, item.getState());
 	}
 
 	@Test
@@ -113,14 +114,14 @@ public class AttachmentRetrieverIntegrationTest {
 		AttachmentHeader h = new AttachmentHeader(msgId, "image/png");
 		InputStream is = getAssetInputStream("image_io_crash.png");
 		Attachment a = new Attachment(h, is);
-		AttachmentItem item = retriever.getAttachmentItem(a, true);
+		AttachmentItem item = retriever.createAttachmentItem(a, true);
 		assertEquals(1184, item.getWidth());
 		assertEquals(448, item.getHeight());
 		assertEquals(dimensions.maxWidth, item.getThumbnailWidth());
 		assertEquals(dimensions.minHeight, item.getThumbnailHeight());
 		assertEquals("image/png", item.getMimeType());
 		assertEquals("png", item.getExtension());
-		assertFalse(item.hasError());
+		assertEquals(AVAILABLE, item.getState());
 	}
 
 	@Test
@@ -128,14 +129,14 @@ public class AttachmentRetrieverIntegrationTest {
 		AttachmentHeader h = new AttachmentHeader(msgId, "image/gif");
 		InputStream is = getAssetInputStream("gimp_crash.gif");
 		Attachment a = new Attachment(h, is);
-		AttachmentItem item = retriever.getAttachmentItem(a, true);
+		AttachmentItem item = retriever.createAttachmentItem(a, true);
 		assertEquals(1, item.getWidth());
 		assertEquals(1, item.getHeight());
 		assertEquals(dimensions.minHeight, item.getThumbnailWidth());
 		assertEquals(dimensions.minHeight, item.getThumbnailHeight());
 		assertEquals("image/gif", item.getMimeType());
 		assertEquals("gif", item.getExtension());
-		assertFalse(item.hasError());
+		assertEquals(AVAILABLE, item.getState());
 	}
 
 	@Test
@@ -143,14 +144,14 @@ public class AttachmentRetrieverIntegrationTest {
 		AttachmentHeader h = new AttachmentHeader(msgId, "image/gif");
 		InputStream is = getAssetInputStream("opti_png_afl.gif");
 		Attachment a = new Attachment(h, is);
-		AttachmentItem item = retriever.getAttachmentItem(a, true);
+		AttachmentItem item = retriever.createAttachmentItem(a, true);
 		assertEquals(32, item.getWidth());
 		assertEquals(32, item.getHeight());
 		assertEquals(dimensions.minHeight, item.getThumbnailWidth());
 		assertEquals(dimensions.minHeight, item.getThumbnailHeight());
 		assertEquals("image/gif", item.getMimeType());
 		assertEquals("gif", item.getExtension());
-		assertFalse(item.hasError());
+		assertEquals(AVAILABLE, item.getState());
 	}
 
 	@Test
@@ -158,8 +159,8 @@ public class AttachmentRetrieverIntegrationTest {
 		AttachmentHeader h = new AttachmentHeader(msgId, "image/jpeg");
 		InputStream is = getAssetInputStream("libraw_error.jpg");
 		Attachment a = new Attachment(h, is);
-		AttachmentItem item = retriever.getAttachmentItem(a, true);
-		assertTrue(item.hasError());
+		AttachmentItem item = retriever.createAttachmentItem(a, true);
+		assertEquals(ERROR, item.getState());
 	}
 
 	@Test
@@ -167,14 +168,14 @@ public class AttachmentRetrieverIntegrationTest {
 		AttachmentHeader h = new AttachmentHeader(msgId, "image/gif");
 		InputStream is = getAssetInputStream("animated.gif");
 		Attachment a = new Attachment(h, is);
-		AttachmentItem item = retriever.getAttachmentItem(a, true);
+		AttachmentItem item = retriever.createAttachmentItem(a, true);
 		assertEquals(65535, item.getWidth());
 		assertEquals(65535, item.getHeight());
 		assertEquals(dimensions.maxWidth, item.getThumbnailWidth());
 		assertEquals(dimensions.maxWidth, item.getThumbnailHeight());
 		assertEquals("image/gif", item.getMimeType());
 		assertEquals("gif", item.getExtension());
-		assertFalse(item.hasError());
+		assertEquals(AVAILABLE, item.getState());
 	}
 
 	@Test
@@ -182,14 +183,14 @@ public class AttachmentRetrieverIntegrationTest {
 		AttachmentHeader h = new AttachmentHeader(msgId, "image/gif");
 		InputStream is = getAssetInputStream("animated2.gif");
 		Attachment a = new Attachment(h, is);
-		AttachmentItem item = retriever.getAttachmentItem(a, true);
+		AttachmentItem item = retriever.createAttachmentItem(a, true);
 		assertEquals(10000, item.getWidth());
 		assertEquals(10000, item.getHeight());
 		assertEquals(dimensions.maxWidth, item.getThumbnailWidth());
 		assertEquals(dimensions.maxWidth, item.getThumbnailHeight());
 		assertEquals("image/gif", item.getMimeType());
 		assertEquals("gif", item.getExtension());
-		assertFalse(item.hasError());
+		assertEquals(AVAILABLE, item.getState());
 	}
 
 	@Test
@@ -197,14 +198,14 @@ public class AttachmentRetrieverIntegrationTest {
 		AttachmentHeader h = new AttachmentHeader(msgId, "image/gif");
 		InputStream is = getAssetInputStream("error_large.gif");
 		Attachment a = new Attachment(h, is);
-		AttachmentItem item = retriever.getAttachmentItem(a, true);
+		AttachmentItem item = retriever.createAttachmentItem(a, true);
 		assertEquals(16384, item.getWidth());
 		assertEquals(16384, item.getHeight());
 		assertEquals(dimensions.maxWidth, item.getThumbnailWidth());
 		assertEquals(dimensions.maxWidth, item.getThumbnailHeight());
 		assertEquals("image/gif", item.getMimeType());
 		assertEquals("gif", item.getExtension());
-		assertFalse(item.hasError());
+		assertEquals(AVAILABLE, item.getState());
 	}
 
 	@Test
@@ -212,14 +213,14 @@ public class AttachmentRetrieverIntegrationTest {
 		AttachmentHeader h = new AttachmentHeader(msgId, "image/jpeg");
 		InputStream is = getAssetInputStream("error_high.jpg");
 		Attachment a = new Attachment(h, is);
-		AttachmentItem item = retriever.getAttachmentItem(a, true);
+		AttachmentItem item = retriever.createAttachmentItem(a, true);
 		assertEquals(1, item.getWidth());
 		assertEquals(10000, item.getHeight());
 		assertEquals(dimensions.minWidth, item.getThumbnailWidth());
 		assertEquals(dimensions.maxHeight, item.getThumbnailHeight());
 		assertEquals("image/jpeg", item.getMimeType());
 		assertJpgOrJpeg(item.getExtension());
-		assertFalse(item.hasError());
+		assertEquals(AVAILABLE, item.getState());
 	}
 
 	@Test
@@ -227,14 +228,14 @@ public class AttachmentRetrieverIntegrationTest {
 		AttachmentHeader h = new AttachmentHeader(msgId, "image/jpeg");
 		InputStream is = getAssetInputStream("error_wide.jpg");
 		Attachment a = new Attachment(h, is);
-		AttachmentItem item = retriever.getAttachmentItem(a, true);
+		AttachmentItem item = retriever.createAttachmentItem(a, true);
 		assertEquals(1920, item.getWidth());
 		assertEquals(1, item.getHeight());
 		assertEquals(dimensions.maxWidth, item.getThumbnailWidth());
 		assertEquals(dimensions.minHeight, item.getThumbnailHeight());
 		assertEquals("image/jpeg", item.getMimeType());
 		assertJpgOrJpeg(item.getExtension());
-		assertFalse(item.hasError());
+		assertEquals(AVAILABLE, item.getState());
 	}
 
 	private InputStream getAssetInputStream(String name) throws Exception {

briar-android/src/main/AndroidManifest.xml

@@ -1,46 +1,46 @@
 <?xml version="1.0" encoding="utf-8"?>
-<manifest
-	package="org.briarproject.briar"
-	xmlns:android="http://schemas.android.com/apk/res/android"
-	xmlns:tools="http://schemas.android.com/tools">
+<manifest xmlns:android="http://schemas.android.com/apk/res/android"
+	xmlns:tools="http://schemas.android.com/tools"
+	package="org.briarproject.briar">
 
 	<uses-feature
 		android:name="android.hardware.bluetooth"
-		android:required="false"/>
+		android:required="false" />
 	<uses-feature
 		android:name="android.hardware.camera"
-		android:required="false"/>
+		android:required="false" />
 	<uses-feature
 		android:name="android.hardware.touchscreen"
-		android:required="false"/>
-	<uses-feature android:name="android.software.leanback"
-        android:required="false" />
+		android:required="false" />
+	<uses-feature
+		android:name="android.software.leanback"
+		android:required="false" />
 
-	<uses-permission android:name="android.permission.ACCESS_NETWORK_STATE"/>
-	<uses-permission android:name="android.permission.ACCESS_WIFI_STATE"/>
-	<uses-permission android:name="android.permission.BLUETOOTH"/>
-	<uses-permission android:name="android.permission.BLUETOOTH_ADMIN"/>
-	<uses-permission android:name="android.permission.CAMERA"/>
-	<uses-permission android:name="android.permission.INTERNET"/>
-	<uses-permission android:name="android.permission.RECEIVE_BOOT_COMPLETED"/>
+	<uses-permission android:name="android.permission.ACCESS_NETWORK_STATE" />
+	<uses-permission android:name="android.permission.ACCESS_WIFI_STATE" />
+	<uses-permission android:name="android.permission.BLUETOOTH" />
+	<uses-permission android:name="android.permission.BLUETOOTH_ADMIN" />
+	<uses-permission android:name="android.permission.CAMERA" />
+	<uses-permission android:name="android.permission.INTERNET" />
+	<uses-permission android:name="android.permission.RECEIVE_BOOT_COMPLETED" />
 	<!--suppress DeprecatedClassUsageInspection -->
-	<uses-permission android:name="android.permission.USE_FINGERPRINT"/>
-	<uses-permission android:name="android.permission.VIBRATE"/>
-	<uses-permission android:name="android.permission.WAKE_LOCK"/>
-	<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"/>
+	<uses-permission android:name="android.permission.USE_FINGERPRINT" />
+	<uses-permission android:name="android.permission.VIBRATE" />
+	<uses-permission android:name="android.permission.WAKE_LOCK" />
+	<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />
 
-	<uses-permission-sdk-23 android:name="android.permission.ACCESS_FINE_LOCATION"/>
-	<uses-permission-sdk-23 android:name="android.permission.REQUEST_IGNORE_BATTERY_OPTIMIZATIONS"/>
-	<uses-permission-sdk-23 android:name="android.permission.USE_BIOMETRIC"/>
-	<uses-permission-sdk-23 android:name="android.permission.FOREGROUND_SERVICE"/>
+	<uses-permission-sdk-23 android:name="android.permission.ACCESS_FINE_LOCATION" />
+	<uses-permission-sdk-23 android:name="android.permission.REQUEST_IGNORE_BATTERY_OPTIMIZATIONS" />
+	<uses-permission-sdk-23 android:name="android.permission.USE_BIOMETRIC" />
+	<uses-permission-sdk-23 android:name="android.permission.FOREGROUND_SERVICE" />
 
 	<application
 		android:name="org.briarproject.briar.android.BriarApplicationImpl"
 		android:allowBackup="false"
+		android:banner="@mipmap/tv_banner"
 		android:icon="@mipmap/ic_launcher_round"
 		android:label="@string/app_name"
 		android:logo="@mipmap/ic_launcher_round"
-		android:banner="@mipmap/tv_banner"
 		android:supportsRtl="true"
 		android:theme="@style/BriarTheme"
 		tools:ignore="GoogleAppIndexingWarning,UnusedAttribute"
@@ -50,8 +50,8 @@
 			android:name="org.briarproject.briar.android.login.SignInReminderReceiver"
 			android:exported="false">
 			<intent-filter>
-				<action android:name="android.intent.action.BOOT_COMPLETED"/>
-				<action android:name="android.intent.action.MY_PACKAGE_REPLACED"/>
+				<action android:name="android.intent.action.BOOT_COMPLETED" />
+				<action android:name="android.intent.action.MY_PACKAGE_REPLACED" />
 			</intent-filter>
 		</receiver>
 
@@ -59,14 +59,13 @@
 			android:name="org.briarproject.briar.android.BriarService"
 			android:exported="false">
 			<intent-filter>
-				<action android:name="org.briarproject.briar.android.BriarService"/>
+				<action android:name="org.briarproject.briar.android.BriarService" />
 			</intent-filter>
 		</service>
 
 		<service
 			android:name="org.briarproject.briar.android.NotificationCleanupService"
-			android:exported="false">
-		</service>
+			android:exported="false"></service>
 
 		<activity
 			android:name="org.briarproject.briar.android.reporting.DevReportActivity"
@@ -76,32 +75,29 @@
 			android:label="@string/crash_report_title"
 			android:launchMode="singleInstance"
 			android:theme="@style/BriarTheme.NoActionBar"
-			android:windowSoftInputMode="adjustResize|stateHidden">
-		</activity>
+			android:windowSoftInputMode="adjustResize|stateHidden"></activity>
 
 		<activity
 			android:name="org.briarproject.briar.android.splash.ExpiredActivity"
-			android:label="@string/app_name">
-		</activity>
+			android:label="@string/app_name"></activity>
 
 		<activity
 			android:name="org.briarproject.briar.android.login.StartupActivity"
-			android:label="@string/app_name">
-		</activity>
+			android:label="@string/app_name"></activity>
 
 		<activity
 			android:name="org.briarproject.briar.android.account.SetupActivity"
 			android:label="@string/setup_title"
-			android:windowSoftInputMode="adjustResize|stateAlwaysVisible">
-		</activity>
+			android:windowSoftInputMode="adjustResize|stateAlwaysVisible"></activity>
 
 		<activity
 			android:name="org.briarproject.briar.android.splash.SplashScreenActivity"
 			android:label="@string/app_name"
 			android:theme="@style/BriarTheme.NoActionBar">
 			<intent-filter>
-				<action android:name="android.intent.action.MAIN"/>
-				<category android:name="android.intent.category.LAUNCHER"/>
+				<action android:name="android.intent.action.MAIN" />
+
+				<category android:name="android.intent.category.LAUNCHER" />
 				<category android:name="android.intent.category.LEANBACK_LAUNCHER" />
 			</intent-filter>
 		</activity>
@@ -111,17 +107,17 @@
 			android:launchMode="singleTask"
 			android:theme="@style/BriarTheme.NoActionBar">
 			<intent-filter android:label="@string/add_contact_remotely_title_case">
-				<action android:name="android.intent.action.VIEW"/>
+				<action android:name="android.intent.action.VIEW" />
 
-				<category android:name="android.intent.category.DEFAULT"/>
-				<category android:name="android.intent.category.BROWSABLE"/>
+				<category android:name="android.intent.category.DEFAULT" />
+				<category android:name="android.intent.category.BROWSABLE" />
 
-				<data android:scheme="briar"/>
+				<data android:scheme="briar" />
 			</intent-filter>
 			<intent-filter android:label="@string/add_contact_remotely_title_case">
-				<action android:name="android.intent.action.SEND"/>
-				<category android:name="android.intent.category.DEFAULT"/>
-				<data android:mimeType="text/plain"/>
+				<action android:name="android.intent.action.SEND" />
+				<category android:name="android.intent.category.DEFAULT" />
+				<data android:mimeType="text/plain" />
 			</intent-filter>
 		</activity>
 
@@ -133,7 +129,7 @@
 			android:windowSoftInputMode="adjustResize|stateUnchanged">
 			<meta-data
 				android:name="android.support.PARENT_ACTIVITY"
-				android:value="org.briarproject.briar.android.navdrawer.NavDrawerActivity"/>
+				android:value="org.briarproject.briar.android.navdrawer.NavDrawerActivity" />
 		</activity>
 
 		<activity
@@ -142,7 +138,7 @@
 			android:theme="@style/BriarTheme.ActionBarOverlay">
 			<meta-data
 				android:name="android.support.PARENT_ACTIVITY"
-				android:value="org.briarproject.briar.android.conversation.ConversationActivity"/>
+				android:value="org.briarproject.briar.android.conversation.ConversationActivity" />
 		</activity>
 
 		<activity
@@ -152,7 +148,7 @@
 			android:windowSoftInputMode="adjustResize|stateAlwaysVisible">
 			<meta-data
 				android:name="android.support.PARENT_ACTIVITY"
-				android:value="org.briarproject.briar.android.navdrawer.NavDrawerActivity"/>
+				android:value="org.briarproject.briar.android.navdrawer.NavDrawerActivity" />
 		</activity>
 
 		<activity
@@ -163,7 +159,7 @@
 			android:windowSoftInputMode="adjustResize|stateHidden">
 			<meta-data
 				android:name="android.support.PARENT_ACTIVITY"
-				android:value="org.briarproject.briar.android.navdrawer.NavDrawerActivity"/>
+				android:value="org.briarproject.briar.android.navdrawer.NavDrawerActivity" />
 		</activity>
 
 		<activity
@@ -172,7 +168,7 @@
 			android:parentActivityName="org.briarproject.briar.android.navdrawer.NavDrawerActivity">
 			<meta-data
 				android:name="android.support.PARENT_ACTIVITY"
-				android:value="org.briarproject.briar.android.navdrawer.NavDrawerActivity"/>
+				android:value="org.briarproject.briar.android.navdrawer.NavDrawerActivity" />
 		</activity>
 
