Bump version numbers for 1.3.8 release.

Remove jar signatures to avoid SecurityException when repacking headless jar

See merge request briar/briar!1532

.gitlab-ci.yml

@@ -33,7 +33,7 @@ test:
   stage: test
   script:
     - ./gradlew --no-daemon -Djava.security.egd=file:/dev/urandom animalSnifferMain animalSnifferTest
-    - ./gradlew --no-daemon -Djava.security.egd=file:/dev/urandom check
+    - ./gradlew --no-daemon -Djava.security.egd=file:/dev/urandom compileOfficialDebugAndroidTestSources compileScreenshotDebugAndroidTestSources check
   rules:
     - if: '$CI_PIPELINE_SOURCE == "merge_request_event"'
       when: always

.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" />
@@ -197,9 +188,9 @@
     </codeStyleSettings>
     <codeStyleSettings language="kotlin">
       <option name="CODE_STYLE_DEFAULTS" value="KOTLIN_OFFICIAL" />
-      <option name="PARAMETER_ANNOTATION_WRAP" value="1" />
-      <option name="VARIABLE_ANNOTATION_WRAP" value="1" />
-      <option name="ENUM_CONSTANTS_WRAP" value="1" />
+      <indentOptions>
+        <option name="CONTINUATION_INDENT_SIZE" value="4" />
+      </indentOptions>
     </codeStyleSettings>
   </code_scheme>
 </component>

README.md

@@ -1 +1,28 @@
-Briar is a messaging app designed for activists, journalists, and anyone else who needs a safe, easy and robust way to communicate. Unlike traditional messaging tools such as email, Twitter or Telegram, Briar doesn't rely on a central server - messages are synchronized directly between the users' devices. If the Internet's down, Briar can sync via Bluetooth or Wi-Fi, keeping the information flowing in a crisis. If the Internet's up, Briar can sync via the Tor network, protecting users and their relationships from surveillance.
+# Briar
+Briar is a messaging app designed for activists, journalists, and anyone else who needs a safe, easy and robust way to communicate.
+
+Unlike traditional messaging tools such as email, Twitter or Telegram, Briar doesn't rely on a central server - messages are synchronized directly between the users' devices. 
+
+If the Internet's down, Briar can sync via Bluetooth or Wi-Fi, keeping information flowing in a crisis. If the Internet's up, Briar can sync via the Tor network, protecting users and their relationships from surveillance.
+
+## Download Briar
+
+[<img src="https://briarproject.org//img/fdroid_badge.png"  width="240">](https://briarproject.org/fdroid)
+[<img src="https://briarproject.org/img/google_play_badge_web_generic.png"  width="240">](https://play.google.com/store/apps/details?id=org.briarproject.briar.android)
+
+You can also [download the APK file](https://briarproject.org/apk) directly from
+our site.
+
+## Useful links
+[briarproject.org](https://briarproject.org/)
+
+[Source code](https://code.briarproject.org/briar/briar/tree/master)
+
+[Manual](https://briarproject.org/manual/)
+
+[Wiki](https://code.briarproject.org/briar/briar/-/wikis/home)
+
+## Donate
+
+[![Donate using Liberapay](https://briarproject.org/img/liberapay.svg)](https://liberapay.com/Briar/donate) [![Flattr this](https://briarproject.org/img/flattr-badge-large.png "Flattr this")](https://flattr.com/t/592836/)   
+Bitcoin and BCH: 1NZCKkUCtJV2U2Y9hDb9uq8S7ksFCFGR6K

bramble-android/build.gradle

@@ -15,8 +15,8 @@ android {
 	defaultConfig {
 		minSdkVersion 16
 		targetSdkVersion 30
-		versionCode 10306
-		versionName "1.3.6"
+		versionCode 10308
+		versionName "1.3.8"
 		consumerProguardFiles 'proguard-rules.txt'
 
 		testInstrumentationRunner "androidx.test.runner.AndroidJUnitRunner"

bramble-android/src/main/java/org/briarproject/bramble/plugin/tcp/AndroidLanTcpPlugin.java

