Only add Tor transport properties to our social backup

Social backup restore activity

See merge request briar/briar!1444

.idea/codeStyles/Project.xml

@@ -31,15 +31,6 @@
       <option name="PACKAGES_TO_USE_STAR_IMPORTS">
         <value />
       </option>
-      <option name="PACKAGES_IMPORT_LAYOUT">
-        <value>
-          <package name="" alias="false" withSubpackages="true" />
-          <package name="java" alias="false" withSubpackages="true" />
-          <package name="javax" alias="false" withSubpackages="true" />
-          <package name="kotlin" alias="false" withSubpackages="true" />
-          <package name="" alias="true" withSubpackages="true" />
-        </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" />

bramble-api/src/main/java/org/briarproject/bramble/api/account/AccountManager.java

@@ -2,6 +2,7 @@ package org.briarproject.bramble.api.account;
 
 import org.briarproject.bramble.api.crypto.DecryptionException;
 import org.briarproject.bramble.api.crypto.SecretKey;
+import org.briarproject.bramble.api.identity.Identity;
 import org.briarproject.bramble.api.identity.IdentityManager;
 import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
 
@@ -43,6 +44,17 @@ public interface AccountManager {
 	 */
 	boolean createAccount(String name, String password);
 
+	/**
+	 * Restores a given identity by registering it with the
+	 * {@link IdentityManager}.  Creates a database key, encrypts it with the
+	 * given password and stores it on disk. {@link #accountExists()} will
+	 * return true after this method returns true.
+ 	 * @param identity
+	 * @param password
+	 * @return
+	 */
+	boolean restoreAccount(Identity identity, String password);
+
 	/**
 	 * Deletes all account state from disk. {@link #accountExists()} will
 	 * return false after this method returns.

bramble-api/src/main/java/org/briarproject/bramble/api/contact/ContactExchangeConstants.java

@@ -1,6 +1,6 @@
-package org.briarproject.bramble.contact;
+package org.briarproject.bramble.api.contact;
 
-interface ContactExchangeConstants {
+public interface ContactExchangeConstants {
 
 	/**
 	 * The current version of the contact exchange protocol.

bramble-api/src/main/java/org/briarproject/bramble/api/contact/ContactExchangeCrypto.java

@@ -1,4 +1,4 @@
-package org.briarproject.bramble.contact;
+package org.briarproject.bramble.api.contact;
 
 import org.briarproject.bramble.api.crypto.PrivateKey;
 import org.briarproject.bramble.api.crypto.PublicKey;
@@ -6,7 +6,7 @@ import org.briarproject.bramble.api.crypto.SecretKey;
 import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
 
 @NotNullByDefault
-interface ContactExchangeCrypto {
+public interface ContactExchangeCrypto {
 
 	/**
 	 * Derives the header key for a contact exchange stream from the master key.

bramble-api/src/main/java/org/briarproject/bramble/api/contact/ContactExchangeRecordTypes.java

@@ -0,0 +1,9 @@
+package org.briarproject.bramble.api.contact;
+
+/**
+ * Record types for the contact exchange protocol.
+ */
+public interface ContactExchangeRecordTypes {
+
+	byte CONTACT_INFO = 0;
+}

bramble-api/src/main/java/org/briarproject/bramble/api/contact/ContactManager.java

@@ -3,6 +3,7 @@ package org.briarproject.bramble.api.contact;
 import org.briarproject.bramble.api.FormatException;
 import org.briarproject.bramble.api.Pair;
 import org.briarproject.bramble.api.UnsupportedVersionException;
+import org.briarproject.bramble.api.crypto.PublicKey;
 import org.briarproject.bramble.api.crypto.SecretKey;
 import org.briarproject.bramble.api.db.ContactExistsException;
 import org.briarproject.bramble.api.db.DbException;
@@ -48,6 +49,10 @@ public interface ContactManager {
 			SecretKey rootKey, long timestamp, boolean alice, boolean verified,
 			boolean active) throws DbException;
 
+	ContactId addContact(Transaction txn, Author remote, AuthorId local,
+			PublicKey handshake, boolean verified)
+			throws DbException, GeneralSecurityException;
+
 	/**
 	 * Stores a contact associated with the given local and remote pseudonyms,
 	 * replacing the given pending contact, derives and stores handshake mode
@@ -205,6 +210,18 @@ public interface ContactManager {
 	void setContactAlias(ContactId c, @Nullable String alias)
 			throws DbException;
 
+	/**
+	 * Sets the contact's handshake public key
+	 */
+	void setHandshakePublicKey(Transaction txn, ContactId c,
+			PublicKey handshakePublicKey) throws DbException;
+
+	/**
+	 * Sets the contact's handshake public key
+	 */
+	void setHandshakePublicKey(ContactId c, PublicKey handshakePublicKey)
+			throws DbException;
+
 	/**
 	 * Returns true if a contact with this {@code remoteAuthorId} belongs to
 	 * the local pseudonym with this {@code localAuthorId}.

bramble-api/src/main/java/org/briarproject/bramble/api/contact/HandshakeManager.java

@@ -24,6 +24,19 @@ public interface HandshakeManager {
 	HandshakeResult handshake(PendingContactId p, InputStream in,
 			StreamWriter out) throws DbException, IOException;
 
+	/**
+	 * Handshakes with the given contact. Returns an ephemeral master key
+	 * authenticated with both parties' handshake key pairs and a flag
+	 * indicating whether the local peer is Alice or Bob.
+	 *
+	 * @param in An incoming stream for the handshake, which must be secured in
+	 * handshake mode
+	 * @param out An outgoing stream for the handshake, which must be secured
+	 * in handshake mode
+	 */
+	HandshakeResult handshake(ContactId c, InputStream in, StreamWriter out)
+			throws DbException, IOException;
+
 	class HandshakeResult {
 
 		private final SecretKey masterKey;

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

@@ -1,12 +1,11 @@
-package org.briarproject.bramble.crypto;
+package org.briarproject.bramble.api.crypto;
 
-import org.briarproject.bramble.api.crypto.SecretKey;
 import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
 
 import java.security.GeneralSecurityException;
 
 @NotNullByDefault
-interface AuthenticatedCipher {
+public interface AuthenticatedCipher {
 
 	/**
 	 * Initializes this cipher for encryption or decryption with a key and an

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

@@ -546,6 +546,11 @@ public interface DatabaseComponent extends TransactionManager {
 	void setContactAlias(Transaction txn, ContactId c, @Nullable String alias)
 			throws DbException;
 
+	/**
+	 * Sets the remote handshake public key for a given contact
+	 */
+	void setHandshakePublicKey(Transaction txn, ContactId c, PublicKey handshakePublicKey) throws DbException;
+
 	/**
 	 * Sets the given group's visibility to the given contact.
 	 */

bramble-api/src/main/java/org/briarproject/bramble/api/identity/IdentityManager.java

@@ -26,6 +26,11 @@ public interface IdentityManager {
 	 */
 	void registerIdentity(Identity i);
 
+	/**
+	 * Returns the cached local identity or loads it from the database.
+	 */
+	Identity getIdentity(Transaction txn) throws DbException;
+
 	/**
 	 * Returns the cached local identity or loads it from the database.
 	 */

bramble-api/src/main/java/org/briarproject/bramble/api/properties/TransportPropertyManager.java

@@ -74,6 +74,13 @@ public interface TransportPropertyManager {
 	TransportProperties getRemoteProperties(ContactId c, TransportId t)
 			throws DbException;
 
+	/**
+	 * Returns the remote transport properties for the given contact and
+	 * transport.
+	 */
+	TransportProperties getRemoteProperties(Transaction txn, ContactId c,
+			TransportId t) throws DbException;
+
 	/**
 	 * Merges the given properties with the existing local properties for the
 	 * given transport.

bramble-api/src/main/java/org/briarproject/bramble/api/transport/KeyManager.java

@@ -35,6 +35,20 @@ public interface KeyManager {
 			ContactId c, SecretKey rootKey, long timestamp, boolean alice,
 			boolean active) throws DbException;
 
+	/**
+	 * Derives and stores a set of rotation mode transport keys for
+	 * communicating with the given contact over each transport and returns the
+	 * key set IDs.
+	 * <p/>
+	 * {@link StreamContext StreamContexts} for the contact can be created
+	 * after this method has returned.
+	 *
+	 * @param alice True if the local party is Alice
+	 * @param active Whether the derived keys can be used for outgoing streams
+	 */
+	Map<TransportId, KeySetId> addRotationKeys(ContactId c, SecretKey rootKey,
+			long timestamp, boolean alice, boolean active) throws DbException;
+
 	/**
 	 * Informs the key manager that a new contact has been added. Derives and
 	 * stores a set of handshake mode transport keys for communicating with the

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

@@ -176,6 +176,18 @@ class AccountManagerImpl implements AccountManager {
 		}
 	}
 
+	public boolean restoreAccount(Identity identity, String password) {
+		synchronized (stateChangeLock) {
+			if (hasDatabaseKey())
+				throw new AssertionError("Already have a database key");
+			identityManager.registerIdentity(identity);
+			SecretKey key = crypto.generateSecretKey();
+			if (!encryptAndStoreDatabaseKey(key, password)) return false;
+			databaseKey = key;
+			return true;
+		}
+	}
+
 	@GuardedBy("stateChangeLock")
 	private boolean encryptAndStoreDatabaseKey(SecretKey key, String password) {
 		byte[] plaintext = key.getBytes();

bramble-core/src/main/java/org/briarproject/bramble/connection/ConnectionManagerImpl.java

@@ -76,7 +76,7 @@ class ConnectionManagerImpl implements ConnectionManager {
 		ioExecutor.execute(new IncomingDuplexSyncConnection(keyManager,
 				connectionRegistry, streamReaderFactory, streamWriterFactory,
 				syncSessionFactory, transportPropertyManager, ioExecutor,
-				t, d));
+				t, d, handshakeManager));
 	}
 
 	@Override
@@ -101,7 +101,7 @@ class ConnectionManagerImpl implements ConnectionManager {
 		ioExecutor.execute(new OutgoingDuplexSyncConnection(keyManager,
 				connectionRegistry, streamReaderFactory, streamWriterFactory,
 				syncSessionFactory, transportPropertyManager, ioExecutor,
-				secureRandom, c, t, d));
+				secureRandom, handshakeManager, c, t, d));
 	}
 
 	@Override

bramble-core/src/main/java/org/briarproject/bramble/connection/DuplexSyncConnection.java

@@ -3,6 +3,7 @@ package org.briarproject.bramble.connection;
 import org.briarproject.bramble.api.connection.ConnectionRegistry;
 import org.briarproject.bramble.api.connection.InterruptibleConnection;
 import org.briarproject.bramble.api.contact.ContactId;
+import org.briarproject.bramble.api.contact.HandshakeManager;
 import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
 import org.briarproject.bramble.api.plugin.TransportConnectionReader;
 import org.briarproject.bramble.api.plugin.TransportConnectionWriter;

bramble-core/src/main/java/org/briarproject/bramble/connection/IncomingDuplexSyncConnection.java

@@ -2,6 +2,7 @@ package org.briarproject.bramble.connection;
 
 import org.briarproject.bramble.api.connection.ConnectionRegistry;
 import org.briarproject.bramble.api.contact.ContactId;
+import org.briarproject.bramble.api.contact.HandshakeManager;
 import org.briarproject.bramble.api.db.DbException;
 import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
 import org.briarproject.bramble.api.plugin.TransportId;
@@ -13,9 +14,11 @@ import org.briarproject.bramble.api.sync.SyncSessionFactory;
 import org.briarproject.bramble.api.transport.KeyManager;
 import org.briarproject.bramble.api.transport.StreamContext;
 import org.briarproject.bramble.api.transport.StreamReaderFactory;
+import org.briarproject.bramble.api.transport.StreamWriter;
 import org.briarproject.bramble.api.transport.StreamWriterFactory;
 
 import java.io.IOException;
+import java.io.InputStream;
 import java.util.concurrent.Executor;
 
 import static java.util.logging.Level.WARNING;
@@ -24,6 +27,10 @@ import static org.briarproject.bramble.util.LogUtils.logException;
 @NotNullByDefault
 class IncomingDuplexSyncConnection extends DuplexSyncConnection
 		implements Runnable {
+	private final HandshakeManager handshakeManager;
+
+	// FIXME: Exchange timestamp as part of handshake protocol?
+	private static final long TIMESTAMP = 1617235200; // 1 April 2021 00:00 UTC
 
 	IncomingDuplexSyncConnection(KeyManager keyManager,
 			ConnectionRegistry connectionRegistry,
@@ -32,14 +39,18 @@ class IncomingDuplexSyncConnection extends DuplexSyncConnection
 			SyncSessionFactory syncSessionFactory,
 			TransportPropertyManager transportPropertyManager,
 			Executor ioExecutor, TransportId transportId,
-			DuplexTransportConnection connection) {
+			DuplexTransportConnection connection,
+			HandshakeManager handshakeManager) {
 		super(keyManager, connectionRegistry, streamReaderFactory,
 				streamWriterFactory, syncSessionFactory,
 				transportPropertyManager, ioExecutor, transportId, connection);
+		this.handshakeManager = handshakeManager;
 	}
 
 	@Override
 	public void run() {
+		LOG.info("Running IncomingDuplexSyncConnection on transport " +
+				transportId.getString());
 		// Read and recognise the tag
 		StreamContext ctx = recogniseTag(reader, transportId);
 		if (ctx == null) {
@@ -54,10 +65,22 @@ class IncomingDuplexSyncConnection extends DuplexSyncConnection
 			return;
 		}
 		if (ctx.isHandshakeMode()) {
-			// TODO: Support handshake mode for contacts
-			LOG.warning("Received handshake tag, expected rotation mode");
-			onReadError(true);
-			return;
+			if (!performHandshake(ctx, contactId)) {
+				LOG.warning("Handshake failed");
+				return;
+			}
+			// Allocate a rotation mode stream context
+			ctx = allocateStreamContext(contactId, transportId);
+			if (ctx == null) {
+				LOG.warning("Could not allocate stream context");
+				onWriteError();
+				return;
+			}
+			if (ctx.isHandshakeMode()) {
+				LOG.warning("Got handshake mode context after handshaking");
+				onWriteError();
+				return;
+			}
 		}
 		connectionRegistry.registerIncomingConnection(contactId, transportId,
 				this);
@@ -103,5 +126,35 @@ class IncomingDuplexSyncConnection extends DuplexSyncConnection
 			onWriteError();
 		}
 	}
+
+	private boolean performHandshake(StreamContext ctxIn, ContactId contactId) {
+		LOG.info("Performing handshake (Incoming)");
+		// Allocate the outgoing stream context
+		StreamContext ctxOut =
+				allocateStreamContext(contactId, transportId);
+		if (ctxOut == null) {
+			LOG.warning("Could not allocate stream context");
+			onReadError(true);
+			return false;
+		}
+		try {
+			InputStream in = streamReaderFactory.createStreamReader(
+					reader.getInputStream(), ctxIn);
+			// Flush the output stream to send the outgoing stream header
+			StreamWriter out = streamWriterFactory.createStreamWriter(
+					writer.getOutputStream(), ctxOut);
+			out.getOutputStream().flush();
+			HandshakeManager.HandshakeResult result =
+					handshakeManager.handshake(contactId, in, out);
+			keyManager.addRotationKeys(contactId, result.getMasterKey(),
+					TIMESTAMP, result.isAlice(), true);
+			LOG.info("Rotation keys added");
+			return true;
+		} catch (IOException | DbException e) {
+			logException(LOG, WARNING, e);
+			onReadError(true);
+			return false;
+		}
+	}
 }
 

bramble-core/src/main/java/org/briarproject/bramble/connection/OutgoingDuplexSyncConnection.java

@@ -2,6 +2,7 @@ package org.briarproject.bramble.connection;
 
 import org.briarproject.bramble.api.connection.ConnectionRegistry;
 import org.briarproject.bramble.api.contact.ContactId;
+import org.briarproject.bramble.api.contact.HandshakeManager;
 import org.briarproject.bramble.api.db.DbException;
 import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
 import org.briarproject.bramble.api.plugin.TransportId;
@@ -14,9 +15,11 @@ import org.briarproject.bramble.api.sync.SyncSessionFactory;
 import org.briarproject.bramble.api.transport.KeyManager;
 import org.briarproject.bramble.api.transport.StreamContext;
 import org.briarproject.bramble.api.transport.StreamReaderFactory;
+import org.briarproject.bramble.api.transport.StreamWriter;
 import org.briarproject.bramble.api.transport.StreamWriterFactory;
 
 import java.io.IOException;
+import java.io.InputStream;
 import java.security.SecureRandom;
 import java.util.concurrent.Executor;
 
@@ -28,26 +31,38 @@ import static org.briarproject.bramble.util.LogUtils.logException;
 class OutgoingDuplexSyncConnection extends DuplexSyncConnection
 		implements Runnable {
 
+	// FIXME: Exchange timestamp as part of handshake protocol?
+	private static final long TIMESTAMP = 1617235200; // 1 April 2021 00:00 UTC
+
 	private final SecureRandom secureRandom;
+	private final HandshakeManager handshakeManager;
 	private final ContactId contactId;
 
-	OutgoingDuplexSyncConnection(KeyManager keyManager,
+	OutgoingDuplexSyncConnection(
+			KeyManager keyManager,
 			ConnectionRegistry connectionRegistry,
 			StreamReaderFactory streamReaderFactory,
 			StreamWriterFactory streamWriterFactory,
 			SyncSessionFactory syncSessionFactory,
 			TransportPropertyManager transportPropertyManager,
-			Executor ioExecutor, SecureRandom secureRandom, ContactId contactId,
-			TransportId transportId, DuplexTransportConnection connection) {
+			Executor ioExecutor,
+			SecureRandom secureRandom,
+			HandshakeManager handshakeManager,
+			ContactId contactId,
+			TransportId transportId,
+			DuplexTransportConnection connection) {
 		super(keyManager, connectionRegistry, streamReaderFactory,
 				streamWriterFactory, syncSessionFactory,
 				transportPropertyManager, ioExecutor, transportId, connection);
 		this.secureRandom = secureRandom;
+		this.handshakeManager = handshakeManager;
 		this.contactId = contactId;
 	}
 
 	@Override
 	public void run() {
+		LOG.info("Running OutgoingDuplexSyncConnection on transport " +
+				transportId.getString());
 		// Allocate a stream context
 		StreamContext ctx = allocateStreamContext(contactId, transportId);
 		if (ctx == null) {
@@ -56,10 +71,22 @@ class OutgoingDuplexSyncConnection extends DuplexSyncConnection
 			return;
 		}
 		if (ctx.isHandshakeMode()) {
-			// TODO: Support handshake mode for contacts
-			LOG.warning("Cannot use handshake mode stream context");
-			onWriteError();
-			return;
+			if (!performHandshake(ctx)) {
+				LOG.warning("Handshake failed");
+				return;
+			}
+			// Allocate a rotation mode stream context
+			ctx = allocateStreamContext(contactId, transportId);
+			if (ctx == null) {
+				LOG.warning("Could not allocate stream context");
+				onWriteError();
+				return;
+			}
+			if (ctx.isHandshakeMode()) {
+				LOG.warning("Got handshake mode context after handshaking");
+				onWriteError();
+				return;
+			}
 		}
 		// Start the incoming session on another thread
 		Priority priority = generatePriority();
@@ -127,6 +154,59 @@ class OutgoingDuplexSyncConnection extends DuplexSyncConnection
 		}
 	}
 
+	private boolean performHandshake(StreamContext ctxOut) {
+		LOG.info("Performing handshake (Outgoing)");
+		// Flush the output stream to send the outgoing stream header
+		StreamWriter out;
+		try {
+			out = streamWriterFactory.createStreamWriter(
+					writer.getOutputStream(), ctxOut);
+			out.getOutputStream().flush();
+		} catch (IOException e) {
+			logException(LOG, WARNING, e);
+			onWriteError();
+			return false;
+		}
+		// Read and recognise the tag
+		StreamContext ctxIn = recogniseTag(reader, transportId);
+		// Unrecognised tags are suspicious in this case
+		if (ctxIn == null) {
+			LOG.warning("Unrecognised tag for returning stream");
+			onReadError();
+			return false;
+		}
+		// Check that the stream comes from the expected contact
+		ContactId inContactId = ctxIn.getContactId();
+		if (contactId == null) {
+			LOG.warning("Expected contact tag, got rendezvous tag");
+			onReadError();
+			return false;
+		}
+		if (!inContactId.equals(contactId)) {
+			LOG.warning("Wrong contact ID for returning stream");
+			onReadError();
+			return false;
+		}
+		// TODO: Register the connection, close it if it's redundant
+		// Handshake and exchange contacts
+		try {
+			InputStream in = streamReaderFactory.createStreamReader(
+					reader.getInputStream(), ctxIn);
+			HandshakeManager.HandshakeResult result =
+					handshakeManager.handshake(contactId, in, out);
+			keyManager.addRotationKeys(contactId, result.getMasterKey(),
+					TIMESTAMP, result.isAlice(), true);
+			LOG.info("Rotation keys added");
+			return true;
+		} catch (IOException | DbException e) {
+			logException(LOG, WARNING, e);
+			onWriteError();
+			return false;
+		} finally {
+			// TODO: Unregister the connection
+		}
+	}
+
 	private void onReadError() {
 		// 'Recognised' is always true for outgoing connections
 		onReadError(true);

bramble-core/src/main/java/org/briarproject/bramble/contact/ContactExchangeCryptoImpl.java

@@ -1,5 +1,6 @@
 package org.briarproject.bramble.contact;
 
+import org.briarproject.bramble.api.contact.ContactExchangeCrypto;
 import org.briarproject.bramble.api.crypto.CryptoComponent;
 import org.briarproject.bramble.api.crypto.PrivateKey;
 import org.briarproject.bramble.api.crypto.PublicKey;
@@ -10,12 +11,12 @@ import java.security.GeneralSecurityException;
 
 import javax.inject.Inject;
 
-import static org.briarproject.bramble.contact.ContactExchangeConstants.ALICE_KEY_LABEL;
-import static org.briarproject.bramble.contact.ContactExchangeConstants.ALICE_NONCE_LABEL;
-import static org.briarproject.bramble.contact.ContactExchangeConstants.BOB_KEY_LABEL;
-import static org.briarproject.bramble.contact.ContactExchangeConstants.BOB_NONCE_LABEL;
-import static org.briarproject.bramble.contact.ContactExchangeConstants.PROTOCOL_VERSION;
-import static org.briarproject.bramble.contact.ContactExchangeConstants.SIGNING_LABEL;
+import static org.briarproject.bramble.api.contact.ContactExchangeConstants.ALICE_KEY_LABEL;
+import static org.briarproject.bramble.api.contact.ContactExchangeConstants.ALICE_NONCE_LABEL;
+import static org.briarproject.bramble.api.contact.ContactExchangeConstants.BOB_KEY_LABEL;
+import static org.briarproject.bramble.api.contact.ContactExchangeConstants.BOB_NONCE_LABEL;
+import static org.briarproject.bramble.api.contact.ContactExchangeConstants.PROTOCOL_VERSION;
+import static org.briarproject.bramble.api.contact.ContactExchangeConstants.SIGNING_LABEL;
 
 @NotNullByDefault
 class ContactExchangeCryptoImpl implements ContactExchangeCrypto {

bramble-core/src/main/java/org/briarproject/bramble/contact/ContactExchangeManagerImpl.java

@@ -4,6 +4,7 @@ import org.briarproject.bramble.api.FormatException;
 import org.briarproject.bramble.api.Predicate;
 import org.briarproject.bramble.api.client.ClientHelper;
 import org.briarproject.bramble.api.contact.Contact;
+import org.briarproject.bramble.api.contact.ContactExchangeCrypto;
 import org.briarproject.bramble.api.contact.ContactExchangeManager;
 import org.briarproject.bramble.api.contact.ContactId;
 import org.briarproject.bramble.api.contact.ContactManager;
@@ -47,8 +48,8 @@ import javax.inject.Inject;
 
 import static java.util.logging.Logger.getLogger;
 import static org.briarproject.bramble.api.identity.AuthorConstants.MAX_SIGNATURE_LENGTH;
-import static org.briarproject.bramble.contact.ContactExchangeConstants.PROTOCOL_VERSION;
-import static org.briarproject.bramble.contact.ContactExchangeRecordTypes.CONTACT_INFO;
+import static org.briarproject.bramble.api.contact.ContactExchangeConstants.PROTOCOL_VERSION;
+import static org.briarproject.bramble.api.contact.ContactExchangeRecordTypes.CONTACT_INFO;
 import static org.briarproject.bramble.util.ValidationUtils.checkLength;
 import static org.briarproject.bramble.util.ValidationUtils.checkSize;
 
@@ -81,7 +82,8 @@ class ContactExchangeManagerImpl implements ContactExchangeManager {
 	private final ContactManager contactManager;
 	private final IdentityManager identityManager;
 	private final TransportPropertyManager transportPropertyManager;
-	private final ContactExchangeCrypto contactExchangeCrypto;
+	private final org.briarproject.bramble.api.contact.ContactExchangeCrypto
+			contactExchangeCrypto;
 	private final StreamReaderFactory streamReaderFactory;
 	private final StreamWriterFactory streamWriterFactory;
 

bramble-core/src/main/java/org/briarproject/bramble/contact/ContactExchangeRecordTypes.java

@@ -1,9 +0,0 @@
-package org.briarproject.bramble.contact;
-
-/**
- * Record types for the contact exchange protocol.
- */
-interface ContactExchangeRecordTypes {
-
-	byte CONTACT_INFO = 0;
-}

bramble-core/src/main/java/org/briarproject/bramble/contact/ContactManagerImpl.java

@@ -9,6 +9,7 @@ import org.briarproject.bramble.api.contact.PendingContact;
 import org.briarproject.bramble.api.contact.PendingContactId;
 import org.briarproject.bramble.api.contact.PendingContactState;
 import org.briarproject.bramble.api.contact.event.PendingContactStateChangedEvent;
+import org.briarproject.bramble.api.crypto.CryptoConstants;
 import org.briarproject.bramble.api.crypto.KeyPair;
 import org.briarproject.bramble.api.crypto.PublicKey;
 import org.briarproject.bramble.api.crypto.SecretKey;
@@ -119,6 +120,18 @@ class ContactManagerImpl implements ContactManager, EventListener {
 						verified, active));
 	}
 
+	@Override
+	public ContactId addContact(Transaction txn, Author remote, AuthorId local,
+			PublicKey handshake, boolean verified)
+			throws DbException, GeneralSecurityException {
+		ContactId c = db.addContact(txn, remote, local, handshake, verified);
+		Contact contact = db.getContact(txn, c);
+		KeyPair ourKeyPair = identityManager.getHandshakeKeys(txn);
+		keyManager.addContact(txn, c, handshake, ourKeyPair);
+		for (ContactHook hook : hooks) hook.addingContact(txn, contact);
+		return c;
+	}
+
 	@Override
 	public String getHandshakeLink() throws DbException {
 		KeyPair keyPair = db.transactionWithResult(true,
@@ -234,6 +247,23 @@ class ContactManagerImpl implements ContactManager, EventListener {
 		db.transaction(false, txn -> setContactAlias(txn, c, alias));
 	}
 