 		<activity
@@ -181,7 +177,7 @@
 			android:parentActivityName="org.briarproject.briar.android.privategroup.conversation.GroupActivity">
 			<meta-data
 				android:name="android.support.PARENT_ACTIVITY"
-				android:value="org.briarproject.briar.android.privategroup.conversation.GroupActivity"/>
+				android:value="org.briarproject.briar.android.privategroup.conversation.GroupActivity" />
 		</activity>
 
 		<activity
@@ -190,7 +186,7 @@
 			android:parentActivityName="org.briarproject.briar.android.privategroup.conversation.GroupActivity">
 			<meta-data
 				android:name="android.support.PARENT_ACTIVITY"
-				android:value="org.briarproject.briar.android.privategroup.conversation.GroupActivity"/>
+				android:value="org.briarproject.briar.android.privategroup.conversation.GroupActivity" />
 		</activity>
 
 		<activity
@@ -200,7 +196,7 @@
 			android:windowSoftInputMode="adjustResize|stateHidden">
 			<meta-data
 				android:name="android.support.PARENT_ACTIVITY"
-				android:value="org.briarproject.briar.android.privategroup.conversation.GroupActivity"/>
+				android:value="org.briarproject.briar.android.privategroup.conversation.GroupActivity" />
 		</activity>
 
 		<activity
@@ -209,7 +205,7 @@
 			android:parentActivityName="org.briarproject.briar.android.navdrawer.NavDrawerActivity">
 			<meta-data
 				android:name="android.support.PARENT_ACTIVITY"
-				android:value="org.briarproject.briar.android.navdrawer.NavDrawerActivity"/>
+				android:value="org.briarproject.briar.android.navdrawer.NavDrawerActivity" />
 		</activity>
 
 		<activity
@@ -218,7 +214,7 @@
 			android:parentActivityName="org.briarproject.briar.android.conversation.ConversationActivity">
 			<meta-data
 				android:name="android.support.PARENT_ACTIVITY"
-				android:value="org.briarproject.briar.android.conversation.ConversationActivity"/>
+				android:value="org.briarproject.briar.android.conversation.ConversationActivity" />
 		</activity>
 
 		<activity
@@ -228,7 +224,7 @@
 			android:windowSoftInputMode="adjustResize|stateAlwaysVisible">
 			<meta-data
 				android:name="android.support.PARENT_ACTIVITY"
-				android:value="org.briarproject.briar.android.navdrawer.NavDrawerActivity"/>
+				android:value="org.briarproject.briar.android.navdrawer.NavDrawerActivity" />
 		</activity>
 
 		<activity
@@ -239,7 +235,7 @@
 			android:windowSoftInputMode="adjustResize|stateHidden">
 			<meta-data
 				android:name="android.support.PARENT_ACTIVITY"
-				android:value="org.briarproject.briar.android.navdrawer.NavDrawerActivity"/>
+				android:value="org.briarproject.briar.android.navdrawer.NavDrawerActivity" />
 		</activity>
 
 		<activity
@@ -249,7 +245,7 @@
 			android:windowSoftInputMode="adjustResize|stateHidden">
 			<meta-data
 				android:name="android.support.PARENT_ACTIVITY"
-				android:value="org.briarproject.briar.android.forum.ForumActivity"/>
+				android:value="org.briarproject.briar.android.forum.ForumActivity" />
 		</activity>
 
 		<activity
@@ -259,7 +255,7 @@
 			android:windowSoftInputMode="adjustResize|stateHidden">
 			<meta-data
 				android:name="android.support.PARENT_ACTIVITY"
-				android:value="org.briarproject.briar.android.blog.BlogActivity"/>
+				android:value="org.briarproject.briar.android.blog.BlogActivity" />
 		</activity>
 
 		<activity
@@ -268,8 +264,7 @@
 			android:parentActivityName="org.briarproject.briar.android.forum.ForumActivity">
 			<meta-data
 				android:name="android.support.PARENT_ACTIVITY"
-				android:value="org.briarproject.briar.android.forum.ForumActivity"
-				/>
+				android:value="org.briarproject.briar.android.forum.ForumActivity" />
 		</activity>
 
 		<activity
@@ -278,7 +273,7 @@
 			android:parentActivityName="org.briarproject.briar.android.blog.BlogActivity">
 			<meta-data
 				android:name="android.support.PARENT_ACTIVITY"
-				android:value="org.briarproject.briar.android.blog.BlogActivity"/>
+				android:value="org.briarproject.briar.android.blog.BlogActivity" />
 		</activity>
 
 		<activity
@@ -287,7 +282,7 @@
 			android:theme="@style/BriarTheme.NoActionBar">
 			<meta-data
 				android:name="android.support.PARENT_ACTIVITY"
-				android:value="org.briarproject.briar.android.navdrawer.NavDrawerActivity"/>
+				android:value="org.briarproject.briar.android.navdrawer.NavDrawerActivity" />
 		</activity>
 
 		<activity
@@ -297,7 +292,7 @@
 			android:windowSoftInputMode="adjustResize|stateAlwaysVisible">
 			<meta-data
 				android:name="android.support.PARENT_ACTIVITY"
-				android:value="org.briarproject.briar.android.blog.BlogActivity"/>
+				android:value="org.briarproject.briar.android.blog.BlogActivity" />
 		</activity>
 
 		<activity
@@ -307,7 +302,7 @@
 			android:windowSoftInputMode="adjustResize|stateHidden">
 			<meta-data
 				android:name="android.support.PARENT_ACTIVITY"
-				android:value="org.briarproject.briar.android.blog.BlogActivity"/>
+				android:value="org.briarproject.briar.android.blog.BlogActivity" />
 		</activity>
 
 		<activity
@@ -317,7 +312,7 @@
 			android:windowSoftInputMode="adjustResize|stateAlwaysVisible">
 			<meta-data
 				android:name="android.support.PARENT_ACTIVITY"
-				android:value="org.briarproject.briar.android.navdrawer.NavDrawerActivity"/>
+				android:value="org.briarproject.briar.android.navdrawer.NavDrawerActivity" />
 		</activity>
 
 		<activity
@@ -326,7 +321,7 @@
 			android:parentActivityName="org.briarproject.briar.android.navdrawer.NavDrawerActivity">
 			<meta-data
 				android:name="android.support.PARENT_ACTIVITY"
-				android:value="org.briarproject.briar.android.navdrawer.NavDrawerActivity"/>
+				android:value="org.briarproject.briar.android.navdrawer.NavDrawerActivity" />
 		</activity>
 
 		<activity
@@ -336,7 +331,7 @@
 			android:theme="@style/BriarTheme.NoActionBar">
 			<meta-data
 				android:name="android.support.PARENT_ACTIVITY"
-				android:value="org.briarproject.briar.android.navdrawer.NavDrawerActivity"/>
+				android:value="org.briarproject.briar.android.navdrawer.NavDrawerActivity" />
 		</activity>
 
 		<activity
@@ -346,13 +341,12 @@
 			android:windowSoftInputMode="adjustResize|stateHidden">
 			<meta-data
 				android:name="android.support.PARENT_ACTIVITY"
-				android:value="org.briarproject.briar.android.conversation.ConversationActivity"/>
+				android:value="org.briarproject.briar.android.conversation.ConversationActivity" />
 		</activity>
 
 		<activity
 			android:name="org.briarproject.briar.android.StartupFailureActivity"
-			android:label="@string/startup_failed_activity_title">
-		</activity>
+			android:label="@string/startup_failed_activity_title"></activity>
 
 		<activity
 			android:name="org.briarproject.briar.android.settings.SettingsActivity"
@@ -361,13 +355,22 @@
 			android:permission="android.permission.READ_NETWORK_USAGE_HISTORY">
 			<meta-data
 				android:name="android.support.PARENT_ACTIVITY"
-				android:value="org.briarproject.briar.android.navdrawer.NavDrawerActivity"/>
+				android:value="org.briarproject.briar.android.navdrawer.NavDrawerActivity" />
 			<intent-filter>
-				<action android:name="android.intent.action.MANAGE_NETWORK_USAGE"/>
-				<category android:name="android.intent.category.DEFAULT"/>
+				<action android:name="android.intent.action.MANAGE_NETWORK_USAGE" />
+				<category android:name="android.intent.category.DEFAULT" />
 			</intent-filter>
 		</activity>
 
+		<activity
+			android:name="org.briarproject.briar.android.navdrawer.TransportsActivity"
+			android:label="@string/network_settings_title"
+			android:parentActivityName="org.briarproject.briar.android.navdrawer.NavDrawerActivity">
+			<meta-data
+				android:name="android.support.PARENT_ACTIVITY"
+				android:value="org.briarproject.briar.android.navdrawer.NavDrawerActivity" />
+		</activity>
+
 		<activity
 			android:name="org.briarproject.briar.android.login.ChangePasswordActivity"
 			android:label="@string/change_password"
@@ -375,7 +378,7 @@
 			android:windowSoftInputMode="adjustResize|stateAlwaysVisible">
 			<meta-data
 				android:name="android.support.PARENT_ACTIVITY"
-				android:value="org.briarproject.briar.android.settings.SettingsActivity"/>
+				android:value="org.briarproject.briar.android.settings.SettingsActivity" />
 		</activity>
 
 		<activity
@@ -384,7 +387,7 @@
 			android:parentActivityName="org.briarproject.briar.android.settings.SettingsActivity">
 			<meta-data
 				android:name="android.support.PARENT_ACTIVITY"
-				android:value="org.briarproject.briar.android.settings.SettingsActivity"/>
+				android:value="org.briarproject.briar.android.settings.SettingsActivity" />
 		</activity>
 
 		<activity
@@ -393,7 +396,7 @@
 			android:parentActivityName="org.briarproject.briar.android.settings.SettingsActivity">
 			<meta-data
 				android:name="android.support.PARENT_ACTIVITY"
-				android:value="org.briarproject.briar.android.settings.SettingsActivity"/>
+				android:value="org.briarproject.briar.android.settings.SettingsActivity" />
 		</activity>
 
 		<activity
@@ -402,37 +405,35 @@
 			android:theme="@style/TranslucentTheme">
 			<!-- this can never have launchMode singleTask or singleInstance! -->
 			<intent-filter>
-				<action android:name="info.guardianproject.panic.action.TRIGGER"/>
-				<category android:name="android.intent.category.DEFAULT"/>
+				<action android:name="info.guardianproject.panic.action.TRIGGER" />
+				<category android:name="android.intent.category.DEFAULT" />
 			</intent-filter>
 		</activity>
 
 		<activity
 			android:name="org.briarproject.briar.android.logout.ExitActivity"
-			android:theme="@android:style/Theme.NoDisplay">
-		</activity>
+			android:theme="@android:style/Theme.NoDisplay"></activity>
 
 		<activity
 			android:name=".android.logout.HideUiActivity"
-			android:theme="@android:style/Theme.NoDisplay">
-		</activity>
+			android:theme="@android:style/Theme.NoDisplay"></activity>
 
 		<activity
 			android:name=".android.account.UnlockActivity"
 			android:label="@string/lock_unlock"
 			android:launchMode="singleTask"
-			android:theme="@style/BriarTheme.NoActionBar"/>
+			android:theme="@style/BriarTheme.NoActionBar" />
 
 		<activity
 			android:name=".android.contact.add.remote.AddContactActivity"
 			android:label="@string/add_contact_remotely_title_case"
 			android:theme="@style/BriarTheme"
-			android:windowSoftInputMode="adjustResize|stateHidden"/>
+			android:windowSoftInputMode="adjustResize|stateHidden" />
 
 		<activity
 			android:name=".android.contact.add.remote.PendingContactListActivity"
 			android:label="@string/pending_contact_requests"
-			android:theme="@style/BriarTheme"/>
+			android:theme="@style/BriarTheme" />
 
 	</application>
 </manifest>

briar-android/src/main/java/org/briarproject/briar/android/account/UnlockActivity.java

@@ -117,14 +117,24 @@ public class UnlockActivity extends BaseActivity {
 
 	@RequiresApi(api = 28)
 	private void requestFingerprintUnlock() {
-		BiometricPrompt biometricPrompt = new Builder(this)
-				.setTitle(getString(R.string.lock_unlock))
-				.setDescription(
-						getString(R.string.lock_unlock_fingerprint_description))
-				.setNegativeButton(getString(R.string.lock_unlock_password),
-						getMainExecutor(),
-						(dialog, which) -> requestKeyguardUnlock())
-				.build();
+		BiometricPrompt biometricPrompt;
+		if (SDK_INT >= 29) {
+			biometricPrompt = new Builder(this)
+					.setTitle(getString(R.string.lock_unlock))
+					.setDescription(getString(
+							R.string.lock_unlock_fingerprint_description))
+					.setDeviceCredentialAllowed(true)
+					.build();
+		} else {
+			biometricPrompt = new Builder(this)
+					.setTitle(getString(R.string.lock_unlock))
+					.setDescription(getString(
+							R.string.lock_unlock_fingerprint_description))
+					.setNegativeButton(getString(R.string.lock_unlock_password),
+							getMainExecutor(),
+							(dialog, which) -> requestKeyguardUnlock())
+					.build();
+		}
 		CancellationSignal signal = new CancellationSignal();
 		AuthenticationCallback callback = new AuthenticationCallback() {
 			@Override

briar-android/src/main/java/org/briarproject/briar/android/activity/ActivityComponent.java

@@ -47,6 +47,7 @@ import org.briarproject.briar.android.login.OpenDatabaseFragment;
 import org.briarproject.briar.android.login.PasswordFragment;
 import org.briarproject.briar.android.login.StartupActivity;
 import org.briarproject.briar.android.navdrawer.NavDrawerActivity;
+import org.briarproject.briar.android.navdrawer.TransportsActivity;
 import org.briarproject.briar.android.panic.PanicPreferencesActivity;
 import org.briarproject.briar.android.panic.PanicResponderActivity;
 import org.briarproject.briar.android.privategroup.conversation.GroupActivity;
@@ -163,6 +164,8 @@ public interface ActivityComponent {
 
 	void inject(SettingsActivity activity);
 
+	void inject(TransportsActivity activity);
+
 	void inject(TestDataActivity activity);
 
 	void inject(ChangePasswordActivity activity);

briar-android/src/main/java/org/briarproject/briar/android/attachment/AttachmentCreatorImpl.java

@@ -34,6 +34,7 @@ import androidx.lifecycle.MutableLiveData;
 import static java.util.logging.Level.WARNING;
 import static java.util.logging.Logger.getLogger;
 import static org.briarproject.bramble.util.LogUtils.logException;
+import static org.briarproject.briar.android.attachment.AttachmentItem.State.ERROR;
 import static org.briarproject.briar.android.util.UiUtils.observeForeverOnce;
 import static org.briarproject.briar.api.messaging.MessagingConstants.MAX_IMAGE_SIZE;
 
@@ -75,8 +76,12 @@ class AttachmentCreatorImpl implements AttachmentCreator {
 	@UiThread
 	public LiveData<AttachmentResult> storeAttachments(
 			LiveData<GroupId> groupId, Collection<Uri> newUris) {
-		if (task != null || result != null || !uris.isEmpty())
+		if (task != null || result != null || !uris.isEmpty()) {
+			if (task != null) LOG.warning("Task already exists!");
+			if (result != null) LOG.warning("Result already exists!");
+			if (!uris.isEmpty()) LOG.warning("Uris available: " + uris);
 			throw new IllegalStateException();
+		}
 		MutableLiveData<AttachmentResult> result = new MutableLiveData<>();
 		this.result = result;
 		uris.addAll(newUris);
@@ -95,8 +100,12 @@ class AttachmentCreatorImpl implements AttachmentCreator {
 	@UiThread
 	public LiveData<AttachmentResult> getLiveAttachments() {
 		MutableLiveData<AttachmentResult> result = this.result;
-		if (task == null || result == null || uris.isEmpty())
+		if (task == null || result == null || uris.isEmpty()) {
+			if (task == null) LOG.warning("No Task!");
+			if (result == null) LOG.warning("No Result!");
+			if (uris.isEmpty()) LOG.warning("Uris empty!");
 			throw new IllegalStateException();
+		}
 		// A task is already running. It will update the result LiveData.
 		// So nothing more to do here.
 		return result;
@@ -109,8 +118,8 @@ class AttachmentCreatorImpl implements AttachmentCreator {
 		// get and cache AttachmentItem for ImagePreview
 		try {
 			Attachment a = retriever.getMessageAttachment(h);
-			AttachmentItem item = retriever.getAttachmentItem(a, needsSize);
-			if (item.hasError()) throw new IOException();
+			AttachmentItem item = retriever.createAttachmentItem(a, needsSize);
+			if (item.getState() == ERROR) throw new IOException();
 			AttachmentItemResult itemResult =
 					new AttachmentItemResult(uri, item);
 			itemResults.add(itemResult);
@@ -167,21 +176,13 @@ class AttachmentCreatorImpl implements AttachmentCreator {
 	@Override
 	@UiThread
 	public void onAttachmentsSent(MessageId id) {
-		List<AttachmentItem> items = new ArrayList<>(itemResults.size());
-		for (AttachmentItemResult itemResult : itemResults) {
-			// check if we are trying to send attachment items with errors
-			if (itemResult.getItem() == null) throw new IllegalStateException();
-			items.add(itemResult.getItem());
-		}
-		retriever.cachePut(id, items);
 		resetState();
 	}
 
 	@Override
 	@UiThread
 	public void cancel() {
-		if (task == null) throw new AssertionError();
-		task.cancel();
+		if (task != null) task.cancel();
 		deleteUnsentAttachments();
 		resetState();
 	}

briar-android/src/main/java/org/briarproject/briar/android/attachment/AttachmentItem.java

@@ -7,24 +7,33 @@ import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
 import org.briarproject.bramble.api.sync.MessageId;
 import org.briarproject.briar.api.messaging.AttachmentHeader;
 
-import java.util.concurrent.atomic.AtomicLong;
-
 import javax.annotation.concurrent.Immutable;
 
 import androidx.annotation.Nullable;
 