@@ -29,6 +29,7 @@ import java.net.UnknownHostException;
 import java.util.List;
 import java.util.concurrent.Executor;
 import java.util.logging.Logger;
+import java.util.regex.Pattern;
 
 import javax.annotation.Nullable;
 import javax.net.SocketFactory;
@@ -48,6 +49,7 @@ import static org.briarproject.bramble.api.plugin.Plugin.State.ACTIVE;
 import static org.briarproject.bramble.api.plugin.Plugin.State.INACTIVE;
 import static org.briarproject.bramble.util.IoUtils.tryToClose;
 import static org.briarproject.bramble.util.LogUtils.logException;
+import static org.briarproject.bramble.util.NetworkUtils.getNetworkInterfaces;
 
 @NotNullByDefault
 class AndroidLanTcpPlugin extends LanTcpPlugin {
@@ -55,6 +57,13 @@ class AndroidLanTcpPlugin extends LanTcpPlugin {
 	private static final Logger LOG =
 			getLogger(AndroidLanTcpPlugin.class.getName());
 
+	/**
+	 * The interface name is used as a heuristic for deciding whether the
+	 * device is providing a wifi access point.
+	 */
+	private static final Pattern AP_INTERFACE_NAME =
+			Pattern.compile("^(wlan|ap|p2p)[-0-9]");
+
 	private final Executor connectionStatusExecutor;
 	private final ConnectivityManager connectivityManager;
 	@Nullable
@@ -130,17 +139,14 @@ class AndroidLanTcpPlugin extends LanTcpPlugin {
 		if (info != null && info.getIpAddress() != 0) {
 			return new Pair<>(intToInetAddress(info.getIpAddress()), false);
 		}
-		List<InterfaceAddress> ifAddrs = getLocalInterfaceAddresses();
-		// If we're providing a normal access point, return its address
-		for (InterfaceAddress ifAddr : ifAddrs) {
-			if (isAndroidWifiApAddress(ifAddr)) {
-				return new Pair<>(ifAddr.getAddress(), true);
-			}
-		}
-		// If we're providing a wifi direct access point, return its address
-		for (InterfaceAddress ifAddr : ifAddrs) {
-			if (isAndroidWifiDirectApAddress(ifAddr)) {
-				return new Pair<>(ifAddr.getAddress(), true);
+		// If we're providing an access point, return its address
+		for (NetworkInterface iface : getNetworkInterfaces()) {
+			if (AP_INTERFACE_NAME.matcher(iface.getName()).find()) {
+				for (InterfaceAddress ifAddr : iface.getInterfaceAddresses()) {
+					if (isPossibleWifiApInterface(ifAddr)) {
+						return new Pair<>(ifAddr.getAddress(), true);
+					}
+				}
 			}
 		}
 		// Not connected to wifi
@@ -148,33 +154,18 @@ class AndroidLanTcpPlugin extends LanTcpPlugin {
 	}
 
 	/**
-	 * Returns true if the given address belongs to a network provided by an
-	 * Android access point (including the access point's own address).
+	 * Returns true if the given address may belong to an interface providing
+	 * a wifi access point (including wifi direct legacy mode access points).
 	 * <p>
-	 * The access point's address is usually 192.168.43.1, but at least one
-	 * device (Honor 8A) may use other addresses in the range 192.168.43.0/24.
+	 * This method may return true for wifi client interfaces as well, but
+	 * we've already checked for a wifi client connection above.
 	 */
-	private boolean isAndroidWifiApAddress(InterfaceAddress ifAddr) {
+	private boolean isPossibleWifiApInterface(InterfaceAddress ifAddr) {
 		if (ifAddr.getNetworkPrefixLength() != 24) return false;
 		byte[] ip = ifAddr.getAddress().getAddress();
 		return ip.length == 4
 				&& ip[0] == (byte) 192
-				&& ip[1] == (byte) 168
-				&& ip[2] == (byte) 43;
-	}
-
-	/**
-	 * Returns true if the given address belongs to a network provided by an
-	 * Android wifi direct legacy mode access point (including the access
-	 * point's own address).
-	 */
-	private boolean isAndroidWifiDirectApAddress(InterfaceAddress ifAddr) {
-		if (ifAddr.getNetworkPrefixLength() != 24) return false;
-		byte[] ip = ifAddr.getAddress().getAddress();
-		return ip.length == 4
-				&& ip[0] == (byte) 192
-				&& ip[1] == (byte) 168
-				&& ip[2] == (byte) 49;
+				&& ip[1] == (byte) 168;
 	}
 
 	/**

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

@@ -11,7 +11,7 @@ public interface FeatureFlags {
 
 	boolean shouldEnableDisappearingMessages();
 