+	@Override
+	public void setHandshakePublicKey(Transaction txn, ContactId c,
+			PublicKey handshakePublicKey) throws DbException {
+		if (handshakePublicKey.getKeyType() !=
+				CryptoConstants.KEY_TYPE_AGREEMENT) {
+			throw new IllegalArgumentException();
+		}
+		db.setHandshakePublicKey(txn, c, handshakePublicKey);
+	}
+
+	@Override
+	public void setHandshakePublicKey(ContactId c, PublicKey handshakePublicKey)
+			throws DbException {
+		db.transaction(false,
+				txn -> setHandshakePublicKey(txn, c, handshakePublicKey));
+	}
+
 	@Override
 	public boolean contactExists(Transaction txn, AuthorId remoteAuthorId,
 			AuthorId localAuthorId) throws DbException {

bramble-core/src/main/java/org/briarproject/bramble/contact/ContactModule.java

@@ -1,5 +1,6 @@
 package org.briarproject.bramble.contact;
 
+import org.briarproject.bramble.api.contact.ContactExchangeCrypto;
 import org.briarproject.bramble.api.contact.ContactExchangeManager;
 import org.briarproject.bramble.api.contact.ContactManager;
 import org.briarproject.bramble.api.contact.HandshakeManager;

bramble-core/src/main/java/org/briarproject/bramble/contact/HandshakeManagerImpl.java

@@ -3,6 +3,8 @@ package org.briarproject.bramble.contact;
 import org.briarproject.bramble.api.FormatException;
 import org.briarproject.bramble.api.Pair;
 import org.briarproject.bramble.api.Predicate;
+import org.briarproject.bramble.api.contact.Contact;
+import org.briarproject.bramble.api.contact.ContactId;
 import org.briarproject.bramble.api.contact.ContactManager;
 import org.briarproject.bramble.api.contact.HandshakeManager;
 import org.briarproject.bramble.api.contact.PendingContact;
@@ -88,6 +90,27 @@ class HandshakeManagerImpl implements HandshakeManager {
 		});
 		PublicKey theirStaticPublicKey = keys.getFirst();
 		KeyPair ourStaticKeyPair = keys.getSecond();
+		return handshake(theirStaticPublicKey, ourStaticKeyPair, in, out);
+	}
+
+	@Override
+	public HandshakeResult handshake(ContactId c, InputStream in,
+			StreamWriter out) throws DbException, IOException {
+		Pair<PublicKey, KeyPair> keys = db.transactionWithResult(true, txn -> {
+			Contact contact = contactManager.getContact(txn, c);
+			PublicKey handshakePublicKey = contact.getHandshakePublicKey();
+			if (handshakePublicKey == null) throw new DbException();
+			KeyPair keyPair = identityManager.getHandshakeKeys(txn);
+			return new Pair<>(handshakePublicKey, keyPair);
+		});
+		PublicKey theirStaticPublicKey = keys.getFirst();
+		KeyPair ourStaticKeyPair = keys.getSecond();
+		return handshake(theirStaticPublicKey, ourStaticKeyPair, in, out);
+	}
+
+	private HandshakeResult handshake(PublicKey theirStaticPublicKey,
+			KeyPair ourStaticKeyPair, InputStream in, StreamWriter out)
+			throws IOException {
 		boolean alice = transportCrypto.isAlice(theirStaticPublicKey,
 				ourStaticKeyPair);
 		RecordReader recordReader = recordReaderFactory.createRecordReader(in);

bramble-core/src/main/java/org/briarproject/bramble/crypto/CryptoComponentImpl.java

@@ -6,6 +6,7 @@ import net.i2p.crypto.eddsa.KeyPairGenerator;
 
 import org.briarproject.bramble.api.crypto.AgreementPrivateKey;
 import org.briarproject.bramble.api.crypto.AgreementPublicKey;
+import org.briarproject.bramble.api.crypto.AuthenticatedCipher;
 import org.briarproject.bramble.api.crypto.CryptoComponent;
 import org.briarproject.bramble.api.crypto.DecryptionException;
 import org.briarproject.bramble.api.crypto.KeyPair;

bramble-core/src/main/java/org/briarproject/bramble/crypto/CryptoModule.java

@@ -1,5 +1,6 @@
 package org.briarproject.bramble.crypto;
 
+import org.briarproject.bramble.api.crypto.AuthenticatedCipher;
 import org.briarproject.bramble.api.crypto.CryptoComponent;
 import org.briarproject.bramble.api.crypto.KeyAgreementCrypto;
 import org.briarproject.bramble.api.crypto.PasswordStrengthEstimator;

bramble-core/src/main/java/org/briarproject/bramble/crypto/StreamDecrypterFactoryImpl.java

@@ -1,5 +1,6 @@
 package org.briarproject.bramble.crypto;
 
+import org.briarproject.bramble.api.crypto.AuthenticatedCipher;
 import org.briarproject.bramble.api.crypto.SecretKey;
 import org.briarproject.bramble.api.crypto.StreamDecrypter;
 import org.briarproject.bramble.api.crypto.StreamDecrypterFactory;

bramble-core/src/main/java/org/briarproject/bramble/crypto/StreamDecrypterImpl.java

@@ -1,6 +1,7 @@
 package org.briarproject.bramble.crypto;
 
 import org.briarproject.bramble.api.FormatException;
+import org.briarproject.bramble.api.crypto.AuthenticatedCipher;
 import org.briarproject.bramble.api.crypto.SecretKey;
 import org.briarproject.bramble.api.crypto.StreamDecrypter;
 import org.briarproject.bramble.api.nullsafety.NotNullByDefault;

bramble-core/src/main/java/org/briarproject/bramble/crypto/StreamEncrypterFactoryImpl.java

@@ -1,5 +1,6 @@
 package org.briarproject.bramble.crypto;
 
+import org.briarproject.bramble.api.crypto.AuthenticatedCipher;
 import org.briarproject.bramble.api.crypto.CryptoComponent;
 import org.briarproject.bramble.api.crypto.SecretKey;
 import org.briarproject.bramble.api.crypto.StreamEncrypter;

bramble-core/src/main/java/org/briarproject/bramble/crypto/StreamEncrypterImpl.java

@@ -1,5 +1,6 @@
 package org.briarproject.bramble.crypto;
 
+import org.briarproject.bramble.api.crypto.AuthenticatedCipher;
 import org.briarproject.bramble.api.crypto.SecretKey;
 import org.briarproject.bramble.api.crypto.StreamEncrypter;
 import org.briarproject.bramble.api.nullsafety.NotNullByDefault;

bramble-core/src/main/java/org/briarproject/bramble/crypto/XSalsa20Poly1305AuthenticatedCipher.java

@@ -1,5 +1,6 @@
 package org.briarproject.bramble.crypto;
 
+import org.briarproject.bramble.api.crypto.AuthenticatedCipher;
 import org.briarproject.bramble.api.crypto.SecretKey;
 import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
 import org.spongycastle.crypto.DataLengthException;

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

@@ -32,6 +32,7 @@ import org.briarproject.bramble.api.transport.KeySetId;
 import org.briarproject.bramble.api.transport.TransportKeySet;
 import org.briarproject.bramble.api.transport.TransportKeys;
 
+import java.sql.Connection;
 import java.util.Collection;
 import java.util.List;
 import java.util.Map;
@@ -695,6 +696,11 @@ interface Database<T> {
 	void setHandshakeKeyPair(T txn, AuthorId local, PublicKey publicKey,
 			PrivateKey privateKey) throws DbException;
 
+	/**
+	 * Sets the handshake public key for a given contact
+	 */
+	void setHandshakePublicKey(T txn, ContactId c, PublicKey handshakePublicKey) throws DbException;
+
 	/**
 	 * Marks the given message as permanent, i.e. not temporary.
 	 */

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

@@ -1040,6 +1040,15 @@ class DatabaseComponentImpl<T> implements DatabaseComponent {
 		}
 	}
 
+	@Override
+	public void setHandshakePublicKey(Transaction transaction, ContactId c, PublicKey handshakePublicKey) throws DbException {
+		if (transaction.isReadOnly()) throw new IllegalArgumentException();
+		T txn = unbox(transaction);
+		if (!db.containsContact(txn, c))
+			throw new NoSuchContactException();
+		db.setHandshakePublicKey(txn, c, handshakePublicKey);
+	}
+
 	@Override
 	public void setHandshakeKeyPair(Transaction transaction, AuthorId local,
 			PublicKey publicKey, PrivateKey privateKey) throws DbException {

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

@@ -3058,6 +3058,23 @@ abstract class JdbcDatabase implements Database<Connection> {
 		}
 	}
 
+	@Override
+	public void setHandshakePublicKey(Connection txn, ContactId c, PublicKey handshakePublicKey) throws DbException {
+		PreparedStatement ps = null;
+		try {
+			String sql = "UPDATE contacts SET handshakePublicKey = ? WHERE contactId = ?";
+			ps = txn.prepareStatement(sql);
+			ps.setBytes(1, handshakePublicKey.getEncoded());
+			ps.setInt(2, c.getInt());
+			int affected = ps.executeUpdate();
+			if (affected < 0 || affected > 1) throw new DbStateException();
+			ps.close();
+		} catch (SQLException e) {
+			tryToClose(ps, LOG, WARNING);
+			throw new DbException(e);
+		}
+	}
+
 	@Override
 	public void setGroupVisibility(Connection txn, ContactId c, GroupId g,
 			boolean shared) throws DbException {

bramble-core/src/main/java/org/briarproject/bramble/identity/IdentityManagerImpl.java

@@ -118,6 +118,11 @@ class IdentityManagerImpl implements IdentityManager, OpenDatabaseHook {
 		return cached.getLocalAuthor();
 	}
 
+	@Override
+	public Identity getIdentity(Transaction txn) throws DbException {
+		return getCachedIdentity(txn);
+	}
+
 	@Override
 	public LocalAuthor getLocalAuthor(Transaction txn) throws DbException {
 		return getCachedIdentity(txn).getLocalAuthor();

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

@@ -127,6 +127,7 @@ class KeyAgreementConnector {
 		List<Pair<DuplexPlugin, BdfList>> transports = new ArrayList<>();
 		for (TransportId id : PREFERRED_TRANSPORTS) {
 			TransportDescriptor d = descriptors.get(id);
+			LOG.info("id: " + id + " d: " + d);
 			Plugin p = pluginManager.getPlugin(id);
 			if (d != null && p instanceof DuplexPlugin) {
 				if (LOG.isLoggable(INFO))
@@ -137,6 +138,9 @@ class KeyAgreementConnector {
 
 		// TODO: If we don't have any transports in common with the peer,
 		//  warn the user and give up (#1224)
+        if (transports.isEmpty()) {
+           LOG.info("No transports found");
+        }
 
 		if (!transports.isEmpty()) {
 			byte[] commitment = remotePayload.getCommitment();

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

@@ -34,12 +34,12 @@ class KeyAgreementTransport {
 			Logger.getLogger(KeyAgreementTransport.class.getName());
 
 	// Accept records with current protocol version, known record type
-	private static Predicate<Record> ACCEPT = r ->
+	private static final Predicate<Record> ACCEPT = r ->
 			r.getProtocolVersion() == PROTOCOL_VERSION &&
 					isKnownRecordType(r.getRecordType());
 
 	// Ignore records with current protocol version, unknown record type
-	private static Predicate<Record> IGNORE = r ->
+	private static final Predicate<Record> IGNORE = r ->
 			r.getProtocolVersion() == PROTOCOL_VERSION &&
 					!isKnownRecordType(r.getRecordType());
 

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

@@ -294,7 +294,13 @@ class TransportPropertyManagerImpl implements TransportPropertyManager,
 	public TransportProperties getRemoteProperties(ContactId c, TransportId t)
 			throws DbException {
 		return db.transactionWithResult(true, txn ->
-				getRemoteProperties(txn, db.getContact(txn, c), t));
+				getRemoteProperties(txn, c, t));
+	}
+
+	@Override
+	public TransportProperties getRemoteProperties(Transaction txn,
+			ContactId c, TransportId t) throws DbException {
+		return getRemoteProperties(txn, db.getContact(txn, c), t);
 	}
 
 	@Override

bramble-core/src/main/java/org/briarproject/bramble/transport/KeyManagerImpl.java

@@ -101,9 +101,9 @@ class KeyManagerImpl implements KeyManager, Service, EventListener {
 	}
 
 	@Override
-	public Map<TransportId, KeySetId> addRotationKeys(
-			Transaction txn, ContactId c, SecretKey rootKey, long timestamp,
-			boolean alice, boolean active) throws DbException {
+	public Map<TransportId, KeySetId> addRotationKeys(Transaction txn,
+			ContactId c, SecretKey rootKey, long timestamp, boolean alice,
+			boolean active) throws DbException {
 		Map<TransportId, KeySetId> ids = new HashMap<>();
 		for (Entry<TransportId, TransportKeyManager> e : managers.entrySet()) {
 			TransportId t = e.getKey();
@@ -114,6 +114,14 @@ class KeyManagerImpl implements KeyManager, Service, EventListener {
 		return ids;
 	}
 
+	@Override
+	public Map<TransportId, KeySetId> addRotationKeys(ContactId c,
+			SecretKey rootKey, long timestamp, boolean alice, boolean active)
+			throws DbException {
+		return db.transactionWithResult(false, txn ->
+				addRotationKeys(txn, c, rootKey, timestamp, alice, active));
+	}
+
 	@Override
 	public Map<TransportId, KeySetId> addContact(Transaction txn, ContactId c,
 			PublicKey theirPublicKey, KeyPair ourKeyPair)
@@ -137,7 +145,7 @@ class KeyManagerImpl implements KeyManager, Service, EventListener {
 			PendingContactId p, PublicKey theirPublicKey, KeyPair ourKeyPair)
 			throws DbException, GeneralSecurityException {
 		SecretKey staticMasterKey = transportCrypto
-					.deriveStaticMasterKey(theirPublicKey, ourKeyPair);
+				.deriveStaticMasterKey(theirPublicKey, ourKeyPair);
 		SecretKey rootKey =
 				transportCrypto.deriveHandshakeRootKey(staticMasterKey, true);
 		boolean alice = transportCrypto.isAlice(theirPublicKey, ourKeyPair);

bramble-core/src/test/java/org/briarproject/bramble/crypto/StreamDecrypterImplTest.java

@@ -1,5 +1,6 @@
 package org.briarproject.bramble.crypto;
 
+import org.briarproject.bramble.api.crypto.AuthenticatedCipher;
 import org.briarproject.bramble.api.crypto.SecretKey;
 import org.briarproject.bramble.test.BrambleTestCase;
 import org.briarproject.bramble.test.TestUtils;

bramble-core/src/test/java/org/briarproject/bramble/crypto/StreamEncrypterImplTest.java

@@ -1,5 +1,6 @@
 package org.briarproject.bramble.crypto;
 
+import org.briarproject.bramble.api.crypto.AuthenticatedCipher;
 import org.briarproject.bramble.api.crypto.SecretKey;
 import org.briarproject.bramble.test.BrambleTestCase;
 import org.briarproject.bramble.test.TestUtils;

bramble-core/src/test/java/org/briarproject/bramble/crypto/TestAuthenticatedCipher.java

@@ -1,5 +1,6 @@
 package org.briarproject.bramble.crypto;
 
+import org.briarproject.bramble.api.crypto.AuthenticatedCipher;
 import org.briarproject.bramble.api.crypto.SecretKey;
 import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
 

bramble-core/src/test/java/org/briarproject/bramble/crypto/XSalsa20Poly1305AuthenticatedCipherTest.java

@@ -1,5 +1,6 @@
 package org.briarproject.bramble.crypto;
 
+import org.briarproject.bramble.api.crypto.AuthenticatedCipher;
 import org.briarproject.bramble.api.crypto.SecretKey;
 import org.briarproject.bramble.test.BrambleTestCase;
 import org.briarproject.bramble.util.StringUtils;

briar-android/build.gradle

@@ -28,7 +28,7 @@ android {
 		targetSdkVersion 29
 		versionCode 10218
 		versionName "1.2.18"
-		applicationId "org.briarproject.briar.android"
+		applicationId "org.briarproject.briar.socialbackup"
 
 		vectorDrawables.useSupportLibrary = true
 		buildConfigField "String", "GitHash",
@@ -106,6 +106,7 @@ dependencies {
 	implementation 'androidx.constraintlayout:constraintlayout:2.0.4'
 	implementation 'com.google.android.material:material:1.2.1'
 	implementation 'androidx.recyclerview:recyclerview-selection:1.1.0-rc03'
+	implementation 'org.magmacollective.darkcrystal:dark-crystal-secret-sharing-wrapper:1.1.0'
 
 	implementation 'info.guardianproject.panic:panic:1.0'
 	implementation 'info.guardianproject.trustedintents:trustedintents:0.2'

briar-android/proguard-rules.txt

@@ -40,3 +40,5 @@
 
 # Dependency injection annotations, needed for UI tests on older API levels
 -keep class javax.inject.**
+
+-keep class com.sun.jna.** { *; }

briar-android/src/debug/res/values/strings.xml

@@ -1,5 +1,5 @@
 <?xml version="1.0" encoding="utf-8"?>
 <resources>
-	<string name="app_name" translatable="false">Briar Debug</string>
-	<string name="app_package" translatable="false">org.briarproject.briar.android.debug</string>
+	<string name="app_name" translatable="false">Briar SB Debug</string>
+	<string name="app_package" translatable="false">org.briarproject.briar.socialbackup.debug</string>
 </resources>

briar-android/src/main/AndroidManifest.xml

@@ -138,6 +138,51 @@
 			</intent-filter>
 		</activity>
 
+		<activity
+			android:name="org.briarproject.briar.android.account.NewOrRecoverActivity"
+			android:label="@string/activity_name_new_or_recover_account"
+			android:parentActivityName="org.briarproject.briar.android.login.StartupActivity">
+			<meta-data
+				android:name="android.support.PARENT_ACTIVITY"
+				android:value="org.briarproject.briar.android.login.StartupActivity" />
+		</activity>
+
+		<activity
+			android:name="org.briarproject.briar.android.socialbackup.DistributedBackupActivity"
+			android:label="@string/activity_name_distributed_backup"
+			android:parentActivityName="org.briarproject.briar.android.settings.SettingsActivity">
+			<meta-data
+				android:name="android.support.PARENT_ACTIVITY"
+				android:value="org.briarproject.briar.android.settings.SettingsActivity" />
+		</activity>
+
+		<activity
+			android:name="org.briarproject.briar.android.socialbackup.recover.CustodianReturnShardActivity"
+			android:label="@string/activity_name_custodian_help_recovery"
+			android:parentActivityName="org.briarproject.briar.android.conversation.ConversationActivity">
+			<meta-data
+				android:name="android.support.PARENT_ACTIVITY"
+				android:value="org.briarproject.briar.android.conversation.ConversationActivity" />
+		</activity>
+
+		<activity
+			android:name="org.briarproject.briar.android.socialbackup.recover.OwnerReturnShardActivity"
+			android:label="@string/activity_name_recovery"
+			android:parentActivityName="org.briarproject.briar.android.account.NewOrRecoverActivity">
+			<meta-data
+				android:name="android.support.PARENT_ACTIVITY"
+				android:value="org.briarproject.briar.android.account.NewOrRecoverActivity" />
+		</activity>
+
+		<activity
+			android:name="org.briarproject.briar.android.socialbackup.recover.RestoreAccountActivity"
+			android:label="@string/activity_name_restore_account"
+			android:parentActivityName="org.briarproject.briar.android.socialbackup.recover.OwnerReturnShardActivity">
+			<meta-data
+				android:name="android.support.PARENT_ACTIVITY"
+				android:value="org.briarproject.briar.android.socialbackup.recover.OwnerReturnShardActivity" />
+		</activity>
+
 		<activity
 			android:name="org.briarproject.briar.android.conversation.ConversationActivity"
 			android:label="@string/app_name"
@@ -342,7 +387,7 @@
 		</activity>
 
 		<activity
-			android:name="org.briarproject.briar.android.keyagreement.ContactExchangeActivity"
+			android:name="org.briarproject.briar.android.contact.add.nearby.AddNearbyContactActivity"
 			android:label="@string/add_contact_title"
 			android:parentActivityName="org.briarproject.briar.android.navdrawer.NavDrawerActivity"
 			android:theme="@style/BriarTheme.NoActionBar">

briar-android/src/main/java/org/briarproject/briar/android/AndroidComponent.java

@@ -8,11 +8,13 @@ import org.briarproject.bramble.BrambleCoreModule;
 import org.briarproject.bramble.account.BriarAccountModule;
 import org.briarproject.bramble.api.FeatureFlags;
 import org.briarproject.bramble.api.account.AccountManager;
+import org.briarproject.bramble.api.client.ClientHelper;
 import org.briarproject.bramble.api.connection.ConnectionRegistry;
 import org.briarproject.bramble.api.contact.ContactExchangeManager;
 import org.briarproject.bramble.api.contact.ContactManager;
 import org.briarproject.bramble.api.crypto.CryptoExecutor;
 import org.briarproject.bramble.api.crypto.PasswordStrengthEstimator;
+import org.briarproject.bramble.api.db.DatabaseComponent;
 import org.briarproject.bramble.api.db.DatabaseExecutor;
 import org.briarproject.bramble.api.db.TransactionManager;
 import org.briarproject.bramble.api.event.EventBus;
@@ -59,6 +61,7 @@ import org.briarproject.briar.api.privategroup.PrivateGroupFactory;
 import org.briarproject.briar.api.privategroup.PrivateGroupManager;
 import org.briarproject.briar.api.privategroup.invitation.GroupInvitationFactory;
 import org.briarproject.briar.api.privategroup.invitation.GroupInvitationManager;
+import org.briarproject.briar.api.socialbackup.SocialBackupManager;
 import org.briarproject.briar.api.test.TestDataCreator;
 
 import java.util.concurrent.Executor;
@@ -184,6 +187,12 @@ public interface AndroidComponent
 
 	Thread.UncaughtExceptionHandler exceptionHandler();
 
+	SocialBackupManager socialBackupManager();
+
+    DatabaseComponent databaseComponent();
+
+    ClientHelper clientHelper();
+
 	void inject(SignInReminderReceiver briarService);
 
 	void inject(BriarService briarService);

briar-android/src/main/java/org/briarproject/briar/android/AppModule.java

@@ -31,9 +31,9 @@ import org.briarproject.briar.android.account.DozeHelperModule;
 import org.briarproject.briar.android.account.LockManagerImpl;
 import org.briarproject.briar.android.account.SetupModule;
 import org.briarproject.briar.android.contact.ContactListModule;
+import org.briarproject.briar.android.contact.add.nearby.AddNearbyContactModule;
 import org.briarproject.briar.android.forum.ForumModule;
 import org.briarproject.briar.android.introduction.IntroductionModule;
-import org.briarproject.briar.android.keyagreement.ContactExchangeModule;
 import org.briarproject.briar.android.logging.LoggingModule;
 import org.briarproject.briar.android.login.LoginModule;
 import org.briarproject.briar.android.navdrawer.NavDrawerModule;
@@ -42,6 +42,8 @@ import org.briarproject.briar.android.privategroup.list.GroupListModule;
 import org.briarproject.briar.android.reporting.DevReportModule;
 import org.briarproject.briar.android.settings.SettingsModule;
 import org.briarproject.briar.android.sharing.SharingModule;
+import org.briarproject.briar.android.socialbackup.recover.CustodianReturnShardModule;
+import org.briarproject.briar.android.socialbackup.recover.OwnerReturnShardModule;
 import org.briarproject.briar.android.test.TestAvatarCreatorImpl;
 import org.briarproject.briar.android.viewmodel.ViewModelModule;
 import org.briarproject.briar.api.android.AndroidNotificationManager;
@@ -49,6 +51,7 @@ import org.briarproject.briar.api.android.DozeWatchdog;
 import org.briarproject.briar.api.android.LockManager;
 import org.briarproject.briar.api.android.ScreenFilterMonitor;
 import org.briarproject.briar.api.test.TestAvatarCreator;
+import org.briarproject.briar.socialbackup.AndroidDarkCrystalModule;
 
 import java.io.File;
 import java.security.GeneralSecurityException;
@@ -75,7 +78,7 @@ import static org.briarproject.briar.android.TestingConstants.IS_DEBUG_BUILD;
 @Module(includes = {
 		SetupModule.class,
 		DozeHelperModule.class,
-		ContactExchangeModule.class,
+		AddNearbyContactModule.class,
 		LoggingModule.class,
 		LoginModule.class,
 		NavDrawerModule.class,
@@ -83,12 +86,15 @@ import static org.briarproject.briar.android.TestingConstants.IS_DEBUG_BUILD;
 		SettingsModule.class,
 		DevReportModule.class,
 		ContactListModule.class,
+		AndroidDarkCrystalModule.class,
 		IntroductionModule.class,
 		// below need to be within same scope as ViewModelProvider.Factory
 		ForumModule.class,
 		GroupListModule.class,
 		GroupConversationModule.class,
 		SharingModule.class,
+		OwnerReturnShardModule.class,
+		CustodianReturnShardModule.class
 })
 public class AppModule {
 

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

@@ -2,7 +2,7 @@ package org.briarproject.briar.android.account;
 
 import android.content.Context;
 
-interface DozeHelper {
+public interface DozeHelper {
 
 	boolean needToShowDozeFragment(Context context);
 }

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

@@ -14,7 +14,7 @@ import static org.briarproject.briar.android.util.UiUtils.needsDozeWhitelisting;
 
 @UiThread
 @NotNullByDefault
-class DozeView extends PowerView {
+public class DozeView extends PowerView {
 
 	@Nullable
 	private Runnable onButtonClickListener;

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

@@ -21,7 +21,7 @@ import static android.os.Build.VERSION.SDK_INT;
 
 @UiThread
 @NotNullByDefault
-class HuaweiView extends PowerView {
+public class HuaweiView extends PowerView {
 
 	private final static String PACKAGE_NAME = "com.huawei.systemmanager";
 	private final static String CLASS_NAME =