+import static java.lang.System.arraycopy;
 import static java.util.Objects.requireNonNull;
+import static org.briarproject.bramble.util.StringUtils.toHexString;
+import static org.briarproject.briar.android.attachment.AttachmentItem.State.LOADING;
+import static org.briarproject.briar.android.attachment.AttachmentItem.State.MISSING;
 
 @Immutable
 @NotNullByDefault
 public class AttachmentItem implements Parcelable {
 
+	public enum State {
+		LOADING, MISSING, AVAILABLE, ERROR;
+
+		public boolean isFinal() {
+			return this == AVAILABLE || this == ERROR;
+		}
+	}
+
 	private final AttachmentHeader header;
 	private final int width, height;
 	private final String extension;
 	private final int thumbnailWidth, thumbnailHeight;
-	private final boolean hasError;
-	private final long instanceId;
+	private final State state;
 
 	public static final Creator<AttachmentItem> CREATOR =
 			new Creator<AttachmentItem>() {
@@ -39,19 +48,33 @@ public class AttachmentItem implements Parcelable {
 				}
 			};
 
-	private static final AtomicLong NEXT_INSTANCE_ID = new AtomicLong(0);
-
 	AttachmentItem(AttachmentHeader header, int width, int height,
 			String extension, int thumbnailWidth, int thumbnailHeight,
-			boolean hasError) {
+			State state) {
 		this.header = header;
 		this.width = width;
 		this.height = height;
 		this.extension = extension;
 		this.thumbnailWidth = thumbnailWidth;
 		this.thumbnailHeight = thumbnailHeight;
-		this.hasError = hasError;
-		instanceId = NEXT_INSTANCE_ID.getAndIncrement();
+		this.state = state;
+	}
+
+	/**
+	 * Use only for {@link State MISSING} or {@link State LOADING} items.
+	 */
+	AttachmentItem(AttachmentHeader header, int width, int height,
+			State state) {
+		this(header, width, height, "", width, height, state);
+		if (state != MISSING && state != LOADING)
+			throw new IllegalArgumentException();
+	}
+
+	/**
+	 * Use when the item does not need a size.
+	 */
+	AttachmentItem(AttachmentHeader header, String extension, State state) {
+		this(header, 0, 0, extension, 0, 0, state);
 	}
 
 	protected AttachmentItem(Parcel in) {
@@ -64,8 +87,7 @@ public class AttachmentItem implements Parcelable {
 		extension = requireNonNull(in.readString());
 		thumbnailWidth = in.readInt();
 		thumbnailHeight = in.readInt();
-		hasError = in.readByte() != 0;
-		instanceId = in.readLong();
+		state = State.valueOf(requireNonNull(in.readString()));
 		header = new AttachmentHeader(messageId, mimeType);
 	}
 
@@ -101,12 +123,16 @@ public class AttachmentItem implements Parcelable {
 		return thumbnailHeight;
 	}
 
-	public boolean hasError() {
-		return hasError;
+	public State getState() {
+		return state;
 	}
 
-	public String getTransitionName() {
-		return String.valueOf(instanceId);
+	public String getTransitionName(MessageId conversationItemId) {
+		int len = MessageId.LENGTH;
+		byte[] instanceId = new byte[len * 2];
+		arraycopy(header.getMessageId().getBytes(), 0, instanceId, 0, len);
+		arraycopy(conversationItemId.getBytes(), 0, instanceId, len, len);
+		return toHexString(instanceId);
 	}
 
 	@Override
@@ -123,14 +149,23 @@ public class AttachmentItem implements Parcelable {
 		dest.writeString(extension);
 		dest.writeInt(thumbnailWidth);
 		dest.writeInt(thumbnailHeight);
-		dest.writeByte((byte) (hasError ? 1 : 0));
-		dest.writeLong(instanceId);
+		dest.writeString(state.name());
 	}
 
+	/**
+	 * This is used to identity if two items are the same,
+	 * irrespective of their state or size.
+	 */
 	@Override
 	public boolean equals(@Nullable Object o) {
 		return o instanceof AttachmentItem &&
-				instanceId == ((AttachmentItem) o).instanceId;
+				header.getMessageId().equals(
+						((AttachmentItem) o).header.getMessageId()
+				);
 	}
 
+	@Override
+	public int hashCode() {
+		return header.getMessageId().hashCode();
+	}
 }

briar-android/src/main/java/org/briarproject/briar/android/attachment/AttachmentRetriever.java

@@ -1,29 +1,63 @@
 package org.briarproject.briar.android.attachment;
 
+import org.briarproject.bramble.api.db.DatabaseExecutor;
 import org.briarproject.bramble.api.db.DbException;
 import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
 import org.briarproject.bramble.api.sync.MessageId;
 import org.briarproject.briar.api.messaging.Attachment;
 import org.briarproject.briar.api.messaging.AttachmentHeader;
+import org.briarproject.briar.api.messaging.PrivateMessageHeader;
+import org.briarproject.briar.api.messaging.event.AttachmentReceivedEvent;
 
 import java.io.InputStream;
 import java.util.List;
 
-import androidx.annotation.Nullable;
+import androidx.lifecycle.LiveData;
+
 
 @NotNullByDefault
 public interface AttachmentRetriever {
 
-	void cachePut(MessageId messageId, List<AttachmentItem> attachments);
-
-	@Nullable
-	List<AttachmentItem> cacheGet(MessageId messageId);
-
+	@DatabaseExecutor
 	Attachment getMessageAttachment(AttachmentHeader h) throws DbException;
 
+	/**
+	 * Returns a list of observable {@link LiveData}
+	 * that get updated as the state of their {@link AttachmentItem}s changes.
+	 */
+	List<LiveData<AttachmentItem>> getAttachmentItems(
+			PrivateMessageHeader messageHeader);
+
+	/**
+	 * Retrieves item size and adds the item to the cache, if available.
+	 * <p>
+	 * Use this to eagerly load the attachment size before it gets displayed.
+	 * This is needed for messages containing a single attachment.
+	 * Messages with more than one attachment use a standard size.
+	 */
+	@DatabaseExecutor
+	void cacheAttachmentItemWithSize(MessageId conversationMessageId,
+			AttachmentHeader h) throws DbException;
+
 	/**
 	 * Creates an {@link AttachmentItem} from the {@link Attachment}'s
 	 * {@link InputStream} which will be closed when this method returns.
 	 */
-	AttachmentItem getAttachmentItem(Attachment a, boolean needsSize);
+	AttachmentItem createAttachmentItem(Attachment a, boolean needsSize);
+
+	/**
+	 * Loads an {@link AttachmentItem}
+	 * that arrived via an {@link AttachmentReceivedEvent}
+	 * and notifies the associated {@link LiveData}.
+	 *
+	 * Note that you need to call {@link #getAttachmentItems(PrivateMessageHeader)}
+	 * first to get the LiveData.
+	 *
+	 * It is possible that no LiveData is available,
+	 * because the message of the AttachmentItem did not arrive, yet.
+	 * In this case, the load wil be deferred until the message arrives.
+	 */
+	@DatabaseExecutor
+	void loadAttachmentItem(MessageId attachmentId);
+
 }

briar-android/src/main/java/org/briarproject/briar/android/attachment/AttachmentRetrieverImpl.java

@@ -1,25 +1,39 @@
 package org.briarproject.briar.android.attachment;
 
+import org.briarproject.bramble.api.db.DatabaseExecutor;
 import org.briarproject.bramble.api.db.DbException;
+import org.briarproject.bramble.api.db.NoSuchMessageException;
 import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
 import org.briarproject.bramble.api.sync.MessageId;
+import org.briarproject.briar.android.attachment.AttachmentItem.State;
 import org.briarproject.briar.api.messaging.Attachment;
 import org.briarproject.briar.api.messaging.AttachmentHeader;
 import org.briarproject.briar.api.messaging.MessagingManager;
+import org.briarproject.briar.api.messaging.PrivateMessageHeader;
 
 import java.io.BufferedInputStream;
 import java.io.InputStream;
+import java.util.ArrayList;
 import java.util.List;
-import java.util.Map;
 import java.util.concurrent.ConcurrentHashMap;
+import java.util.concurrent.ConcurrentMap;
+import java.util.concurrent.Executor;
 import java.util.logging.Logger;
 
 import javax.inject.Inject;
 
-import androidx.annotation.Nullable;
+import androidx.lifecycle.LiveData;
+import androidx.lifecycle.MutableLiveData;
 
+import static java.util.Objects.requireNonNull;
 import static java.util.logging.Level.WARNING;
 import static java.util.logging.Logger.getLogger;
+import static org.briarproject.bramble.util.IoUtils.tryToClose;
+import static org.briarproject.bramble.util.LogUtils.logException;
+import static org.briarproject.briar.android.attachment.AttachmentItem.State.AVAILABLE;
+import static org.briarproject.briar.android.attachment.AttachmentItem.State.ERROR;
+import static org.briarproject.briar.android.attachment.AttachmentItem.State.LOADING;
+import static org.briarproject.briar.android.attachment.AttachmentItem.State.MISSING;
 
 @NotNullByDefault
 class AttachmentRetrieverImpl implements AttachmentRetriever {
@@ -27,6 +41,8 @@ class AttachmentRetrieverImpl implements AttachmentRetriever {
 	private static final Logger LOG =
 			getLogger(AttachmentRetrieverImpl.class.getName());
 
+	@DatabaseExecutor
+	private final Executor dbExecutor;
 	private final MessagingManager messagingManager;
 	private final ImageHelper imageHelper;
 	private final ImageSizeCalculator imageSizeCalculator;
@@ -34,13 +50,17 @@ class AttachmentRetrieverImpl implements AttachmentRetriever {
 	private final int minWidth, maxWidth;
 	private final int minHeight, maxHeight;
 
-	private final Map<MessageId, List<AttachmentItem>> attachmentCache =
-			new ConcurrentHashMap<>();
+	private final ConcurrentMap<MessageId, MutableLiveData<AttachmentItem>>
+			itemsWithSize = new ConcurrentHashMap<>();
+	private final ConcurrentMap<MessageId, MutableLiveData<AttachmentItem>>
+			itemsWithoutSize = new ConcurrentHashMap<>();
 
 	@Inject
-	AttachmentRetrieverImpl(MessagingManager messagingManager,
+	AttachmentRetrieverImpl(@DatabaseExecutor Executor dbExecutor,
+			MessagingManager messagingManager,
 			AttachmentDimensions dimensions, ImageHelper imageHelper,
 			ImageSizeCalculator imageSizeCalculator) {
+		this.dbExecutor = dbExecutor;
 		this.messagingManager = messagingManager;
 		this.imageHelper = imageHelper;
 		this.imageSizeCalculator = imageSizeCalculator;
@@ -52,40 +72,143 @@ class AttachmentRetrieverImpl implements AttachmentRetriever {
 	}
 
 	@Override
-	public void cachePut(MessageId messageId,
-			List<AttachmentItem> attachments) {
-		attachmentCache.put(messageId, attachments);
-	}
-
-	@Override
-	@Nullable
-	public List<AttachmentItem> cacheGet(MessageId messageId) {
-		return attachmentCache.get(messageId);
-	}
-
-	@Override
+	@DatabaseExecutor
 	public Attachment getMessageAttachment(AttachmentHeader h)
 			throws DbException {
 		return messagingManager.getAttachment(h);
 	}
 
 	@Override
-	public AttachmentItem getAttachmentItem(Attachment a, boolean needsSize) {
-		AttachmentHeader h = a.getHeader();
-		if (!needsSize) {
-			String extension =
-					imageHelper.getExtensionFromMimeType(h.getContentType());
-			boolean hasError = false;
-			if (extension == null) {
-				extension = "";
-				hasError = true;
+	public List<LiveData<AttachmentItem>> getAttachmentItems(
+			PrivateMessageHeader messageHeader) {
+		List<AttachmentHeader> headers = messageHeader.getAttachmentHeaders();
+		List<LiveData<AttachmentItem>> items = new ArrayList<>(headers.size());
+		boolean needsSize = headers.size() == 1;
+		for (AttachmentHeader h : headers) {
+			// try cache for existing item live data
+			MutableLiveData<AttachmentItem> liveData;
+			if (needsSize) liveData = itemsWithSize.get(h.getMessageId());
+			else {
+				// try items with size first, as they work as well
+				liveData = itemsWithSize.get(h.getMessageId());
+				if (liveData == null)
+					liveData = itemsWithoutSize.get(h.getMessageId());
 			}
-			return new AttachmentItem(h, 0, 0, extension, 0, 0, hasError);
+
+			// create new live data with LOADING item if cache miss
+			if (liveData == null) {
+				AttachmentItem item = new AttachmentItem(h,
+						defaultSize, defaultSize, LOADING);
+				liveData = new MutableLiveData<>(item);
+				// add new LiveData to cache, checking for concurrent updates
+				MutableLiveData<AttachmentItem> oldLiveData;
+				if (needsSize) {
+					oldLiveData = itemsWithSize.putIfAbsent(h.getMessageId(),
+							liveData);
+				} else {
+					oldLiveData = itemsWithoutSize.putIfAbsent(h.getMessageId(),
+							liveData);
+				}
+				if (oldLiveData == null) {
+					// kick-off loading of attachment, will post to live data
+					MutableLiveData<AttachmentItem> finalLiveData = liveData;
+					dbExecutor.execute(() ->
+							loadAttachmentItem(h, needsSize, finalLiveData));
+				} else {
+					// Concurrent cache update - use the existing live data
+					liveData = oldLiveData;
+				}
+			}
+			items.add(liveData);
+		}
+		return items;
+	}
+
+	@Override
+	@DatabaseExecutor
+	public void cacheAttachmentItemWithSize(MessageId conversationMessageId,
+			AttachmentHeader h) throws DbException {
+		// If a live data is already cached we don't need to do anything
+		if (itemsWithSize.containsKey(h.getMessageId())) return;
+		try {
+			Attachment a = messagingManager.getAttachment(h);
+			AttachmentItem item = createAttachmentItem(a, true);
+			MutableLiveData<AttachmentItem> liveData =
+					new MutableLiveData<>(item);
+			// If a live data was concurrently cached, don't replace it
+			itemsWithSize.putIfAbsent(h.getMessageId(), liveData);
+		} catch (NoSuchMessageException e) {
+			LOG.info("Attachment not received yet");
+		}
+	}
+
+	@Override
+	@DatabaseExecutor
+	public void loadAttachmentItem(MessageId attachmentId) {
+		// try to find LiveData for attachment in both caches
+		MutableLiveData<AttachmentItem> liveData;
+		boolean needsSize = true;
+		liveData = itemsWithSize.get(attachmentId);
+		if (liveData == null) {
+			needsSize = false;
+			liveData = itemsWithoutSize.get(attachmentId);
 		}
 
-		InputStream is = new BufferedInputStream(a.getStream());
-		Size size = imageSizeCalculator.getSize(is, h.getContentType());
+		// If no LiveData for the attachment exists,
+		// its message did not yet arrive and we can ignore it for now.
+		if (liveData == null) return;
 
+		// actually load the attachment item
+		AttachmentHeader h = requireNonNull(liveData.getValue()).getHeader();
+		loadAttachmentItem(h, needsSize, liveData);
+	}
+
+	/**
+	 * Loads an {@link AttachmentItem} from the database
+	 * and notifies the given {@link LiveData}.
+	 */
+	@DatabaseExecutor
+	private void loadAttachmentItem(AttachmentHeader h, boolean needsSize,
+			MutableLiveData<AttachmentItem> liveData) {
+		Attachment a;
+		AttachmentItem item;
+		try {
+			a = messagingManager.getAttachment(h);
+			item = createAttachmentItem(a, needsSize);
+		} catch (NoSuchMessageException e) {
+			LOG.info("Attachment not received yet");
+			item = new AttachmentItem(h, defaultSize, defaultSize, MISSING);
+		} catch (DbException e) {
+			logException(LOG, WARNING, e);
+			item = new AttachmentItem(h, "", ERROR);
+		}
+		liveData.postValue(item);
+	}
+
+	@Override
+	public AttachmentItem createAttachmentItem(Attachment a,
+			boolean needsSize) {
+		AttachmentItem item;
+		AttachmentHeader h = a.getHeader();
+		if (needsSize) {
+			InputStream is = new BufferedInputStream(a.getStream());
+			Size size = imageSizeCalculator.getSize(is, h.getContentType());
+			tryToClose(is, LOG, WARNING);
+			item = createAttachmentItem(h, size);
+		} else {
+			String extension =
+					imageHelper.getExtensionFromMimeType(h.getContentType());
+			State state = AVAILABLE;
+			if (extension == null) {
+				extension = "";
+				state = ERROR;
+			}
+			item = new AttachmentItem(h, extension, state);
+		}
+		return item;
+	}
+
+	private AttachmentItem createAttachmentItem(AttachmentHeader h, Size size) {
 		// calculate thumbnail size
 		Size thumbnailSize = new Size(defaultSize, defaultSize, size.mimeType);
 		if (!size.error) {
@@ -104,8 +227,9 @@ class AttachmentRetrieverImpl implements AttachmentRetriever {
 			hasError = true;
 		}
 		if (extension == null) extension = "";
-		return new AttachmentItem(h, size.width, size.height, extension,
-				thumbnailSize.width, thumbnailSize.height, hasError);
+		State state = hasError ? ERROR : AVAILABLE;
+		return new AttachmentItem(h, size.width, size.height,
+				extension, thumbnailSize.width, thumbnailSize.height, state);
 	}
 
 	private Size getThumbnailSize(int width, int height, String mimeType) {

briar-android/src/main/java/org/briarproject/briar/android/conversation/ConversationActivity.java