-	boolean shouldEnableConnectViaBluetooth();
-
 	boolean shouldEnableTransferData();
+
+	boolean shouldEnableShareAppViaOfflineHotspot();
 }

bramble-api/src/main/java/org/briarproject/bramble/util/NetworkUtils.java

@@ -0,0 +1,34 @@
+package org.briarproject.bramble.util;
+
+import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
+
+import java.net.NetworkInterface;
+import java.net.SocketException;
+import java.util.Enumeration;
+import java.util.List;
+import java.util.logging.Logger;
+
+import static java.util.Collections.emptyList;
+import static java.util.Collections.list;
+import static java.util.logging.Level.WARNING;
+import static java.util.logging.Logger.getLogger;
+import static org.briarproject.bramble.util.LogUtils.logException;
+
+@NotNullByDefault
+public class NetworkUtils {
+
+	private static final Logger LOG = getLogger(NetworkUtils.class.getName());
+
+	public static List<NetworkInterface> getNetworkInterfaces() {
+		try {
+			Enumeration<NetworkInterface> ifaces =
+					NetworkInterface.getNetworkInterfaces();
+			// Despite what the docs say, the return value can be null
+			//noinspection ConstantConditions
+			return ifaces == null ? emptyList() : list(ifaces);
+		} catch (SocketException e) {
+			logException(LOG, WARNING, e);
+			return emptyList();
+		}
+	}
+}

bramble-api/witness.gradle

@@ -10,8 +10,8 @@ dependencyVerification {
         'net.jcip:jcip-annotations:1.0:jcip-annotations-1.0.jar:be5805392060c71474bf6c9a67a099471274d30b83eef84bfc4e0889a4f1dcc0',
         'org.apache-extras.beanshell:bsh:2.0b6:bsh-2.0b6.jar:a17955976070c0573235ee662f2794a78082758b61accffce8d3f8aedcd91047',
         'org.codehaus.mojo.signature:java16:1.1:java16-1.1.signature:53799223a2c98dba2d0add810bed76315460df285c69e4f397ae6098f87dd619',
-        'org.codehaus.mojo:animal-sniffer-ant-tasks:1.16:animal-sniffer-ant-tasks-1.16.jar:890040976fbe2d584619a6a61b1fd2e925b3b5eb342a85eb2762c467c0d64e90',
-        'org.codehaus.mojo:animal-sniffer:1.16:animal-sniffer-1.16.jar:72be8bcc226ba43b937c722a08a07852bfa1b11400089265d5df0ee7b38b1d52',
+        'org.codehaus.mojo:animal-sniffer-ant-tasks:1.20:animal-sniffer-ant-tasks-1.20.jar:bb7d2498144118311d968bb08ff6fae3fc535fb1cb9cca8b8e9ea65b189422ac',
+        'org.codehaus.mojo:animal-sniffer:1.20:animal-sniffer-1.20.jar:80c422523c38db91260c6d78e5ee4b012862ab61cc55020c9e243dd7b5c62249',
         'org.hamcrest:hamcrest-core:2.1:hamcrest-core-2.1.jar:e09109e54a289d88506b9bfec987ddd199f4217c9464132668351b9a4f00bee9',
         'org.hamcrest:hamcrest-library:2.1:hamcrest-library-2.1.jar:b7e2b6895b3b679f0e47b6380fda391b225e9b78505db9d8bdde8d3cc8d52a21',
         'org.hamcrest:hamcrest:2.1:hamcrest-2.1.jar:ba93b2e3a562322ba432f0a1b53addcc55cb188253319a020ed77f824e692050',
@@ -21,7 +21,7 @@ dependencyVerification {
         'org.jmock:jmock-testjar:2.12.0:jmock-testjar-2.12.0.jar:efefbcf6cd294d0e29f0c46eb2a3380d4ca4e1763ff719c69e2f2ac62f564a04',
         'org.jmock:jmock:2.12.0:jmock-2.12.0.jar:266d07314c0cd343c46ff8a55601272de8cf406807caf55e6f313295f83d10be',
         'org.objenesis:objenesis:3.0.1:objenesis-3.0.1.jar:7a8ff780b9ff48415d7c705f60030b0acaa616e7f823c98eede3b63508d4e984',
-        'org.ow2.asm:asm-all:5.2:asm-all-5.2.jar:7fbffbc1db3422e2101689fd88df8384b15817b52b9b2b267b9f6d2511dc198d',
         'org.ow2.asm:asm:7.1:asm-7.1.jar:4ab2fa2b6d2cc9ccb1eaa05ea329c407b47b13ed2915f62f8c4b8cc96258d4de',
+        'org.ow2.asm:asm:9.1:asm-9.1.jar:cda4de455fab48ff0bcb7c48b4639447d4de859a7afc30a094a986f0936beba2',
     ]
 }