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

@@ -0,0 +1,60 @@
+package org.briarproject.briar.android.account;
+
+import android.content.Intent;
+import android.os.Bundle;
+
+import org.briarproject.briar.R;
+import org.briarproject.briar.android.activity.ActivityComponent;
+import org.briarproject.briar.android.activity.BaseActivity;
+import org.briarproject.briar.android.fragment.BaseFragment;
+import org.briarproject.briar.android.socialbackup.recover.OwnerReturnShardActivity;
+
+import static android.content.Intent.FLAG_ACTIVITY_CLEAR_TASK;
+import static android.content.Intent.FLAG_ACTIVITY_CLEAR_TOP;
+import static android.content.Intent.FLAG_ACTIVITY_NEW_TASK;
+import static android.content.Intent.FLAG_ACTIVITY_TASK_ON_HOME;
+
+public class NewOrRecoverActivity extends BaseActivity implements
+		BaseFragment.BaseFragmentListener, SetupNewAccountChosenListener,
+		RecoverAccountListener {
+
+	@Override
+	public void injectActivity(ActivityComponent component) {
+		component.inject(this);
+	}
+
+	@Override
+	public void onCreate(Bundle state) {
+		super.onCreate(state);
+		// fade-in after splash screen instead of default animation
+		// TODO the fade in is not working
+		overridePendingTransition(R.anim.fade_in, R.anim.fade_out);
+		setContentView(R.layout.activity_fragment_container);
+		NewOrRecoverFragment fragment = NewOrRecoverFragment.newInstance();
+		showInitialFragment(fragment);
+	}
+
+	@Override
+	public void setupNewAccountChosen() {
+		finish();
+		Intent i = new Intent(this, SetupActivity.class);
+		i.addFlags(FLAG_ACTIVITY_NEW_TASK | FLAG_ACTIVITY_CLEAR_TOP |
+				FLAG_ACTIVITY_CLEAR_TASK | FLAG_ACTIVITY_TASK_ON_HOME);
+		startActivity(i);
+	}
+
+	@Override
+	public void recoverAccountChosen() {
+		finish();
+		Intent i = new Intent(this, OwnerReturnShardActivity.class);
+		i.addFlags(FLAG_ACTIVITY_NEW_TASK | FLAG_ACTIVITY_CLEAR_TOP |
+				FLAG_ACTIVITY_CLEAR_TASK | FLAG_ACTIVITY_TASK_ON_HOME);
+		startActivity(i);
+	}
+
+	@Override
+	@Deprecated
+	public void runOnDbThread(Runnable runnable) {
+		throw new RuntimeException("Don't use this deprecated method here.");
+	}
+}

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

@@ -0,0 +1,70 @@
+package org.briarproject.briar.android.account;
+
+import android.content.Context;
+import android.os.Bundle;
+import android.view.LayoutInflater;
+import android.view.View;
+import android.view.ViewGroup;
+import android.widget.Button;
+
+import org.briarproject.briar.R;
+import org.briarproject.briar.android.activity.ActivityComponent;
+import org.briarproject.briar.android.fragment.BaseFragment;
+
+import androidx.annotation.NonNull;
+import androidx.annotation.Nullable;
+
+public class NewOrRecoverFragment extends BaseFragment {
+
+	public static final String TAG = NewOrRecoverFragment.class.getName();
+
+	protected SetupNewAccountChosenListener setupNewAccountListener;
+	protected RecoverAccountListener recoverAccountListener;
+
+	public static NewOrRecoverFragment newInstance() {
+		Bundle bundle = new Bundle();
+		NewOrRecoverFragment fragment = new NewOrRecoverFragment();
+		fragment.setArguments(bundle);
+		return fragment;
+	}
+	@Override
+	public void onCreate(@Nullable Bundle savedInstanceState) {
+		super.onCreate(savedInstanceState);
+		requireActivity().setTitle(R.string.setup_title);
+	}
+
+	@Nullable
+	@Override
+	public View onCreateView(@NonNull LayoutInflater inflater, @Nullable
+			ViewGroup container, @Nullable Bundle savedInstanceState) {
+		View view = inflater.inflate(R.layout.fragment_new_or_recover,
+				container, false);
+		Button newAccountButton = view.findViewById(R.id.buttonSetupNewAccount);
+		newAccountButton.setOnClickListener(e -> {
+			setupNewAccountListener.setupNewAccountChosen();
+		});
+
+		Button recoverAccountButton = view.findViewById(R.id.buttonRestoreAccount);
+		recoverAccountButton.setOnClickListener(e -> {
+			recoverAccountListener.recoverAccountChosen();
+		});
+		return view;
+	}
+
+	@Override
+	public void onAttach(Context context) {
+		super.onAttach(context);
+		setupNewAccountListener = (SetupNewAccountChosenListener) context;
+		recoverAccountListener = (RecoverAccountListener) context;
+	}
+
+	@Override
+	public String getUniqueTag() {
+		return TAG;
+	}
+
+	@Override
+	public void injectFragment(ActivityComponent component) {
+		component.inject(this);
+	}
+}

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

@@ -24,7 +24,7 @@ import static org.briarproject.briar.android.util.UiUtils.showOnboardingDialog;
 
 @UiThread
 @NotNullByDefault
-abstract class PowerView extends ConstraintLayout {
+public abstract class PowerView extends ConstraintLayout {
 
 	private final TextView textView;
 	private final ImageView checkImage;
@@ -156,7 +156,7 @@ abstract class PowerView extends ConstraintLayout {
 		};
 	}
 
-	interface OnCheckedChangedListener {
+	public interface OnCheckedChangedListener {
 		void onCheckedChanged();
 	}
 

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

@@ -0,0 +1,8 @@
+package org.briarproject.briar.android.account;
+
+import androidx.annotation.UiThread;
+
+public interface RecoverAccountListener {
+	@UiThread
+	void recoverAccountChosen();
+}

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

@@ -0,0 +1,8 @@
+package org.briarproject.briar.android.account;
+
+import androidx.annotation.UiThread;
+
+public interface SetupNewAccountChosenListener {
+	@UiThread
+	void setupNewAccountChosen();
+}

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

@@ -29,6 +29,7 @@ import static org.briarproject.briar.android.account.SetupViewModel.State.SET_PA
 
 @MethodsNotNullByDefault
 @ParametersNotNullByDefault
+public
 class SetupViewModel extends AndroidViewModel {
 	enum State {AUTHOR_NAME, SET_PASSWORD, DOZE, CREATED, FAILED}
 

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

@@ -2,10 +2,13 @@ package org.briarproject.briar.android.activity;
 
 import android.app.Activity;
 
+import org.briarproject.bramble.api.db.DatabaseComponent;
 import org.briarproject.briar.android.AndroidComponent;
 import org.briarproject.briar.android.StartupFailureActivity;
 import org.briarproject.briar.android.account.AuthorNameFragment;
 import org.briarproject.briar.android.account.DozeFragment;
+import org.briarproject.briar.android.account.NewOrRecoverActivity;
+import org.briarproject.briar.android.account.NewOrRecoverFragment;
 import org.briarproject.briar.android.account.SetPasswordFragment;
 import org.briarproject.briar.android.account.SetupActivity;
 import org.briarproject.briar.android.account.UnlockActivity;
@@ -21,6 +24,10 @@ import org.briarproject.briar.android.blog.RssFeedImportActivity;
 import org.briarproject.briar.android.blog.RssFeedManageActivity;
 import org.briarproject.briar.android.blog.WriteBlogPostActivity;
 import org.briarproject.briar.android.contact.ContactListFragment;
+import org.briarproject.briar.android.contact.add.nearby.AddNearbyContactActivity;
+import org.briarproject.briar.android.contact.add.nearby.AddNearbyContactErrorFragment;
+import org.briarproject.briar.android.contact.add.nearby.AddNearbyContactFragment;
+import org.briarproject.briar.android.contact.add.nearby.AddNearbyContactIntroFragment;
 import org.briarproject.briar.android.contact.add.remote.AddContactActivity;
 import org.briarproject.briar.android.contact.add.remote.LinkExchangeFragment;
 import org.briarproject.briar.android.contact.add.remote.NicknameFragment;
@@ -36,10 +43,6 @@ import org.briarproject.briar.android.fragment.ScreenFilterDialogFragment;
 import org.briarproject.briar.android.introduction.ContactChooserFragment;
 import org.briarproject.briar.android.introduction.IntroductionActivity;
 import org.briarproject.briar.android.introduction.IntroductionMessageFragment;
-import org.briarproject.briar.android.keyagreement.ContactExchangeActivity;
-import org.briarproject.briar.android.keyagreement.ContactExchangeErrorFragment;
-import org.briarproject.briar.android.keyagreement.KeyAgreementActivity;
-import org.briarproject.briar.android.keyagreement.KeyAgreementFragment;
 import org.briarproject.briar.android.login.ChangePasswordActivity;
 import org.briarproject.briar.android.login.OpenDatabaseFragment;
 import org.briarproject.briar.android.login.PasswordFragment;
@@ -77,20 +80,42 @@ import org.briarproject.briar.android.sharing.ShareBlogFragment;
 import org.briarproject.briar.android.sharing.ShareForumActivity;
 import org.briarproject.briar.android.sharing.ShareForumFragment;
 import org.briarproject.briar.android.sharing.SharingModule;
+import org.briarproject.briar.android.socialbackup.recover.CustodianRecoveryModeExplainerFragment;
+import org.briarproject.briar.android.socialbackup.CustodianSelectorFragment;
+import org.briarproject.briar.android.socialbackup.DistributedBackupActivity;
+import org.briarproject.briar.android.socialbackup.ExistingBackupFragment;
+import org.briarproject.briar.android.socialbackup.recover.CustodianReturnShardActivity;
+import org.briarproject.briar.android.socialbackup.recover.CustodianReturnShardErrorFragment;
+import org.briarproject.briar.android.socialbackup.recover.CustodianReturnShardFragment;
+import org.briarproject.briar.android.socialbackup.recover.CustodianReturnShardSuccessFragment;
+import org.briarproject.briar.android.socialbackup.recover.OwnerRecoveryModeErrorFragment;
+import org.briarproject.briar.android.socialbackup.recover.OwnerRecoveryModeExplainerFragment;
+import org.briarproject.briar.android.socialbackup.recover.OwnerRecoveryModeMainFragment;
+import org.briarproject.briar.android.socialbackup.recover.OwnerReturnShardActivity;
+import org.briarproject.briar.android.socialbackup.recover.OwnerReturnShardFragment;
+import org.briarproject.briar.android.socialbackup.ShardsSentFragment;
+import org.briarproject.briar.android.socialbackup.ThresholdSelectorFragment;
+import org.briarproject.briar.android.socialbackup.creation.CreateBackupModule;
+import org.briarproject.briar.android.socialbackup.recover.OwnerReturnShardSuccessFragment;
+import org.briarproject.briar.android.socialbackup.recover.RestoreAccountActivity;
+import org.briarproject.briar.android.socialbackup.recover.RestoreAccountDozeFragment;
+import org.briarproject.briar.android.socialbackup.recover.RestoreAccountSetPasswordFragment;
 import org.briarproject.briar.android.splash.SplashScreenActivity;
 import org.briarproject.briar.android.test.TestDataActivity;
+import org.briarproject.briar.api.socialbackup.recovery.RestoreAccount;
 
 import dagger.Component;
 
 @ActivityScope
-@Component(modules = {
+@Component(modules ={
 		ActivityModule.class,
 		BlogModule.class,
 		CreateGroupModule.class,
 		GroupInvitationModule.class,
 		GroupMemberModule.class,
 		GroupRevealModule.class,
-		SharingModule.SharingLegacyModule.class
+		SharingModule.SharingLegacyModule.class,
+		CreateBackupModule.class
 }, dependencies = AndroidComponent.class)
 public interface ActivityComponent {
 
@@ -108,9 +133,7 @@ public interface ActivityComponent {
 
 	void inject(PanicPreferencesActivity activity);
 
-	void inject(ContactExchangeActivity activity);
-
-	void inject(KeyAgreementActivity activity);
+	void inject(AddNearbyContactActivity activity);
 
 	void inject(ConversationActivity activity);
 
@@ -182,6 +205,16 @@ public interface ActivityComponent {
 
 	void inject(CrashReportActivity crashReportActivity);
 
+	void inject(NewOrRecoverActivity newOrRecoverActivity);
+
+	void inject(CustodianReturnShardActivity custodianReturnShardActivity);
+
+    void inject(OwnerReturnShardActivity ownerReturnShardActivity);
+
+    void inject(OwnerRecoveryModeMainFragment ownerRecoveryModeMainFragment);
+
+    void inject(RestoreAccountActivity restoreAccountActivity);
+
 	// Fragments
 
 	void inject(AuthorNameFragment fragment);
@@ -208,7 +241,9 @@ public interface ActivityComponent {
 
 	void inject(FeedFragment fragment);
 
-	void inject(KeyAgreementFragment fragment);
+	void inject(AddNearbyContactIntroFragment fragment);
+
+	void inject(AddNearbyContactFragment fragment);
 
 	void inject(LinkExchangeFragment fragment);
 
@@ -226,7 +261,7 @@ public interface ActivityComponent {
 
 	void inject(ScreenFilterDialogFragment fragment);
 
-	void inject(ContactExchangeErrorFragment fragment);
+	void inject(AddNearbyContactErrorFragment fragment);
 
 	void inject(AliasDialogFragment aliasDialogFragment);
 
@@ -238,4 +273,37 @@ public interface ActivityComponent {
 
 	void inject(ConfirmAvatarDialogFragment fragment);
 
+	void inject(ThresholdSelectorFragment thresholdSelectorFragment);
+
+	void inject(DistributedBackupActivity distributedBackupActivity);
+
+	void inject(DatabaseComponent databaseComponent);
+
+	void inject(CustodianSelectorFragment custodianSelectorFragment);
+
+	void inject(ShardsSentFragment shardsSentFragment);
+
+	void inject(OwnerRecoveryModeExplainerFragment ownerRecoveryModeExplainerFragment);
+
+	void inject(ExistingBackupFragment existingBackupFragment);
+
+	void inject(NewOrRecoverFragment newOrRecoverFragment);
+
+	void inject(CustodianRecoveryModeExplainerFragment custodianRecoveryModeExplainerFragment);
+
+	void inject(CustodianReturnShardFragment custodianReturnShardFragment);
+
+	void inject(OwnerReturnShardFragment ownerReturnShardFragment);
+
+	void inject(CustodianReturnShardSuccessFragment custodianReturnShardSuccessFragment);
+
+	void inject(RestoreAccountSetPasswordFragment restoreAccountSetPasswordFragment);
+
+	void inject(RestoreAccountDozeFragment restoreAccountDozeFragment);
+
+	void inject(OwnerReturnShardSuccessFragment ownerReturnShardSuccessFragment);
+
+	void inject(OwnerRecoveryModeErrorFragment ownerRecoveryModeErrorFragment);
+
+	void inject(CustodianReturnShardErrorFragment custodianReturnShardErrorFragment);
 }

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

@@ -9,9 +9,7 @@ public interface RequestCodes {
 	int REQUEST_WRITE_BLOG_POST = 5;
 	int REQUEST_SHARE_BLOG = 6;
 	int REQUEST_RINGTONE = 7;
-	int REQUEST_PERMISSION_CAMERA_LOCATION = 8;
 	int REQUEST_DOZE_WHITELISTING = 9;
-	int REQUEST_BLUETOOTH_DISCOVERABLE = 10;
 	int REQUEST_UNLOCK = 11;
 	int REQUEST_KEYGUARD_UNLOCK = 12;
 	int REQUEST_ATTACH_IMAGE = 13;

briar-android/src/main/java/org/briarproject/briar/android/contact/ContactListFragment.java

@@ -15,11 +15,11 @@ 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.contact.add.nearby.AddNearbyContactActivity;
 import org.briarproject.briar.android.contact.add.remote.AddContactActivity;
 import org.briarproject.briar.android.contact.add.remote.PendingContactListActivity;
 import org.briarproject.briar.android.conversation.ConversationActivity;
 import org.briarproject.briar.android.fragment.BaseFragment;
-import org.briarproject.briar.android.keyagreement.ContactExchangeActivity;
 import org.briarproject.briar.android.util.BriarSnackbarBuilder;
 import org.briarproject.briar.android.view.BriarRecyclerView;
 
@@ -125,7 +125,8 @@ public class ContactListFragment extends BaseFragment
 		switch (itemId) {
 			case R.id.action_add_contact_nearby:
 				Intent intent =
-						new Intent(getContext(), ContactExchangeActivity.class);
+						new Intent(getContext(),
+								AddNearbyContactActivity.class);
 				startActivity(intent);
 				return;
 			case R.id.action_add_contact_remotely:

briar-android/src/main/java/org/briarproject/briar/android/contact/add/nearby/AddContactState.java

@@ -0,0 +1,76 @@
+package org.briarproject.briar.android.contact.add.nearby;
+
+import android.graphics.Bitmap;
+
+import org.briarproject.bramble.api.identity.Author;
+
+import androidx.annotation.Nullable;
+
+abstract class AddContactState {
+
+	static class KeyAgreementListening extends AddContactState {
+		final Bitmap qrCode;
+
+		KeyAgreementListening(Bitmap qrCode) {
+			this.qrCode = qrCode;
+		}
+	}
+
+	static class QrCodeScanned extends AddContactState {
+	}
+
+	static class KeyAgreementWaiting extends AddContactState {
+	}
+
+	static class KeyAgreementStarted extends AddContactState {
+	}
+
+	static class ContactExchangeStarted extends AddContactState {
+	}
+
+	static class ContactExchangeFinished extends AddContactState {
+		final ContactExchangeResult result;
+
+		ContactExchangeFinished(ContactExchangeResult result) {
+			this.result = result;
+		}
+	}
+
+	static class Failed extends AddContactState {
+		/**
+		 * Non-null if failed due to the scanned QR code version.
+		 * True if the app producing the code is too old.
+		 * False if the scanning app is too old.
+		 */
+		@Nullable
+		final Boolean qrCodeTooOld;
+
+		Failed(@Nullable Boolean qrCodeTooOld) {
+			this.qrCodeTooOld = qrCodeTooOld;
+		}
+
+		Failed() {
+			this(null);
+		}
+	}
+
+	abstract static class ContactExchangeResult {
+		static class Success extends ContactExchangeResult {
+			final Author remoteAuthor;
+
+			Success(Author remoteAuthor) {
+				this.remoteAuthor = remoteAuthor;
+			}
+		}
+
+		static class Error extends ContactExchangeResult {
+			@Nullable
+			final Author duplicateAuthor;
+
+			Error(@Nullable Author duplicateAuthor) {
+				this.duplicateAuthor = duplicateAuthor;
+			}
+		}
+	} // end ContactExchangeResult
+
+}

briar-android/src/main/java/org/briarproject/briar/android/contact/add/nearby/AddNearbyContactActivity.java

@@ -0,0 +1,204 @@
+package org.briarproject.briar.android.contact.add.nearby;
+
+import android.content.Intent;
+import android.os.Bundle;
+import android.view.MenuItem;
+import android.widget.Toast;
+
+import org.briarproject.bramble.api.identity.Author;
+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.activity.BriarActivity;
+import org.briarproject.briar.android.contact.add.nearby.AddContactState.ContactExchangeFinished;
+import org.briarproject.briar.android.contact.add.nearby.AddContactState.ContactExchangeResult;
+import org.briarproject.briar.android.contact.add.nearby.AddContactState.Failed;
+import org.briarproject.briar.android.contact.add.nearby.AddNearbyContactViewModel.BluetoothDecision;
+import org.briarproject.briar.android.fragment.BaseFragment;
+import org.briarproject.briar.android.fragment.BaseFragment.BaseFragmentListener;
+import org.briarproject.briar.android.util.RequestBluetoothDiscoverable;
+
+import java.util.logging.Logger;
+
+import javax.annotation.Nullable;
+import javax.inject.Inject;
+
+import androidx.activity.result.ActivityResultLauncher;
+import androidx.appcompat.widget.Toolbar;
+import androidx.fragment.app.FragmentManager;
+import androidx.lifecycle.ViewModelProvider;
+
+import static android.bluetooth.BluetoothAdapter.ACTION_REQUEST_DISCOVERABLE;
+import static android.content.Intent.FLAG_ACTIVITY_CLEAR_TOP;
+import static android.widget.Toast.LENGTH_LONG;
+import static java.util.Objects.requireNonNull;
+import static java.util.logging.Logger.getLogger;
+import static org.briarproject.briar.android.contact.add.nearby.AddNearbyContactViewModel.BluetoothDecision.ACCEPTED;
+import static org.briarproject.briar.android.contact.add.nearby.AddNearbyContactViewModel.BluetoothDecision.REFUSED;
+
+@MethodsNotNullByDefault
+@ParametersNotNullByDefault
+public class AddNearbyContactActivity extends BriarActivity
+		implements BaseFragmentListener {
+
+	private static final Logger LOG =
+			getLogger(AddNearbyContactActivity.class.getName());
+
+	@Inject
+	ViewModelProvider.Factory viewModelFactory;
+
+	private AddNearbyContactViewModel viewModel;
+	private final ActivityResultLauncher<Integer> bluetoothLauncher =
+			registerForActivityResult(new RequestBluetoothDiscoverable(),
+					this::onBluetoothDiscoverableResult);
+
+	@Override
+	public void injectActivity(ActivityComponent component) {
+		component.inject(this);
+		viewModel = new ViewModelProvider(this, viewModelFactory)
+				.get(AddNearbyContactViewModel.class);
+	}
+
+	@Override
+	public void onCreate(@Nullable Bundle state) {
+		super.onCreate(state);
+		setContentView(R.layout.activity_fragment_container_toolbar);
+		Toolbar toolbar = findViewById(R.id.toolbar);
+		setSupportActionBar(toolbar);
+		requireNonNull(getSupportActionBar()).setDisplayHomeAsUpEnabled(true);
+		if (state == null) {
+			showInitialFragment(AddNearbyContactIntroFragment.newInstance());
+		}
+		viewModel.getRequestBluetoothDiscoverable().observeEvent(this, r ->
+				requestBluetoothDiscoverable()); // never false
+		viewModel.getShowQrCodeFragment().observeEvent(this, show -> {
+			if (show) showQrCodeFragment();
+		});
+		requireNonNull(getSupportActionBar())
+				.setTitle(R.string.add_contact_title);
+		viewModel.getState()
+				.observe(this, this::onAddContactStateChanged);
+	}
+
+	@Override
+	protected void onPostResume() {
+		super.onPostResume();
+		viewModel.setIsActivityResumed(true);
+	}
+
+	@Override
+	protected void onPause() {
+		super.onPause();
+		viewModel.setIsActivityResumed(false);
+	}
+
+	private void onBluetoothDiscoverableResult(boolean discoverable) {
+		if (discoverable) {
+			LOG.info("Bluetooth discoverability was accepted");
+			viewModel.setBluetoothDecision(ACCEPTED);
+		} else {
+			LOG.info("Bluetooth discoverability was refused");
+			viewModel.setBluetoothDecision(REFUSED);
+		}
+	}
+
+	@Override
+	public boolean onOptionsItemSelected(MenuItem item) {
+		if (item.getItemId() == android.R.id.home) {
+			onBackPressed();
+			return true;
+		}
+		return super.onOptionsItemSelected(item);
+	}
+
+	@Override
+	public void onBackPressed() {
+		if (viewModel.getState().getValue() instanceof Failed) {
+			// re-create this activity when going back in failed state
+			Intent i = new Intent(this, AddNearbyContactActivity.class);
+			i.setFlags(FLAG_ACTIVITY_CLEAR_TOP);
+			startActivity(i);
+		} else {
+			super.onBackPressed();
+		}
+	}
+
+	private void requestBluetoothDiscoverable() {
+		Intent i = new Intent(ACTION_REQUEST_DISCOVERABLE);
+		if (i.resolveActivity(getPackageManager()) != null) {
+			LOG.info("Asking for Bluetooth discoverability");
+			viewModel.setBluetoothDecision(BluetoothDecision.WAITING);
+			bluetoothLauncher.launch(120); // 2min discoverable
+		} else {
+			viewModel.setBluetoothDecision(BluetoothDecision.NO_ADAPTER);
+		}
+	}
+
+	private void showQrCodeFragment() {
+		// FIXME #824
+		FragmentManager fm = getSupportFragmentManager();
+		if (fm.findFragmentByTag(AddNearbyContactFragment.TAG) == null) {
+			BaseFragment f = AddNearbyContactFragment.newInstance();
+			fm.beginTransaction()
+					.replace(R.id.fragmentContainer, f, f.getUniqueTag())
+					.addToBackStack(f.getUniqueTag())
+					.commit();
+		}
+	}
+
+	private void onAddContactStateChanged(@Nullable AddContactState state) {
+		if (state instanceof ContactExchangeFinished) {
+			ContactExchangeResult result =
+					((ContactExchangeFinished) state).result;
+			onContactExchangeResult(result);
+		} else if (state instanceof Failed) {
+			Boolean qrCodeTooOld = ((Failed) state).qrCodeTooOld;
+			onAddingContactFailed(qrCodeTooOld);
+		}
+	}
+
+	private void onContactExchangeResult(ContactExchangeResult result) {
+		if (result instanceof ContactExchangeResult.Success) {
+			Author remoteAuthor =
+					((ContactExchangeResult.Success) result).remoteAuthor;
+			String contactName = remoteAuthor.getName();
+			String text = getString(R.string.contact_added_toast, contactName);
+			Toast.makeText(this, text, LENGTH_LONG).show();
+			supportFinishAfterTransition();
+		} else if (result instanceof ContactExchangeResult.Error) {
+			Author duplicateAuthor =
+					((ContactExchangeResult.Error) result).duplicateAuthor;
+			if (duplicateAuthor == null) {
+				showErrorFragment();
+			} else {
+				String contactName = duplicateAuthor.getName();
+				String text =
+						getString(R.string.contact_already_exists, contactName);
+				Toast.makeText(this, text, LENGTH_LONG).show();
+				supportFinishAfterTransition();
+			}
+		} else throw new AssertionError();
+	}
+
+	private void onAddingContactFailed(@Nullable Boolean qrCodeTooOld) {
+		if (qrCodeTooOld == null) {
+			showErrorFragment();
+		} else {
+			String msg;
+			if (qrCodeTooOld) {
+				msg = getString(R.string.qr_code_too_old,
+						getString(R.string.app_name));
+			} else {
+				msg = getString(R.string.qr_code_too_new,
+						getString(R.string.app_name));
+			}
+			showNextFragment(AddNearbyContactErrorFragment.newInstance(msg));
+		}
+	}
+
+	private void showErrorFragment() {
+		showNextFragment(new AddNearbyContactErrorFragment());
+	}
+
+}

briar-android/src/main/java/org/briarproject/briar/android/contact/add/nearby/AddNearbyContactErrorFragment.java

@@ -1,4 +1,4 @@
-package org.briarproject.briar.android.keyagreement;
+package org.briarproject.briar.android.contact.add.nearby;
 
 import android.content.Intent;
 import android.os.Bundle;
@@ -24,14 +24,14 @@ import static org.briarproject.briar.android.util.UiUtils.onSingleLinkClick;
 
 @MethodsNotNullByDefault
 @ParametersNotNullByDefault
-public class ContactExchangeErrorFragment extends BaseFragment {
+public class AddNearbyContactErrorFragment extends BaseFragment {
 
 	public static final String TAG =
-			ContactExchangeErrorFragment.class.getName();
+			AddNearbyContactErrorFragment.class.getName();
 	private static final String ERROR_MSG = "errorMessage";
 