@@ -28,7 +28,6 @@ import org.briarproject.bramble.api.contact.event.ContactRemovedEvent;
 import org.briarproject.bramble.api.db.DatabaseExecutor;
 import org.briarproject.bramble.api.db.DbException;
 import org.briarproject.bramble.api.db.NoSuchContactException;
-import org.briarproject.bramble.api.db.NoSuchMessageException;
 import org.briarproject.bramble.api.event.Event;
 import org.briarproject.bramble.api.event.EventBus;
 import org.briarproject.bramble.api.event.EventListener;
@@ -65,17 +64,16 @@ import org.briarproject.briar.api.client.ProtocolStateException;
 import org.briarproject.briar.api.client.SessionId;
 import org.briarproject.briar.api.conversation.ConversationManager;
 import org.briarproject.briar.api.conversation.ConversationMessageHeader;
+import org.briarproject.briar.api.conversation.ConversationMessageVisitor;
 import org.briarproject.briar.api.conversation.ConversationRequest;
 import org.briarproject.briar.api.conversation.ConversationResponse;
 import org.briarproject.briar.api.conversation.DeletionResult;
 import org.briarproject.briar.api.conversation.event.ConversationMessageReceivedEvent;
 import org.briarproject.briar.api.forum.ForumSharingManager;
 import org.briarproject.briar.api.introduction.IntroductionManager;
-import org.briarproject.briar.api.messaging.Attachment;
 import org.briarproject.briar.api.messaging.AttachmentHeader;
 import org.briarproject.briar.api.messaging.MessagingManager;
 import org.briarproject.briar.api.messaging.PrivateMessageHeader;
-import org.briarproject.briar.api.messaging.event.AttachmentReceivedEvent;
 import org.briarproject.briar.api.privategroup.invitation.GroupInvitationManager;
 
 import java.util.ArrayList;
@@ -97,6 +95,7 @@ import androidx.appcompat.widget.Toolbar;
 import androidx.core.app.ActivityCompat;
 import androidx.core.app.ActivityOptionsCompat;
 import androidx.core.content.ContextCompat;
+import androidx.lifecycle.LiveData;
 import androidx.lifecycle.Observer;
 import androidx.lifecycle.ViewModelProvider;
 import androidx.lifecycle.ViewModelProviders;
@@ -118,8 +117,6 @@ import static androidx.core.app.ActivityOptionsCompat.makeSceneTransitionAnimati
 import static androidx.core.view.ViewCompat.setTransitionName;
 import static androidx.lifecycle.Lifecycle.State.STARTED;
 import static androidx.recyclerview.widget.SortedList.INVALID_POSITION;
-import static java.util.Collections.emptyList;
-import static java.util.Collections.singletonList;
 import static java.util.Collections.sort;
 import static java.util.Objects.requireNonNull;
 import static java.util.logging.Level.INFO;
@@ -136,6 +133,7 @@ import static org.briarproject.briar.android.activity.RequestCodes.REQUEST_INTRO
 import static org.briarproject.briar.android.conversation.ImageActivity.ATTACHMENTS;
 import static org.briarproject.briar.android.conversation.ImageActivity.ATTACHMENT_POSITION;
 import static org.briarproject.briar.android.conversation.ImageActivity.DATE;
+import static org.briarproject.briar.android.conversation.ImageActivity.ITEM_ID;
 import static org.briarproject.briar.android.conversation.ImageActivity.NAME;
 import static org.briarproject.briar.android.util.UiUtils.getAvatarTransitionName;
 import static org.briarproject.briar.android.util.UiUtils.getBulbTransitionName;
@@ -185,8 +183,6 @@ public class ConversationActivity extends BriarActivity
 	volatile GroupInvitationManager groupInvitationManager;
 
 	private final Map<MessageId, String> textCache = new ConcurrentHashMap<>();
-	private final Map<MessageId, PrivateMessageHeader> missingAttachments =
-			new ConcurrentHashMap<>();
 	private final Observer<String> contactNameObserver = name -> {
 		requireNonNull(name);
 		loadMessages();
@@ -540,6 +536,7 @@ public class ConversationActivity extends BriarActivity
 		});
 	}
 
+	@DatabaseExecutor
 	private void eagerlyLoadMessageSize(PrivateMessageHeader h) {
 		try {
 			MessageId id = h.getId();
@@ -556,21 +553,11 @@ public class ConversationActivity extends BriarActivity
 			// images we use a grid so the size is fixed
 			List<AttachmentHeader> headers = h.getAttachmentHeaders();
 			if (headers.size() == 1) {
-				List<AttachmentItem> items = attachmentRetriever.cacheGet(id);
-				if (items == null) {
-					LOG.info("Eagerly loading image size for latest message");
-					AttachmentHeader header = headers.get(0);
-					try {
-						Attachment a = attachmentRetriever
-								.getMessageAttachment(header);
-						AttachmentItem item =
-								attachmentRetriever.getAttachmentItem(a, true);
-						attachmentRetriever.cachePut(id, singletonList(item));
-					} catch (NoSuchMessageException e) {
-						LOG.info("Attachment not received yet");
-						missingAttachments.put(header.getMessageId(), h);
-					}
-				}
+				LOG.info("Eagerly loading image size for latest message");
+				AttachmentHeader header = headers.get(0);
+				// get the item to retrieve its size
+				attachmentRetriever
+						.cacheAttachmentItemWithSize(h.getId(), header);
 			}
 		} catch (DbException e) {
 			logException(LOG, WARNING, e);
@@ -651,59 +638,18 @@ public class ConversationActivity extends BriarActivity
 				&& adapter.isScrolledToBottom(layoutManager);
 	}
 
-	private void loadMessageAttachments(PrivateMessageHeader h) {
-		// TODO: Use placeholders for missing/invalid attachments
-		runOnDbThread(() -> {
-			try {
-				// TODO move getting the items off to IoExecutor, if size == 1
-				List<AttachmentHeader> headers = h.getAttachmentHeaders();
-				boolean needsSize = headers.size() == 1;
-				List<AttachmentItem> items = new ArrayList<>(headers.size());
-				for (AttachmentHeader header : headers) {
-					try {
-						Attachment a = attachmentRetriever
-								.getMessageAttachment(header);
-						AttachmentItem item = attachmentRetriever
-								.getAttachmentItem(a, needsSize);
-						items.add(item);
-					} catch (NoSuchMessageException e) {
-						LOG.info("Attachment not received yet");
-						missingAttachments.put(header.getMessageId(), h);
-						return;
-					}
-				}
-				// Don't cache items unless all are present and valid
-				attachmentRetriever.cachePut(h.getId(), items);
-				displayMessageAttachments(h.getId(), items);
-			} catch (DbException e) {
-				logException(LOG, WARNING, e);
-			}
-		});
-	}
-
-	private void displayMessageAttachments(MessageId m,
-			List<AttachmentItem> items) {
-		runOnUiThreadUnlessDestroyed(() -> {
-			Pair<Integer, ConversationMessageItem> pair =
-					adapter.getMessageItem(m);
-			if (pair != null) {
-				boolean scroll = shouldScrollWhenUpdatingMessage();
-				pair.getSecond().setAttachments(items);
-				adapter.notifyItemChanged(pair.getFirst());
-				if (scroll) scrollToBottom();
-			}
-		});
+	@UiThread
+	private void updateMessageAttachment(MessageId m, AttachmentItem item) {
+		Pair<Integer, ConversationMessageItem> pair = adapter.getMessageItem(m);
+		if (pair != null && pair.getSecond().updateAttachments(item)) {
+			boolean scroll = shouldScrollWhenUpdatingMessage();
+			adapter.notifyItemChanged(pair.getFirst());
+			if (scroll) scrollToBottom();
+		}
 	}
 
 	@Override
 	public void eventOccurred(Event e) {
-		if (e instanceof AttachmentReceivedEvent) {
-			AttachmentReceivedEvent a = (AttachmentReceivedEvent) e;
-			if (a.getContactId().equals(contactId)) {
-				LOG.info("Attachment received");
-				onAttachmentReceived(a.getMessageId());
-			}
-		}
 		if (e instanceof ContactRemovedEvent) {
 			ContactRemovedEvent c = (ContactRemovedEvent) e;
 			if (c.getContactId().equals(contactId)) {
@@ -763,15 +709,6 @@ public class ConversationActivity extends BriarActivity
 			scrollToBottom();
 	}
 
-	@UiThread
-	private void onAttachmentReceived(MessageId attachmentId) {
-		PrivateMessageHeader h = missingAttachments.remove(attachmentId);
-		if (h != null) {
-			LOG.info("Missing attachment received");
-			loadMessageAttachments(h);
-		}
-	}
-
 	@UiThread
 	private void onNewConversationMessage(ConversationMessageHeader h) {
 		if (h instanceof ConversationRequest ||
@@ -780,7 +717,7 @@ public class ConversationActivity extends BriarActivity
 			observeOnce(viewModel.getContactDisplayName(), this,
 					name -> addConversationItem(h.accept(visitor)));
 		} else {
-			// visitor also loads message text (if existing)
+			// visitor also loads message text and attachments (if existing)
 			addConversationItem(h.accept(visitor));
 		}
 	}
@@ -1107,8 +1044,9 @@ public class ConversationActivity extends BriarActivity
 		i.putExtra(ATTACHMENT_POSITION, attachments.indexOf(item));
 		i.putExtra(NAME, name);
 		i.putExtra(DATE, messageItem.getTime());
+		i.putExtra(ITEM_ID, messageItem.getId().getBytes());
 		// restoring list position should not trigger android bug #224270
-		String transitionName = item.getTransitionName();
+		String transitionName = item.getTransitionName(messageItem.getId());
 		ActivityOptionsCompat options =
 				makeSceneTransitionAnimation(this, view, transitionName);
 		ActivityCompat.startActivity(this, i, options.toBundle());
@@ -1147,15 +1085,41 @@ public class ConversationActivity extends BriarActivity
 		return text;
 	}
 
+	/**
+	 * Called by {@link PrivateMessageHeader#accept(ConversationMessageVisitor)}
+	 */
 	@Override
 	public List<AttachmentItem> getAttachmentItems(PrivateMessageHeader h) {
-		List<AttachmentItem> attachments =
-				attachmentRetriever.cacheGet(h.getId());
-		if (attachments == null) {
-			loadMessageAttachments(h);
-			return emptyList();
+		List<LiveData<AttachmentItem>> liveDataList =
+				attachmentRetriever.getAttachmentItems(h);
+		List<AttachmentItem> items = new ArrayList<>(liveDataList.size());
+		for (LiveData<AttachmentItem> liveData : liveDataList) {
+			// first remove all our observers to avoid having more than one
+			// in case we reload the conversation, e.g. after deleting messages
+			liveData.removeObservers(this);
+			// add a new observer
+			liveData.observe(this, new AttachmentObserver(h.getId(), liveData));
+			items.add(requireNonNull(liveData.getValue()));
+		}
+		return items;
+	}
+
+	private class AttachmentObserver implements Observer<AttachmentItem> {
+		private final MessageId conversationMessageId;
+		private final LiveData<AttachmentItem> liveData;
+
+		private AttachmentObserver(MessageId conversationMessageId,
+				LiveData<AttachmentItem> liveData) {
+			this.conversationMessageId = conversationMessageId;
+			this.liveData = liveData;
+		}
+
+		@Override
+		public void onChanged(AttachmentItem attachmentItem) {
+			updateMessageAttachment(conversationMessageId, attachmentItem);
+			if (attachmentItem.getState().isFinal())
+				liveData.removeObserver(this);
 		}
-		return attachments;
 	}
 
 }

briar-android/src/main/java/org/briarproject/briar/android/conversation/ConversationMessageItem.java

@@ -9,12 +9,13 @@ import java.util.List;
 import javax.annotation.concurrent.NotThreadSafe;
 
 import androidx.annotation.LayoutRes;
+import androidx.annotation.UiThread;
 
 @NotThreadSafe
 @NotNullByDefault
 class ConversationMessageItem extends ConversationItem {
 
-	private List<AttachmentItem> attachments;
+	private final List<AttachmentItem> attachments;
 
 	ConversationMessageItem(@LayoutRes int layoutRes, PrivateMessageHeader h,
 			List<AttachmentItem> attachments) {
@@ -26,8 +27,14 @@ class ConversationMessageItem extends ConversationItem {
 		return attachments;
 	}
 
-	void setAttachments(List<AttachmentItem> attachments) {
-		this.attachments = attachments;
+	@UiThread
+	boolean updateAttachments(AttachmentItem item) {
+		int pos = attachments.indexOf(item);
+		if (pos != -1 && attachments.get(pos).getState() != item.getState()) {
+			attachments.set(pos, item);
+			return true;
+		}
+		return false;
 	}
 
 }

briar-android/src/main/java/org/briarproject/briar/android/conversation/ConversationViewModel.java

@@ -11,6 +11,9 @@ import org.briarproject.bramble.api.db.DatabaseExecutor;
 import org.briarproject.bramble.api.db.DbException;
 import org.briarproject.bramble.api.db.NoSuchContactException;
 import org.briarproject.bramble.api.db.TransactionManager;
+import org.briarproject.bramble.api.event.Event;
+import org.briarproject.bramble.api.event.EventBus;
+import org.briarproject.bramble.api.event.EventListener;
 import org.briarproject.bramble.api.identity.AuthorId;
 import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
 import org.briarproject.bramble.api.settings.Settings;
@@ -30,6 +33,7 @@ import org.briarproject.briar.api.messaging.MessagingManager;
 import org.briarproject.briar.api.messaging.PrivateMessage;
 import org.briarproject.briar.api.messaging.PrivateMessageFactory;
 import org.briarproject.briar.api.messaging.PrivateMessageHeader;
+import org.briarproject.briar.api.messaging.event.AttachmentReceivedEvent;
 
 import java.util.Collection;
 import java.util.List;
@@ -56,7 +60,7 @@ import static org.briarproject.briar.android.util.UiUtils.observeForeverOnce;
 
 @NotNullByDefault
 public class ConversationViewModel extends AndroidViewModel
-		implements AttachmentManager {
+		implements EventListener, AttachmentManager {
 
 	private static Logger LOG =
 			getLogger(ConversationViewModel.class.getName());
@@ -69,6 +73,7 @@ public class ConversationViewModel extends AndroidViewModel
 	@DatabaseExecutor
 	private final Executor dbExecutor;
 	private final TransactionManager db;
+	private final EventBus eventBus;
 	private final MessagingManager messagingManager;
 	private final ContactManager contactManager;
 	private final SettingsManager settingsManager;
@@ -101,6 +106,7 @@ public class ConversationViewModel extends AndroidViewModel
 	ConversationViewModel(Application application,
 			@DatabaseExecutor Executor dbExecutor,
 			TransactionManager db,
+			EventBus eventBus,
 			MessagingManager messagingManager,
 			ContactManager contactManager,
 			SettingsManager settingsManager,
@@ -110,6 +116,7 @@ public class ConversationViewModel extends AndroidViewModel
 		super(application);
 		this.dbExecutor = dbExecutor;
 		this.db = db;
+		this.eventBus = eventBus;
 		this.messagingManager = messagingManager;
 		this.contactManager = contactManager;
 		this.settingsManager = settingsManager;
@@ -119,12 +126,27 @@ public class ConversationViewModel extends AndroidViewModel
 		messagingGroupId = Transformations
 				.map(contact, c -> messagingManager.getContactGroup(c).getId());
 		contactDeleted.setValue(false);
+
+		eventBus.addListener(this);
 	}
 
 	@Override
 	protected void onCleared() {
 		super.onCleared();
-		attachmentCreator.deleteUnsentAttachments();
+		attachmentCreator.cancel();  // also deletes unsent attachments
+		eventBus.removeListener(this);
+	}
+
+	@Override
+	public void eventOccurred(Event e) {
+		if (e instanceof AttachmentReceivedEvent) {
+			AttachmentReceivedEvent a = (AttachmentReceivedEvent) e;
+			if (a.getContactId().equals(contactId)) {
+				LOG.info("Attachment received");
+				dbExecutor.execute(() -> attachmentRetriever
+						.loadAttachmentItem(a.getMessageId()));
+			}
+		}
 	}
 
 	/**
@@ -252,6 +274,7 @@ public class ConversationViewModel extends AndroidViewModel
 		settingsManager.mergeSettings(settings, SETTINGS_NAMESPACE);
 	}
 
+	@UiThread
 	private void createMessage(GroupId groupId, @Nullable String text,
 			List<AttachmentHeader> headers, long timestamp,
 			boolean hasImageSupport) {
@@ -270,6 +293,7 @@ public class ConversationViewModel extends AndroidViewModel
 		}
 	}
 
+	@UiThread
 	private void storeMessage(PrivateMessage m) {
 		attachmentCreator.onAttachmentsSent(m.getMessage().getId());
 		dbExecutor.execute(() -> {

briar-android/src/main/java/org/briarproject/briar/android/conversation/ImageActivity.java

@@ -16,6 +16,7 @@ import com.google.android.material.appbar.AppBarLayout;
 
 import org.briarproject.bramble.api.nullsafety.MethodsNotNullByDefault;
 import org.briarproject.bramble.api.nullsafety.ParametersNotNullByDefault;
+import org.briarproject.bramble.api.sync.MessageId;
 import org.briarproject.briar.R;
 import org.briarproject.briar.android.activity.ActivityComponent;
 import org.briarproject.briar.android.activity.BriarActivity;
@@ -67,6 +68,7 @@ public class ImageActivity extends BriarActivity
 	final static String ATTACHMENT_POSITION = "position";
 	final static String NAME = "name";
 	final static String DATE = "date";
+	final static String ITEM_ID = "itemId";
 
 	@RequiresApi(api = 16)
 	private final static int UI_FLAGS_DEFAULT =
@@ -80,6 +82,7 @@ public class ImageActivity extends BriarActivity
 	private AppBarLayout appBarLayout;
 	private ViewPager viewPager;
 	private List<AttachmentItem> attachments;
+	private MessageId conversationMessageId;
 