bramble-core/build.gradle

@@ -10,7 +10,7 @@ apply from: '../dagger.gradle'
 
 dependencies {
 	implementation project(path: ':bramble-api', configuration: 'default')
-	implementation 'com.madgag.spongycastle:core:1.58.0.0'
+	implementation 'org.bouncycastle:bcprov-jdk15on:1.69'
 	implementation 'com.h2database:h2:1.4.192' // The last version that supports Java 1.6
 	implementation 'org.bitlet:weupnp:0.1.4'
 	implementation 'net.i2p.crypto:eddsa:0.2.0'
@@ -32,6 +32,14 @@ dependencies {
 	signature 'org.codehaus.mojo.signature:java16:1.1@signature'
 }
 
+animalsniffer {
+	// Allow requireNonNull: Android desugaring rewrites it (so it's safe for us to use),
+	// and it gets used when passing method references instead of lambdas with Java 11.
+	// Note that this line allows *all* methods from java.util.Objects.
+	// That's the best that we can do with the configuration options that Animal Sniffer offers.
+	ignore 'java.util.Objects'
+}
+
 // needed to make test output available to bramble-java
 configurations {
 	testOutput.extendsFrom(testCompile)

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

@@ -4,6 +4,9 @@ import net.i2p.crypto.eddsa.EdDSAPrivateKey;
 import net.i2p.crypto.eddsa.EdDSAPublicKey;
 import net.i2p.crypto.eddsa.KeyPairGenerator;
 
+import org.bouncycastle.crypto.CryptoException;
+import org.bouncycastle.crypto.Digest;
+import org.bouncycastle.crypto.digests.Blake2bDigest;
 import org.briarproject.bramble.api.crypto.AgreementPrivateKey;
 import org.briarproject.bramble.api.crypto.AgreementPublicKey;
 import org.briarproject.bramble.api.crypto.CryptoComponent;
@@ -20,9 +23,6 @@ import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
 import org.briarproject.bramble.api.system.SecureRandomProvider;
 import org.briarproject.bramble.util.ByteUtils;
 import org.briarproject.bramble.util.StringUtils;
-import org.spongycastle.crypto.CryptoException;
-import org.spongycastle.crypto.Digest;
-import org.spongycastle.crypto.digests.Blake2bDigest;
 import org.whispersystems.curve25519.Curve25519;
 import org.whispersystems.curve25519.Curve25519KeyPair;
 

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

@@ -1,38 +1,38 @@
 package org.briarproject.bramble.crypto;
 