-	public static ContactExchangeErrorFragment newInstance(String errorMsg) {
-		ContactExchangeErrorFragment f = new ContactExchangeErrorFragment();
+	public static AddNearbyContactErrorFragment newInstance(String errorMsg) {
+		AddNearbyContactErrorFragment f = new AddNearbyContactErrorFragment();
 		Bundle args = new Bundle();
 		args.putString(ERROR_MSG, errorMsg);
 		f.setArguments(args);
@@ -72,7 +72,7 @@ public class ContactExchangeErrorFragment extends BaseFragment {
 		tryAgain.setOnClickListener(view -> {
 			// Recreate the activity so we return to the intro fragment
 			FragmentActivity activity = requireActivity();
-			Intent i = new Intent(activity, ContactExchangeActivity.class);
+			Intent i = new Intent(activity, AddNearbyContactActivity.class);
 			i.setFlags(FLAG_ACTIVITY_CLEAR_TOP);
 			activity.startActivity(i);
 		});

briar-android/src/main/java/org/briarproject/briar/android/contact/add/nearby/AddNearbyContactFragment.java

@@ -0,0 +1,202 @@
+package org.briarproject.briar.android.contact.add.nearby;
+
+import android.graphics.Bitmap;
+import android.os.Bundle;
+import android.view.LayoutInflater;
+import android.view.View;
+import android.view.ViewGroup;
+import android.widget.LinearLayout;
+import android.widget.LinearLayout.LayoutParams;
+import android.widget.TextView;
+import android.widget.Toast;
+
+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.contact.add.nearby.AddContactState.ContactExchangeStarted;
+import org.briarproject.briar.android.contact.add.nearby.AddContactState.Failed;
+import org.briarproject.briar.android.contact.add.nearby.AddContactState.KeyAgreementStarted;
+import org.briarproject.briar.android.contact.add.nearby.AddContactState.KeyAgreementWaiting;
+import org.briarproject.briar.android.contact.add.nearby.AddContactState.QrCodeScanned;
+import org.briarproject.briar.android.fragment.BaseFragment;
+import org.briarproject.briar.android.view.QrCodeView;
+
+import java.util.logging.Logger;
+
+import javax.annotation.Nullable;
+import javax.inject.Inject;
+
+import androidx.annotation.UiThread;
+import androidx.lifecycle.ViewModelProvider;
+
+import static android.content.pm.ActivityInfo.SCREEN_ORIENTATION_NOSENSOR;
+import static android.content.pm.ActivityInfo.SCREEN_ORIENTATION_UNSPECIFIED;
+import static android.view.View.INVISIBLE;
+import static android.view.View.VISIBLE;
+import static android.view.ViewGroup.LayoutParams.MATCH_PARENT;
+import static android.widget.LinearLayout.HORIZONTAL;
+import static android.widget.Toast.LENGTH_LONG;
+import static java.util.logging.Level.WARNING;
+import static org.briarproject.bramble.util.LogUtils.logException;
+
+@MethodsNotNullByDefault
+@ParametersNotNullByDefault
+public class AddNearbyContactFragment extends BaseFragment
+		implements QrCodeView.FullscreenListener {
+
+	public static final String TAG = AddNearbyContactFragment.class.getName();
+
+	private static final Logger LOG = Logger.getLogger(TAG);
+
+	@Inject
+	ViewModelProvider.Factory viewModelFactory;
+
+	private AddNearbyContactViewModel viewModel;
+	private CameraView cameraView;
+	private LinearLayout cameraOverlay;
+	private View statusView;
+	private QrCodeView qrCodeView;
+	private TextView status;
+
+	public static AddNearbyContactFragment newInstance() {
+		Bundle args = new Bundle();
+		AddNearbyContactFragment fragment = new AddNearbyContactFragment();
+		fragment.setArguments(args);
+		return fragment;
+	}
+
+	@Override
+	public void injectFragment(ActivityComponent component) {
+		component.inject(this);
+		viewModel = new ViewModelProvider(requireActivity(), viewModelFactory)
+				.get(AddNearbyContactViewModel.class);
+	}
+
+	@Nullable
+	@Override
+	public View onCreateView(LayoutInflater inflater,
+			@Nullable ViewGroup container,
+			@Nullable Bundle savedInstanceState) {
+		return inflater.inflate(R.layout.fragment_keyagreement_qr, container,
+				false);
+	}
+
+	@Override
+	public void onViewCreated(View view, @Nullable Bundle savedInstanceState) {
+		super.onViewCreated(view, savedInstanceState);
+		cameraView = view.findViewById(R.id.camera_view);
+		cameraOverlay = view.findViewById(R.id.camera_overlay);
+		statusView = view.findViewById(R.id.status_container);
+		status = view.findViewById(R.id.connect_status);
+		qrCodeView = view.findViewById(R.id.qr_code_view);
+		qrCodeView.setFullscreenListener(this);
+
+		viewModel.getState().observe(getViewLifecycleOwner(),
+				this::onAddContactStateChanged);
+	}
+
+	@Override
+	public void onActivityCreated(@Nullable Bundle savedInstanceState) {
+		super.onActivityCreated(savedInstanceState);
+		requireActivity().setRequestedOrientation(SCREEN_ORIENTATION_NOSENSOR);
+		cameraView.setPreviewConsumer(viewModel.getQrCodeDecoder());
+	}
+
+	@Override
+	public void onStart() {
+		super.onStart();
+		try {
+			cameraView.start();
+		} catch (CameraException e) {
+			logCameraExceptionAndFinish(e);
+		}
+	}
+
+	@Override
+	public void onStop() {
+		super.onStop();
+		try {
+			cameraView.stop();
+		} catch (CameraException e) {
+			logCameraExceptionAndFinish(e);
+		}
+	}
+
+	@Override
+	public void onDestroy() {
+		requireActivity()
+				.setRequestedOrientation(SCREEN_ORIENTATION_UNSPECIFIED);
+		super.onDestroy();
+	}
+
+	@Override
+	public void setFullscreen(boolean fullscreen) {
+		LinearLayout.LayoutParams statusParams, qrCodeParams;
+		if (fullscreen) {
+			// Grow the QR code view to fill its parent
+			statusParams = new LayoutParams(0, 0, 0f);
+			qrCodeParams = new LayoutParams(MATCH_PARENT, MATCH_PARENT, 1f);
+		} else {
+			// Shrink the QR code view to fill half its parent
+			if (cameraOverlay.getOrientation() == HORIZONTAL) {
+				statusParams = new LayoutParams(0, MATCH_PARENT, 1f);
+				qrCodeParams = new LayoutParams(0, MATCH_PARENT, 1f);
+			} else {
+				statusParams = new LayoutParams(MATCH_PARENT, 0, 1f);
+				qrCodeParams = new LayoutParams(MATCH_PARENT, 0, 1f);
+			}
+		}
+		statusView.setLayoutParams(statusParams);
+		qrCodeView.setLayoutParams(qrCodeParams);
+		cameraOverlay.invalidate();
+	}
+
+	@UiThread
+	private void onAddContactStateChanged(@Nullable AddContactState state) {
+		if (state instanceof AddContactState.KeyAgreementListening) {
+			Bitmap qrCode =
+					((AddContactState.KeyAgreementListening) state).qrCode;
+			qrCodeView.setQrCode(qrCode);
+		} else if (state instanceof QrCodeScanned) {
+			try {
+				cameraView.stop();
+			} catch (CameraException e) {
+				logCameraExceptionAndFinish(e);
+			}
+			cameraView.setVisibility(INVISIBLE);
+			statusView.setVisibility(VISIBLE);
+			status.setText(R.string.connecting_to_device);
+		} else if (state instanceof KeyAgreementWaiting) {
+			status.setText(R.string.waiting_for_contact_to_scan);
+		} else if (state instanceof KeyAgreementStarted) {
+			qrCodeView.setVisibility(INVISIBLE);
+			status.setText(R.string.authenticating_with_device);
+		} else if (state instanceof ContactExchangeStarted) {
+			status.setText(R.string.exchanging_contact_details);
+		} else if (state instanceof Failed) {
+			// the activity will replace this fragment with an error fragment
+			statusView.setVisibility(INVISIBLE);
+			cameraView.setVisibility(INVISIBLE);
+		}
+	}
+
+	@Override
+	public String getUniqueTag() {
+		return TAG;
+	}
+
+	@UiThread
+	private void logCameraExceptionAndFinish(CameraException e) {
+		logException(LOG, WARNING, e);
+		Toast.makeText(getActivity(), R.string.camera_error,
+				LENGTH_LONG).show();
+		finish();
+	}
+
+	@Override
+	protected void finish() {
+		requireActivity().getSupportFragmentManager().popBackStack();
+	}
+
+}

briar-android/src/main/java/org/briarproject/briar/android/contact/add/nearby/AddNearbyContactIntroFragment.java

@@ -0,0 +1,91 @@
+package org.briarproject.briar.android.contact.add.nearby;
+
+import android.os.Bundle;
+import android.view.LayoutInflater;
+import android.view.View;
+import android.view.ViewGroup;
+import android.widget.ScrollView;
+
+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;
+
+import androidx.activity.result.ActivityResultLauncher;
+import androidx.activity.result.contract.ActivityResultContracts.RequestMultiplePermissions;
+import androidx.lifecycle.ViewModelProvider;
+
+import static android.view.View.FOCUS_DOWN;
+
+@MethodsNotNullByDefault
+@ParametersNotNullByDefault
+public class AddNearbyContactIntroFragment extends BaseFragment {
+
+	public static final String TAG =
+			AddNearbyContactIntroFragment.class.getName();
+
+	@Inject
+	ViewModelProvider.Factory viewModelFactory;
+
+	private AddNearbyContactViewModel viewModel;
+	private AddNearbyContactPermissionManager permissionManager;
+
+	private ScrollView scrollView;
+
+	private final ActivityResultLauncher<String[]> permissionLauncher =
+			registerForActivityResult(new RequestMultiplePermissions(), r ->
+					permissionManager.onRequestPermissionResult(r,
+							viewModel::showQrCodeFragmentIfAllowed));
+
+	public static AddNearbyContactIntroFragment newInstance() {
+		Bundle args = new Bundle();
+		AddNearbyContactIntroFragment
+				fragment = new AddNearbyContactIntroFragment();
+		fragment.setArguments(args);
+		return fragment;
+	}
+
+	@Override
+	public void injectFragment(ActivityComponent component) {
+		component.inject(this);
+		viewModel = new ViewModelProvider(requireActivity(), viewModelFactory)
+				.get(AddNearbyContactViewModel.class);
+		permissionManager = new AddNearbyContactPermissionManager(
+				requireActivity(), permissionLauncher::launch,
+				viewModel.isBluetoothSupported());
+	}
+
+	@Nullable
+	@Override
+	public View onCreateView(LayoutInflater inflater,
+			@Nullable ViewGroup container,
+			@Nullable Bundle savedInstanceState) {
+
+		View v = inflater.inflate(R.layout.fragment_keyagreement_id, container,
+				false);
+		scrollView = v.findViewById(R.id.scrollView);
+		View button = v.findViewById(R.id.continueButton);
+		button.setOnClickListener(view -> viewModel.onContinueClicked(() ->
+				permissionManager.checkPermissions()
+		));
+		return v;
+	}
+
+	@Override
+	public void onStart() {
+		super.onStart();
+		// Permissions may have been granted manually while we were stopped
+		permissionManager.resetPermissions();
+		scrollView.post(() -> scrollView.fullScroll(FOCUS_DOWN));
+	}
+
+	@Override
+	public String getUniqueTag() {
+		return TAG;
+	}
+
+}

briar-android/src/main/java/org/briarproject/briar/android/contact/add/nearby/AddNearbyContactModule.java

@@ -1,4 +1,4 @@
-package org.briarproject.briar.android.keyagreement;
+package org.briarproject.briar.android.contact.add.nearby;
 
 import org.briarproject.briar.android.viewmodel.ViewModelKey;
 
@@ -8,12 +8,12 @@ import dagger.Module;
 import dagger.multibindings.IntoMap;
 
 @Module
-public abstract class ContactExchangeModule {
+public abstract class AddNearbyContactModule {
 
 	@Binds
 	@IntoMap
-	@ViewModelKey(ContactExchangeViewModel.class)
+	@ViewModelKey(AddNearbyContactViewModel.class)
 	abstract ViewModel bindContactExchangeViewModel(
-			ContactExchangeViewModel contactExchangeViewModel);
+			AddNearbyContactViewModel addNearbyContactViewModel);
 
 }

briar-android/src/main/java/org/briarproject/briar/android/contact/add/nearby/AddNearbyContactPermissionManager.java

@@ -0,0 +1,209 @@
+package org.briarproject.briar.android.contact.add.nearby;
+
+import android.content.ActivityNotFoundException;
+import android.content.Context;
+import android.content.Intent;
+import android.location.LocationManager;
+import android.widget.Toast;
+
+import org.briarproject.briar.R;
+
+import java.util.Map;
+
+import androidx.annotation.StringRes;
+import androidx.appcompat.app.AlertDialog;
+import androidx.core.util.Consumer;
+import androidx.fragment.app.FragmentActivity;
+
+import static android.Manifest.permission.ACCESS_FINE_LOCATION;
+import static android.Manifest.permission.CAMERA;
+import static android.content.pm.PackageManager.PERMISSION_GRANTED;
+import static android.os.Build.VERSION.SDK_INT;
+import static android.provider.Settings.ACTION_LOCATION_SOURCE_SETTINGS;
+import static android.widget.Toast.LENGTH_LONG;
+import static androidx.core.app.ActivityCompat.shouldShowRequestPermissionRationale;
+import static androidx.core.content.ContextCompat.checkSelfPermission;
+import static org.briarproject.briar.android.util.UiUtils.getGoToSettingsListener;
+
+public class AddNearbyContactPermissionManager {
+
+	private enum Permission {
+		UNKNOWN, GRANTED, SHOW_RATIONALE, PERMANENTLY_DENIED
+	}
+
+	private Permission cameraPermission = Permission.UNKNOWN;
+	private Permission locationPermission = Permission.UNKNOWN;
+
+	private final FragmentActivity ctx;
+	private final Consumer<String[]> requestPermissions;
+	private final boolean isBluetoothSupported;
+
+	public AddNearbyContactPermissionManager(FragmentActivity ctx,
+			Consumer<String[]> requestPermissions,
+			boolean isBluetoothSupported) {
+		this.ctx = ctx;
+		this.requestPermissions = requestPermissions;
+		this.isBluetoothSupported = isBluetoothSupported;
+	}
+
+	public void resetPermissions() {
+		cameraPermission = Permission.UNKNOWN;
+		locationPermission = Permission.UNKNOWN;
+	}
+
+	/**
+	 * @return true if location is enabled,
+	 * or it isn't required due to this being a SDK < 28 device.
+	 */
+	static boolean isLocationEnabled(Context ctx) {
+		if (SDK_INT >= 28) {
+			LocationManager lm = ctx.getSystemService(LocationManager.class);
+			return lm.isLocationEnabled();
+		} else {
+			return true;
+		}
+	}
+
+	public static boolean areEssentialPermissionsGranted(Context ctx,
+			boolean isBluetoothSupported) {
+		int ok = PERMISSION_GRANTED;
+		return checkSelfPermission(ctx, CAMERA) == ok &&
+				(SDK_INT < 23 ||
+						checkSelfPermission(ctx, ACCESS_FINE_LOCATION) == ok ||
+						!isBluetoothSupported);
+	}
+
+	private boolean areEssentialPermissionsGranted() {
+		return cameraPermission == Permission.GRANTED &&
+				(SDK_INT < 23 || locationPermission == Permission.GRANTED ||
+						!isBluetoothSupported);
+	}
+
+	public boolean checkPermissions() {
+		boolean locationEnabled = isLocationEnabled(ctx);
+		if (locationEnabled && areEssentialPermissionsGranted()) return true;
+		// If an essential permission has been permanently denied, ask the
+		// user to change the setting
+		if (cameraPermission == Permission.PERMANENTLY_DENIED) {
+			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?
+		if (cameraPermission == Permission.SHOW_RATIONALE &&
+				locationPermission == Permission.SHOW_RATIONALE) {
+			showRationale(R.string.permission_camera_location_title,
+					R.string.permission_camera_location_request_body);
+		} else if (cameraPermission == Permission.SHOW_RATIONALE) {
+			showRationale(R.string.permission_camera_title,
+					R.string.permission_camera_request_body);
+		} else if (locationPermission == Permission.SHOW_RATIONALE) {
+			showRationale(R.string.permission_location_title,
+					R.string.permission_location_request_body);
+		} else if (isLocationEnabled(ctx)) {
+			requestPermissions();
+		} else {
+			showLocationDialog(ctx);
+		}
+		return false;
+	}
+
+	private void showDenialDialog(@StringRes int title, @StringRes int body) {
+		AlertDialog.Builder builder =
+				new AlertDialog.Builder(ctx, R.style.BriarDialogTheme);
+		builder.setTitle(title);
+		builder.setMessage(body);
+		builder.setPositiveButton(R.string.ok, getGoToSettingsListener(ctx));
+		builder.setNegativeButton(R.string.cancel,
+				(dialog, which) -> ctx.supportFinishAfterTransition());
+		builder.show();
+	}
+
+	private void showRationale(@StringRes int title, @StringRes int body) {
+		AlertDialog.Builder builder =
+				new AlertDialog.Builder(ctx, R.style.BriarDialogTheme);
+		builder.setTitle(title);
+		builder.setMessage(body);
+		builder.setNeutralButton(R.string.continue_button,
+				(dialog, which) -> requestPermissions());
+		builder.show();
+	}
+
+	private static void showLocationDialog(Context ctx) {
+		AlertDialog.Builder builder =
+				new AlertDialog.Builder(ctx, R.style.BriarDialogTheme);
+		builder.setTitle(R.string.permission_location_setting_title);
+		builder.setMessage(R.string.permission_location_setting_body);
+		builder.setNegativeButton(R.string.cancel, null);
+		builder.setPositiveButton(R.string.permission_location_setting_button,
+				(dialog, which) -> {
+					Intent i = new Intent(ACTION_LOCATION_SOURCE_SETTINGS);
+					try {
+						ctx.startActivity(i);
+					} catch (ActivityNotFoundException e) {
+						Toast.makeText(ctx, R.string.error_start_activity,
+								LENGTH_LONG).show();
+					}
+				});
+		builder.show();
+	}
+
+	private void requestPermissions() {
+		String[] permissions;
+		if (isBluetoothSupported) {
+			permissions = new String[] {CAMERA, ACCESS_FINE_LOCATION};
+		} else {
+			permissions = new String[] {CAMERA};
+		}
+		requestPermissions.accept(permissions);
+	}
+
+	public void onRequestPermissionResult(Map<String, Boolean> result,
+			Runnable onPermissionsGranted) {
+		if (gotPermission(CAMERA, result)) {
+			cameraPermission = Permission.GRANTED;
+		} else if (shouldShowRationale(CAMERA)) {
+			cameraPermission = Permission.SHOW_RATIONALE;
+		} else {
+			cameraPermission = Permission.PERMANENTLY_DENIED;
+		}
+		if (isBluetoothSupported) {
+			if (gotPermission(ACCESS_FINE_LOCATION, result)) {
+				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
+		// https://code.google.com/p/android/issues/detail?id=190966.
+		// In that case the isResumed flag prevents the fragment from being
+		// shown here, and showQrCodeFragmentIfAllowed() will be called again
+		// from onPostResume().
+		if (checkPermissions()) onPermissionsGranted.run();
+	}
+
+	private boolean gotPermission(String permission,
+			Map<String, Boolean> result) {
+		Boolean permissionResult = result.get(permission);
+		return permissionResult == null ?
+				isGranted(permission) : permissionResult;
+	}
+
+	private boolean isGranted(String permission) {
+		return checkSelfPermission(ctx, permission) == PERMISSION_GRANTED;
+	}
+
+	private boolean shouldShowRationale(String permission) {
+		return shouldShowRequestPermissionRationale(ctx, permission);
+	}
+
+}

briar-android/src/main/java/org/briarproject/briar/android/contact/add/nearby/AddNearbyContactViewModel.java