 	@Override
 	public void injectActivity(ActivityComponent component) {
@@ -98,9 +101,20 @@ public class ImageActivity extends BriarActivity
 			setSceneTransitionAnimation(transition, null, transition);
 		}
 
+		// Intent Extras
+		Intent i = getIntent();
+		attachments =
+				requireNonNull(i.getParcelableArrayListExtra(ATTACHMENTS));
+		int position = i.getIntExtra(ATTACHMENT_POSITION, -1);
+		if (position == -1) throw new IllegalStateException();
+		String name = i.getStringExtra(NAME);
+		long time = i.getLongExtra(DATE, 0);
+		byte[] messageIdBytes = requireNonNull(i.getByteArrayExtra(ITEM_ID));
+
 		// get View Model
 		viewModel = ViewModelProviders.of(this, viewModelFactory)
 				.get(ImageViewModel.class);
+		viewModel.expectAttachments(attachments);
 		viewModel.getSaveState().observeEvent(this,
 				this::onImageSaveStateChanged);
 
@@ -124,16 +138,11 @@ public class ImageActivity extends BriarActivity
 		TextView contactName = toolbar.findViewById(R.id.contactName);
 		TextView dateView = toolbar.findViewById(R.id.dateView);
 
-		// Intent Extras
-		Intent i = getIntent();
-		attachments = i.getParcelableArrayListExtra(ATTACHMENTS);
-		int position = i.getIntExtra(ATTACHMENT_POSITION, -1);
-		if (position == -1) throw new IllegalStateException();
-		String name = i.getStringExtra(NAME);
-		long time = i.getLongExtra(DATE, 0);
+		// Set contact name and message time
 		String date = formatDateAbsolute(this, time);
 		contactName.setText(name);
 		dateView.setText(date);
+		conversationMessageId = new MessageId(messageIdBytes);
 
 		// Set up image ViewPager
 		viewPager = findViewById(R.id.viewPager);
@@ -320,8 +329,8 @@ public class ImageActivity extends BriarActivity
 
 		@Override
 		public Fragment getItem(int position) {
-			Fragment f = ImageFragment
-					.newInstance(attachments.get(position), isFirst);
+			Fragment f = ImageFragment.newInstance(
+					attachments.get(position), conversationMessageId, isFirst);
 			isFirst = false;
 			return f;
 		}

briar-android/src/main/java/org/briarproject/briar/android/conversation/ImageAdapter.java

@@ -49,7 +49,8 @@ class ImageAdapter extends Adapter<ImageViewHolder> {
 	public ImageViewHolder onCreateViewHolder(ViewGroup viewGroup, int type) {
 		View v = LayoutInflater.from(viewGroup.getContext()).inflate(
 				R.layout.list_item_image, viewGroup, false);
-		return new ImageViewHolder(v, imageSize);
+		requireNonNull(conversationItem);
+		return new ImageViewHolder(v, imageSize, conversationItem.getId());
 	}
 
 	@Override

briar-android/src/main/java/org/briarproject/briar/android/conversation/ImageFragment.java

@@ -15,6 +15,7 @@ import com.bumptech.glide.request.target.Target;
 import com.github.chrisbanes.photoview.PhotoView;
 
 import org.briarproject.bramble.api.nullsafety.MethodsNotNullByDefault;
+import org.briarproject.bramble.api.sync.MessageId;
 import org.briarproject.briar.R;
 import org.briarproject.briar.android.activity.BaseActivity;
 import org.briarproject.briar.android.attachment.AttachmentItem;
@@ -23,6 +24,7 @@ import org.briarproject.briar.android.conversation.glide.GlideApp;
 import javax.annotation.ParametersAreNonnullByDefault;
 import javax.inject.Inject;
 
+import androidx.annotation.DrawableRes;
 import androidx.annotation.Nullable;
 import androidx.fragment.app.Fragment;
 import androidx.lifecycle.ViewModelProvider;
@@ -32,27 +34,36 @@ import static android.os.Build.VERSION.SDK_INT;
 import static android.widget.ImageView.ScaleType.FIT_START;
 import static com.bumptech.glide.load.engine.DiskCacheStrategy.NONE;
 import static org.briarproject.bramble.api.nullsafety.NullSafety.requireNonNull;
+import static org.briarproject.briar.android.attachment.AttachmentItem.State.AVAILABLE;
+import static org.briarproject.briar.android.attachment.AttachmentItem.State.ERROR;
 import static org.briarproject.briar.android.conversation.ImageActivity.ATTACHMENT_POSITION;
+import static org.briarproject.briar.android.conversation.ImageActivity.ITEM_ID;
 
 @MethodsNotNullByDefault
 @ParametersAreNonnullByDefault
-public class ImageFragment extends Fragment {
+public class ImageFragment extends Fragment
+		implements RequestListener<Drawable> {
 
 	private final static String IS_FIRST = "isFirst";
+	@DrawableRes
+	private static final int ERROR_RES = R.drawable.ic_image_broken;
 
 	@Inject
 	ViewModelProvider.Factory viewModelFactory;
 
 	private AttachmentItem attachment;
 	private boolean isFirst;
+	private MessageId conversationItemId;
 	private ImageViewModel viewModel;
 	private PhotoView photoView;
 
-	static ImageFragment newInstance(AttachmentItem a, boolean isFirst) {
+	static ImageFragment newInstance(AttachmentItem a,
+			MessageId conversationMessageId, boolean isFirst) {
 		ImageFragment f = new ImageFragment();
 		Bundle args = new Bundle();
 		args.putParcelable(ATTACHMENT_POSITION, a);
 		args.putBoolean(IS_FIRST, isFirst);
+		args.putByteArray(ITEM_ID, conversationMessageId.getBytes());
 		f.setArguments(args);
 		return f;
 	}
@@ -70,6 +81,8 @@ public class ImageFragment extends Fragment {
 		Bundle args = requireNonNull(getArguments());
 		attachment = requireNonNull(args.getParcelable(ATTACHMENT_POSITION));
 		isFirst = args.getBoolean(IS_FIRST);
+		conversationItemId =
+				new MessageId(requireNonNull(args.getByteArray(ITEM_ID)));
 	}
 
 	@Nullable
@@ -87,50 +100,68 @@ public class ImageFragment extends Fragment {
 		photoView.setScaleLevels(1, 2, 4);
 		photoView.setOnClickListener(view -> viewModel.clickImage());
 
-		// Request Listener
-		RequestListener<Drawable> listener = new RequestListener<Drawable>() {
-
-			@Override
-			public boolean onLoadFailed(@Nullable GlideException e,
-					Object model, Target<Drawable> target,
-					boolean isFirstResource) {
-				if (getActivity() != null && isFirst)
-					getActivity().supportStartPostponedEnterTransition();
-				return false;
-			}
-
-			@Override
-			public boolean onResourceReady(Drawable resource, Object model,
-					Target<Drawable> target, DataSource dataSource,
-					boolean isFirstResource) {
-				if (SDK_INT >= 21 && !(resource instanceof Animatable)) {
-					// set transition name only when not animatable,
-					// because the animation won't start otherwise
-					photoView.setTransitionName(
-							attachment.getTransitionName());
-				}
-				// Move image to the top if overlapping toolbar
-				if (viewModel.isOverlappingToolbar(photoView, resource)) {
-					photoView.setScaleType(FIT_START);
-				}
-				if (getActivity() != null && isFirst) {
-					getActivity().supportStartPostponedEnterTransition();
-				}
-				return false;
-			}
-		};
-
-		// Load Image
-		GlideApp.with(this)
-				.load(attachment)
-				// TODO allow if size < maxTextureSize ?
-//				.override(SIZE_ORIGINAL)
-				.diskCacheStrategy(NONE)
-				.error(R.drawable.ic_image_broken)
-				.addListener(listener)
-				.into(photoView);
+		if (attachment.getState() == AVAILABLE) {
+			loadImage();
+			// postponed transition will be started when Image was loaded
+		} else if (attachment.getState() == ERROR) {
+			photoView.setImageResource(ERROR_RES);
+			startPostponedTransition();
+		} else {
+			photoView.setImageResource(R.drawable.ic_image_missing);
+			startPostponedTransition();
+			// state is not final, so observe state changes
+			viewModel.getOnAttachmentReceived(attachment.getMessageId())
+					.observeEvent(this, this::onAttachmentReceived);
+		}
 
 		return v;
 	}
 
+	private void loadImage() {
+		GlideApp.with(this)
+				.load(attachment)
+				// TODO allow if size < maxTextureSize ?
+//					.override(SIZE_ORIGINAL)
+				.diskCacheStrategy(NONE)
+				.error(ERROR_RES)
+				.addListener(this)
+				.into(photoView);
+	}
+
+	private void onAttachmentReceived(Boolean received) {
+		if (received) loadImage();
+	}
+
+	@Override
+	public boolean onLoadFailed(@Nullable GlideException e,
+			Object model, Target<Drawable> target,
+			boolean isFirstResource) {
+		startPostponedTransition();
+		return false;
+	}
+
+	@Override
+	public boolean onResourceReady(Drawable resource, Object model,
+			Target<Drawable> target, DataSource dataSource,
+			boolean isFirstResource) {
+		if (SDK_INT >= 21 && !(resource instanceof Animatable)) {
+			// set transition name only when not animatable,
+			// because the animation won't start otherwise
+			photoView.setTransitionName(
+					attachment.getTransitionName(conversationItemId));
+		}
+		// Move image to the top if overlapping toolbar
+		if (viewModel.isOverlappingToolbar(photoView, resource)) {
+			photoView.setScaleType(FIT_START);
+		}
+		startPostponedTransition();
+		return false;
+	}
+
+	private void startPostponedTransition() {
+		if (getActivity() != null && isFirst) {
+			getActivity().supportStartPostponedEnterTransition();
+		}
+	}
+
 }

briar-android/src/main/java/org/briarproject/briar/android/conversation/ImageViewHolder.java

@@ -7,6 +7,7 @@ import android.widget.ImageView;
 import com.bumptech.glide.load.Transformation;
 
 import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
+import org.briarproject.bramble.api.sync.MessageId;
 import org.briarproject.briar.R;
 import org.briarproject.briar.android.attachment.AttachmentItem;
 import org.briarproject.briar.android.conversation.glide.BriarImageTransformation;
@@ -18,8 +19,12 @@ import androidx.recyclerview.widget.RecyclerView.ViewHolder;
 import androidx.recyclerview.widget.StaggeredGridLayoutManager.LayoutParams;
 
 import static android.os.Build.VERSION.SDK_INT;
+import static android.widget.ImageView.ScaleType.CENTER_CROP;
+import static android.widget.ImageView.ScaleType.FIT_CENTER;
 import static com.bumptech.glide.load.engine.DiskCacheStrategy.NONE;
 import static com.bumptech.glide.load.resource.drawable.DrawableTransitionOptions.withCrossFade;
+import static org.briarproject.briar.android.attachment.AttachmentItem.State.AVAILABLE;
+import static org.briarproject.briar.android.attachment.AttachmentItem.State.ERROR;
 
 @NotNullByDefault
 class ImageViewHolder extends ViewHolder {
@@ -29,25 +34,33 @@ class ImageViewHolder extends ViewHolder {
 
 	protected final ImageView imageView;
 	private final int imageSize;
+	private final MessageId conversationItemId;
 
-	ImageViewHolder(View v, int imageSize) {
+	ImageViewHolder(View v, int imageSize, MessageId conversationItemId) {
 		super(v);
 		imageView = v.findViewById(R.id.imageView);
 		this.imageSize = imageSize;
+		this.conversationItemId = conversationItemId;
 	}
 
 	void bind(AttachmentItem attachment, Radii r, boolean single,
 			boolean needsStretch) {
-		if (attachment.hasError()) {
-			GlideApp.with(imageView)
-					.clear(imageView);
-			imageView.setImageResource(ERROR_RES);
-		} else {
-			setImageViewDimensions(attachment, single, needsStretch);
-			loadImage(attachment, r);
-			if (SDK_INT >= 21) {
-				imageView.setTransitionName(attachment.getTransitionName());
+		setImageViewDimensions(attachment, single, needsStretch);
+		if (attachment.getState() != AVAILABLE) {
+			GlideApp.with(imageView).clear(imageView);
+			if (attachment.getState() == ERROR) {
+				imageView.setImageResource(ERROR_RES);
+			} else {
+				imageView.setImageResource(R.drawable.ic_image_missing);
 			}
+			imageView.setScaleType(FIT_CENTER);
+		} else {
+			loadImage(attachment, r);
+			imageView.setScaleType(CENTER_CROP);
+		}
+		if (SDK_INT >= 21) {
+			imageView.setTransitionName(
+					attachment.getTransitionName(conversationItemId));
 		}
 	}
 

briar-android/src/main/java/org/briarproject/briar/android/conversation/ImageViewModel.java

@@ -7,13 +7,18 @@ import android.view.View;
 
 import org.briarproject.bramble.api.db.DatabaseExecutor;
 import org.briarproject.bramble.api.db.DbException;
+import org.briarproject.bramble.api.event.Event;
+import org.briarproject.bramble.api.event.EventBus;
+import org.briarproject.bramble.api.event.EventListener;
 import org.briarproject.bramble.api.lifecycle.IoExecutor;
 import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
+import org.briarproject.bramble.api.sync.MessageId;
 import org.briarproject.briar.android.attachment.AttachmentItem;
 import org.briarproject.briar.android.viewmodel.LiveEvent;
 import org.briarproject.briar.android.viewmodel.MutableLiveEvent;
 import org.briarproject.briar.api.messaging.Attachment;
 import org.briarproject.briar.api.messaging.MessagingManager;
+import org.briarproject.briar.api.messaging.event.AttachmentReceivedEvent;
 
 import java.io.File;
 import java.io.FileOutputStream;
@@ -22,6 +27,8 @@ import java.io.InputStream;
 import java.io.OutputStream;
 import java.text.SimpleDateFormat;
 import java.util.Date;
+import java.util.HashMap;
+import java.util.List;
 import java.util.Locale;
 import java.util.concurrent.Executor;
 import java.util.logging.Logger;
@@ -35,22 +42,28 @@ import androidx.lifecycle.AndroidViewModel;
 import static android.media.MediaScannerConnection.scanFile;
 import static android.os.Environment.DIRECTORY_PICTURES;
 import static android.os.Environment.getExternalStoragePublicDirectory;
+import static java.util.Objects.requireNonNull;
 import static java.util.logging.Level.WARNING;
 import static java.util.logging.Logger.getLogger;
 import static org.briarproject.bramble.util.IoUtils.copyAndClose;
 import static org.briarproject.bramble.util.LogUtils.logException;
 
 @NotNullByDefault
-public class ImageViewModel extends AndroidViewModel {
+public class ImageViewModel extends AndroidViewModel implements EventListener {
 
 	private static Logger LOG = getLogger(ImageViewModel.class.getName());
 
 	private final MessagingManager messagingManager;
+	private final EventBus eventBus;
 	@DatabaseExecutor
 	private final Executor dbExecutor;
 	@IoExecutor
 	private final Executor ioExecutor;
 
+	private boolean receivedAttachmentsInitialized = false;
+	private HashMap<MessageId, MutableLiveEvent<Boolean>> receivedAttachments =
+			new HashMap<>();
+
 	/**
 	 * true means there was an error saving the image, false if image was saved.
 	 */
@@ -62,13 +75,60 @@ public class ImageViewModel extends AndroidViewModel {
 
 	@Inject
 	ImageViewModel(Application application,
-			MessagingManager messagingManager,
+			MessagingManager messagingManager, EventBus eventBus,
 			@DatabaseExecutor Executor dbExecutor,
 			@IoExecutor Executor ioExecutor) {
 		super(application);
 		this.messagingManager = messagingManager;
+		this.eventBus = eventBus;
 		this.dbExecutor = dbExecutor;
 		this.ioExecutor = ioExecutor;
+
+		eventBus.addListener(this);
+	}
+
+	@Override
+	protected void onCleared() {
+		super.onCleared();
+		eventBus.removeListener(this);
+	}
+
+	@UiThread
+	@Override
+	public void eventOccurred(Event e) {
+		if (e instanceof AttachmentReceivedEvent) {
+			MessageId id = ((AttachmentReceivedEvent) e).getMessageId();
+			MutableLiveEvent<Boolean> oldEvent;
+			if (receivedAttachmentsInitialized) {
+				oldEvent = receivedAttachments.get(id);
+				if (oldEvent != null) oldEvent.postEvent(true);
+			} else {
+				receivedAttachments.put(id, new MutableLiveEvent<>(true));
+			}
+		}
+	}
+
+	@UiThread
+	public void expectAttachments(List<AttachmentItem> attachments) {
+		for (AttachmentItem item : attachments) {
+			// no need to track items that are in a final state already
+			if (item.getState().isFinal()) continue;
+			// add new live events, if not already added by eventOccurred()
+			MessageId id = item.getMessageId();
+			if (!receivedAttachments.containsKey(id)) {
+				receivedAttachments.put(id, new MutableLiveEvent<>());
+			}
+		}
+		receivedAttachmentsInitialized = true;
+	}
+
+	/**
+	 * Returns a LiveData for attachments in a non-final state.
+	 * Note that you need to call {@link #expectAttachments(List)} first.
+	 */
+	@UiThread
+	LiveEvent<Boolean> getOnAttachmentReceived(MessageId messageId) {
+		return requireNonNull(receivedAttachments.get(messageId));
 	}
 
 	void clickImage() {

briar-android/src/main/java/org/briarproject/briar/android/keyagreement/ContactExchangeActivity.java