+import org.bouncycastle.asn1.teletrust.TeleTrusTNamedCurves;
+import org.bouncycastle.asn1.x9.X9ECParameters;
+import org.bouncycastle.crypto.AsymmetricCipherKeyPair;
+import org.bouncycastle.crypto.BasicAgreement;
+import org.bouncycastle.crypto.BlockCipher;
+import org.bouncycastle.crypto.CipherParameters;
+import org.bouncycastle.crypto.CryptoException;
+import org.bouncycastle.crypto.DerivationFunction;
+import org.bouncycastle.crypto.KeyEncoder;
+import org.bouncycastle.crypto.Mac;
+import org.bouncycastle.crypto.agreement.ECDHCBasicAgreement;
+import org.bouncycastle.crypto.digests.SHA256Digest;
+import org.bouncycastle.crypto.engines.AESLightEngine;
+import org.bouncycastle.crypto.engines.IESEngine;
+import org.bouncycastle.crypto.generators.ECKeyPairGenerator;
+import org.bouncycastle.crypto.generators.EphemeralKeyPairGenerator;
+import org.bouncycastle.crypto.generators.KDF2BytesGenerator;
+import org.bouncycastle.crypto.macs.HMac;
+import org.bouncycastle.crypto.modes.CBCBlockCipher;
+import org.bouncycastle.crypto.paddings.PaddedBufferedBlockCipher;
+import org.bouncycastle.crypto.params.AsymmetricKeyParameter;
+import org.bouncycastle.crypto.params.ECDomainParameters;
+import org.bouncycastle.crypto.params.ECKeyGenerationParameters;
+import org.bouncycastle.crypto.params.ECPrivateKeyParameters;
+import org.bouncycastle.crypto.params.ECPublicKeyParameters;
+import org.bouncycastle.crypto.params.IESWithCipherParameters;
+import org.bouncycastle.crypto.parsers.ECIESPublicKeyParser;
 import org.briarproject.bramble.api.crypto.KeyPair;
 import org.briarproject.bramble.api.crypto.KeyParser;
 import org.briarproject.bramble.api.crypto.PrivateKey;
 import org.briarproject.bramble.api.crypto.PublicKey;
 import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
 import org.briarproject.bramble.util.StringUtils;
-import org.spongycastle.asn1.teletrust.TeleTrusTNamedCurves;
-import org.spongycastle.asn1.x9.X9ECParameters;
-import org.spongycastle.crypto.AsymmetricCipherKeyPair;
-import org.spongycastle.crypto.BasicAgreement;
-import org.spongycastle.crypto.BlockCipher;
-import org.spongycastle.crypto.CipherParameters;
-import org.spongycastle.crypto.CryptoException;
-import org.spongycastle.crypto.DerivationFunction;
-import org.spongycastle.crypto.KeyEncoder;
-import org.spongycastle.crypto.Mac;
-import org.spongycastle.crypto.agreement.ECDHCBasicAgreement;
-import org.spongycastle.crypto.digests.SHA256Digest;
-import org.spongycastle.crypto.engines.AESLightEngine;
-import org.spongycastle.crypto.engines.IESEngine;
-import org.spongycastle.crypto.generators.ECKeyPairGenerator;
-import org.spongycastle.crypto.generators.EphemeralKeyPairGenerator;
-import org.spongycastle.crypto.generators.KDF2BytesGenerator;
-import org.spongycastle.crypto.macs.HMac;
-import org.spongycastle.crypto.modes.CBCBlockCipher;
-import org.spongycastle.crypto.paddings.PaddedBufferedBlockCipher;
-import org.spongycastle.crypto.params.AsymmetricKeyParameter;
-import org.spongycastle.crypto.params.ECDomainParameters;
-import org.spongycastle.crypto.params.ECKeyGenerationParameters;
-import org.spongycastle.crypto.params.ECPrivateKeyParameters;
-import org.spongycastle.crypto.params.ECPublicKeyParameters;
-import org.spongycastle.crypto.params.IESWithCipherParameters;
-import org.spongycastle.crypto.parsers.ECIESPublicKeyParser;
 
 import java.io.FileInputStream;
 import java.io.FileOutputStream;

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

@@ -1,9 +1,9 @@
 package org.briarproject.bramble.crypto;
 
+import org.bouncycastle.crypto.generators.SCrypt;
 import org.briarproject.bramble.api.crypto.SecretKey;
 import org.briarproject.bramble.api.system.Clock;
 import org.briarproject.bramble.util.StringUtils;
-import org.spongycastle.crypto.generators.SCrypt;
 
 import java.util.logging.Logger;
 

bramble-core/src/main/java/org/briarproject/bramble/crypto/Sec1KeyParser.java

@@ -1,14 +1,14 @@
 package org.briarproject.bramble.crypto;
 
+import org.bouncycastle.crypto.params.ECDomainParameters;
+import org.bouncycastle.crypto.params.ECPrivateKeyParameters;
+import org.bouncycastle.crypto.params.ECPublicKeyParameters;
+import org.bouncycastle.math.ec.ECCurve;
+import org.bouncycastle.math.ec.ECPoint;
 import org.briarproject.bramble.api.crypto.KeyParser;
 import org.briarproject.bramble.api.crypto.PrivateKey;
 import org.briarproject.bramble.api.crypto.PublicKey;
 import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
-import org.spongycastle.crypto.params.ECDomainParameters;
-import org.spongycastle.crypto.params.ECPrivateKeyParameters;
-import org.spongycastle.crypto.params.ECPublicKeyParameters;
-import org.spongycastle.math.ec.ECCurve;
-import org.spongycastle.math.ec.ECPoint;
 
 import java.math.BigInteger;
 import java.security.GeneralSecurityException;

bramble-core/src/main/java/org/briarproject/bramble/crypto/Sec1PrivateKey.java

@@ -1,8 +1,8 @@
 package org.briarproject.bramble.crypto;
 