@@ -0,0 +1,532 @@
+package org.briarproject.briar.android.contact.add.nearby;
+
+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 android.graphics.Bitmap;
+import android.util.DisplayMetrics;
+import android.widget.Toast;
+
+import com.google.zxing.Result;
+
+import org.briarproject.bramble.api.UnsupportedVersionException;
+import org.briarproject.bramble.api.connection.ConnectionManager;
+import org.briarproject.bramble.api.contact.Contact;
+import org.briarproject.bramble.api.contact.ContactExchangeManager;
+import org.briarproject.bramble.api.crypto.SecretKey;
+import org.briarproject.bramble.api.db.ContactExistsException;
+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.keyagreement.KeyAgreementResult;
+import org.briarproject.bramble.api.keyagreement.KeyAgreementTask;
+import org.briarproject.bramble.api.keyagreement.Payload;
+import org.briarproject.bramble.api.keyagreement.PayloadEncoder;
+import org.briarproject.bramble.api.keyagreement.PayloadParser;
+import org.briarproject.bramble.api.keyagreement.event.KeyAgreementAbortedEvent;
+import org.briarproject.bramble.api.keyagreement.event.KeyAgreementFailedEvent;
+import org.briarproject.bramble.api.keyagreement.event.KeyAgreementFinishedEvent;
+import org.briarproject.bramble.api.keyagreement.event.KeyAgreementListeningEvent;
+import org.briarproject.bramble.api.keyagreement.event.KeyAgreementStartedEvent;
+import org.briarproject.bramble.api.keyagreement.event.KeyAgreementWaitingEvent;
+import org.briarproject.bramble.api.lifecycle.IoExecutor;
+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.Plugin.State;
+import org.briarproject.bramble.api.plugin.PluginManager;
+import org.briarproject.bramble.api.plugin.TransportId;
+import org.briarproject.bramble.api.plugin.duplex.DuplexTransportConnection;
+import org.briarproject.bramble.api.plugin.event.TransportStateEvent;
+import org.briarproject.bramble.api.system.AndroidExecutor;
+import org.briarproject.briar.R;
+import org.briarproject.briar.android.contact.add.nearby.AddContactState.ContactExchangeFinished;
+import org.briarproject.briar.android.contact.add.nearby.AddContactState.ContactExchangeResult.Error;
+import org.briarproject.briar.android.contact.add.nearby.AddContactState.ContactExchangeResult.Success;
+import org.briarproject.briar.android.contact.add.nearby.AddContactState.ContactExchangeStarted;
+import org.briarproject.briar.android.contact.add.nearby.AddContactState.KeyAgreementListening;
+import org.briarproject.briar.android.contact.add.nearby.AddContactState.KeyAgreementStarted;
+import org.briarproject.briar.android.contact.add.nearby.AddContactState.KeyAgreementWaiting;
+import org.briarproject.briar.android.viewmodel.LiveEvent;
+import org.briarproject.briar.android.viewmodel.MutableLiveEvent;
+
+import java.io.IOException;
+import java.nio.charset.Charset;
+import java.util.concurrent.Executor;
+import java.util.logging.Logger;
+
+import javax.inject.Inject;
+import javax.inject.Provider;
+
+import androidx.annotation.Nullable;
+import androidx.annotation.UiThread;
+import androidx.core.util.Supplier;
+import androidx.lifecycle.AndroidViewModel;
+import androidx.lifecycle.LiveData;
+import androidx.lifecycle.MutableLiveData;
+
+import static android.bluetooth.BluetoothAdapter.ACTION_SCAN_MODE_CHANGED;
+import static android.bluetooth.BluetoothAdapter.EXTRA_SCAN_MODE;
+import static android.bluetooth.BluetoothAdapter.SCAN_MODE_CONNECTABLE_DISCOVERABLE;
+import static android.widget.Toast.LENGTH_LONG;
+import static java.util.Objects.requireNonNull;
+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.State.ACTIVE;
+import static org.briarproject.bramble.api.plugin.Plugin.State.DISABLED;
+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.bramble.util.LogUtils.logException;
+import static org.briarproject.briar.android.contact.add.nearby.AddNearbyContactPermissionManager.areEssentialPermissionsGranted;
+import static org.briarproject.briar.android.contact.add.nearby.AddNearbyContactPermissionManager.isLocationEnabled;
+import static org.briarproject.briar.android.contact.add.nearby.AddNearbyContactViewModel.BluetoothDecision.NO_ADAPTER;
+import static org.briarproject.briar.android.contact.add.nearby.AddNearbyContactViewModel.BluetoothDecision.REFUSED;
+import static org.briarproject.briar.android.contact.add.nearby.AddNearbyContactViewModel.BluetoothDecision.UNKNOWN;
+
+@NotNullByDefault
+class AddNearbyContactViewModel extends AndroidViewModel
+		implements EventListener, QrCodeDecoder.ResultCallback {
+
+	private static final Logger LOG =
+			getLogger(AddNearbyContactViewModel.class.getName());
+
+	enum BluetoothDecision {
+		/**
+		 * We haven't asked the user about Bluetooth discoverability.
+		 */
+		UNKNOWN,
+
+		/**
+		 * The device doesn't have a Bluetooth adapter.
+		 */
+		NO_ADAPTER,
+
+		/**
+		 * We're waiting for the user to accept or refuse discoverability.
+		 */
+		WAITING,
+
+		/**
+		 * The user has accepted discoverability.
+		 */
+		ACCEPTED,
+
+		/**
+		 * The user has refused discoverability.
+		 */
+		REFUSED
+	}
+
+	@SuppressWarnings("CharsetObjectCanBeUsed") // Requires minSdkVersion >= 19
+	private static final Charset ISO_8859_1 = Charset.forName("ISO-8859-1");
+
+	private final EventBus eventBus;
+	private final AndroidExecutor androidExecutor;
+	private final Executor ioExecutor;
+	private final PluginManager pluginManager;
+	private final PayloadEncoder payloadEncoder;
+	private final PayloadParser payloadParser;
+	private final Provider<KeyAgreementTask> keyAgreementTaskProvider;
+	private final ContactExchangeManager contactExchangeManager;
+	private final ConnectionManager connectionManager;
+
+	private final MutableLiveEvent<Boolean> requestBluetoothDiscoverable =
+			new MutableLiveEvent<>();
+	private final MutableLiveEvent<Boolean> showQrCodeFragment =
+			new MutableLiveEvent<>();
+	private final MutableLiveData<AddContactState> state =
+			new MutableLiveData<>();
+
+	private final QrCodeDecoder qrCodeDecoder;
+	private final BroadcastReceiver bluetoothReceiver =
+			new BluetoothStateReceiver();
+
+	@Nullable
+	private final BluetoothAdapter bt;
+	@Nullable
+	private final Plugin wifiPlugin, bluetoothPlugin;
+
+	// UiThread
+	private BluetoothDecision bluetoothDecision = BluetoothDecision.UNKNOWN;
+
+	private boolean wasContinueClicked = false;
+	private boolean isActivityResumed = false;
+
+	/**
+	 * Records whether we've enabled the wifi plugin so we don't enable it more
+	 * than once.
+	 */
+	private boolean hasEnabledWifi = false;
+
+	/**
+	 * Records whether we've enabled the Bluetooth plugin so we don't enable it
+	 * more than once.
+	 */
+	private boolean hasEnabledBluetooth = false;
+
+	@Nullable
+	private volatile KeyAgreementTask task;
+	private volatile boolean gotLocalPayload = false, gotRemotePayload = false;
+
+	@Inject
+	AddNearbyContactViewModel(Application app,
+			EventBus eventBus,
+			AndroidExecutor androidExecutor,
+			@IoExecutor Executor ioExecutor,
+			PluginManager pluginManager,
+			PayloadEncoder payloadEncoder,
+			PayloadParser payloadParser,
+			Provider<KeyAgreementTask> keyAgreementTaskProvider,
+			ContactExchangeManager contactExchangeManager,
+			ConnectionManager connectionManager) {
+		super(app);
+		this.eventBus = eventBus;
+		this.androidExecutor = androidExecutor;
+		this.ioExecutor = ioExecutor;
+		this.pluginManager = pluginManager;
+		this.payloadEncoder = payloadEncoder;
+		this.payloadParser = payloadParser;
+		this.keyAgreementTaskProvider = keyAgreementTaskProvider;
+		this.contactExchangeManager = contactExchangeManager;
+		this.connectionManager = connectionManager;
+		bt = BluetoothAdapter.getDefaultAdapter();
+		wifiPlugin = pluginManager.getPlugin(LanTcpConstants.ID);
+		bluetoothPlugin = pluginManager.getPlugin(BluetoothConstants.ID);
+		qrCodeDecoder = new QrCodeDecoder(androidExecutor, ioExecutor, this);
+		eventBus.addListener(this);
+		IntentFilter filter = new IntentFilter(ACTION_SCAN_MODE_CHANGED);
+		getApplication().registerReceiver(bluetoothReceiver, filter);
+	}
+
+	@Override
+	protected void onCleared() {
+		super.onCleared();
+		getApplication().unregisterReceiver(bluetoothReceiver);
+		eventBus.removeListener(this);
+		stopListening();
+	}
+
+	@UiThread
+	void onContinueClicked(Supplier<Boolean> checkPermissions) {
+		if (bluetoothDecision == REFUSED) {
+			bluetoothDecision = UNKNOWN; // Ask again
+		}
+		wasContinueClicked = true;
+		if (checkPermissions.get()) showQrCodeFragmentIfAllowed();
+	}
+
+	@UiThread
+	boolean isBluetoothSupported() {
+		return bt != null && bluetoothPlugin != null;
+	}
+
+	@UiThread
+	private boolean isWifiReady() {
+		if (wifiPlugin == null) return true; // Continue without wifi
+		State state = wifiPlugin.getState();
+		// Wait for plugin to become enabled
+		return state == ACTIVE || state == INACTIVE;
+	}
+
+	@UiThread
+	private boolean isBluetoothReady() {
+		if (bt == null || bluetoothPlugin == null) {
+			// Continue without Bluetooth
+			return true;
+		}
+		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;
+		}
+		// Wait for plugin to become active
+		return bluetoothPlugin.getState() == ACTIVE;
+	}
+
+	@UiThread
+	private void enableWifiIfWeShould() {
+		if (hasEnabledWifi) return;
+		if (wifiPlugin == null) return;
+		State state = wifiPlugin.getState();
+		if (state == STARTING_STOPPING || state == DISABLED) {
+			LOG.info("Enabling wifi plugin");
+			hasEnabledWifi = true;
+			pluginManager.setPluginEnabled(LanTcpConstants.ID, true);
+		}
+	}
+
+	@UiThread
+	private void enableBluetoothIfWeShould() {
+		if (bluetoothDecision != BluetoothDecision.ACCEPTED) return;
+		if (hasEnabledBluetooth) return;
+		if (bluetoothPlugin == null || !isBluetoothSupported()) return;
+		State state = bluetoothPlugin.getState();
+		if (state == STARTING_STOPPING || state == DISABLED) {
+			LOG.info("Enabling Bluetooth plugin");
+			hasEnabledBluetooth = true;
+			pluginManager.setPluginEnabled(BluetoothConstants.ID, true);
+		}
+	}
+
+	@UiThread
+	private void startAddingContact() {
+		// If we return to the intro fragment, the continue button needs to be
+		// clicked again before showing the QR code fragment
+		wasContinueClicked = false;
+		// If we return to the intro fragment, ask for Bluetooth
+		// discoverability again before showing the QR code fragment
+		bluetoothDecision = UNKNOWN;
+		// If we return to the intro fragment, we may need to enable wifi and
+		// Bluetooth again
+		hasEnabledWifi = false;
+		hasEnabledBluetooth = false;
+		// reset state, so we don't show an old QR code again
+		state.setValue(null);
+		// start to listen with a KeyAgreementTask
+		startListening();
+		showQrCodeFragment.setEvent(true);
+	}
+
+	/**
+	 * Call this once Bluetooth and Wi-Fi are ready to be used.
+	 * It is possible to call this more than once over the ViewModel's lifetime.
+	 */
+	@UiThread
+	private void startListening() {
+		KeyAgreementTask oldTask = task;
+		KeyAgreementTask newTask = keyAgreementTaskProvider.get();
+		task = newTask;
+		ioExecutor.execute(() -> {
+			if (oldTask != null) oldTask.stopListening();
+			newTask.listen();
+		});
+	}
+
+	@UiThread
+	private void stopListening() {
+		KeyAgreementTask oldTask = task;
+		ioExecutor.execute(() -> {
+			if (oldTask != null) oldTask.stopListening();
+		});
+	}
+
+	@Override
+	public void eventOccurred(Event e) {
+		if (e instanceof TransportStateEvent) {
+			TransportStateEvent t = (TransportStateEvent) e;
+			if (t.getTransportId().equals(BluetoothConstants.ID)) {
+				if (LOG.isLoggable(INFO)) {
+					LOG.info("Bluetooth state changed to " + t.getState());
+				}
+				showQrCodeFragmentIfAllowed();
+			} else if (t.getTransportId().equals(LanTcpConstants.ID)) {
+				if (LOG.isLoggable(INFO)) {
+					LOG.info("Wifi state changed to " + t.getState());
+				}
+				showQrCodeFragmentIfAllowed();
+			}
+		} else if (e instanceof KeyAgreementListeningEvent) {
+			LOG.info("KeyAgreementListeningEvent received");
+			KeyAgreementListeningEvent event = (KeyAgreementListeningEvent) e;
+			onLocalPayloadReceived(event.getLocalPayload());
+		} else if (e instanceof KeyAgreementWaitingEvent) {
+			LOG.info("KeyAgreementWaitingEvent received");
+			state.setValue(new KeyAgreementWaiting());
+		} else if (e instanceof KeyAgreementStartedEvent) {
+			LOG.info("KeyAgreementStartedEvent received");
+			state.setValue(new KeyAgreementStarted());
+		} else if (e instanceof KeyAgreementFinishedEvent) {
+			LOG.info("KeyAgreementFinishedEvent received");
+			KeyAgreementResult result =
+					((KeyAgreementFinishedEvent) e).getResult();
+			startContactExchange(result);
+			state.setValue(new ContactExchangeStarted());
+		} else if (e instanceof KeyAgreementAbortedEvent) {
+			LOG.info("KeyAgreementAbortedEvent received");
+			resetPayloadFlags();
+			state.setValue(new AddContactState.Failed());
+		} else if (e instanceof KeyAgreementFailedEvent) {
+			LOG.info("KeyAgreementFailedEvent received");
+			resetPayloadFlags();
+			state.setValue(new AddContactState.Failed());
+		}
+	}
+
+	@SuppressWarnings("StatementWithEmptyBody")
+	@UiThread
+	void showQrCodeFragmentIfAllowed() {
+		boolean permissionsGranted = areEssentialPermissionsGranted(
+				getApplication(), isBluetoothSupported());
+		boolean locationEnabled = isLocationEnabled(getApplication());
+		if (isActivityResumed && wasContinueClicked && permissionsGranted &&
+				locationEnabled) {
+			if (isWifiReady() && isBluetoothReady()) {
+				LOG.info("Wifi and Bluetooth are ready");
+				startAddingContact();
+			} else {
+				enableWifiIfWeShould();
+				if (bluetoothDecision == UNKNOWN) {
+					if (isBluetoothSupported()) {
+						requestBluetoothDiscoverable.setEvent(true);
+					} else {
+						bluetoothDecision = NO_ADAPTER;
+					}
+				} else if (bluetoothDecision == REFUSED) {
+					// Ask again when the user clicks "continue"
+				} else {
+					enableBluetoothIfWeShould();
+				}
+			}
+		}
+	}
+
+	/**
+	 * This sets the QR code by setting the state to KeyAgreementListening.
+	 */
+	private void onLocalPayloadReceived(Payload localPayload) {
+		if (gotLocalPayload) return;
+		DisplayMetrics dm = getApplication().getResources().getDisplayMetrics();
+		ioExecutor.execute(() -> {
+			byte[] payloadBytes = payloadEncoder.encode(localPayload);
+			if (LOG.isLoggable(INFO)) {
+				LOG.info("Local payload is " + payloadBytes.length
+						+ " bytes");
+			}
+			// Use ISO 8859-1 to encode bytes directly as a string
+			String content = new String(payloadBytes, ISO_8859_1);
+			Bitmap qrCode = QrCodeUtils.createQrCode(dm, content);
+			gotLocalPayload = true;
+			state.postValue(new KeyAgreementListening(qrCode));
+		});
+	}
+
+	@Override
+	@IoExecutor
+	public void onQrCodeDecoded(Result result) {
+		LOG.info("Got result from decoder");
+		// Ignore results until the KeyAgreementTask is ready
+		if (!gotLocalPayload || gotRemotePayload) return;
+		try {
+			byte[] payloadBytes = result.getText().getBytes(ISO_8859_1);
+			if (LOG.isLoggable(INFO))
+				LOG.info("Remote payload is " + payloadBytes.length + " bytes");
+			Payload remotePayload = payloadParser.parse(payloadBytes);
+			gotRemotePayload = true;
+			requireNonNull(task).connectAndRunProtocol(remotePayload);
+			state.postValue(new AddContactState.QrCodeScanned());
+		} catch (UnsupportedVersionException e) {
+			resetPayloadFlags();
+			state.postValue(new AddContactState.Failed(e.isTooOld()));
+		} catch (IOException | IllegalArgumentException e) {
+			LOG.log(WARNING, "QR Code Invalid", e);
+			androidExecutor.runOnUiThread(() -> Toast.makeText(getApplication(),
+					R.string.qr_code_invalid, LENGTH_LONG).show());
+			resetPayloadFlags();
+			state.postValue(new AddContactState.Failed());
+		}
+	}
+
+	private void resetPayloadFlags() {
+		gotRemotePayload = false;
+		gotLocalPayload = false;
+	}
+
+	@UiThread
+	private void startContactExchange(KeyAgreementResult result) {
+		TransportId t = result.getTransportId();
+		DuplexTransportConnection conn = result.getConnection();
+		SecretKey masterKey = result.getMasterKey();
+		boolean alice = result.wasAlice();
+		ioExecutor.execute(() -> {
+			try {
+				Contact contact = contactExchangeManager.exchangeContacts(conn,
+						masterKey, alice, true);
+				// Reuse the connection as a transport connection
+				connectionManager
+						.manageOutgoingConnection(contact.getId(), t, conn);
+				Success success = new Success(contact.getAuthor());
+				state.postValue(new ContactExchangeFinished(success));
+			} catch (ContactExistsException e) {
+				tryToClose(conn);
+				Error error = new Error(e.getRemoteAuthor());
+				state.postValue(new ContactExchangeFinished(error));
+			} catch (DbException | IOException e) {
+				tryToClose(conn);
+				logException(LOG, WARNING, e);
+				Error error = new Error(null);
+				state.postValue(new ContactExchangeFinished(error));
+			}
+		});
+	}
+
+	private class BluetoothStateReceiver extends BroadcastReceiver {
+		@UiThread
+		@Override
+		public void onReceive(Context context, Intent intent) {
+			int scanMode = intent.getIntExtra(EXTRA_SCAN_MODE, -1);
+			LOG.info("Bluetooth scan mode changed: " + scanMode);
+			showQrCodeFragmentIfAllowed();
+		}
+	}
+
+	private void tryToClose(DuplexTransportConnection conn) {
+		try {
+			conn.getReader().dispose(true, true);
+			conn.getWriter().dispose(true);
+		} catch (IOException e) {
+			logException(LOG, WARNING, e);
+		}
+	}
+
+	/**
+	 * Set to true in onPostResume() and false in onPause(). This prevents the
+	 * QR code fragment from being shown if onRequestPermissionsResult() is
+	 * called while the activity is paused, which could cause a crash due to
+	 * https://issuetracker.google.com/issues/37067655.
+	 * TODO check if this is still happening with new permission requesting
+	 */
+	@UiThread
+	void setIsActivityResumed(boolean resumed) {
+		isActivityResumed = resumed;
+		// Workaround for
+		// https://code.google.com/p/android/issues/detail?id=190966
+		showQrCodeFragmentIfAllowed();
+	}
+
+	@UiThread
+	void setBluetoothDecision(BluetoothDecision decision) {
+		bluetoothDecision = decision;
+		showQrCodeFragmentIfAllowed();
+	}
+
+	QrCodeDecoder getQrCodeDecoder() {
+		return qrCodeDecoder;
+	}
+
+	LiveEvent<Boolean> getRequestBluetoothDiscoverable() {
+		return requestBluetoothDiscoverable;
+	}
+
+	LiveEvent<Boolean> getShowQrCodeFragment() {
+		return showQrCodeFragment;
+	}
+
+	/**
+	 * This LiveData will be null initially.
+	 */
+	LiveData<AddContactState> getState() {
+		return state;
+	}
+
+}

briar-android/src/main/java/org/briarproject/briar/android/contact/add/nearby/CameraException.java

@@ -1,8 +1,8 @@
-package org.briarproject.briar.android.keyagreement;
+package org.briarproject.briar.android.contact.add.nearby;
 
 import java.io.IOException;
 
-class CameraException extends IOException {
+public class CameraException extends IOException {
 
 	CameraException(String message) {
 		super(message);

briar-android/src/main/java/org/briarproject/briar/android/contact/add/nearby/CameraView.java

@@ -1,4 +1,4 @@
-package org.briarproject.briar.android.keyagreement;
+package org.briarproject.briar.android.contact.add.nearby;
 
 import android.content.Context;
 import android.hardware.Camera;
@@ -40,7 +40,6 @@ import static java.util.logging.Level.INFO;
 import static java.util.logging.Level.WARNING;
 import static org.briarproject.bramble.util.LogUtils.logException;
 
-@SuppressWarnings("deprecation")
 @MethodsNotNullByDefault
 @ParametersNotNullByDefault
 public class CameraView extends SurfaceView implements SurfaceHolder.Callback,
@@ -126,8 +125,14 @@ public class CameraView extends SurfaceView implements SurfaceHolder.Callback,
 			throw new CameraException(e);
 		}
 		setDisplayOrientation(getScreenRotationDegrees());
+		if (camera == null) throw new CameraException("No camera found");
 		// Use barcode scene mode if it's available
-		Parameters params = camera.getParameters();
+		Parameters params;
+		try {
+			params = camera.getParameters();
+		} catch (RuntimeException e) {
+			throw new CameraException(e);
+		}
 		params = setSceneMode(camera, params);
 		if (SCENE_MODE_BARCODE.equals(params.getSceneMode())) {
 			// If the scene mode enabled the flash, try to disable it

briar-android/src/main/java/org/briarproject/briar/android/contact/add/nearby/PreviewConsumer.java

@@ -1,4 +1,4 @@
-package org.briarproject.briar.android.keyagreement;
+package org.briarproject.briar.android.contact.add.nearby;
 
 import android.hardware.Camera;
 
@@ -6,7 +6,6 @@ import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
 
 import androidx.annotation.UiThread;
 
-@SuppressWarnings("deprecation")
 @NotNullByDefault
 interface PreviewConsumer {
 

briar-android/src/main/java/org/briarproject/briar/android/contact/add/nearby/QrCodeDecoder.java

@@ -1,10 +1,9 @@
-package org.briarproject.briar.android.keyagreement;
+package org.briarproject.briar.android.contact.add.nearby;
 
 import android.hardware.Camera;
 import android.hardware.Camera.CameraInfo;
 import android.hardware.Camera.PreviewCallback;
 import android.hardware.Camera.Size;
-import android.os.AsyncTask;
 
 import com.google.zxing.BinaryBitmap;
 import com.google.zxing.LuminanceSource;
@@ -15,10 +14,13 @@ import com.google.zxing.Result;
 import com.google.zxing.common.HybridBinarizer;
 import com.google.zxing.qrcode.QRCodeReader;
 
+import org.briarproject.bramble.api.lifecycle.IoExecutor;
 import org.briarproject.bramble.api.nullsafety.MethodsNotNullByDefault;
 import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
 import org.briarproject.bramble.api.nullsafety.ParametersNotNullByDefault;
+import org.briarproject.bramble.api.system.AndroidExecutor;
 
+import java.util.concurrent.Executor;
 import java.util.logging.Logger;
 
 import androidx.annotation.UiThread;
@@ -26,22 +28,26 @@ import androidx.annotation.UiThread;
 import static com.google.zxing.DecodeHintType.CHARACTER_SET;
 import static java.util.Collections.singletonMap;
 import static java.util.logging.Level.WARNING;
+import static java.util.logging.Logger.getLogger;
 
-@SuppressWarnings("deprecation")
 @MethodsNotNullByDefault
 @ParametersNotNullByDefault
-class QrCodeDecoder implements PreviewConsumer, PreviewCallback {
+public class QrCodeDecoder implements PreviewConsumer, PreviewCallback {
 
-	private static final Logger LOG =
-			Logger.getLogger(QrCodeDecoder.class.getName());
+	private static final Logger LOG = getLogger(QrCodeDecoder.class.getName());
 
+	private final AndroidExecutor androidExecutor;
+	private final Executor ioExecutor;
 	private final Reader reader = new QRCodeReader();
 	private final ResultCallback callback;
 
 	private Camera camera = null;
 	private int cameraIndex = 0;
 
-	QrCodeDecoder(ResultCallback callback) {
+	public QrCodeDecoder(AndroidExecutor androidExecutor,
+			@IoExecutor Executor ioExecutor, ResultCallback callback) {
+		this.androidExecutor = androidExecutor;
+		this.ioExecutor = ioExecutor;
 		this.callback = callback;
 	}
 
@@ -74,8 +80,7 @@ class QrCodeDecoder implements PreviewConsumer, PreviewCallback {
 				if (data.length == size.width * size.height * 3 / 2) {
 					CameraInfo info = new CameraInfo();
 					Camera.getCameraInfo(cameraIndex, info);
-					new DecoderTask(data, size.width, size.height,
-							info.orientation).execute();
+					decode(data, size.width, size.height, info.orientation);
 				} else {
 					// Camera parameters have changed - ask for a new preview
 					LOG.info("Preview size does not match camera parameters");
@@ -89,43 +94,23 @@ class QrCodeDecoder implements PreviewConsumer, PreviewCallback {
 		}
 	}
 
-	private class DecoderTask extends AsyncTask<Void, Void, Void> {
-
-		private final byte[] data;
-		private final int width, height, orientation;
-
-		private DecoderTask(byte[] data, int width, int height,
-				int orientation) {
-			this.data = data;
-			this.width = width;
-			this.height = height;
-			this.orientation = orientation;
-		}
-
-		@Override
-		protected Void doInBackground(Void... params) {
+	private void decode(byte[] data, int width, int height, int orientation) {
+		ioExecutor.execute(() -> {
 			BinaryBitmap bitmap = binarize(data, width, height, orientation);
 			Result result;
 			try {
 				result = reader.decode(bitmap,
 						singletonMap(CHARACTER_SET, "ISO8859_1"));
+				callback.onQrCodeDecoded(result);
 			} catch (ReaderException e) {
 				// No barcode found
-				return null;
 			} catch (RuntimeException e) {
 				LOG.warning("Invalid preview frame");
-				return null;
 			} finally {
 				reader.reset();
+				androidExecutor.runOnUiThread(this::askForPreviewFrame);
 			}
-			callback.handleResult(result);
-			return null;
-		}
-
-		@Override
-		protected void onPostExecute(Void result) {
-			askForPreviewFrame();
-		}
+		});
 	}
 
 	private static BinaryBitmap binarize(byte[] data, int width, int height,
@@ -142,8 +127,8 @@ class QrCodeDecoder implements PreviewConsumer, PreviewCallback {
 	}
 
 	@NotNullByDefault
-	interface ResultCallback {
-
-		void handleResult(Result result);
+	public interface ResultCallback {
+		@IoExecutor
+		void onQrCodeDecoded(Result result);
 	}
 }

briar-android/src/main/java/org/briarproject/briar/android/contact/add/nearby/QrCodeUtils.java

@@ -1,4 +1,4 @@
-package org.briarproject.briar.android.keyagreement;
+package org.briarproject.briar.android.contact.add.nearby;
 
 import android.graphics.Bitmap;
 import android.util.DisplayMetrics;
@@ -18,16 +18,16 @@ import static android.graphics.Color.BLACK;
 import static android.graphics.Color.WHITE;
 import static com.google.zxing.BarcodeFormat.QR_CODE;
 import static java.util.logging.Level.WARNING;
+import static java.util.logging.Logger.getLogger;
 import static org.briarproject.bramble.util.LogUtils.logException;
 
 @NotNullByDefault
-class QrCodeUtils {
+public class QrCodeUtils {
 
-	private static final Logger LOG =
-			Logger.getLogger(QrCodeUtils.class.getName());
+	private static final Logger LOG = getLogger(QrCodeUtils.class.getName());
 
 	@Nullable
-	static Bitmap createQrCode(DisplayMetrics dm, String input) {
+	public static Bitmap createQrCode(DisplayMetrics dm, String input) {
 		int smallestDimen = Math.min(dm.widthPixels, dm.heightPixels);
 		try {
 			// Generate QR code

briar-android/src/main/java/org/briarproject/briar/android/contactselection/BaseContactSelectorFragment.java

@@ -56,8 +56,11 @@ public abstract class BaseContactSelectorFragment<I extends SelectableContactIte
 
 		Bundle args = requireArguments();
 		byte[] b = args.getByteArray(GROUP_ID);
-		if (b == null) throw new IllegalStateException("No GroupId");
-		groupId = new GroupId(b);
+//		if (b == null) throw new IllegalStateException("No GroupId");
+		// TODO find what the groupId should be when selecting custodians
+		if (b != null) {
+			groupId = new GroupId(b);
+		}
 	}
 
 	@Override

briar-android/src/main/java/org/briarproject/briar/android/contactselection/ContactSelectorFragment.java

@@ -18,7 +18,7 @@ public abstract class ContactSelectorFragment extends
 
 	public static final String TAG = ContactSelectorFragment.class.getName();
 
-	private Menu menu;
+	protected Menu menu;
 
 	@Override
 	protected ContactSelectorAdapter getAdapter(Context context,

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

@@ -52,6 +52,7 @@ import org.briarproject.briar.android.conversation.ConversationVisitor.TextCache
 import org.briarproject.briar.android.forum.ForumActivity;
 import org.briarproject.briar.android.introduction.IntroductionActivity;
 import org.briarproject.briar.android.privategroup.conversation.GroupActivity;
+import org.briarproject.briar.android.socialbackup.recover.CustodianReturnShardActivity;
 import org.briarproject.briar.android.util.BriarSnackbarBuilder;
 import org.briarproject.briar.android.view.BriarRecyclerView;
 import org.briarproject.briar.android.view.ImagePreview;
@@ -396,6 +397,12 @@ public class ConversationActivity extends BriarActivity
 			case R.id.action_social_remove_person:
 				askToRemoveContact();
 				return true;
+			case R.id.action_help_recover_account:
+				if (contactId == null) return false;
+				Intent i = new Intent(this, CustodianReturnShardActivity.class);
+				i.putExtra(CONTACT_ID, contactId.getInt());
+				startActivity(i);
+				return true;
 			default:
 				return super.onOptionsItemSelected(item);
 		}

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

@@ -3,6 +3,7 @@ package org.briarproject.briar.android.conversation;
 import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
 import org.briarproject.briar.api.conversation.ConversationRequest;
 import org.briarproject.briar.api.conversation.ConversationResponse;
+import org.briarproject.briar.api.socialbackup.ShardMessageHeader;
 
 import javax.annotation.Nullable;
 import javax.annotation.concurrent.NotThreadSafe;
@@ -30,6 +31,13 @@ class ConversationNoticeItem extends ConversationItem {
 		this.msgText = null;
 	}
 
+	ConversationNoticeItem(@LayoutRes int layoutRes, String text,
+			ShardMessageHeader r) {
+		super(layoutRes, r);
+		this.text = text;
+		this.msgText = null;
+	}
+
 	@Nullable
 	String getMsgText() {
 		return msgText;

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

@@ -16,6 +16,7 @@ import org.briarproject.briar.api.introduction.IntroductionResponse;
 import org.briarproject.briar.api.messaging.PrivateMessageHeader;
 import org.briarproject.briar.api.privategroup.invitation.GroupInvitationRequest;
 import org.briarproject.briar.api.privategroup.invitation.GroupInvitationResponse;
+import org.briarproject.briar.api.socialbackup.ShardMessageHeader;
 
 import java.util.List;
 
@@ -292,6 +293,21 @@ class ConversationVisitor implements
 		}
 	}
 
+	@Override
+	public ConversationItem visitShardMessage(ShardMessageHeader r) {
+		if (r.isLocal()) {
+			String text = ctx.getString(R.string.social_backup_shard_sent,
+					contactName.getValue());
+			return new ConversationNoticeItem(
+					R.layout.list_item_conversation_notice_out, text, r);
+		} else {
+			String text = ctx.getString(R.string.social_backup_shard_received,
+					contactName.getValue());
+			return new ConversationNoticeItem(
+					R.layout.list_item_conversation_notice_in, text, r);
+		}
+	}
+
 	interface TextCache {
 		@Nullable
 		String getText(MessageId m);