@@ -9,7 +9,6 @@ import org.briarproject.bramble.api.nullsafety.MethodsNotNullByDefault;
 import org.briarproject.bramble.api.nullsafety.ParametersNotNullByDefault;
 import org.briarproject.briar.R;
 import org.briarproject.briar.android.activity.ActivityComponent;
-import org.briarproject.briar.android.fragment.BaseFragment;
 
 import javax.annotation.Nullable;
 import javax.inject.Inject;
@@ -114,9 +113,7 @@ public class ContactExchangeActivity extends KeyAgreementActivity {
 		return getString(R.string.exchanging_contact_details);
 	}
 
-	protected void showErrorFragment() {
-		String errorMsg = getString(R.string.connection_error_explanation);
-		BaseFragment f = ContactExchangeErrorFragment.newInstance(errorMsg);
-		showNextFragment(f);
+	private void showErrorFragment() {
+		showNextFragment(new ContactExchangeErrorFragment());
 	}
 }

briar-android/src/main/java/org/briarproject/briar/android/keyagreement/ContactExchangeErrorFragment.java

@@ -1,5 +1,6 @@
 package org.briarproject.briar.android.keyagreement;
 
+import android.content.Intent;
 import android.os.Bundle;
 import android.view.LayoutInflater;
 import android.view.View;
@@ -18,7 +19,10 @@ import org.briarproject.briar.android.util.UiUtils;
 import javax.inject.Inject;
 
 import androidx.annotation.Nullable;
+import androidx.fragment.app.FragmentActivity;
 
+import static android.content.Intent.FLAG_ACTIVITY_CLEAR_TOP;
+import static android.view.View.GONE;
 import static org.briarproject.briar.android.util.UiUtils.onSingleLinkClick;
 
 @MethodsNotNullByDefault
@@ -58,13 +62,12 @@ public class ContactExchangeErrorFragment extends BaseFragment {
 		View v = inflater.inflate(R.layout.fragment_error_contact_exchange,
 				container, false);
 
-		// set humanized error message
+		// set optional error message
 		TextView explanation = v.findViewById(R.id.errorMessage);
 		Bundle args = getArguments();
-		if (args == null) {
-			throw new IllegalArgumentException("Use newInstance()");
-		}
-		explanation.setText(args.getString(ERROR_MSG));
+		String errorMessage = args == null ? null : args.getString(ERROR_MSG);
+		if (errorMessage == null) explanation.setVisibility(GONE);
+		else explanation.setText(args.getString(ERROR_MSG));
 
 		// make feedback link clickable
 		TextView sendFeedback = v.findViewById(R.id.sendFeedback);
@@ -73,7 +76,11 @@ public class ContactExchangeErrorFragment extends BaseFragment {
 		// buttons
 		Button tryAgain = v.findViewById(R.id.tryAgainButton);
 		tryAgain.setOnClickListener(view -> {
-			if (getActivity() != null) getActivity().onBackPressed();
+			// Recreate the activity so we return to the intro fragment
+			FragmentActivity activity = requireActivity();
+			Intent i = new Intent(activity, ContactExchangeActivity.class);
+			i.setFlags(FLAG_ACTIVITY_CLEAR_TOP);
+			activity.startActivity(i);
 		});
 		Button cancel = v.findViewById(R.id.cancelButton);
 		cancel.setOnClickListener(view -> finish());

briar-android/src/main/java/org/briarproject/briar/android/keyagreement/KeyAgreementActivity.java

@@ -18,7 +18,6 @@ import org.briarproject.bramble.api.plugin.LanTcpConstants;
 import org.briarproject.bramble.api.plugin.Plugin;
 import org.briarproject.bramble.api.plugin.Plugin.State;
 import org.briarproject.bramble.api.plugin.PluginManager;
-import org.briarproject.bramble.api.plugin.event.BluetoothEnabledEvent;
 import org.briarproject.bramble.api.plugin.event.TransportStateEvent;
 import org.briarproject.briar.R;
 import org.briarproject.briar.android.activity.ActivityComponent;
@@ -27,7 +26,6 @@ import org.briarproject.briar.android.fragment.BaseFragment;
 import org.briarproject.briar.android.fragment.BaseFragment.BaseFragmentListener;
 import org.briarproject.briar.android.keyagreement.IntroFragment.IntroScreenSeenListener;
 import org.briarproject.briar.android.keyagreement.KeyAgreementFragment.KeyAgreementEventListener;
-import org.briarproject.briar.android.util.UiUtils;
 
 import java.util.logging.Logger;
 
@@ -47,6 +45,7 @@ import static android.bluetooth.BluetoothAdapter.ACTION_REQUEST_DISCOVERABLE;
 import static android.bluetooth.BluetoothAdapter.ACTION_SCAN_MODE_CHANGED;
 import static android.bluetooth.BluetoothAdapter.SCAN_MODE_CONNECTABLE_DISCOVERABLE;
 import static android.content.pm.PackageManager.PERMISSION_GRANTED;
+import static android.os.Build.VERSION.SDK_INT;
 import static java.util.logging.Level.INFO;
 import static java.util.logging.Logger.getLogger;
 import static org.briarproject.bramble.api.nullsafety.NullSafety.requireNonNull;
@@ -56,6 +55,7 @@ import static org.briarproject.bramble.api.plugin.Plugin.State.INACTIVE;
 import static org.briarproject.bramble.api.plugin.Plugin.State.STARTING_STOPPING;
 import static org.briarproject.briar.android.activity.RequestCodes.REQUEST_BLUETOOTH_DISCOVERABLE;
 import static org.briarproject.briar.android.activity.RequestCodes.REQUEST_PERMISSION_CAMERA_LOCATION;
+import static org.briarproject.briar.android.util.UiUtils.getGoToSettingsListener;
 
 @MethodsNotNullByDefault
 @ParametersNotNullByDefault
@@ -118,13 +118,6 @@ public abstract class KeyAgreementActivity extends BriarActivity implements
 	 */
 	private boolean continueClicked = false;
 
-	/**
-	 * Records whether the Bluetooth adapter was already enabled before we
-	 * asked for Bluetooth discoverability, so we know whether to broadcast a
-	 * {@link BluetoothEnabledEvent}.
-	 */
-	private boolean wasAdapterEnabled = false;
-
 	/**
 	 * Records whether we've enabled the wifi plugin so we don't enable it more
 	 * than once.
@@ -141,6 +134,8 @@ public abstract class KeyAgreementActivity extends BriarActivity implements
 	private Permission locationPermission = Permission.UNKNOWN;
 	private BluetoothDecision bluetoothDecision = BluetoothDecision.UNKNOWN;
 	private BroadcastReceiver bluetoothReceiver = null;
+	private Plugin wifiPlugin = null, bluetoothPlugin = null;
+	private BluetoothAdapter bt = null;
 
 	@Override
 	public void injectActivity(ActivityComponent component) {
@@ -160,6 +155,9 @@ public abstract class KeyAgreementActivity extends BriarActivity implements
 		IntentFilter filter = new IntentFilter(ACTION_SCAN_MODE_CHANGED);
 		bluetoothReceiver = new BluetoothStateReceiver();
 		registerReceiver(bluetoothReceiver, filter);
+		wifiPlugin = pluginManager.getPlugin(LanTcpConstants.ID);
+		bluetoothPlugin = pluginManager.getPlugin(BluetoothConstants.ID);
+		bt = BluetoothAdapter.getDefaultAdapter();
 	}
 
 	@Override
@@ -195,6 +193,7 @@ public abstract class KeyAgreementActivity extends BriarActivity implements
 		showQrCodeFragmentIfAllowed();
 	}
 
+	@SuppressWarnings("StatementWithEmptyBody")
 	private void showQrCodeFragmentIfAllowed() {
 		if (isResumed && continueClicked && areEssentialPermissionsGranted()) {
 			if (isWifiReady() && isBluetoothReady()) {
@@ -208,6 +207,8 @@ public abstract class KeyAgreementActivity extends BriarActivity implements
 				}
 				if (bluetoothDecision == BluetoothDecision.UNKNOWN) {
 					requestBluetoothDiscoverable();
+				} else if (bluetoothDecision == BluetoothDecision.REFUSED) {
+					// Ask again when the user clicks "continue"
 				} else if (shouldEnableBluetooth()) {
 					LOG.info("Enabling Bluetooth plugin");
 					hasEnabledBluetooth = true;
@@ -218,55 +219,50 @@ public abstract class KeyAgreementActivity extends BriarActivity implements
 	}
 
 	private boolean areEssentialPermissionsGranted() {
-		// If the camera permission has been granted, and the location
-		// permission has been granted or permanently denied, we can continue
 		return cameraPermission == Permission.GRANTED &&
-				(locationPermission == Permission.GRANTED ||
-						locationPermission == Permission.PERMANENTLY_DENIED);
+				(SDK_INT < 23 || locationPermission == Permission.GRANTED ||
+						!isBluetoothSupported());
+	}
+
+	private boolean isBluetoothSupported() {
+		return bt != null && bluetoothPlugin != null;
 	}
 
 	private boolean isWifiReady() {
-		Plugin p = pluginManager.getPlugin(LanTcpConstants.ID);
-		if (p == null) return true; // Continue without wifi
-		State state = p.getState();
+		if (wifiPlugin == null) return true; // Continue without wifi
+		State state = wifiPlugin.getState();
 		// Wait for plugin to become enabled
 		return state == ACTIVE || state == INACTIVE;
 	}
 
 	private boolean isBluetoothReady() {
-		if (bluetoothDecision == BluetoothDecision.UNKNOWN ||
-				bluetoothDecision == BluetoothDecision.WAITING) {
-			// Wait for decision
-			return false;
-		}
-		if (bluetoothDecision == BluetoothDecision.NO_ADAPTER
-				|| bluetoothDecision == BluetoothDecision.REFUSED) {
+		if (!isBluetoothSupported()) {
 			// Continue without Bluetooth
 			return true;
 		}
-		BluetoothAdapter bt = BluetoothAdapter.getDefaultAdapter();
-		if (bt == null) return true; // Continue without Bluetooth
+		if (bluetoothDecision == BluetoothDecision.UNKNOWN ||
+				bluetoothDecision == BluetoothDecision.WAITING ||
+				bluetoothDecision == BluetoothDecision.REFUSED) {
+			// Wait for user to accept
+			return false;
+		}
 		if (bt.getScanMode() != SCAN_MODE_CONNECTABLE_DISCOVERABLE) {
 			// Wait for adapter to become discoverable
 			return false;
 		}
-		Plugin p = pluginManager.getPlugin(BluetoothConstants.ID);
-		if (p == null) return true; // Continue without Bluetooth
 		// Wait for plugin to become active
-		return p.getState() == ACTIVE;
+		return bluetoothPlugin.getState() == ACTIVE;
 	}
 
 	private boolean shouldEnableWifi() {
 		if (hasEnabledWifi) return false;
-		Plugin p = pluginManager.getPlugin(LanTcpConstants.ID);
-		if (p == null) return false;
-		State state = p.getState();
+		if (wifiPlugin == null) return false;
+		State state = wifiPlugin.getState();
 		return state == STARTING_STOPPING || state == DISABLED;
 	}
 
 	private void requestBluetoothDiscoverable() {
-		BluetoothAdapter bt = BluetoothAdapter.getDefaultAdapter();
-		if (bt == null) {
+		if (!isBluetoothSupported()) {
 			bluetoothDecision = BluetoothDecision.NO_ADAPTER;
 			showQrCodeFragmentIfAllowed();
 		} else {
@@ -274,7 +270,6 @@ public abstract class KeyAgreementActivity extends BriarActivity implements
 			if (i.resolveActivity(getPackageManager()) != null) {
 				LOG.info("Asking for Bluetooth discoverability");
 				bluetoothDecision = BluetoothDecision.WAITING;
-				wasAdapterEnabled = bt.isEnabled();
 				startActivityForResult(i, REQUEST_BLUETOOTH_DISCOVERABLE);
 			} else {
 				bluetoothDecision = BluetoothDecision.NO_ADAPTER;
@@ -286,9 +281,8 @@ public abstract class KeyAgreementActivity extends BriarActivity implements
 	private boolean shouldEnableBluetooth() {
 		if (bluetoothDecision != BluetoothDecision.ACCEPTED) return false;
 		if (hasEnabledBluetooth) return false;
-		Plugin p = pluginManager.getPlugin(BluetoothConstants.ID);
-		if (p == null) return false;
-		State state = p.getState();
+		if (!isBluetoothSupported()) return false;
+		State state = bluetoothPlugin.getState();
 		return state == STARTING_STOPPING || state == DISABLED;
 	}
 
@@ -307,6 +301,9 @@ public abstract class KeyAgreementActivity extends BriarActivity implements
 	@Override
 	public void showNextScreen() {
 		continueClicked = true;
+		if (bluetoothDecision == BluetoothDecision.REFUSED) {
+			bluetoothDecision = BluetoothDecision.UNKNOWN; // Ask again
+		}
 		if (checkPermissions()) showQrCodeFragmentIfAllowed();
 	}
 
@@ -320,11 +317,6 @@ public abstract class KeyAgreementActivity extends BriarActivity implements
 			} else {
 				LOG.info("Bluetooth discoverability was accepted");
 				bluetoothDecision = BluetoothDecision.ACCEPTED;
-				if (!wasAdapterEnabled) {
-					LOG.info("Bluetooth adapter was enabled by us");
-					eventBus.broadcast(new BluetoothEnabledEvent());
-					wasAdapterEnabled = true;
-				}
 			}
 			showQrCodeFragmentIfAllowed();
 		} else super.onActivityResult(request, result, data);
@@ -355,17 +347,17 @@ public abstract class KeyAgreementActivity extends BriarActivity implements
 
 	private boolean checkPermissions() {
 		if (areEssentialPermissionsGranted()) return true;
-		// If the camera permission has been permanently denied, ask the
+		// If an essential permission has been permanently denied, ask the
 		// user to change the setting
 		if (cameraPermission == Permission.PERMANENTLY_DENIED) {
-			Builder builder = new Builder(this, R.style.BriarDialogTheme);
-			builder.setTitle(R.string.permission_camera_title);
-			builder.setMessage(R.string.permission_camera_denied_body);
-			builder.setPositiveButton(R.string.ok,
-					UiUtils.getGoToSettingsListener(this));
-			builder.setNegativeButton(R.string.cancel,
-					(dialog, which) -> supportFinishAfterTransition());
-			builder.show();
+			showDenialDialog(R.string.permission_camera_title,
+					R.string.permission_camera_denied_body);
+			return false;
+		}
+		if (isBluetoothSupported() &&
+				locationPermission == Permission.PERMANENTLY_DENIED) {
+			showDenialDialog(R.string.permission_location_title,
+					R.string.permission_location_denied_body);
 			return false;
 		}
 		// Should we show the rationale for one or both permissions?
@@ -385,6 +377,16 @@ public abstract class KeyAgreementActivity extends BriarActivity implements
 		return false;
 	}
 
+	private void showDenialDialog(@StringRes int title, @StringRes int body) {
+		Builder builder = new Builder(this, R.style.BriarDialogTheme);
+		builder.setTitle(title);
+		builder.setMessage(body);
+		builder.setPositiveButton(R.string.ok, getGoToSettingsListener(this));
+		builder.setNegativeButton(R.string.cancel,
+				(dialog, which) -> supportFinishAfterTransition());
+		builder.show();
+	}
+
 	private void showRationale(@StringRes int title, @StringRes int body) {
 		Builder builder = new Builder(this, R.style.BriarDialogTheme);
 		builder.setTitle(title);
@@ -395,8 +397,13 @@ public abstract class KeyAgreementActivity extends BriarActivity implements
 	}
 
 	private void requestPermissions() {
-		ActivityCompat.requestPermissions(this,
-				new String[] {CAMERA, ACCESS_FINE_LOCATION},
+		String[] permissions;
+		if (isBluetoothSupported()) {
+			permissions = new String[] {CAMERA, ACCESS_FINE_LOCATION};
+		} else {
+			permissions = new String[] {CAMERA};
+		}
+		ActivityCompat.requestPermissions(this, permissions,
 				REQUEST_PERMISSION_CAMERA_LOCATION);
 	}
 
@@ -413,12 +420,15 @@ public abstract class KeyAgreementActivity extends BriarActivity implements
 		} else {
 			cameraPermission = Permission.PERMANENTLY_DENIED;
 		}
-		if (gotPermission(ACCESS_FINE_LOCATION, permissions, grantResults)) {
-			locationPermission = Permission.GRANTED;
-		} else if (shouldShowRationale(ACCESS_FINE_LOCATION)) {
-			locationPermission = Permission.SHOW_RATIONALE;
-		} else {
-			locationPermission = Permission.PERMANENTLY_DENIED;
+		if (isBluetoothSupported()) {
+			if (gotPermission(ACCESS_FINE_LOCATION, permissions,
+					grantResults)) {
+				locationPermission = Permission.GRANTED;
+			} else if (shouldShowRationale(ACCESS_FINE_LOCATION)) {
+				locationPermission = Permission.SHOW_RATIONALE;
+			} else {
+				locationPermission = Permission.PERMANENTLY_DENIED;
+			}
 		}
 		// If a permission dialog has been shown, showing the QR code fragment
 		// on this call path would cause a crash due to

briar-android/src/main/java/org/briarproject/briar/android/navdrawer/NavDrawerActivity.java