+import org.bouncycastle.crypto.params.ECPrivateKeyParameters;
 import org.briarproject.bramble.api.crypto.PrivateKey;
 import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
-import org.spongycastle.crypto.params.ECPrivateKeyParameters;
 
 import javax.annotation.concurrent.Immutable;
 

bramble-core/src/main/java/org/briarproject/bramble/crypto/Sec1PublicKey.java

@@ -1,8 +1,8 @@
 package org.briarproject.bramble.crypto;
 
+import org.bouncycastle.crypto.params.ECPublicKeyParameters;
 import org.briarproject.bramble.api.crypto.PublicKey;
 import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
-import org.spongycastle.crypto.params.ECPublicKeyParameters;
 
 import javax.annotation.concurrent.Immutable;
 

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

@@ -1,5 +1,7 @@
 package org.briarproject.bramble.crypto;
 
+import org.bouncycastle.crypto.Digest;
+import org.bouncycastle.crypto.digests.Blake2bDigest;
 import org.briarproject.bramble.api.crypto.CryptoComponent;
 import org.briarproject.bramble.api.crypto.KeyPair;
 import org.briarproject.bramble.api.crypto.PublicKey;
@@ -9,8 +11,6 @@ import org.briarproject.bramble.api.plugin.TransportId;
 import org.briarproject.bramble.api.transport.IncomingKeys;
 import org.briarproject.bramble.api.transport.OutgoingKeys;
 import org.briarproject.bramble.api.transport.TransportKeys;
-import org.spongycastle.crypto.Digest;
-import org.spongycastle.crypto.digests.Blake2bDigest;
 
 import java.security.GeneralSecurityException;
 

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

@@ -1,13 +1,13 @@
 package org.briarproject.bramble.crypto;
 
+import org.bouncycastle.crypto.DataLengthException;
+import org.bouncycastle.crypto.engines.XSalsa20Engine;
+import org.bouncycastle.crypto.generators.Poly1305KeyGenerator;
+import org.bouncycastle.crypto.macs.Poly1305;
+import org.bouncycastle.crypto.params.KeyParameter;
+import org.bouncycastle.crypto.params.ParametersWithIV;
 import org.briarproject.bramble.api.crypto.SecretKey;
 import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
-import org.spongycastle.crypto.DataLengthException;
-import org.spongycastle.crypto.engines.XSalsa20Engine;
-import org.spongycastle.crypto.generators.Poly1305KeyGenerator;
-import org.spongycastle.crypto.macs.Poly1305;
-import org.spongycastle.crypto.params.KeyParameter;
-import org.spongycastle.crypto.params.ParametersWithIV;
 
 import java.security.GeneralSecurityException;
 

bramble-core/src/main/java/org/briarproject/bramble/plugin/tcp/TcpPlugin.java

@@ -28,11 +28,9 @@ import java.net.InterfaceAddress;
 import java.net.NetworkInterface;
 import java.net.ServerSocket;
 import java.net.Socket;
-import java.net.SocketException;
 import java.net.UnknownHostException;
 import java.util.ArrayList;
 import java.util.Collection;
-import java.util.Enumeration;
 import java.util.List;
 import java.util.concurrent.Executor;
 import java.util.concurrent.atomic.AtomicBoolean;
@@ -53,7 +51,7 @@ 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.IoUtils.tryToClose;
-import static org.briarproject.bramble.util.LogUtils.logException;
+import static org.briarproject.bramble.util.NetworkUtils.getNetworkInterfaces;
 import static org.briarproject.bramble.util.PrivacyUtils.scrubSocketAddress;
 import static org.briarproject.bramble.util.StringUtils.isNullOrEmpty;
 
@@ -98,7 +96,6 @@ abstract class TcpPlugin implements DuplexPlugin, EventListener {
 	/**
 	 * Returns true if connections to the given address can be attempted.
 	 */
-	@SuppressWarnings("BooleanMethodIsAlwaysInverted")
 	protected abstract boolean isConnectable(InterfaceAddress local,
 			InetSocketAddress remote);
 
@@ -398,17 +395,6 @@ abstract class TcpPlugin implements DuplexPlugin, EventListener {
 		return addrs;
 	}
 
-	private List<NetworkInterface> getNetworkInterfaces() {
-		try {
-			Enumeration<NetworkInterface> ifaces =
-					NetworkInterface.getNetworkInterfaces();
-			return ifaces == null ? emptyList() : list(ifaces);
-		} catch (SocketException e) {
-			logException(LOG, WARNING, e);
-			return emptyList();
-		}
-	}
-
 	@Override
 	public void eventOccurred(Event e) {
 		if (e instanceof SettingsUpdatedEvent) {