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

@@ -1,119 +0,0 @@
-package org.briarproject.briar.android.keyagreement;
-
-import android.os.Bundle;
-import android.widget.Toast;
-
-import org.briarproject.bramble.api.identity.Author;
-import org.briarproject.bramble.api.keyagreement.KeyAgreementResult;
-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 javax.annotation.Nullable;
-import javax.inject.Inject;
-
-import androidx.annotation.UiThread;
-import androidx.lifecycle.ViewModelProvider;
-import androidx.lifecycle.ViewModelProviders;
-
-import static android.widget.Toast.LENGTH_LONG;
-import static java.util.Objects.requireNonNull;
-
-@MethodsNotNullByDefault
-@ParametersNotNullByDefault
-public class ContactExchangeActivity extends KeyAgreementActivity {
-
-	@Inject
-	ViewModelProvider.Factory viewModelFactory;
-
-	private ContactExchangeViewModel viewModel;
-
-	@Override
-	public void injectActivity(ActivityComponent component) {
-		component.inject(this);
-	}
-
-	@Override
-	public void onCreate(@Nullable Bundle state) {
-		super.onCreate(state);
-		requireNonNull(getSupportActionBar())
-				.setTitle(R.string.add_contact_title);
-		viewModel = ViewModelProviders.of(this, viewModelFactory)
-				.get(ContactExchangeViewModel.class);
-	}
-
-	private void startContactExchange(KeyAgreementResult result) {
-		viewModel.getSucceeded().observe(this, succeeded -> {
-			if (succeeded == null) return;
-			if (succeeded) {
-				Author remote = requireNonNull(viewModel.getRemoteAuthor());
-				contactExchangeSucceeded(remote);
-			} else {
-				Author duplicate = viewModel.getDuplicateAuthor();
-				if (duplicate == null) contactExchangeFailed();
-				else duplicateContact(duplicate);
-			}
-		});
-		viewModel.startContactExchange(result.getTransportId(),
-				result.getConnection(), result.getMasterKey(),
-				result.wasAlice());
-	}
-
-	@UiThread
-	private void contactExchangeSucceeded(Author remoteAuthor) {
-		String contactName = remoteAuthor.getName();
-		String text = getString(R.string.contact_added_toast, contactName);
-		Toast.makeText(this, text, LENGTH_LONG).show();
-		supportFinishAfterTransition();
-	}
-
-	@UiThread
-	private void duplicateContact(Author remoteAuthor) {
-		String contactName = remoteAuthor.getName();
-		String format = getString(R.string.contact_already_exists);
-		String text = String.format(format, contactName);
-		Toast.makeText(this, text, LENGTH_LONG).show();
-		finish();
-	}
-
-	@UiThread
-	private void contactExchangeFailed() {
-		showErrorFragment();
-	}
-
-	@UiThread
-	@Override
-	public void keyAgreementFailed() {
-		showErrorFragment();
-	}
-
-	@UiThread
-	@Override
-	public String keyAgreementWaiting() {
-		return getString(R.string.waiting_for_contact_to_scan);
-	}
-
-	@UiThread
-	@Override
-	public String keyAgreementStarted() {
-		return getString(R.string.authenticating_with_device);
-	}
-
-	@UiThread
-	@Override
-	public void keyAgreementAborted(boolean remoteAborted) {
-		showErrorFragment();
-	}
-
-	@UiThread
-	@Override
-	public String keyAgreementFinished(KeyAgreementResult result) {
-		startContactExchange(result);
-		return getString(R.string.exchanging_contact_details);
-	}
-
-	private void showErrorFragment() {
-		showNextFragment(new ContactExchangeErrorFragment());
-	}
-}

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

@@ -1,105 +0,0 @@
-package org.briarproject.briar.android.keyagreement;
-
-import android.app.Application;
-
-import org.briarproject.bramble.api.connection.ConnectionManager;
-import org.briarproject.bramble.api.contact.Contact;
-import org.briarproject.bramble.api.contact.ContactExchangeManager;
-import org.briarproject.bramble.api.crypto.SecretKey;
-import org.briarproject.bramble.api.db.ContactExistsException;
-import org.briarproject.bramble.api.db.DbException;
-import org.briarproject.bramble.api.identity.Author;
-import org.briarproject.bramble.api.lifecycle.IoExecutor;
-import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
-import org.briarproject.bramble.api.plugin.TransportId;
-import org.briarproject.bramble.api.plugin.duplex.DuplexTransportConnection;
-
-import java.io.IOException;
-import java.util.concurrent.Executor;
-import java.util.logging.Logger;
-
-import javax.annotation.Nullable;
-import javax.inject.Inject;
-
-import androidx.annotation.UiThread;
-import androidx.lifecycle.AndroidViewModel;
-import androidx.lifecycle.LiveData;
-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;
-
-@NotNullByDefault
-class ContactExchangeViewModel extends AndroidViewModel {
-
-	private static final Logger LOG =
-			getLogger(ContactExchangeViewModel.class.getName());
-
-	private final Executor ioExecutor;
-	private final ContactExchangeManager contactExchangeManager;
-	private final ConnectionManager connectionManager;
-	private final MutableLiveData<Boolean> succeeded = new MutableLiveData<>();
-
-	@Nullable
-	private volatile Author remoteAuthor, duplicateAuthor;
-
-	@Inject
-	ContactExchangeViewModel(Application app, @IoExecutor Executor ioExecutor,
-			ContactExchangeManager contactExchangeManager,
-			ConnectionManager connectionManager) {
-		super(app);
-		this.ioExecutor = ioExecutor;
-		this.contactExchangeManager = contactExchangeManager;
-		this.connectionManager = connectionManager;
-	}
-
-	@UiThread
-	void startContactExchange(TransportId t, DuplexTransportConnection conn,
-			SecretKey masterKey, boolean alice) {
-		ioExecutor.execute(() -> {
-			try {
-				Contact contact = contactExchangeManager.exchangeContacts(conn,
-						masterKey, alice, true);
-				// Reuse the connection as a transport connection
-				connectionManager.manageOutgoingConnection(contact.getId(),
-						t, conn);
-				remoteAuthor = contact.getAuthor();
-				succeeded.postValue(true);
-			} catch (ContactExistsException e) {
-				tryToClose(conn);
-				duplicateAuthor = e.getRemoteAuthor();
-				succeeded.postValue(false);
-			} catch (DbException | IOException e) {
-				tryToClose(conn);
-				logException(LOG, WARNING, e);
-				succeeded.postValue(false);
-			}
-		});
-	}
-
-	private void tryToClose(DuplexTransportConnection conn) {
-		try {
-			conn.getReader().dispose(true, true);
-			conn.getWriter().dispose(true);
-		} catch (IOException e) {
-			logException(LOG, WARNING, e);
-		}
-	}
-
-	@UiThread
-	@Nullable
-	Author getRemoteAuthor() {
-		return remoteAuthor;
-	}
-
-	@UiThread
-	@Nullable
-	Author getDuplicateAuthor() {
-		return duplicateAuthor;
-	}
-
-	LiveData<Boolean> getSucceeded() {
-		return succeeded;
-	}
-}

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

@@ -1,72 +0,0 @@
-package org.briarproject.briar.android.keyagreement;
-
-import android.content.Context;
-import android.os.Bundle;
-import android.view.LayoutInflater;
-import android.view.View;
-import android.view.ViewGroup;
-import android.widget.ScrollView;
-
-import org.briarproject.bramble.api.nullsafety.MethodsNotNullByDefault;
-import org.briarproject.bramble.api.nullsafety.ParametersNotNullByDefault;
-import org.briarproject.briar.R;
-import org.briarproject.briar.android.fragment.BaseFragment;
-
-import javax.annotation.Nullable;
-
-import static android.view.View.FOCUS_DOWN;
-
-@MethodsNotNullByDefault
-@ParametersNotNullByDefault
-public class IntroFragment extends BaseFragment {
-
-	interface IntroScreenSeenListener {
-		void showNextScreen();
-	}
-
-	public static final String TAG = IntroFragment.class.getName();
-
-	private IntroScreenSeenListener screenSeenListener;
-	private ScrollView scrollView;
-
-	public static IntroFragment newInstance() {
-
-		Bundle args = new Bundle();
-
-		IntroFragment fragment = new IntroFragment();
-		fragment.setArguments(args);
-		return fragment;
-	}
-
-	@Override
-	public void onAttach(Context context) {
-		super.onAttach(context);
-		screenSeenListener = (IntroScreenSeenListener) context;
-	}
-
-	@Override
-	public String getUniqueTag() {
-		return TAG;
-	}
-
-	@Nullable
-	@Override
-	public View onCreateView(LayoutInflater inflater,
-			@Nullable ViewGroup container,
-			@Nullable Bundle savedInstanceState) {
-
-		View v = inflater.inflate(R.layout.fragment_keyagreement_id, container,
-				false);
-		scrollView = v.findViewById(R.id.scrollView);
-		View button = v.findViewById(R.id.continueButton);
-		button.setOnClickListener(view -> screenSeenListener.showNextScreen());
-		return v;
-	}
-
-	@Override
-	public void onStart() {
-		super.onStart();
-		scrollView.post(() -> scrollView.fullScroll(FOCUS_DOWN));
-	}
-
-}

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

@@ -1,484 +0,0 @@
-package org.briarproject.briar.android.keyagreement;
-
-import android.bluetooth.BluetoothAdapter;
-import android.content.BroadcastReceiver;
-import android.content.Context;
-import android.content.Intent;
-import android.content.IntentFilter;
-import android.os.Bundle;
-import android.view.MenuItem;
-
-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.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;
-import org.briarproject.bramble.api.plugin.Plugin.State;
-import org.briarproject.bramble.api.plugin.PluginManager;
-import org.briarproject.bramble.api.plugin.event.TransportStateEvent;
-import org.briarproject.briar.R;
-import org.briarproject.briar.android.activity.ActivityComponent;
-import org.briarproject.briar.android.activity.BriarActivity;
-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 java.util.logging.Logger;
-
-import javax.annotation.Nullable;
-import javax.inject.Inject;
-
-import androidx.annotation.StringRes;
-import androidx.annotation.UiThread;
-import androidx.appcompat.app.AlertDialog.Builder;
-import androidx.appcompat.widget.Toolbar;
-import androidx.core.app.ActivityCompat;
-import androidx.fragment.app.FragmentManager;
-
-import static android.Manifest.permission.ACCESS_FINE_LOCATION;
-import static android.Manifest.permission.CAMERA;
-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;
-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.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
-public abstract class KeyAgreementActivity extends BriarActivity implements
-		BaseFragmentListener, IntroScreenSeenListener,
-		KeyAgreementEventListener, EventListener {
-
-	private enum BluetoothDecision {
-		/**
-		 * We haven't asked the user about Bluetooth discoverability.
-		 */
-		UNKNOWN,
-
-		/**
-		 * The device doesn't have a Bluetooth adapter.
-		 */
-		NO_ADAPTER,
-
-		/**
-		 * We're waiting for the user to accept or refuse discoverability.
-		 */
-		WAITING,
-
-		/**
-		 * The user has accepted discoverability.
-		 */
-		ACCEPTED,
-
-		/**
-		 * The user has refused discoverability.
-		 */
-		REFUSED
-	}
-
-	private enum Permission {
-		UNKNOWN, GRANTED, SHOW_RATIONALE, PERMANENTLY_DENIED
-	}
-
-	private static final Logger LOG =
-			getLogger(KeyAgreementActivity.class.getName());
-
-	@Inject
-	EventBus eventBus;
-
-	@Inject
-	PluginManager pluginManager;
-
-	/**
-	 * Set to true in onPostResume() and false in onPause(). This prevents the
-	 * QR code fragment from being shown if onRequestPermissionsResult() is
-	 * called while the activity is paused, which could cause a crash due to
-	 * https://issuetracker.google.com/issues/37067655.
-	 */
-	private boolean isResumed = false;
-
-	/**
-	 * Set to true when the continue button is clicked, and false when the QR
-	 * code fragment is shown. This prevents the QR code fragment from being
-	 * shown automatically before the continue button has been clicked.
-	 */
-	private boolean continueClicked = false;
-
-	/**
-	 * Records whether we've enabled the wifi plugin so we don't enable it more
-	 * than once.
-	 */
-	private boolean hasEnabledWifi = false;
-
-	/**
-	 * Records whether we've enabled the Bluetooth plugin so we don't enable it
-	 * more than once.
-	 */
-	private boolean hasEnabledBluetooth = false;
-
-	private Permission cameraPermission = Permission.UNKNOWN;
-	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) {
-		component.inject(this);
-	}
-
-	@Override
-	public void onCreate(@Nullable Bundle state) {
-		super.onCreate(state);
-		setContentView(R.layout.activity_fragment_container_toolbar);
-		Toolbar toolbar = findViewById(R.id.toolbar);
-		setSupportActionBar(toolbar);
-		requireNonNull(getSupportActionBar()).setDisplayHomeAsUpEnabled(true);
-		if (state == null) {
-			showInitialFragment(IntroFragment.newInstance());
-		}
-		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
-	public void onDestroy() {
-		super.onDestroy();
-		if (bluetoothReceiver != null) unregisterReceiver(bluetoothReceiver);
-	}
-
-	@Override
-	public boolean onOptionsItemSelected(MenuItem item) {
-		if (item.getItemId() == android.R.id.home) {
-			onBackPressed();
-			return true;
-		}
-		return super.onOptionsItemSelected(item);
-	}
-
-	@Override
-	public void onStart() {
-		super.onStart();
-		eventBus.addListener(this);
-		// Permissions may have been granted manually while we were stopped
-		cameraPermission = Permission.UNKNOWN;
-		locationPermission = Permission.UNKNOWN;
-	}
-
-	@Override
-	protected void onPostResume() {
-		super.onPostResume();
-		isResumed = true;
-		// Workaround for
-		// https://code.google.com/p/android/issues/detail?id=190966
-		showQrCodeFragmentIfAllowed();
-	}
-
-	@SuppressWarnings("StatementWithEmptyBody")
-	private void showQrCodeFragmentIfAllowed() {
-		if (isResumed && continueClicked && areEssentialPermissionsGranted()) {
-			if (isWifiReady() && isBluetoothReady()) {
-				LOG.info("Wifi and Bluetooth are ready");
-				showQrCodeFragment();
-			} else {
-				if (shouldEnableWifi()) {
-					LOG.info("Enabling wifi plugin");
-					hasEnabledWifi = true;
-					pluginManager.setPluginEnabled(LanTcpConstants.ID, true);
-				}
-				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;
-					pluginManager.setPluginEnabled(BluetoothConstants.ID, true);
-				}
-			}
-		}
-	}
-
-	private boolean areEssentialPermissionsGranted() {
-		return cameraPermission == Permission.GRANTED &&
-				(SDK_INT < 23 || locationPermission == Permission.GRANTED ||
-						!isBluetoothSupported());
-	}
-
-	private boolean isBluetoothSupported() {
-		return bt != null && bluetoothPlugin != null;
-	}
-
-	private boolean isWifiReady() {
-		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 (!isBluetoothSupported()) {
-			// Continue without Bluetooth
-			return true;
-		}
-		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;
-		}
-		// Wait for plugin to become active
-		return bluetoothPlugin.getState() == ACTIVE;
-	}
-
-	private boolean shouldEnableWifi() {
-		if (hasEnabledWifi) return false;
-		if (wifiPlugin == null) return false;
-		State state = wifiPlugin.getState();
-		return state == STARTING_STOPPING || state == DISABLED;
-	}
-
-	private void requestBluetoothDiscoverable() {
-		if (!isBluetoothSupported()) {
-			bluetoothDecision = BluetoothDecision.NO_ADAPTER;
-			showQrCodeFragmentIfAllowed();
-		} else {
-			Intent i = new Intent(ACTION_REQUEST_DISCOVERABLE);
-			if (i.resolveActivity(getPackageManager()) != null) {
-				LOG.info("Asking for Bluetooth discoverability");
-				bluetoothDecision = BluetoothDecision.WAITING;
-				startActivityForResult(i, REQUEST_BLUETOOTH_DISCOVERABLE);
-			} else {
-				bluetoothDecision = BluetoothDecision.NO_ADAPTER;
-				showQrCodeFragmentIfAllowed();
-			}
-		}
-	}
-
-	private boolean shouldEnableBluetooth() {
-		if (bluetoothDecision != BluetoothDecision.ACCEPTED) return false;
-		if (hasEnabledBluetooth) return false;
-		if (!isBluetoothSupported()) return false;
-		State state = bluetoothPlugin.getState();
-		return state == STARTING_STOPPING || state == DISABLED;
-	}
-
-	@Override
-	protected void onPause() {
-		super.onPause();
-		isResumed = false;
-	}
-
-	@Override
-	protected void onStop() {
-		super.onStop();
-		eventBus.removeListener(this);
-	}
-
-	@Override
-	public void showNextScreen() {
-		continueClicked = true;
-		if (bluetoothDecision == BluetoothDecision.REFUSED) {
-			bluetoothDecision = BluetoothDecision.UNKNOWN; // Ask again
-		}
-		if (checkPermissions()) showQrCodeFragmentIfAllowed();
-	}
-
-	@Override
-	public void onActivityResult(int request, int result,
-			@Nullable Intent data) {
-		if (request == REQUEST_BLUETOOTH_DISCOVERABLE) {
-			if (result == RESULT_CANCELED) {
-				LOG.info("Bluetooth discoverability was refused");
-				bluetoothDecision = BluetoothDecision.REFUSED;
-			} else {
-				LOG.info("Bluetooth discoverability was accepted");
-				bluetoothDecision = BluetoothDecision.ACCEPTED;
-			}
-			showQrCodeFragmentIfAllowed();
-		} else super.onActivityResult(request, result, data);
-	}
-
-	private void showQrCodeFragment() {
-		// If we return to the intro fragment, the continue button needs to be
-		// clicked again before showing the QR code fragment
-		continueClicked = false;
-		// If we return to the intro fragment, ask for Bluetooth
-		// discoverability again before showing the QR code fragment
-		bluetoothDecision = BluetoothDecision.UNKNOWN;
-		// If we return to the intro fragment, we may need to enable wifi and
-		// Bluetooth again
-		hasEnabledWifi = false;
-		hasEnabledBluetooth = false;
-
-		// FIXME #824
-		FragmentManager fm = getSupportFragmentManager();
-		if (fm.findFragmentByTag(KeyAgreementFragment.TAG) == null) {
-			BaseFragment f = KeyAgreementFragment.newInstance();
-			fm.beginTransaction()
-					.replace(R.id.fragmentContainer, f, f.getUniqueTag())
-					.addToBackStack(f.getUniqueTag())
-					.commit();
-		}
-	}
-
-	private boolean checkPermissions() {
-		if (areEssentialPermissionsGranted()) return true;
-		// If an essential permission has been permanently denied, ask the
-		// user to change the setting
-		if (cameraPermission == Permission.PERMANENTLY_DENIED) {
-			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?
-		if (cameraPermission == Permission.SHOW_RATIONALE &&
-				locationPermission == Permission.SHOW_RATIONALE) {
-			showRationale(R.string.permission_camera_location_title,
-					R.string.permission_camera_location_request_body);
-		} else if (cameraPermission == Permission.SHOW_RATIONALE) {
-			showRationale(R.string.permission_camera_title,
-					R.string.permission_camera_request_body);
-		} else if (locationPermission == Permission.SHOW_RATIONALE) {
-			showRationale(R.string.permission_location_title,
-					R.string.permission_location_request_body);
-		} else {
-			requestPermissions();
-		}
-		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);
-		builder.setMessage(body);
-		builder.setNeutralButton(R.string.continue_button,
-				(dialog, which) -> requestPermissions());
-		builder.show();
-	}
-
-	private void requestPermissions() {
-		String[] permissions;
-		if (isBluetoothSupported()) {
-			permissions = new String[] {CAMERA, ACCESS_FINE_LOCATION};
-		} else {
-			permissions = new String[] {CAMERA};
-		}
-		ActivityCompat.requestPermissions(this, permissions,
-				REQUEST_PERMISSION_CAMERA_LOCATION);
-	}
-
-	@Override
-	@UiThread
-	public void onRequestPermissionsResult(int requestCode,
-			String[] permissions, int[] grantResults) {
-		super.onRequestPermissionsResult(requestCode, permissions,
-				grantResults);
-		if (requestCode != REQUEST_PERMISSION_CAMERA_LOCATION)
-			throw new AssertionError();
-		if (gotPermission(CAMERA, permissions, grantResults)) {
-			cameraPermission = Permission.GRANTED;
-		} else if (shouldShowRationale(CAMERA)) {
-			cameraPermission = Permission.SHOW_RATIONALE;
-		} else {
-			cameraPermission = 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
-		// https://code.google.com/p/android/issues/detail?id=190966.
-		// In that case the isResumed flag prevents the fragment from being
-		// shown here, and showQrCodeFragmentIfAllowed() will be called again
-		// from onPostResume().
-		if (checkPermissions()) showQrCodeFragmentIfAllowed();
-	}
-
-	private boolean gotPermission(String permission, String[] permissions,
-			int[] grantResults) {
-		for (int i = 0; i < permissions.length; i++) {
-			if (permission.equals(permissions[i]))
-				return grantResults[i] == PERMISSION_GRANTED;
-		}
-		return false;
-	}
-
-	private boolean shouldShowRationale(String permission) {
-		return ActivityCompat.shouldShowRequestPermissionRationale(this,
-				permission);
-	}
-
-	@Override
-	public void eventOccurred(Event e) {
-		if (e instanceof TransportStateEvent) {
-			TransportStateEvent t = (TransportStateEvent) e;
-			if (t.getTransportId().equals(BluetoothConstants.ID)) {
-				if (LOG.isLoggable(INFO)) {
-					LOG.info("Bluetooth state changed to " + t.getState());
-				}
-				showQrCodeFragmentIfAllowed();
-			} else if (t.getTransportId().equals(LanTcpConstants.ID)) {
-				if (LOG.isLoggable(INFO)) {
-					LOG.info("Wifi state changed to " + t.getState());
-				}
-				showQrCodeFragmentIfAllowed();
-			}
-		}
-	}
-
-	private class BluetoothStateReceiver extends BroadcastReceiver {
-
-		@Override
-		public void onReceive(Context context, Intent intent) {
-			LOG.info("Bluetooth scan mode changed");
-			showQrCodeFragmentIfAllowed();
-		}
-	}
-}