@@ -11,6 +11,7 @@ import android.view.ViewGroup;
 import android.widget.BaseAdapter;
 import android.widget.GridView;
 import android.widget.ImageView;
+import android.widget.LinearLayout;
 import android.widget.TextView;
 
 import com.google.android.material.navigation.NavigationView;
@@ -56,8 +57,10 @@ import androidx.core.content.ContextCompat;
 import androidx.drawerlayout.widget.DrawerLayout;
 import androidx.fragment.app.FragmentManager;
 import androidx.fragment.app.FragmentTransaction;
+import androidx.lifecycle.MutableLiveData;
 import androidx.lifecycle.ViewModelProvider;
 import androidx.lifecycle.ViewModelProviders;
+import uk.co.samuelwall.materialtaptargetprompt.MaterialTapTargetPrompt;
 
 import static android.view.View.GONE;
 import static android.view.View.VISIBLE;
@@ -75,6 +78,8 @@ import static org.briarproject.briar.android.TestingConstants.IS_DEBUG_BUILD;
 import static org.briarproject.briar.android.activity.RequestCodes.REQUEST_PASSWORD;
 import static org.briarproject.briar.android.navdrawer.IntentRouter.handleExternalIntent;
 import static org.briarproject.briar.android.util.UiUtils.getDaysUntilExpiry;
+import static org.briarproject.briar.android.util.UiUtils.observeOnce;
+import static org.briarproject.briar.android.util.UiUtils.resolveColorAttribute;
 
 @MethodsNotNullByDefault
 @ParametersNotNullByDefault
@@ -97,6 +102,9 @@ public class NavDrawerActivity extends BriarActivity implements
 	public static Uri SIGN_OUT_URI =
 			Uri.parse("briar-content://org.briarproject.briar/sign-out");
 
+	private final List<Transport> transports = new ArrayList<>(3);
+	private final MutableLiveData<ImageView> torIcon = new MutableLiveData<>();
+
 	private NavDrawerViewModel navDrawerViewModel;
 	private PluginViewModel pluginViewModel;
 	private ActionBarDrawerToggle drawerToggle;
@@ -110,7 +118,6 @@ public class NavDrawerActivity extends BriarActivity implements
 	private DrawerLayout drawerLayout;
 	private NavigationView navigation;
 
-	private List<Transport> transports;
 	private BaseAdapter transportsAdapter;
 
 	@Override
@@ -141,6 +148,11 @@ public class NavDrawerActivity extends BriarActivity implements
 		drawerLayout = findViewById(R.id.drawer_layout);
 		navigation = findViewById(R.id.navigation);
 		GridView transportsView = findViewById(R.id.transportsView);
+		LinearLayout transportsLayout = findViewById(R.id.transports);
+		transportsLayout.setOnClickListener(v -> {
+			LOG.info("Starting transports activity");
+			startActivity(new Intent(this, TransportsActivity.class));
+		});
 
 		setSupportActionBar(toolbar);
 		ActionBar actionBar = requireNonNull(getSupportActionBar());
@@ -149,13 +161,23 @@ public class NavDrawerActivity extends BriarActivity implements
 
 		drawerToggle = new ActionBarDrawerToggle(this, drawerLayout, toolbar,
 				R.string.nav_drawer_open_description,
-				R.string.nav_drawer_close_description);
+				R.string.nav_drawer_close_description) {
+			@Override
+			public void onDrawerOpened(View drawerView) {
+				super.onDrawerOpened(drawerView);
+				navDrawerViewModel.checkTransportsOnboarding();
+			}
+		};
 		drawerLayout.addDrawerListener(drawerToggle);
 		navigation.setNavigationItemSelectedListener(this);
 
 		initializeTransports();
 		transportsView.setAdapter(transportsAdapter);
 
+		observeOnce(navDrawerViewModel.showTransportsOnboarding(), this, show ->
+				observeOnce(torIcon, this, imageView ->
+						showTransportsOnboarding(show, imageView)));
+
 		lockManager.isLockable().observe(this, this::setLockVisible);
 
 		if (lifecycleManager.getLifecycleState().isAfter(RUNNING)) {
@@ -380,8 +402,6 @@ public class NavDrawerActivity extends BriarActivity implements
 	}
 
 	private void initializeTransports() {
-		transports = new ArrayList<>(3);
-
 		transportsAdapter = new BaseAdapter() {
 
 			@Override
@@ -422,6 +442,8 @@ public class NavDrawerActivity extends BriarActivity implements
 				TextView text = view.findViewById(R.id.textView);
 				text.setText(getString(t.label));
 
+				if (t.id.equals(TorConstants.ID)) torIcon.setValue(icon);
+
 				return view;
 			}
 		};
@@ -444,7 +466,7 @@ public class NavDrawerActivity extends BriarActivity implements
 	private Transport createTransport(TransportId id,
 			@DrawableRes int iconDrawable, @StringRes int label) {
 		int iconColor = getIconColor(STARTING_STOPPING);
-		Transport transport = new Transport(iconDrawable, label, iconColor);
+		Transport transport = new Transport(id, iconDrawable, label, iconColor);
 		pluginViewModel.getPluginState(id).observe(this, state -> {
 			transport.iconColor = getIconColor(state);
 			transportsAdapter.notifyDataSetChanged();
@@ -452,8 +474,25 @@ public class NavDrawerActivity extends BriarActivity implements
 		return transport;
 	}
 
+	private void showTransportsOnboarding(boolean show, ImageView imageView) {
+		if (show) {
+			int color = resolveColorAttribute(this, R.attr.colorControlNormal);
+			new MaterialTapTargetPrompt.Builder(NavDrawerActivity.this,
+					R.style.OnboardingDialogTheme).setTarget(imageView)
+					.setPrimaryText(R.string.network_settings_title)
+					.setSecondaryText(R.string.transports_onboarding_text)
+					.setIcon(R.drawable.transport_tor)
+					.setIconDrawableColourFilter(color)
+					.setBackgroundColour(
+							ContextCompat.getColor(this, R.color.briar_primary))
+					.show();
+			navDrawerViewModel.transportsOnboardingShown();
+		}
+	}
+
 	private static class Transport {
 
+		private final TransportId id;
 		@DrawableRes
 		private final int iconDrawable;
 		@StringRes
@@ -462,8 +501,9 @@ public class NavDrawerActivity extends BriarActivity implements
 		@ColorRes
 		private int iconColor;
 
-		private Transport(@DrawableRes int iconDrawable, @StringRes int label,
-				@ColorRes int iconColor) {
+		private Transport(TransportId id, @DrawableRes int iconDrawable,
+				@StringRes int label, @ColorRes int iconColor) {
+			this.id = id;
 			this.iconDrawable = iconDrawable;
 			this.label = label;
 			this.iconColor = iconColor;

briar-android/src/main/java/org/briarproject/briar/android/navdrawer/NavDrawerViewModel.java

@@ -34,6 +34,8 @@ public class NavDrawerViewModel extends AndroidViewModel {
 			getLogger(NavDrawerViewModel.class.getName());
 
 	private static final String EXPIRY_DATE_WARNING = "expiryDateWarning";
+	private static final String SHOW_TRANSPORTS_ONBOARDING =
+			"showTransportsOnboarding";
 
 	@DatabaseExecutor
 	private final Executor dbExecutor;
@@ -43,6 +45,8 @@ public class NavDrawerViewModel extends AndroidViewModel {
 			new MutableLiveData<>();
 	private final MutableLiveData<Boolean> shouldAskForDozeWhitelisting =
 			new MutableLiveData<>();
+	private final MutableLiveData<Boolean> showTransportsOnboarding =
+			new MutableLiveData<>();
 
 	@Inject
 	NavDrawerViewModel(Application app, @DatabaseExecutor Executor dbExecutor,
@@ -128,4 +132,39 @@ public class NavDrawerViewModel extends AndroidViewModel {
 			}
 		});
 	}
+
+	@UiThread
+	LiveData<Boolean> showTransportsOnboarding() {
+		return showTransportsOnboarding;
+	}
+
+	@UiThread
+	void checkTransportsOnboarding() {
+		if (showTransportsOnboarding.getValue() != null) return;
+		dbExecutor.execute(() -> {
+			try {
+				Settings settings =
+						settingsManager.getSettings(SETTINGS_NAMESPACE);
+				boolean show =
+						settings.getBoolean(SHOW_TRANSPORTS_ONBOARDING, true);
+				showTransportsOnboarding.postValue(show);
+			} catch (DbException e) {
+				logException(LOG, WARNING, e);
+			}
+		});
+	}
+
+	@UiThread
+	void transportsOnboardingShown() {
+		showTransportsOnboarding.setValue(false);
+		dbExecutor.execute(() -> {
+			try {
+				Settings settings = new Settings();
+				settings.putBoolean(SHOW_TRANSPORTS_ONBOARDING, false);
+				settingsManager.mergeSettings(settings, SETTINGS_NAMESPACE);
+			} catch (DbException e) {
+				logException(LOG, WARNING, e);
+			}
+		});
+	}
 }

briar-android/src/main/java/org/briarproject/briar/android/navdrawer/PluginViewModel.java

@@ -1,8 +1,20 @@
 package org.briarproject.briar.android.navdrawer;
 
+import android.app.Application;
+import android.bluetooth.BluetoothAdapter;
+import android.content.BroadcastReceiver;
+import android.content.Context;
+import android.content.Intent;
+import android.content.IntentFilter;
+
+import org.briarproject.bramble.api.db.DatabaseExecutor;
+import org.briarproject.bramble.api.db.DbException;
 import org.briarproject.bramble.api.event.Event;
 import org.briarproject.bramble.api.event.EventBus;
 import org.briarproject.bramble.api.event.EventListener;
+import org.briarproject.bramble.api.network.NetworkManager;
+import org.briarproject.bramble.api.network.NetworkStatus;
+import org.briarproject.bramble.api.network.event.NetworkStatusEvent;
 import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
 import org.briarproject.bramble.api.plugin.BluetoothConstants;
 import org.briarproject.bramble.api.plugin.LanTcpConstants;
@@ -12,28 +24,44 @@ import org.briarproject.bramble.api.plugin.PluginManager;
 import org.briarproject.bramble.api.plugin.TorConstants;
 import org.briarproject.bramble.api.plugin.TransportId;
 import org.briarproject.bramble.api.plugin.event.TransportStateEvent;
+import org.briarproject.bramble.api.settings.Settings;
+import org.briarproject.bramble.api.settings.SettingsManager;
+import org.briarproject.bramble.api.settings.event.SettingsUpdatedEvent;
 
+import java.util.concurrent.Executor;
 import java.util.logging.Logger;
 
 import javax.inject.Inject;
 
 import androidx.annotation.Nullable;
+import androidx.lifecycle.AndroidViewModel;
 import androidx.lifecycle.LiveData;
 import androidx.lifecycle.MutableLiveData;
-import androidx.lifecycle.ViewModel;
 
+import static android.bluetooth.BluetoothAdapter.ACTION_STATE_CHANGED;
+import static android.bluetooth.BluetoothAdapter.EXTRA_STATE;
+import static android.bluetooth.BluetoothAdapter.STATE_ON;
 import static java.util.logging.Level.INFO;
+import static java.util.logging.Level.WARNING;
 import static java.util.logging.Logger.getLogger;
+import static org.briarproject.bramble.api.plugin.Plugin.PREF_PLUGIN_ENABLE;
 import static org.briarproject.bramble.api.plugin.Plugin.State.STARTING_STOPPING;
+import static org.briarproject.bramble.util.LogUtils.logDuration;
+import static org.briarproject.bramble.util.LogUtils.logException;
+import static org.briarproject.bramble.util.LogUtils.now;
 
 @NotNullByDefault
-public class PluginViewModel extends ViewModel implements EventListener {
+public class PluginViewModel extends AndroidViewModel implements EventListener {
 
 	private static final Logger LOG =
 			getLogger(PluginViewModel.class.getName());
 
+	private final Application app;
+	private final Executor dbExecutor;
+	private final SettingsManager settingsManager;
 	private final PluginManager pluginManager;
 	private final EventBus eventBus;
+	private final BroadcastReceiver receiver;
 
 	private final MutableLiveData<State> torPluginState =
 			new MutableLiveData<>();
@@ -42,24 +70,68 @@ public class PluginViewModel extends ViewModel implements EventListener {
 	private final MutableLiveData<State> btPluginState =
 			new MutableLiveData<>();
 
+	private final MutableLiveData<Boolean> torEnabledSetting =
+			new MutableLiveData<>(false);
+	private final MutableLiveData<Boolean> wifiEnabledSetting =
+			new MutableLiveData<>(false);
+	private final MutableLiveData<Boolean> btEnabledSetting =
+			new MutableLiveData<>(false);
+
+	private final MutableLiveData<NetworkStatus> networkStatus =
+			new MutableLiveData<>();
+
+	private final MutableLiveData<Boolean> bluetoothTurnedOn =
+			new MutableLiveData<>(false);
+
 	@Inject
-	PluginViewModel(PluginManager pluginManager, EventBus eventBus) {
+	PluginViewModel(Application app, @DatabaseExecutor Executor dbExecutor,
+			SettingsManager settingsManager, PluginManager pluginManager,
+			EventBus eventBus, NetworkManager networkManager) {
+		super(app);
+		this.app = app;
+		this.dbExecutor = dbExecutor;
+		this.settingsManager = settingsManager;
 		this.pluginManager = pluginManager;
 		this.eventBus = eventBus;
 		eventBus.addListener(this);
+		receiver = new BluetoothStateReceiver();
+		app.registerReceiver(receiver, new IntentFilter(ACTION_STATE_CHANGED));
+		networkStatus.setValue(networkManager.getNetworkStatus());
 		torPluginState.setValue(getTransportState(TorConstants.ID));
 		wifiPluginState.setValue(getTransportState(LanTcpConstants.ID));
 		btPluginState.setValue(getTransportState(BluetoothConstants.ID));
+		initialiseBluetoothState();
+		loadSettings();
 	}
 
 	@Override
 	protected void onCleared() {
 		eventBus.removeListener(this);
+		app.unregisterReceiver(receiver);
 	}
 
 	@Override
 	public void eventOccurred(Event e) {
-		if (e instanceof TransportStateEvent) {
+		if (e instanceof NetworkStatusEvent) {
+			networkStatus.setValue(((NetworkStatusEvent) e).getStatus());
+		} else if (e instanceof SettingsUpdatedEvent) {
+			SettingsUpdatedEvent s = (SettingsUpdatedEvent) e;
+			if (s.getNamespace().equals(TorConstants.ID.getString())) {
+				boolean enable = s.getSettings().getBoolean(PREF_PLUGIN_ENABLE,
+						TorConstants.DEFAULT_PREF_PLUGIN_ENABLE);
+				torEnabledSetting.setValue(enable);
+			} else if (s.getNamespace().equals(
+					LanTcpConstants.ID.getString())) {
+				boolean enable = s.getSettings().getBoolean(PREF_PLUGIN_ENABLE,
+						LanTcpConstants.DEFAULT_PREF_PLUGIN_ENABLE);
+				wifiEnabledSetting.setValue(enable);
+			} else if (s.getNamespace().equals(
+					BluetoothConstants.ID.getString())) {
+				boolean enable = s.getSettings().getBoolean(PREF_PLUGIN_ENABLE,
+						BluetoothConstants.DEFAULT_PREF_PLUGIN_ENABLE);
+				btEnabledSetting.setValue(enable);
+			}
+		} else if (e instanceof TransportStateEvent) {
 			TransportStateEvent t = (TransportStateEvent) e;
 			TransportId id = t.getTransportId();
 			State state = t.getState();
@@ -77,6 +149,62 @@ public class PluginViewModel extends ViewModel implements EventListener {
 		return liveData;
 	}
 
+	LiveData<Boolean> getPluginEnabledSetting(TransportId id) {
+		if (id.equals(TorConstants.ID)) return torEnabledSetting;
+		else if (id.equals(LanTcpConstants.ID)) return wifiEnabledSetting;
+		else if (id.equals(BluetoothConstants.ID)) return btEnabledSetting;
+		else throw new IllegalArgumentException();
+	}
+
+	LiveData<NetworkStatus> getNetworkStatus() {
+		return networkStatus;
+	}
+
+	LiveData<Boolean> getBluetoothTurnedOn() {
+		return bluetoothTurnedOn;
+	}
+
+	int getReasonsTorDisabled() {
+		Plugin plugin = pluginManager.getPlugin(TorConstants.ID);
+		return plugin == null ? 0 : plugin.getReasonsDisabled();
+	}
+
+	void enableTransport(TransportId id, boolean enable) {
+		Settings s = new Settings();
+		s.putBoolean(PREF_PLUGIN_ENABLE, enable);
+		mergeSettings(s, id.getString());
+	}
+
+	private void initialiseBluetoothState() {
+		BluetoothAdapter bt = BluetoothAdapter.getDefaultAdapter();
+		if (bt == null) bluetoothTurnedOn.setValue(false);
+		else bluetoothTurnedOn.setValue(bt.getState() == STATE_ON);
+	}
+
+	private void loadSettings() {
+		dbExecutor.execute(() -> {
+			try {
+				boolean tor = isPluginEnabled(TorConstants.ID,
+						TorConstants.DEFAULT_PREF_PLUGIN_ENABLE);
+				torEnabledSetting.postValue(tor);
+				boolean wifi = isPluginEnabled(LanTcpConstants.ID,
+						LanTcpConstants.DEFAULT_PREF_PLUGIN_ENABLE);
+				wifiEnabledSetting.postValue(wifi);
+				boolean bt = isPluginEnabled(BluetoothConstants.ID,
+						BluetoothConstants.DEFAULT_PREF_PLUGIN_ENABLE);
+				btEnabledSetting.postValue(bt);
+			} catch (DbException e) {
+				logException(LOG, WARNING, e);
+			}
+		});
+	}
+
+	private boolean isPluginEnabled(TransportId id, boolean defaultValue)
+			throws DbException {
+		Settings s = settingsManager.getSettings(id.getString());
+		return s.getBoolean(PREF_PLUGIN_ENABLE, defaultValue);
+	}
+
 	private State getTransportState(TransportId id) {
 		Plugin plugin = pluginManager.getPlugin(id);
 		return plugin == null ? STARTING_STOPPING : plugin.getState();
@@ -89,4 +217,26 @@ public class PluginViewModel extends ViewModel implements EventListener {
 		else if (id.equals(BluetoothConstants.ID)) return btPluginState;
 		else return null;
 	}
+
+	private void mergeSettings(Settings s, String namespace) {
+		dbExecutor.execute(() -> {
+			try {
+				long start = now();
+				settingsManager.mergeSettings(s, namespace);
+				logDuration(LOG, "Merging settings", start);
+			} catch (DbException e) {
+				logException(LOG, WARNING, e);
+			}
+		});
+	}
+
+	private class BluetoothStateReceiver extends BroadcastReceiver {
+
+		@Override
+		public void onReceive(Context context, Intent intent) {
+			int state = intent.getIntExtra(EXTRA_STATE, 0);
+			if (state == STATE_ON) bluetoothTurnedOn.postValue(true);
+			else bluetoothTurnedOn.postValue(false);
+		}
+	}
 }

briar-android/src/main/java/org/briarproject/briar/android/navdrawer/TransportsActivity.java

@@ -0,0 +1,360 @@
+package org.briarproject.briar.android.navdrawer;
+
+import android.os.Bundle;
+import android.view.LayoutInflater;
+import android.view.Menu;
+import android.view.MenuInflater;
+import android.view.MenuItem;
+import android.view.View;
+import android.view.ViewGroup;
+import android.widget.BaseAdapter;
+import android.widget.GridView;
+import android.widget.ImageView;
+import android.widget.TextView;
+
+import org.briarproject.bramble.api.network.NetworkStatus;
+import org.briarproject.bramble.api.nullsafety.MethodsNotNullByDefault;
+import org.briarproject.bramble.api.nullsafety.ParametersNotNullByDefault;
+import org.briarproject.bramble.api.plugin.BluetoothConstants;
+import org.briarproject.bramble.api.plugin.LanTcpConstants;
+import org.briarproject.bramble.api.plugin.Plugin.State;
+import org.briarproject.bramble.api.plugin.TorConstants;
+import org.briarproject.bramble.api.plugin.TransportId;
+import org.briarproject.briar.R;
+import org.briarproject.briar.android.activity.ActivityComponent;
+import org.briarproject.briar.android.activity.BriarActivity;
+
+import java.util.ArrayList;
+import java.util.List;
+
+import javax.inject.Inject;
+
+import androidx.annotation.ColorRes;
+import androidx.annotation.DrawableRes;
+import androidx.annotation.Nullable;
+import androidx.annotation.StringRes;
+import androidx.appcompat.app.ActionBar;
+import androidx.appcompat.widget.SwitchCompat;
+import androidx.core.content.ContextCompat;
+import androidx.lifecycle.ViewModelProvider;
+import androidx.lifecycle.ViewModelProviders;
+
+import static android.view.View.GONE;
+import static android.view.View.VISIBLE;
+import static org.briarproject.bramble.api.plugin.Plugin.State.ACTIVE;
+import static org.briarproject.bramble.api.plugin.Plugin.State.DISABLED;
+import static org.briarproject.bramble.api.plugin.Plugin.State.ENABLING;
+import static org.briarproject.bramble.api.plugin.Plugin.State.STARTING_STOPPING;
+import static org.briarproject.bramble.api.plugin.TorConstants.REASON_BATTERY;
+import static org.briarproject.bramble.api.plugin.TorConstants.REASON_COUNTRY_BLOCKED;
+import static org.briarproject.bramble.api.plugin.TorConstants.REASON_MOBILE_DATA;
+import static org.briarproject.briar.android.util.UiUtils.showOnboardingDialog;
+
+@MethodsNotNullByDefault
+@ParametersNotNullByDefault
+public class TransportsActivity extends BriarActivity {
+
+	@Inject
+	ViewModelProvider.Factory viewModelFactory;
+
+	private final List<Transport> transports = new ArrayList<>(3);
+
+	private PluginViewModel viewModel;
+	private BaseAdapter transportsAdapter;
+
+	@Override
+	public void onCreate(@Nullable Bundle state) {
+		super.onCreate(state);
+
+		ActionBar actionBar = getSupportActionBar();
+		if (actionBar != null) {
+			actionBar.setHomeButtonEnabled(true);
+			actionBar.setDisplayHomeAsUpEnabled(true);
+		}
+
+		setContentView(R.layout.activity_transports);
+
+		ViewModelProvider provider =
+				ViewModelProviders.of(this, viewModelFactory);
+		viewModel = provider.get(PluginViewModel.class);
+
+		GridView grid = findViewById(R.id.grid);
+		initializeCards();
+		grid.setAdapter(transportsAdapter);
+	}
+
+	@Override
+	public void injectActivity(ActivityComponent component) {
+		component.inject(this);
+	}
+
+	@Override
+	public boolean onOptionsItemSelected(MenuItem item) {
+		if (item.getItemId() == android.R.id.home) {
+			onBackPressed();
+			return true;
+		} else if (item.getItemId() == R.id.action_help) {
+			String text = getString(R.string.transports_help_text);
+			showOnboardingDialog(this, text);
+			return true;
+		}
+		return false;
+	}
+
+	@Override
+	public boolean onCreateOptionsMenu(Menu menu) {
+		MenuInflater inflater = getMenuInflater();
+		inflater.inflate(R.menu.help_action, menu);
+		return super.onCreateOptionsMenu(menu);
+	}
+
+	private void initializeCards() {
+		transportsAdapter = new BaseAdapter() {
+
+			@Override
+			public int getCount() {
+				return transports.size();
+			}
+
+			@Override
+			public Transport getItem(int position) {
+				return transports.get(position);
+			}
+
+			@Override
+			public long getItemId(int position) {
+				return 0;
+			}
+
+			@Override
+			public View getView(int position, View convertView,
+					ViewGroup parent) {
+				View view;
+				if (convertView != null) {
+					view = convertView;
+				} else {
+					LayoutInflater inflater = getLayoutInflater();
+					view = inflater.inflate(R.layout.list_item_transport_card,
+							parent, false);
+				}
+
+				Transport t = getItem(position);
+
+				ImageView icon = view.findViewById(R.id.icon);
+				icon.setImageDrawable(ContextCompat.getDrawable(
+						TransportsActivity.this, t.iconDrawable));
+				icon.setColorFilter(ContextCompat.getColor(
+						TransportsActivity.this, t.iconColor));
+
+				TextView title = view.findViewById(R.id.title);
+				title.setText(getString(t.title));
+
+				SwitchCompat switchCompat =
+						view.findViewById(R.id.switchCompat);
+				switchCompat.setText(getString(t.switchLabel));
+				switchCompat.setOnClickListener(v ->
+						viewModel.enableTransport(t.id,
+								switchCompat.isChecked()));
+				switchCompat.setChecked(t.isSwitchChecked);
+
+				TextView summary = view.findViewById(R.id.summary);
+				if (t.summary == 0) {
+					summary.setVisibility(GONE);
+				} else {
+					summary.setText(t.summary);
+					summary.setVisibility(VISIBLE);
+				}
+
+				TextView deviceStatus = view.findViewById(R.id.deviceStatus);
+				deviceStatus.setText(getBulletString(t.deviceStatus));
+
+				TextView pluginStatus = view.findViewById(R.id.appStatus);
+				pluginStatus.setText(getBulletString(t.pluginStatus));
+				pluginStatus.setVisibility(t.showPluginStatus ? VISIBLE : GONE);
+
+				return view;
+			}
+		};
+
+		Transport tor = createTransport(TorConstants.ID,
+				R.drawable.transport_tor, R.string.transport_tor,
+				R.string.tor_enable_title, R.string.tor_enable_summary,
+				R.string.tor_device_status_offline,
+				R.string.tor_plugin_status_inactive);
+		transports.add(tor);
+
+		Transport wifi = createTransport(LanTcpConstants.ID,
+				R.drawable.transport_lan, R.string.transport_lan_long,
+				R.string.wifi_setting, 0, R.string.lan_device_status_off,
+				R.string.lan_plugin_status_inactive);
+		transports.add(wifi);
+
+		Transport bt = createTransport(BluetoothConstants.ID,
+				R.drawable.transport_bt, R.string.transport_bt,
+				R.string.bluetooth_setting, 0, R.string.bt_device_status_off,
+				R.string.bt_plugin_status_inactive);
+		transports.add(bt);
+
+		viewModel.getNetworkStatus().observe(this, status -> {
+			updateTorResources(tor, status);
+			updateWifiResources(wifi, status);
+			transportsAdapter.notifyDataSetChanged();
+		});
+
+		viewModel.getBluetoothTurnedOn().observe(this, on -> {
+			updateBtResources(bt, on);
+			transportsAdapter.notifyDataSetChanged();
+		});
+	}
+
+	private String getBulletString(@StringRes int resId) {
+		return "\u2022 " + getString(resId);
+	}
+
+	@ColorRes
+	private int getIconColor(State state) {
+		if (state == ACTIVE) return R.color.briar_lime_400;
+		else if (state == ENABLING) return R.color.briar_orange_500;
+		else return android.R.color.tertiary_text_light;
+	}
+
+	private void updateTorResources(Transport tor, NetworkStatus status) {
+		if (status.isConnected()) {
+			if (status.isWifi()) {
+				tor.deviceStatus = R.string.tor_device_status_online_wifi;
+			} else {
+				tor.deviceStatus = R.string.tor_device_status_online_mobile;
+			}
+			tor.showPluginStatus = true;
+		} else {
+			tor.deviceStatus = R.string.tor_device_status_offline;
+			tor.showPluginStatus = false;
+		}
+	}
+
+	private void updateWifiResources(Transport wifi, NetworkStatus status) {
+		if (status.isWifi()) {
+			wifi.deviceStatus = R.string.lan_device_status_on;
+			wifi.showPluginStatus = true;
+		} else {
+			wifi.deviceStatus = R.string.lan_device_status_off;
+			wifi.showPluginStatus = false;
+		}
+	}
+
+	private void updateBtResources(Transport bt, boolean on) {
+		if (on) {
+			bt.deviceStatus = R.string.bt_device_status_on;
+			bt.showPluginStatus = true;
+		} else {
+			bt.deviceStatus = R.string.bt_device_status_off;
+			bt.showPluginStatus = false;
+		}
+	}
+
+	@StringRes
+	private int getPluginStatus(TransportId id, State state) {
+		if (id.equals(TorConstants.ID)) {
+			return getTorPluginStatus(state);
+		} else if (id.equals(LanTcpConstants.ID)) {
+			return getWifiPluginStatus(state);
+		} else if (id.equals(BluetoothConstants.ID)) {
+			return getBtPluginStatus(state);
+		} else throw new AssertionError();
+	}
+
+	@StringRes
+	private int getTorPluginStatus(State state) {
+		if (state == ENABLING) {
+			return R.string.tor_plugin_status_enabling;
+		} else if (state == ACTIVE) {
+			return R.string.tor_plugin_status_active;
+		} else if (state == DISABLED) {
+			int reasons = viewModel.getReasonsTorDisabled();
+			if ((reasons & REASON_MOBILE_DATA) != 0) {
+				return R.string.tor_plugin_status_disabled_mobile_data;
+			} else if ((reasons & REASON_BATTERY) != 0) {
+				return R.string.tor_plugin_status_disabled_battery;
+			} else if ((reasons & REASON_COUNTRY_BLOCKED) != 0) {
+				return R.string.tor_plugin_status_disabled_country_blocked;
+			} else {
+				return R.string.tor_plugin_status_disabled;
+			}
+		} else {
+			return R.string.tor_plugin_status_inactive;
+		}
+	}
+
+	@StringRes
+	private int getWifiPluginStatus(State state) {
+		if (state == ENABLING) return R.string.lan_plugin_status_enabling;
+		else if (state == ACTIVE) return R.string.lan_plugin_status_active;
+		else if (state == DISABLED) return R.string.lan_plugin_status_disabled;
+		else return R.string.lan_plugin_status_inactive;
+	}
+
+	@StringRes
+	private int getBtPluginStatus(State state) {
+		if (state == ENABLING) return R.string.bt_plugin_status_enabling;
+		else if (state == ACTIVE) return R.string.bt_plugin_status_active;
+		else if (state == DISABLED) return R.string.bt_plugin_status_disabled;
+		else return R.string.bt_plugin_status_inactive;
+	}
+
+	private Transport createTransport(TransportId id,
+			@DrawableRes int iconDrawable, @StringRes int title,
+			@StringRes int switchLabel, @StringRes int summary,
+			@StringRes int deviceStatus, @StringRes int pluginStatus) {
+		int iconColor = getIconColor(STARTING_STOPPING);
+		Transport transport = new Transport(id, iconDrawable, iconColor, title,
+				switchLabel, false, summary, deviceStatus, pluginStatus, false);
+		viewModel.getPluginState(id).observe(this, state -> {
+			transport.iconColor = getIconColor(state);
+			transport.pluginStatus = getPluginStatus(transport.id, state);
+			transportsAdapter.notifyDataSetChanged();
+		});
+		viewModel.getPluginEnabledSetting(id).observe(this, enabled -> {
+			transport.isSwitchChecked = enabled;
+			transportsAdapter.notifyDataSetChanged();
+		});
+		return transport;
+	}
+
+	private static class Transport {
+
+		private final TransportId id;
+
+		@DrawableRes
+		private final int iconDrawable;
+		@StringRes
+		private final int title, switchLabel, summary;
+
+		@ColorRes
+		private int iconColor;
+		@StringRes
+		private int deviceStatus, pluginStatus;
+		private boolean isSwitchChecked, showPluginStatus;
+
+		private Transport(TransportId id,
+				@DrawableRes int iconDrawable,
+				@ColorRes int iconColor,
+				@StringRes int title,
+				@StringRes int switchLabel,
+				boolean isSwitchChecked,
+				@StringRes int summary,
+				@StringRes int deviceStatus,
+				@StringRes int pluginStatus,
+				boolean showPluginStatus) {
+			this.id = id;
+			this.iconDrawable = iconDrawable;
+			this.iconColor = iconColor;
+			this.title = title;
+			this.switchLabel = switchLabel;
+			this.isSwitchChecked = isSwitchChecked;
+			this.summary = summary;
+			this.deviceStatus = deviceStatus;
+			this.pluginStatus = pluginStatus;
+			this.showPluginStatus = showPluginStatus;
+		}
+	}
+}

briar-android/src/main/java/org/briarproject/briar/android/view/ImagePreview.java

@@ -79,7 +79,7 @@ public class ImagePreview extends ConstraintLayout {
 				((ImagePreviewAdapter) imageList.getAdapter());
 		int pos = requireNonNull(adapter).loadItemPreview(result);
 		if (pos != NO_POSITION) {
-			imageList.smoothScrollToPosition(pos);
+			imageList.scrollToPosition(pos);
 		}
 	}
 

briar-android/src/main/java/org/briarproject/briar/android/viewmodel/LiveEvent.java

@@ -12,6 +12,22 @@ import androidx.lifecycle.Observer;
 @NotNullByDefault
 public class LiveEvent<T> extends LiveData<LiveEvent.ConsumableEvent<T>> {
 
+	/**
+	 * Creates a LiveEvent initialized with the given {@code value}.
+	 *
+	 * @param value initial value
+	 */
+	public LiveEvent(T value) {
+		super(new ConsumableEvent<>(value));
+	}
+
+	/**
+	 * Creates a LiveEvent with no value assigned to it.
+	 */
+	public LiveEvent() {
+		super();
+	}
+
 	public void observeEvent(LifecycleOwner owner,
 			LiveEventHandler<T> handler) {
 		LiveEventObserver<T> observer = new LiveEventObserver<>(handler);

briar-android/src/main/java/org/briarproject/briar/android/viewmodel/MutableLiveEvent.java

@@ -5,6 +5,22 @@ import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
 @NotNullByDefault
 public class MutableLiveEvent<T> extends LiveEvent<T> {
 
+	/**
+	 * Creates a MutableLiveEvent initialized with the given {@code value}.
+	 *
+	 * @param value initial value
+	 */
+	public MutableLiveEvent(T value) {
+		super(value);
+	}
+
+	/**
+	 * Creates a MutableLiveEvent with no value assigned to it.
+	 */
+	public MutableLiveEvent() {
+		super();
+	}
+
 	public void postEvent(T value) {
 		super.postValue(new ConsumableEvent<>(value));
 	}

briar-android/src/main/java/org/briarproject/briar/android/widget/TouchInterceptingLinearLayout.java

@@ -0,0 +1,41 @@
+package org.briarproject.briar.android.widget;
+
+import android.annotation.TargetApi;
+import android.content.Context;
+import android.util.AttributeSet;
+import android.view.MotionEvent;
+import android.widget.LinearLayout;
+
+import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
+
+import androidx.annotation.Nullable;
+
+@NotNullByDefault
+public class TouchInterceptingLinearLayout extends LinearLayout {
+
+	public TouchInterceptingLinearLayout(Context context) {
+		super(context);
+	}
+
+	public TouchInterceptingLinearLayout(Context context,
+			@Nullable AttributeSet attrs) {
+		super(context, attrs);
+	}
+
+	public TouchInterceptingLinearLayout(Context context,
+			@Nullable AttributeSet attrs, int defStyleAttr) {
+		super(context, attrs, defStyleAttr);
+	}
+
+	@TargetApi(21)
+	public TouchInterceptingLinearLayout(Context context, AttributeSet attrs,
+			int defStyleAttr, int defStyleRes) {
+		super(context, attrs, defStyleAttr, defStyleRes);
+	}
+
+	@Override
+	public boolean onInterceptTouchEvent(MotionEvent e) {
+		onTouchEvent(e);
+		return false;
+	}
+}

briar-android/src/main/res/drawable/ic_image_broken.xml

@@ -1,6 +1,6 @@
 <vector xmlns:android="http://schemas.android.com/apk/res/android"
-        android:width="200dp"
-        android:height="200dp"
+        android:width="115dp"
+        android:height="115dp"
         android:viewportHeight="24.0"
         android:viewportWidth="24.0">
 	<path