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

@@ -1,375 +0,0 @@
-package org.briarproject.briar.android.keyagreement;
-
-import android.content.Context;
-import android.graphics.Bitmap;
-import android.os.Bundle;
-import android.util.DisplayMetrics;
-import android.view.LayoutInflater;
-import android.view.View;
-import android.view.ViewGroup;
-import android.widget.LinearLayout;
-import android.widget.LinearLayout.LayoutParams;
-import android.widget.TextView;
-import android.widget.Toast;
-
-import com.google.zxing.Result;
-
-import org.briarproject.bramble.api.UnsupportedVersionException;
-import org.briarproject.bramble.api.event.Event;
-import org.briarproject.bramble.api.event.EventBus;
-import org.briarproject.bramble.api.keyagreement.KeyAgreementResult;
-import org.briarproject.bramble.api.keyagreement.KeyAgreementTask;
-import org.briarproject.bramble.api.keyagreement.Payload;
-import org.briarproject.bramble.api.keyagreement.PayloadEncoder;
-import org.briarproject.bramble.api.keyagreement.PayloadParser;
-import org.briarproject.bramble.api.keyagreement.event.KeyAgreementAbortedEvent;
-import org.briarproject.bramble.api.keyagreement.event.KeyAgreementFailedEvent;
-import org.briarproject.bramble.api.keyagreement.event.KeyAgreementFinishedEvent;
-import org.briarproject.bramble.api.keyagreement.event.KeyAgreementListeningEvent;
-import org.briarproject.bramble.api.keyagreement.event.KeyAgreementStartedEvent;
-import org.briarproject.bramble.api.keyagreement.event.KeyAgreementWaitingEvent;
-import org.briarproject.bramble.api.lifecycle.IoExecutor;
-import org.briarproject.bramble.api.nullsafety.MethodsNotNullByDefault;
-import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
-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.BaseEventFragment;
-import org.briarproject.briar.android.view.QrCodeView;
-
-import java.io.IOException;
-import java.nio.charset.Charset;
-import java.util.concurrent.Executor;
-import java.util.logging.Logger;
-
-import javax.annotation.Nullable;
-import javax.inject.Inject;
-import javax.inject.Provider;
-
-import androidx.annotation.UiThread;
-
-import static android.content.pm.ActivityInfo.SCREEN_ORIENTATION_NOSENSOR;
-import static android.view.View.INVISIBLE;
-import static android.view.View.VISIBLE;
-import static android.view.ViewGroup.LayoutParams.MATCH_PARENT;
-import static android.widget.LinearLayout.HORIZONTAL;
-import static android.widget.Toast.LENGTH_LONG;
-import static java.util.logging.Level.INFO;
-import static java.util.logging.Level.WARNING;
-import static org.briarproject.bramble.util.LogUtils.logException;
-
-@MethodsNotNullByDefault
-@ParametersNotNullByDefault
-public class KeyAgreementFragment extends BaseEventFragment
-		implements QrCodeDecoder.ResultCallback, QrCodeView.FullscreenListener {
-
-	static final String TAG = KeyAgreementFragment.class.getName();
-
-	private static final Logger LOG = Logger.getLogger(TAG);
-	@SuppressWarnings("CharsetObjectCanBeUsed") // Requires minSdkVersion >= 19
-	private static final Charset ISO_8859_1 = Charset.forName("ISO-8859-1");
-
-	@Inject
-	Provider<KeyAgreementTask> keyAgreementTaskProvider;
-	@Inject
-	PayloadEncoder payloadEncoder;
-	@Inject
-	PayloadParser payloadParser;
-	@Inject
-	@IoExecutor
-	Executor ioExecutor;
-	@Inject
-	EventBus eventBus;
-
-	private CameraView cameraView;
-	private LinearLayout cameraOverlay;
-	private View statusView;
-	private QrCodeView qrCodeView;
-	private TextView status;
-
-	private boolean gotRemotePayload;
-	private volatile boolean gotLocalPayload;
-	private KeyAgreementTask task;
-	private KeyAgreementEventListener listener;
-
-	public static KeyAgreementFragment newInstance() {
-		Bundle args = new Bundle();
-		KeyAgreementFragment fragment = new KeyAgreementFragment();
-		fragment.setArguments(args);
-		return fragment;
-	}
-
-	@Override
-	public void onAttach(Context context) {
-		super.onAttach(context);
-		listener = (KeyAgreementEventListener) context;
-	}
-
-	@Override
-	public void injectFragment(ActivityComponent component) {
-		component.inject(this);
-	}
-
-	@Override
-	public String getUniqueTag() {
-		return TAG;
-	}
-
-	@Nullable
-	@Override
-	public View onCreateView(LayoutInflater inflater,
-			@Nullable ViewGroup container,
-			@Nullable Bundle savedInstanceState) {
-		return inflater.inflate(R.layout.fragment_keyagreement_qr, container,
-				false);
-	}
-
-	@Override
-	public void onViewCreated(View view, @Nullable Bundle savedInstanceState) {
-		super.onViewCreated(view, savedInstanceState);
-		cameraView = view.findViewById(R.id.camera_view);
-		cameraOverlay = view.findViewById(R.id.camera_overlay);
-		statusView = view.findViewById(R.id.status_container);
-		status = view.findViewById(R.id.connect_status);
-		qrCodeView = view.findViewById(R.id.qr_code_view);
-		qrCodeView.setFullscreenListener(this);
-	}
-
-	@Override
-	public void onActivityCreated(@Nullable Bundle savedInstanceState) {
-		super.onActivityCreated(savedInstanceState);
-		requireActivity().setRequestedOrientation(SCREEN_ORIENTATION_NOSENSOR);
-		cameraView.setPreviewConsumer(new QrCodeDecoder(this));
-	}
-
-	@Override
-	public void onStart() {
-		super.onStart();
-		try {
-			cameraView.start();
-		} catch (CameraException e) {
-			logCameraExceptionAndFinish(e);
-		}
-		startListening();
-	}
-
-	@Override
-	public void setFullscreen(boolean fullscreen) {
-		LinearLayout.LayoutParams statusParams, qrCodeParams;
-		if (fullscreen) {
-			// Grow the QR code view to fill its parent
-			statusParams = new LayoutParams(0, 0, 0f);
-			qrCodeParams = new LayoutParams(MATCH_PARENT, MATCH_PARENT, 1f);
-		} else {
-			// Shrink the QR code view to fill half its parent
-			if (cameraOverlay.getOrientation() == HORIZONTAL) {
-				statusParams = new LayoutParams(0, MATCH_PARENT, 1f);
-				qrCodeParams = new LayoutParams(0, MATCH_PARENT, 1f);
-			} else {
-				statusParams = new LayoutParams(MATCH_PARENT, 0, 1f);
-				qrCodeParams = new LayoutParams(MATCH_PARENT, 0, 1f);
-			}
-		}
-		statusView.setLayoutParams(statusParams);
-		qrCodeView.setLayoutParams(qrCodeParams);
-		cameraOverlay.invalidate();
-	}
-
-	@Override
-	public void onStop() {
-		super.onStop();
-		stopListening();
-		try {
-			cameraView.stop();
-		} catch (CameraException e) {
-			logCameraExceptionAndFinish(e);
-		}
-	}
-
-	@UiThread
-	private void logCameraExceptionAndFinish(CameraException e) {
-		logException(LOG, WARNING, e);
-		Toast.makeText(getActivity(), R.string.camera_error,
-				LENGTH_LONG).show();
-		finish();
-	}
-
-	@UiThread
-	private void startListening() {
-		KeyAgreementTask oldTask = task;
-		KeyAgreementTask newTask = keyAgreementTaskProvider.get();
-		task = newTask;
-		ioExecutor.execute(() -> {
-			if (oldTask != null) oldTask.stopListening();
-			newTask.listen();
-		});
-	}
-
-	@UiThread
-	private void stopListening() {
-		KeyAgreementTask oldTask = task;
-		ioExecutor.execute(() -> {
-			if (oldTask != null) oldTask.stopListening();
-		});
-	}
-
-	@UiThread
-	private void reset() {
-		// If we've stopped the camera view, restart it
-		if (gotRemotePayload) {
-			try {
-				cameraView.start();
-			} catch (CameraException e) {
-				logCameraExceptionAndFinish(e);
-				return;
-			}
-		}
-		statusView.setVisibility(INVISIBLE);
-		cameraView.setVisibility(VISIBLE);
-		gotRemotePayload = false;
-		gotLocalPayload = false;
-		startListening();
-	}
-
-	@UiThread
-	private void qrCodeScanned(String content) {
-		try {
-			byte[] payloadBytes = content.getBytes(ISO_8859_1);
-			if (LOG.isLoggable(INFO))
-				LOG.info("Remote payload is " + payloadBytes.length + " bytes");
-			Payload remotePayload = payloadParser.parse(payloadBytes);
-			gotRemotePayload = true;
-			cameraView.stop();
-			cameraView.setVisibility(INVISIBLE);
-			statusView.setVisibility(VISIBLE);
-			status.setText(R.string.connecting_to_device);
-			task.connectAndRunProtocol(remotePayload);
-		} catch (UnsupportedVersionException e) {
-			reset();
-			String msg;
-			if (e.isTooOld()) {
-				msg = getString(R.string.qr_code_too_old,
-						getString(R.string.app_name));
-			} else {
-				msg = getString(R.string.qr_code_too_new,
-						getString(R.string.app_name));
-			}
-			showNextFragment(ContactExchangeErrorFragment.newInstance(msg));
-		} catch (CameraException e) {
-			logCameraExceptionAndFinish(e);
-		} catch (IOException | IllegalArgumentException e) {
-			LOG.log(WARNING, "QR Code Invalid", e);
-			reset();
-			Toast.makeText(getActivity(), R.string.qr_code_invalid,
-					LENGTH_LONG).show();
-		}
-	}
-
-	@Override
-	public void eventOccurred(Event e) {
-		if (e instanceof KeyAgreementListeningEvent) {
-			KeyAgreementListeningEvent event = (KeyAgreementListeningEvent) e;
-			gotLocalPayload = true;
-			setQrCode(event.getLocalPayload());
-		} else if (e instanceof KeyAgreementFailedEvent) {
-			keyAgreementFailed();
-		} else if (e instanceof KeyAgreementWaitingEvent) {
-			keyAgreementWaiting();
-		} else if (e instanceof KeyAgreementStartedEvent) {
-			keyAgreementStarted();
-		} else if (e instanceof KeyAgreementAbortedEvent) {
-			KeyAgreementAbortedEvent event = (KeyAgreementAbortedEvent) e;
-			keyAgreementAborted(event.didRemoteAbort());
-		} else if (e instanceof KeyAgreementFinishedEvent) {
-			keyAgreementFinished(((KeyAgreementFinishedEvent) e).getResult());
-		}
-	}
-
-	@UiThread
-	private void keyAgreementFailed() {
-		reset();
-		listener.keyAgreementFailed();
-	}
-
-	@UiThread
-	private void keyAgreementWaiting() {
-		status.setText(listener.keyAgreementWaiting());
-	}
-
-	@UiThread
-	private void keyAgreementStarted() {
-		qrCodeView.setVisibility(INVISIBLE);
-		statusView.setVisibility(VISIBLE);
-		status.setText(listener.keyAgreementStarted());
-	}
-
-	@UiThread
-	private void keyAgreementAborted(boolean remoteAborted) {
-		reset();
-		listener.keyAgreementAborted(remoteAborted);
-	}
-
-	@UiThread
-	private void keyAgreementFinished(KeyAgreementResult result) {
-		statusView.setVisibility(VISIBLE);
-		status.setText(listener.keyAgreementFinished(result));
-	}
-
-	private void setQrCode(Payload localPayload) {
-		Context context = getContext();
-		if (context == null) return;
-		DisplayMetrics dm = context.getResources().getDisplayMetrics();
-		ioExecutor.execute(() -> {
-			byte[] payloadBytes = payloadEncoder.encode(localPayload);
-			if (LOG.isLoggable(INFO)) {
-				LOG.info("Local payload is " + payloadBytes.length
-						+ " bytes");
-			}
-			// Use ISO 8859-1 to encode bytes directly as a string
-			String content = new String(payloadBytes, ISO_8859_1);
-			Bitmap qrCode = QrCodeUtils.createQrCode(dm, content);
-			runOnUiThreadUnlessDestroyed(() -> qrCodeView.setQrCode(qrCode));
-		});
-	}
-
-	@Override
-	public void handleResult(Result result) {
-		runOnUiThreadUnlessDestroyed(() -> {
-			LOG.info("Got result from decoder");
-			// Ignore results until the KeyAgreementTask is ready
-			if (!gotLocalPayload) return;
-			if (!gotRemotePayload) qrCodeScanned(result.getText());
-		});
-	}
-
-	@Override
-	protected void finish() {
-		getActivity().getSupportFragmentManager().popBackStack();
-	}
-
-	@NotNullByDefault
-	interface KeyAgreementEventListener {
-
-		@UiThread
-		void keyAgreementFailed();
-
-		// Should return a string to be displayed as status.
-		@UiThread
-		@Nullable
-		String keyAgreementWaiting();
-
-		// Should return a string to be displayed as status.
-		@UiThread
-		@Nullable
-		String keyAgreementStarted();
-
-		// Will show an error fragment.
-		@UiThread
-		void keyAgreementAborted(boolean remoteAborted);
-
-		// Should return a string to be displayed as status.
-		@UiThread
-		@Nullable
-		String keyAgreementFinished(KeyAgreementResult result);
-	}
-}

briar-android/src/main/java/org/briarproject/briar/android/login/StartupActivity.java

@@ -7,6 +7,7 @@ import org.briarproject.bramble.api.nullsafety.MethodsNotNullByDefault;
 import org.briarproject.bramble.api.nullsafety.ParametersNotNullByDefault;
 import org.briarproject.briar.R;
 import org.briarproject.briar.android.BriarService;
+import org.briarproject.briar.android.account.NewOrRecoverActivity;
 import org.briarproject.briar.android.account.SetupActivity;
 import org.briarproject.briar.android.activity.ActivityComponent;
 import org.briarproject.briar.android.activity.BaseActivity;
@@ -107,7 +108,7 @@ public class StartupActivity extends BaseActivity implements
 	private void onAccountDeleted() {
 		setResult(RESULT_CANCELED);
 		finish();
-		Intent i = new Intent(this, SetupActivity.class);
+		Intent i = new Intent(this, NewOrRecoverActivity.class);
 		i.addFlags(FLAG_ACTIVITY_NEW_TASK | FLAG_ACTIVITY_CLEAR_TOP |
 				FLAG_ACTIVITY_CLEAR_TASK | FLAG_ACTIVITY_TASK_ON_HOME);
 		startActivity(i);

briar-android/src/main/java/org/briarproject/briar/android/socialbackup/CustodianSelectorFragment.java

@@ -0,0 +1,93 @@
+package org.briarproject.briar.android.socialbackup;
+
+import android.os.Bundle;
+import android.view.MenuItem;
+import android.widget.Toast;
+
+import org.briarproject.bramble.api.contact.ContactId;
+import org.briarproject.bramble.api.db.DbException;
+import org.briarproject.bramble.api.nullsafety.MethodsNotNullByDefault;
+import org.briarproject.bramble.api.nullsafety.ParametersNotNullByDefault;
+import org.briarproject.bramble.api.sync.GroupId;
+import org.briarproject.briar.R;
+import org.briarproject.briar.android.activity.ActivityComponent;
+import org.briarproject.briar.android.socialbackup.creation.CreateBackupController;
+import org.briarproject.briar.android.contactselection.BaseContactSelectorAdapter;
+import org.briarproject.briar.android.contactselection.ContactSelectorController;
+import org.briarproject.briar.android.contactselection.ContactSelectorFragment;
+import org.briarproject.briar.android.contactselection.SelectableContactItem;
+import org.briarproject.briar.android.controller.handler.ResultExceptionHandler;
+
+import java.util.Collection;
+
+import javax.inject.Inject;
+
+import androidx.annotation.Nullable;
+
+import static java.util.Objects.requireNonNull;
+
+@MethodsNotNullByDefault
+@ParametersNotNullByDefault
+public class CustodianSelectorFragment extends ContactSelectorFragment {
+
+	public static final String TAG = CustodianSelectorFragment.class.getName();
+
+	@Inject
+	CreateBackupController controller;
+
+	public static CustodianSelectorFragment newInstance() {
+		Bundle args = new Bundle();
+
+		CustodianSelectorFragment fragment = new CustodianSelectorFragment();
+		fragment.setArguments(args);
+
+		return fragment;
+	}
+
+	@Override
+	public void injectFragment(ActivityComponent component) {
+		component.inject(this);
+	}
+
+	@Override
+	public void onCreate(@Nullable Bundle savedInstanceState) {
+		super.onCreate(savedInstanceState);
+
+		requireActivity().setTitle(R.string.title_select_custodians);
+	}
+
+	@Override
+	protected ContactSelectorController<SelectableContactItem> getController() {
+		return controller;
+	}
+
+	@Override
+	public String getUniqueTag() {
+		return TAG;
+	}
+
+	@Override
+	protected void onSelectionChanged() {
+		super.onSelectionChanged();
+		if (menu == null) return;
+		MenuItem item = menu.findItem(R.id.action_contacts_selected);
+		if (item == null) return;
+
+		BaseContactSelectorAdapter a = adapter;
+		selectedContacts = a.getSelectedContactIds();
+
+		int n = selectedContacts.size();
+		int min = 2;
+		boolean enough = n >= min;
+
+		item.setVisible(enough);
+		if (n == 0) {
+			Toast.makeText(getContext(), String.format(getString(R.string.select_at_least_n_contacts), min),
+					Toast.LENGTH_SHORT).show();
+		} else if (n < min) {
+			Toast.makeText(getContext(), String.format(getString(R.string.select_at_least_n_more_contacts), min - n),
+					Toast.LENGTH_SHORT).show();
+		}
+	}
+
+}

briar-android/src/main/java/org/briarproject/briar/android/socialbackup/DarkCrystalImpl.java

@@ -0,0 +1,57 @@
+package org.briarproject.briar.android.socialbackup;
+
+import org.briarproject.bramble.api.crypto.SecretKey;
+import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
+import org.briarproject.briar.api.socialbackup.DarkCrystal;
+import org.briarproject.briar.api.socialbackup.Shard;
+import org.magmacollective.darkcrystal.secretsharingwrapper.SecretSharingWrapper;
+
+import java.security.GeneralSecurityException;
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.List;
+import java.util.Random;
+
+import javax.inject.Inject;
+
+import static org.briarproject.briar.socialbackup.SocialBackupConstants.SECRET_ID_BYTES;
+
+@NotNullByDefault
+public class DarkCrystalImpl implements DarkCrystal {
+
+	@Inject
+	DarkCrystalImpl() {
+	}
+
+	@Override
+	public List<Shard> createShards(SecretKey secret, int numShards,
+			int threshold) {
+		Random random = new Random();
+		byte[] secretId = new byte[SECRET_ID_BYTES];
+		random.nextBytes(secretId);
+		List<byte[]> shardsBytes = SecretSharingWrapper
+				.share(secret.getBytes(), numShards, threshold);
+		List<Shard> shards = new ArrayList<>(numShards);
+		for (byte[] shardBytes : shardsBytes) {
+			shards.add(new Shard(secretId, shardBytes));
+		}
+		return shards;
+	}
+
+	@Override
+	public SecretKey combineShards(List<Shard> shards) throws
+			GeneralSecurityException {
+		// Check each shard has the same secret Id
+		byte[] secretId = shards.get(0).getSecretId();
+		for (Shard shard : shards) {
+			if (!Arrays.equals(shard.getSecretId(), secretId))
+				throw new GeneralSecurityException();
+		}
+		List<byte[]> shardsBytes = new ArrayList<>(shards.size());
+		for (Shard shard : shards) {
+			shardsBytes.add(shard.getShard());
+		}
+		byte[] secretBytes = SecretSharingWrapper.combine(shardsBytes);
+		return new SecretKey(secretBytes);
+	}
+}

briar-android/src/main/java/org/briarproject/briar/android/socialbackup/DistributedBackupActivity.java

@@ -0,0 +1,94 @@
+package org.briarproject.briar.android.socialbackup;
+
+import android.os.Bundle;
+import android.widget.Toast;
+
+import org.briarproject.bramble.api.contact.ContactId;
+import org.briarproject.bramble.api.db.DatabaseComponent;
+import org.briarproject.bramble.api.db.DbException;
+import org.briarproject.briar.R;
+import org.briarproject.briar.android.activity.ActivityComponent;
+import org.briarproject.briar.android.activity.BriarActivity;
+import org.briarproject.briar.android.contactselection.ContactSelectorListener;
+import org.briarproject.briar.android.fragment.BaseFragment;
+import org.briarproject.briar.api.socialbackup.BackupMetadata;
+import org.briarproject.briar.api.socialbackup.SocialBackupManager;
+
+import java.util.Collection;
+import java.util.List;
+
+import javax.inject.Inject;
+
+public class DistributedBackupActivity extends BriarActivity implements
+		BaseFragment.BaseFragmentListener, ContactSelectorListener,
+		ThresholdDefinedListener,
+		ShardsSentFragment.ShardsSentDismissedListener {
+
+	private Collection<ContactId> custodians;
+
+	@Inject
+	public SocialBackupManager socialBackupManager;
+
+	@Inject
+	public DatabaseComponent db;
+
+	@Override
+	public void injectActivity(ActivityComponent component) {
+		component.inject(this);
+	}
+
+	@Override
+	public void onCreate(Bundle savedInstanceState) {
+		super.onCreate(savedInstanceState);
+		setContentView(R.layout.activity_distributed_backup);
+
+		try {
+			db.transaction(false, txn -> {
+				BackupMetadata backupMetadata =
+						socialBackupManager.getBackupMetadata(txn);
+				if (backupMetadata == null) throw new DbException();
+				ExistingBackupFragment fragment =
+						ExistingBackupFragment.newInstance(backupMetadata);
+				showInitialFragment(fragment);
+			});
+		} catch (DbException e) {
+			CustodianSelectorFragment fragment =
+					CustodianSelectorFragment.newInstance();
+			showInitialFragment(fragment);
+		}
+	}
+
+	@Override
+	public void contactsSelected(Collection<ContactId> contacts) {
+		Toast.makeText(this,
+				String.format("Selected %d contacts", contacts.size()),
+				Toast.LENGTH_SHORT).show();
+		custodians = contacts;
+		ThresholdSelectorFragment fragment =
+				ThresholdSelectorFragment.newInstance(contacts.size());
+		showNextFragment(fragment);
+	}
+
+	@Override
+	public void thresholdDefined(int threshold) {
+		try {
+			db.transaction(false, txn -> {
+				socialBackupManager
+						.createBackup(txn, (List<ContactId>) custodians,
+								threshold);
+				ShardsSentFragment fragment = new ShardsSentFragment();
+				showNextFragment(fragment);
+			});
+		} catch (DbException e) {
+			Toast.makeText(this,
+					"There was an error when creating the backup",
+					Toast.LENGTH_LONG).show();
+			finish();
+		}
+	}
+
+	@Override
+	public void shardsSentDismissed() {
+		finish();
+	}
+}

briar-android/src/main/java/org/briarproject/briar/android/socialbackup/ExistingBackupFragment.java

@@ -0,0 +1,93 @@
+package org.briarproject.briar.android.socialbackup;
+
+import android.content.Context;
+import android.os.Bundle;
+import android.view.LayoutInflater;
+import android.view.View;
+import android.view.ViewGroup;
+import android.widget.TextView;
+
+import org.briarproject.bramble.api.identity.Author;
+import org.briarproject.briar.R;
+import org.briarproject.briar.android.activity.ActivityComponent;
+import org.briarproject.briar.android.fragment.BaseFragment;
+import org.briarproject.briar.api.socialbackup.BackupMetadata;
+
+import java.util.ArrayList;
+import java.util.List;
+
+import androidx.annotation.NonNull;
+import androidx.annotation.Nullable;
+
+public class ExistingBackupFragment extends BaseFragment {
+
+	private static final String THRESHOLD = "threshold";
+	private static final String CUSTODIANS = "custodians";
+	public static final String TAG = ExistingBackupFragment.class.getName();
+
+	public static ExistingBackupFragment newInstance(
+			BackupMetadata backupMetadata) {
+		Bundle bundle = new Bundle();
+		List<Author> custodians = backupMetadata.getCustodians();
+		ArrayList custodianNames = new ArrayList();
+		for (Author custodian : custodians) {
+			custodianNames.add(custodian.getName());
+		}
+		bundle.putStringArrayList(CUSTODIANS, custodianNames);
+		bundle.putInt(THRESHOLD, backupMetadata.getThreshold());
+		ExistingBackupFragment fragment = new ExistingBackupFragment();
+		fragment.setArguments(bundle);
+		return fragment;
+	}
+
+	@Override
+	public void onCreate(@Nullable Bundle savedInstanceState) {
+		super.onCreate(savedInstanceState);
+		requireActivity().setTitle(R.string.title_distributed_backup);
+
+	}
+
+	@Nullable
+	@Override
+	public View onCreateView(@NonNull LayoutInflater inflater, @Nullable
+			ViewGroup container, @Nullable Bundle savedInstanceState) {
+		View view = inflater.inflate(R.layout.fragment_existing_backup,
+				container, false);
+		Bundle args = requireArguments();
+		ArrayList<String> custodianNames = args.getStringArrayList(CUSTODIANS);
+
+		StringBuilder custodianNamesString = new StringBuilder();
+		for (String custodianName : custodianNames) {
+			custodianNamesString
+					.append("• ")
+					.append(custodianName)
+					.append("\n");
+		}
+
+		TextView textViewThreshold = view.findViewById(R.id.textViewThreshold);
+		textViewThreshold.setText(getString(R.string.existing_backup_explain,
+				args.getInt(THRESHOLD)));
+		TextView textViewCustodians =
+				view.findViewById(R.id.textViewCustodians);
+		textViewCustodians.setText(custodianNamesString);
+		return view;
+	}
+
+	@Override
+	public void onAttach(Context context) {
+		super.onAttach(context);
+//		listener = (ShardsSentDismissedListener) context;
+	}
+
+
+	@Override
+	public String getUniqueTag() {
+		return TAG;
+	}
+
+	@Override
+	public void injectFragment(ActivityComponent component) {
+		component.inject(this);
+	}
+
+}

briar-android/src/main/java/org/briarproject/briar/android/socialbackup/ExplainerDismissedListener.java

@@ -0,0 +1,8 @@
+package org.briarproject.briar.android.socialbackup;
+
+import androidx.annotation.UiThread;
+
+public interface ExplainerDismissedListener {
+	@UiThread
+	void explainerDismissed();
+}

briar-android/src/main/java/org/briarproject/briar/android/socialbackup/ScanQrButtonListener.java

@@ -0,0 +1,8 @@
+package org.briarproject.briar.android.socialbackup;
+
+import androidx.annotation.UiThread;
+
+public interface ScanQrButtonListener {
+	@UiThread
+	void scanQrButtonClicked();
+}

briar-android/src/main/java/org/briarproject/briar/android/socialbackup/ShardsSentFragment.java

@@ -0,0 +1,74 @@
+package org.briarproject.briar.android.socialbackup;
+
+import android.content.Context;
+import android.os.Bundle;
+import android.view.LayoutInflater;
+import android.view.View;
+import android.view.ViewGroup;
+import android.widget.Button;
+
+import org.briarproject.briar.R;
+import org.briarproject.briar.android.activity.ActivityComponent;
+import org.briarproject.briar.android.fragment.BaseFragment;
+
+import androidx.annotation.NonNull;
+import androidx.annotation.Nullable;
+import androidx.annotation.UiThread;
+
+public class ShardsSentFragment extends BaseFragment {
+
+	public static final String TAG = ShardsSentFragment.class.getName();
+
+	interface ShardsSentDismissedListener {
+
+		@UiThread
+		void shardsSentDismissed();
+
+	}
+
+	protected ShardsSentDismissedListener listener;
+
+	@Override
+	public void onCreate(@Nullable Bundle savedInstanceState) {
+		super.onCreate(savedInstanceState);
+		requireActivity().setTitle(R.string.title_distributed_backup);
+	}
+
+	@Nullable
+	@Override
+	public View onCreateView(@NonNull LayoutInflater inflater,
+			@Nullable ViewGroup container,
+			@Nullable Bundle savedInstanceState) {
+		View view = inflater.inflate(R.layout.fragment_shards_sent,
+				container, false);
+
+		Button button = view.findViewById(R.id.button);
+		button.setOnClickListener(e -> {
+			listener.shardsSentDismissed();
+		});
+
+		return view;
+	}
+
+	@Override
+	public void onAttach(Context context) {
+		super.onAttach(context);
+		listener = (ShardsSentDismissedListener) context;
+	}
+
+
+	@Override
+	public String getUniqueTag() {
+		return TAG;
+	}
+
+	@Override
+	public void injectFragment(ActivityComponent component) {
+		component.inject(this);
+	}
+
+    public void onBackPressed() {
+	    listener.shardsSentDismissed();
+    }
+
+}

briar-android/src/main/java/org/briarproject/briar/android/socialbackup/ThresholdDefinedListener.java

@@ -0,0 +1,12 @@
+package org.briarproject.briar.android.socialbackup;
+
+import org.briarproject.bramble.api.db.DbException;
+
+import androidx.annotation.UiThread;
+
+public interface ThresholdDefinedListener {
+
+	@UiThread
+	void thresholdDefined(int threshold) throws DbException;
+
+}

briar-android/src/main/java/org/briarproject/briar/android/socialbackup/ThresholdSelectorFragment.java

@@ -0,0 +1,182 @@
+package org.briarproject.briar.android.socialbackup;
+
+import android.content.Context;
+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.SeekBar;
+import android.widget.TextView;
+
+import org.briarproject.bramble.api.db.DbException;
+import org.briarproject.briar.R;
+import org.briarproject.briar.android.activity.ActivityComponent;
+import org.briarproject.briar.android.fragment.BaseFragment;
+import org.magmacollective.darkcrystal.secretsharingwrapper.SecretSharingWrapper;
+
+import androidx.annotation.NonNull;
+import androidx.annotation.Nullable;
+
+public class ThresholdSelectorFragment extends BaseFragment {
+
+	public static final String TAG = ThresholdSelectorFragment.class.getName();
+	private static final String NUMBER_CUSTODIANS = "numberCustodians";
+
+	protected ThresholdDefinedListener listener;
+
+	private int numberOfCustodians;
+	private int threshold;
+	private int recommendedThreshold;
+	private SeekBar seekBar;
+	private TextView thresholdRepresentation;
+	private TextView message;
+	private TextView mOfn;
+
+	public static ThresholdSelectorFragment newInstance(int numberCustodians) {
+		Bundle bundle = new Bundle();
+		bundle.putInt(NUMBER_CUSTODIANS, numberCustodians);
+		ThresholdSelectorFragment fragment = new ThresholdSelectorFragment();
+		fragment.setArguments(bundle);
+		return fragment;
+	}
+
+	@Override
+	public void onCreate(@Nullable Bundle savedInstanceState) {
+		super.onCreate(savedInstanceState);
+		requireActivity().setTitle(R.string.title_define_threshold);
+	}
+
+	@Nullable
+	@Override
+	public View onCreateView(@NonNull LayoutInflater inflater,
+			@Nullable ViewGroup container,
+			@Nullable Bundle savedInstanceState) {
+		View view = inflater.inflate(R.layout.fragment_select_threshold,
+				container, false);
+		Bundle args = requireArguments();
+		numberOfCustodians = args.getInt(NUMBER_CUSTODIANS);
+		seekBar = view.findViewById(R.id.seekBar);
+		thresholdRepresentation =
+				view.findViewById(R.id.textViewThresholdRepresentation);
+		message = view.findViewById(R.id.textViewMessage);
+		mOfn = view.findViewById(R.id.textViewmOfn);
+
+		if (numberOfCustodians == 2) {
+			message.setText(R.string.threshold_too_few_custodians);
+		}
+		if (numberOfCustodians > 3) {
+			seekBar.setMax(numberOfCustodians -3);
+			seekBar.setProgress(threshold - 2);
+			seekBar.setOnSeekBarChangeListener(new SeekBarListener());
+			recommendedThreshold =
+					SecretSharingWrapper.defaultThreshold(numberOfCustodians);
+			threshold = recommendedThreshold;
+
+		} else {
+			seekBar.setEnabled(false);
+			threshold = 2;
+			seekBar.setMax(numberOfCustodians);
+			seekBar.setProgress(threshold);
+			TextView t = view.findViewById(R.id.title_threshold);
+			t.setText(R.string.threshold_disabled);
+		}
+		thresholdRepresentation.setText(buildThresholdRepresentationString());
+		setmOfnText();
+		return view;
+//        return super.onCreateView(inflater, container, savedInstanceState);
+	}
+
+	private void setmOfnText() {
+		mOfn.setText(String.format(
+				getString(R.string.threshold_m_of_n), threshold,
+				numberOfCustodians));
+	}
+
+	@Override
+	public void onAttach(Context context) {
+		super.onAttach(context);
+		listener = (ThresholdDefinedListener) context;
+	}
+
+
+	@Override
+	public String getUniqueTag() {
+		return TAG;
+	}
+
+	@Override
+	public void injectFragment(ActivityComponent component) {
+		component.inject(this);
+	}
+
+	@Override
+	public void onCreateOptionsMenu(Menu menu, MenuInflater inflater) {
+		inflater.inflate(R.menu.define_threshold_actions, menu);
+		super.onCreateOptionsMenu(menu, inflater);
+	}
+
+	@Override
+	public boolean onOptionsItemSelected(MenuItem item) {
+		switch (item.getItemId()) {
+			case R.id.action_threshold_defined:
+				try {
+					listener.thresholdDefined(threshold);
+				} catch (DbException e) {
+					e.printStackTrace();
+				}
+				return true;
+			default:
+				return super.onOptionsItemSelected(item);
+		}
+	}
+
+	private String buildThresholdRepresentationString() {
+		String thresholdRepresentationText = "";
+		for (int i = 0; i < threshold; i++) {
+			thresholdRepresentationText += getString(R.string.filled_bullet);
+		}
+		for (int i = 0; i < (numberOfCustodians - threshold); i++) {
+			thresholdRepresentationText += getString(R.string.linear_bullet);
+		}
+		return thresholdRepresentationText;
+	}
+
+	private class SeekBarListener implements SeekBar.OnSeekBarChangeListener {
+
+		@Override
+		public void onProgressChanged(SeekBar seekBar, int progress,
+				boolean fromUser) {
+			threshold = progress + 2;
+
+			thresholdRepresentation.setText(
+					buildThresholdRepresentationString()
+			);
+			setmOfnText();
+
+			int sanityLevel = SecretSharingWrapper
+					.thresholdSanity(threshold, numberOfCustodians);
+			int text = R.string.threshold_secure;
+			if (threshold == recommendedThreshold)
+				text = R.string.threshold_recommended;
+			if (sanityLevel < -1) text = R.string.threshold_low_insecure;
+			if (sanityLevel > 0) text = R.string.threshold_high_insecure;
+			message.setText(text);
+			// TODO change colour of thresholdRepresentation to green/red based on sanityLevel
+		}
+
+		@Override
+		public void onStartTrackingTouch(SeekBar seekBar) {
+			// do nothing
+		}
+
+		@Override
+		public void onStopTrackingTouch(SeekBar seekBar) {
+			// do nothing
+		}
+
+	}
+
+}

briar-android/src/main/java/org/briarproject/briar/android/socialbackup/creation/CreateBackupController.java

@@ -0,0 +1,26 @@
+package org.briarproject.briar.android.socialbackup.creation;
+
+import org.briarproject.bramble.api.contact.ContactId;
+import org.briarproject.bramble.api.db.DbException;
+import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
+import org.briarproject.bramble.api.sync.GroupId;
+import org.briarproject.briar.android.contactselection.ContactSelectorController;
+import org.briarproject.briar.android.contactselection.SelectableContactItem;
+import org.briarproject.briar.android.controller.handler.ResultExceptionHandler;
+
+import java.util.Collection;
+
+import androidx.annotation.Nullable;
+
+@NotNullByDefault
+public interface CreateBackupController
+		extends ContactSelectorController<SelectableContactItem> {
+
+	void createGroup(String name,
+			ResultExceptionHandler<GroupId, DbException> result);
+
+	void sendInvitation(GroupId g, Collection<ContactId> contacts,
+			@Nullable String text,
+			ResultExceptionHandler<Void, DbException> result);
+
+}

briar-android/src/main/java/org/briarproject/briar/android/socialbackup/creation/CreateBackupControllerImpl.java

@@ -0,0 +1,206 @@
+package org.briarproject.briar.android.socialbackup.creation;
+
+import org.briarproject.bramble.api.contact.Contact;
+import org.briarproject.bramble.api.contact.ContactId;
+import org.briarproject.bramble.api.contact.ContactManager;
+import org.briarproject.bramble.api.crypto.CryptoExecutor;
+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.identity.IdentityManager;
+import org.briarproject.bramble.api.identity.LocalAuthor;
+import org.briarproject.bramble.api.lifecycle.LifecycleManager;
+import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
+import org.briarproject.bramble.api.sync.GroupId;
+import org.briarproject.bramble.api.system.Clock;
+import org.briarproject.briar.android.contactselection.ContactSelectorControllerImpl;
+import org.briarproject.briar.android.controller.handler.ResultExceptionHandler;
+import org.briarproject.briar.api.identity.AuthorManager;
+import org.briarproject.briar.api.privategroup.GroupMessage;
+import org.briarproject.briar.api.privategroup.GroupMessageFactory;
+import org.briarproject.briar.api.privategroup.PrivateGroup;
+import org.briarproject.briar.api.privategroup.PrivateGroupFactory;
+import org.briarproject.briar.api.privategroup.PrivateGroupManager;
+import org.briarproject.briar.api.privategroup.invitation.GroupInvitationFactory;
+import org.briarproject.briar.api.privategroup.invitation.GroupInvitationManager;
+
+import java.util.ArrayList;
+import java.util.Collection;
+import java.util.List;
+import java.util.concurrent.Executor;
+import java.util.logging.Logger;
+
+import javax.annotation.concurrent.Immutable;
+import javax.inject.Inject;
+
+import androidx.annotation.Nullable;
+
+import static java.util.logging.Level.WARNING;
+import static org.briarproject.bramble.util.LogUtils.logException;
+
+@Immutable
+@NotNullByDefault
+/**
+ * Derived from {@link org.briarproject.briar.android.privategroup.invitation.GroupInvitationControllerImpl}
+ */
+class CreateBackupControllerImpl extends ContactSelectorControllerImpl
+		implements CreateBackupController {
+
+	private static final Logger LOG =
+			Logger.getLogger(
+					CreateBackupControllerImpl.class.getName());
+
+	private final Executor cryptoExecutor;
+	private final ContactManager contactManager;
+	private final IdentityManager identityManager;
+	private final PrivateGroupFactory groupFactory;
+	private final GroupMessageFactory groupMessageFactory;
+	private final PrivateGroupManager groupManager;
+	private final GroupInvitationFactory groupInvitationFactory;
+	private final GroupInvitationManager groupInvitationManager;
+	private final Clock clock;
+
+	@Inject
+	CreateBackupControllerImpl(@DatabaseExecutor Executor dbExecutor,
+			@CryptoExecutor Executor cryptoExecutor,
+			LifecycleManager lifecycleManager, ContactManager contactManager,
+			IdentityManager identityManager, PrivateGroupFactory groupFactory,
+			GroupMessageFactory groupMessageFactory,
+			PrivateGroupManager groupManager,
+			GroupInvitationFactory groupInvitationFactory,
+			GroupInvitationManager groupInvitationManager, Clock clock, AuthorManager authorManager) {
+		super(dbExecutor, lifecycleManager, contactManager, authorManager);
+		this.cryptoExecutor = cryptoExecutor;
+		this.contactManager = contactManager;
+		this.identityManager = identityManager;
+		this.groupFactory = groupFactory;
+		this.groupMessageFactory = groupMessageFactory;
+		this.groupManager = groupManager;
+		this.groupInvitationFactory = groupInvitationFactory;
+		this.groupInvitationManager = groupInvitationManager;
+		this.clock = clock;
+	}
+
+	@Override
+	public void createGroup(String name,
+			ResultExceptionHandler<GroupId, DbException> handler) {
+		runOnDbThread(() -> {
+			try {
+				LocalAuthor author = identityManager.getLocalAuthor();
+				createGroupAndMessages(author, name, handler);
+			} catch (DbException e) {
+				logException(LOG, WARNING, e);
+				handler.onException(e);
+			}
+		});
+	}
+
+	private void createGroupAndMessages(LocalAuthor author, String name,
+			ResultExceptionHandler<GroupId, DbException> handler) {
+		cryptoExecutor.execute(() -> {
+			LOG.info("Creating group...");
+			PrivateGroup group =
+					groupFactory.createPrivateGroup(name, author);
+			LOG.info("Creating new join announcement...");
+			GroupMessage joinMsg =
+					groupMessageFactory.createJoinMessage(group.getId(),
+							clock.currentTimeMillis(), author);
+			storeGroup(group, joinMsg, handler);
+		});
+	}
+
+	private void storeGroup(PrivateGroup group, GroupMessage joinMsg,
+			ResultExceptionHandler<GroupId, DbException> handler) {
+		runOnDbThread(() -> {
+			LOG.info("Adding group to database...");
+			try {
+				groupManager.addPrivateGroup(group, joinMsg, true);
+				handler.onResult(group.getId());
+			} catch (DbException e) {
+				logException(LOG, WARNING, e);
+				handler.onException(e);
+			}
+		});
+	}
+
+	@Override
+	protected boolean isDisabled(GroupId g, Contact c) {
+		return false;
+	}
+
+	@Override
+	public void sendInvitation(GroupId g, Collection<ContactId> contactIds,
+			@Nullable String text,
+			ResultExceptionHandler<Void, DbException> handler) {
+		runOnDbThread(() -> {
+			try {
+				LocalAuthor localAuthor = identityManager.getLocalAuthor();
+				List<Contact> contacts = new ArrayList<>();
+				for (ContactId c : contactIds) {
+					try {
+						contacts.add(contactManager.getContact(c));
+					} catch (NoSuchContactException e) {
+						// Continue
+					}
+				}
+				signInvitations(g, localAuthor, contacts, text, handler);
+			} catch (DbException e) {
+				logException(LOG, WARNING, e);
+				handler.onException(e);
+			}
+		});
+	}
+
+	private void signInvitations(GroupId g, LocalAuthor localAuthor,
+			Collection<Contact> contacts, @Nullable String text,
+			ResultExceptionHandler<Void, DbException> handler) {
+		cryptoExecutor.execute(() -> {
+			long timestamp = clock.currentTimeMillis();
+			List<InvitationContext> contexts = new ArrayList<>();
+			for (Contact c : contacts) {
+				byte[] signature = groupInvitationFactory.signInvitation(c, g,
+						timestamp, localAuthor.getPrivateKey());
+				contexts.add(new InvitationContext(c.getId(), timestamp,
+						signature));
+			}
+			sendInvitations(g, contexts, text, handler);
+		});
+	}
+
+	private void sendInvitations(GroupId g,
+			Collection<InvitationContext> contexts, @Nullable String text,
+			ResultExceptionHandler<Void, DbException> handler) {
+		runOnDbThread(() -> {
+			try {
+				for (InvitationContext context : contexts) {
+					try {
+						groupInvitationManager.sendInvitation(g,
+								context.contactId, text, context.timestamp,
+								context.signature);
+					} catch (NoSuchContactException e) {
+						// Continue
+					}
+				}
+				//noinspection ConstantConditions
+				handler.onResult(null);
+			} catch (DbException e) {
+				logException(LOG, WARNING, e);
+				handler.onException(e);
+			}
+		});
+	}
+
+	private static class InvitationContext {
+
+		private final ContactId contactId;
+		private final long timestamp;
+		private final byte[] signature;
+
+		private InvitationContext(ContactId contactId, long timestamp,
+				byte[] signature) {
+			this.contactId = contactId;
+			this.timestamp = timestamp;
+			this.signature = signature;
+		}
+	}
+}

briar-android/src/main/java/org/briarproject/briar/android/socialbackup/creation/CreateBackupModule.java

@@ -0,0 +1,18 @@
+package org.briarproject.briar.android.socialbackup.creation;
+
+import org.briarproject.briar.android.activity.ActivityScope;
+
+import dagger.Module;
+import dagger.Provides;
+
+@Module
+public class CreateBackupModule {
+
+	@ActivityScope
+	@Provides
+	CreateBackupController provideCreateGroupController(
+			CreateBackupControllerImpl createBackupController) {
+		return createBackupController;
+	}
+
+}

briar-android/src/main/java/org/briarproject/briar/android/socialbackup/recover/CustodianRecoveryModeExplainerFragment.java

@@ -0,0 +1,59 @@
+package org.briarproject.briar.android.socialbackup.recover;
+
+import android.os.Bundle;
+import android.view.LayoutInflater;
+import android.view.View;
+import android.view.ViewGroup;
+import android.widget.Button;
+
+import org.briarproject.briar.R;
+import org.briarproject.briar.android.activity.ActivityComponent;
+import org.briarproject.briar.android.fragment.BaseFragment;
+
+import javax.inject.Inject;
+
+import androidx.annotation.NonNull;
+import androidx.annotation.Nullable;
+import androidx.lifecycle.ViewModelProvider;
+
+public class CustodianRecoveryModeExplainerFragment extends BaseFragment {
+
+	@Inject
+	ViewModelProvider.Factory viewModelFactory;
+
+	private CustodianReturnShardViewModel viewModel;
+
+	public static final String TAG =
+			CustodianRecoveryModeExplainerFragment.class.getName();
+
+	@Override
+	public void injectFragment(ActivityComponent component) {
+		component.inject(this);
+		viewModel = new ViewModelProvider(requireActivity(), viewModelFactory)
+				.get(CustodianReturnShardViewModel.class);
+	}
+//	@Override
+//	public void onCreate(@Nullable Bundle savedInstanceState) {
+//		super.onCreate(savedInstanceState);
+//		requireActivity().setTitle(R.string.title_help_recover);
+//	}
+
+	@Nullable
+	@Override
+	public View onCreateView(@NonNull LayoutInflater inflater, @Nullable
+			ViewGroup container, @Nullable Bundle savedInstanceState) {
+		View view =
+				inflater.inflate(R.layout.fragment_recovery_custodian_explainer,
+						container, false);
+
+		Button button = view.findViewById(R.id.button);
+		button.setOnClickListener(e -> viewModel.onContinueClicked());
+		return view;
+	}
+
+	@Override
+	public String getUniqueTag() {
+		return TAG;
+	}
+}
+

briar-android/src/main/java/org/briarproject/briar/android/socialbackup/recover/CustodianReturnShardActivity.java

@@ -0,0 +1,135 @@
+package org.briarproject.briar.android.socialbackup.recover;
+
+import android.content.Intent;
+import android.os.Bundle;
+import android.widget.Toast;
+
+import org.briarproject.bramble.api.contact.ContactId;
+import org.briarproject.bramble.api.db.DbException;
+import org.briarproject.briar.R;
+import org.briarproject.briar.android.activity.ActivityComponent;
+import org.briarproject.briar.android.activity.BriarActivity;
+import org.briarproject.briar.android.fragment.BaseFragment;
+import org.briarproject.briar.api.socialbackup.recovery.CustodianTask;
+
+import java.io.IOException;
+import java.util.logging.Logger;
+
+import javax.annotation.Nullable;
+import javax.inject.Inject;
+
+import androidx.fragment.app.FragmentManager;
+import androidx.lifecycle.ViewModelProvider;
+
+import static android.content.Intent.FLAG_ACTIVITY_CLEAR_TOP;
+import static java.util.logging.Logger.getLogger;
+import static org.briarproject.briar.android.conversation.ConversationActivity.CONTACT_ID;
+
+public class CustodianReturnShardActivity extends BriarActivity
+		implements BaseFragment.BaseFragmentListener {
+
+	private CustodianReturnShardViewModel viewModel;
+	private static final Logger LOG =
+			getLogger(CustodianReturnShardActivity.class.getName());
+	private ContactId contactId;
+
+	@Inject
+	ViewModelProvider.Factory viewModelFactory;
+
+	@Override
+	public void injectActivity(ActivityComponent component) {
+		component.inject(this);
+		viewModel = new ViewModelProvider(this, viewModelFactory)
+				.get(CustodianReturnShardViewModel.class);
+	}
+
+	@Override
+	public void onCreate(@Nullable Bundle state) {
+		super.onCreate(state);
+
+		setContentView(R.layout.activity_fragment_container);
+		if (state == null) {
+			Intent intent = getIntent();
+			int id = intent.getIntExtra(CONTACT_ID, -1);
+			if (id == -1) throw new IllegalStateException("No ContactId");
+			contactId = new ContactId(id);
+
+			try {
+				viewModel.start(contactId);
+//			} catch (IOException e) {
+//				// TODO improve this
+//				Toast.makeText(this,
+//						"It looks like you are not connected to a Wifi network",
+//						Toast.LENGTH_SHORT).show();
+//				showInitialFragment(new CustodianReturnShardErrorFragment());
+			} catch (DbException e) {
+				Toast.makeText(this,
+						"You do not hold a backup piece for this contact",
+						Toast.LENGTH_SHORT).show();
+				finish();
+			}
+		}
+		showInitialFragment(new CustodianRecoveryModeExplainerFragment());
+
+		viewModel.getContinueClicked().observeEvent(this, clicked -> {
+			if (clicked) beginTransfer();
+		});
+
+		viewModel.getShowCameraFragment().observeEvent(this, show -> {
+			if (show) showCameraFragment();
+		});
+		viewModel.getSuccessDismissed().observeEvent(this, dismissed -> {
+			if (dismissed) finish();
+		});
+		viewModel.getErrorTryAgain().observeEvent(this, tryAgain -> {
+			if (tryAgain) beginTransfer();
+		});
+		viewModel.getState()
+				.observe(this, this::onReturnShardStateChanged);
+	}
+
+	private void beginTransfer() {
+		try {
+			viewModel.beginTransfer();
+		} catch (IOException e) {
+			Toast.makeText(this,
+					"It looks like you are not connected to a Wifi network",
+					Toast.LENGTH_SHORT).show();
+			FragmentManager fm = getSupportFragmentManager();
+			if (fm.findFragmentByTag(CustodianReturnShardFragment.TAG) == null) {
+				BaseFragment f = new CustodianReturnShardErrorFragment();
+				fm.beginTransaction()
+						.replace(R.id.fragmentContainer, f, f.getUniqueTag())
+						.addToBackStack(f.getUniqueTag())
+						.commit();
+			}
+		}
+	}
+
+
+	private void onReturnShardStateChanged(CustodianTask.State state) {
+        if (state instanceof CustodianTask.State.Success) {
+	        CustodianReturnShardSuccessFragment fragment = new CustodianReturnShardSuccessFragment();
+	        showNextFragment(fragment);
+        } else if (state instanceof CustodianTask.State.Failure) {
+        	// TODO error fragment here
+	        // TODO handle reason
+	        Toast.makeText(this,
+			        "Backup piece transfer failed",
+			        Toast.LENGTH_SHORT).show();
+	        finish();
+        }
+	}
+
+	private void showCameraFragment() {
+		// FIXME #824
+		FragmentManager fm = getSupportFragmentManager();
+		if (fm.findFragmentByTag(CustodianReturnShardFragment.TAG) == null) {
+			BaseFragment f = CustodianReturnShardFragment.newInstance();
+			fm.beginTransaction()
+					.replace(R.id.fragmentContainer, f, f.getUniqueTag())
+					.addToBackStack(f.getUniqueTag())
+					.commit();
+		}
+	}
+}

briar-android/src/main/java/org/briarproject/briar/android/socialbackup/recover/CustodianReturnShardErrorFragment.java

@@ -0,0 +1,57 @@
+package org.briarproject.briar.android.socialbackup.recover;
+
+import android.os.Bundle;
+import android.view.LayoutInflater;
+import android.view.View;
+import android.view.ViewGroup;
+import android.widget.Button;
+
+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.inject.Inject;
+
+import androidx.annotation.NonNull;
+import androidx.annotation.Nullable;
+import androidx.lifecycle.ViewModelProvider;
+
+@MethodsNotNullByDefault
+@ParametersNotNullByDefault
+public class CustodianReturnShardErrorFragment extends BaseFragment {
+	public static final String TAG =
+			CustodianReturnShardErrorFragment.class.getName();
+
+	@Inject
+	ViewModelProvider.Factory viewModelFactory;
+
+	private CustodianReturnShardViewModel viewModel;
+
+	@Override
+	public void injectFragment(ActivityComponent component) {
+		component.inject(this);
+		viewModel = new ViewModelProvider(requireActivity(), viewModelFactory)
+				.get(CustodianReturnShardViewModel.class);
+	}
+
+	@Nullable
+	@Override
+	public View onCreateView(@NonNull LayoutInflater inflater,
+			@Nullable ViewGroup container,
+			@Nullable Bundle savedInstanceState) {
+		View view = inflater.inflate(R.layout.fragment_recovery_custodian_error_explainer,
+				container, false);
+		Button button = view.findViewById(R.id.button);
+		button.setOnClickListener(e -> viewModel.onErrorTryAgain());
+        // TODO cancel button
+//		button.setOnClickListener(e -> viewModel.onErrorCancelled());
+		return view;
+	}
+
+	@Override
+	public String getUniqueTag() {
+		return TAG;
+	}
+}

briar-android/src/main/java/org/briarproject/briar/android/socialbackup/recover/CustodianReturnShardFragment.java

@@ -0,0 +1,193 @@
+package org.briarproject.briar.android.socialbackup.recover;
+
+import android.os.Bundle;
+import android.view.LayoutInflater;
+import android.view.View;
+import android.view.ViewGroup;
+import android.widget.LinearLayout;
+import android.widget.TextView;
+import android.widget.Toast;
+
+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.contact.add.nearby.CameraException;
+import org.briarproject.briar.android.contact.add.nearby.CameraView;
+import org.briarproject.briar.android.fragment.BaseFragment;
+import org.briarproject.briar.android.view.QrCodeView;
+import org.briarproject.briar.api.socialbackup.recovery.CustodianTask;
+
+import java.util.logging.Logger;
+
+import javax.annotation.Nullable;
+import javax.inject.Inject;
+
+import androidx.annotation.UiThread;
+import androidx.lifecycle.ViewModelProvider;
+
+import static android.content.pm.ActivityInfo.SCREEN_ORIENTATION_NOSENSOR;
+import static android.content.pm.ActivityInfo.SCREEN_ORIENTATION_UNSPECIFIED;
+import static android.view.View.INVISIBLE;
+import static android.view.View.VISIBLE;
+import static android.view.ViewGroup.LayoutParams.MATCH_PARENT;
+import static android.widget.LinearLayout.HORIZONTAL;
+import static android.widget.Toast.LENGTH_LONG;
+import static java.util.logging.Level.WARNING;
+import static org.briarproject.bramble.util.LogUtils.logException;
+
+@MethodsNotNullByDefault
+@ParametersNotNullByDefault
+public class CustodianReturnShardFragment extends BaseFragment
+		implements QrCodeView.FullscreenListener {
+
+	public static final String TAG = CustodianReturnShardFragment.class.getName();
+
+	private static final Logger LOG = Logger.getLogger(TAG);
+
+	@Inject
+	ViewModelProvider.Factory viewModelFactory;
+
+	private CustodianReturnShardViewModel viewModel;
+	private CameraView cameraView;
+	private LinearLayout cameraOverlay;
+	private View statusView;
+	private TextView status;
+
+	public static CustodianReturnShardFragment newInstance() {
+		Bundle args = new Bundle();
+		CustodianReturnShardFragment fragment = new CustodianReturnShardFragment();
+		fragment.setArguments(args);
+		return fragment;
+	}
+
+	@Override
+	public void injectFragment(ActivityComponent component) {
+		component.inject(this);
+		viewModel = new ViewModelProvider(requireActivity(), viewModelFactory)
+				.get(CustodianReturnShardViewModel.class);
+	}
+
+	@Nullable
+	@Override
+	public View onCreateView(LayoutInflater inflater,
+			@Nullable ViewGroup container,
+			@Nullable Bundle savedInstanceState) {
+		return inflater.inflate(R.layout.fragment_keyagreement_qr, container,
+				false);
+	}
+
+	@Override
+	public void onViewCreated(View view, @Nullable Bundle savedInstanceState) {
+		super.onViewCreated(view, savedInstanceState);
+		cameraView = view.findViewById(R.id.camera_view);
+		cameraOverlay = view.findViewById(R.id.camera_overlay);
+		statusView = view.findViewById(R.id.status_container);
+		status = view.findViewById(R.id.connect_status);
+
+		viewModel.getState().observe(getViewLifecycleOwner(),
+				this::onReturnShardStateChanged);
+	}
+
+	@Override
+	public void onActivityCreated(@Nullable Bundle savedInstanceState) {
+		super.onActivityCreated(savedInstanceState);
+		requireActivity().setRequestedOrientation(SCREEN_ORIENTATION_NOSENSOR);
+		cameraView.setPreviewConsumer(viewModel.getQrCodeDecoder());
+	}
+
+	@Override
+	public void onStart() {
+		super.onStart();
+		try {
+			cameraView.start();
+		} catch (CameraException e) {
+			logCameraExceptionAndFinish(e);
+		}
+	}
+
+	@Override
+	public void onStop() {
+		super.onStop();
+		try {
+			cameraView.stop();
+		} catch (CameraException e) {
+			logCameraExceptionAndFinish(e);
+		}
+	}
+
+	@Override
+	public void onDestroy() {
+		requireActivity()
+				.setRequestedOrientation(SCREEN_ORIENTATION_UNSPECIFIED);
+		super.onDestroy();
+	}
+
+	@Override
+	public void setFullscreen(boolean fullscreen) {
+		LinearLayout.LayoutParams statusParams, qrCodeParams;
+		if (fullscreen) {
+			statusParams = new LinearLayout.LayoutParams(0, 0, 0f);
+		} else {
+			if (cameraOverlay.getOrientation() == HORIZONTAL) {
+				statusParams = new LinearLayout.LayoutParams(0, MATCH_PARENT, 1f);
+			} else {
+				statusParams = new LinearLayout.LayoutParams(MATCH_PARENT, 0, 1f);
+			}
+		}
+		statusView.setLayoutParams(statusParams);
+		cameraOverlay.invalidate();
+	}
+
+	@UiThread
+	private void onReturnShardStateChanged(@Nullable CustodianTask.State state) {
+		LOG.info("State changed");
+//		if (state instanceof CustodianTask.State.Connecting) {
+//			try {
+//				cameraView.stop();
+//			} catch (CameraException e) {
+//				logCameraExceptionAndFinish(e);
+//			}
+//			cameraView.setVisibility(INVISIBLE);
+//			statusView.setVisibility(VISIBLE);
+//			status.setText(R.string.connecting_to_device);
+		if (state instanceof CustodianTask.State.SendingShard) {
+			try {
+				cameraView.stop();
+			} catch (CameraException e) {
+				logCameraExceptionAndFinish(e);
+			}
+			cameraView.setVisibility(INVISIBLE);
+			statusView.setVisibility(VISIBLE);
+			status.setText("Sending shard");
+		} else if (state instanceof CustodianTask.State.ReceivingAck) {
+			status.setText("Receiving Ack");
+		} else if (state instanceof CustodianTask.State.Success) {
+			// TODO
+			status.setText(R.string.exchanging_contact_details);
+		} else if (state instanceof CustodianTask.State.Failure) {
+			// the activity will replace this fragment with an error fragment
+			statusView.setVisibility(INVISIBLE);
+			cameraView.setVisibility(INVISIBLE);
+		}
+	}
+
+	@Override
+	public String getUniqueTag() {
+		return TAG;
+	}
+
+	@UiThread
+	private void logCameraExceptionAndFinish(CameraException e) {
+		logException(LOG, WARNING, e);
+		Toast.makeText(getActivity(), R.string.camera_error,
+				LENGTH_LONG).show();
+		finish();
+	}
+
+	@Override
+	protected void finish() {
+		requireActivity().getSupportFragmentManager().popBackStack();
+	}
+
+}