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

@@ -4,10 +4,10 @@ import net.i2p.crypto.eddsa.spec.EdDSANamedCurveSpec;
 import net.i2p.crypto.eddsa.spec.EdDSANamedCurveTable;
 import net.i2p.crypto.eddsa.spec.EdDSAPrivateKeySpec;
 
+import org.bouncycastle.crypto.Digest;
+import org.bouncycastle.crypto.digests.SHA3Digest;
+import org.bouncycastle.util.encoders.Base64;
 import org.briarproject.bramble.util.Base32;
-import org.spongycastle.crypto.Digest;
-import org.spongycastle.crypto.digests.SHA3Digest;
-import org.spongycastle.util.encoders.Base64;
 
 import java.nio.charset.Charset;
 

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

@@ -1,11 +1,11 @@
 package org.briarproject.bramble.rendezvous;
 
+import org.bouncycastle.crypto.engines.Salsa20Engine;
+import org.bouncycastle.crypto.params.KeyParameter;
+import org.bouncycastle.crypto.params.ParametersWithIV;
 import org.briarproject.bramble.api.crypto.SecretKey;
 import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
 import org.briarproject.bramble.api.rendezvous.KeyMaterialSource;
-import org.spongycastle.crypto.engines.Salsa20Engine;
-import org.spongycastle.crypto.params.KeyParameter;
-import org.spongycastle.crypto.params.ParametersWithIV;
 
 import javax.annotation.concurrent.GuardedBy;
 import javax.annotation.concurrent.ThreadSafe;

bramble-core/src/test/java/org/briarproject/bramble/crypto/Blake2bDigestTest.java

@@ -1,9 +1,9 @@
 package org.briarproject.bramble.crypto;
 
+import org.bouncycastle.crypto.digests.Blake2bDigest;
 import org.briarproject.bramble.test.BrambleTestCase;
 import org.briarproject.bramble.util.StringUtils;
 import org.junit.Test;
-import org.spongycastle.crypto.digests.Blake2bDigest;
 
 import java.util.Random;
 

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

@@ -1,115 +0,0 @@
-package org.briarproject.bramble.crypto;
-
-import org.briarproject.bramble.test.BrambleTestCase;
-import org.junit.Test;
-import org.spongycastle.asn1.teletrust.TeleTrusTNamedCurves;
-import org.spongycastle.asn1.x9.X9ECParameters;
-import org.spongycastle.crypto.AsymmetricCipherKeyPair;
-import org.spongycastle.crypto.agreement.ECDHCBasicAgreement;
-import org.spongycastle.crypto.generators.ECKeyPairGenerator;
-import org.spongycastle.crypto.params.ECDomainParameters;
-import org.spongycastle.crypto.params.ECKeyGenerationParameters;
-import org.spongycastle.crypto.params.ECPrivateKeyParameters;
-import org.spongycastle.crypto.params.ECPublicKeyParameters;
-import org.spongycastle.math.ec.ECCurve;
-import org.spongycastle.math.ec.ECPoint;
-import org.spongycastle.math.ec.MontgomeryLadderMultiplier;
-
-import java.math.BigInteger;
-import java.security.SecureRandom;
-
-import static org.junit.Assert.assertEquals;
-
-public class EllipticCurveMultiplicationTest extends BrambleTestCase {
-
-	@Test
-	public void testMultiplierProducesSameResultsAsDefault() throws Exception {
-		// Instantiate the default implementation of the curve
-		X9ECParameters defaultX9Parameters =
-				TeleTrusTNamedCurves.getByName("brainpoolp256r1");
-		ECCurve defaultCurve = defaultX9Parameters.getCurve();
-		ECPoint defaultG = defaultX9Parameters.getG();
-		BigInteger defaultN = defaultX9Parameters.getN();
-		BigInteger defaultH = defaultX9Parameters.getH();
-		ECDomainParameters defaultParameters = new ECDomainParameters(
-				defaultCurve, defaultG, defaultN, defaultH);
-		// Instantiate an implementation using the Montgomery ladder multiplier
-		ECDomainParameters montgomeryParameters =
-				constantTime(defaultParameters);
-		// Generate two key pairs with each set of parameters, using the same
-		// deterministic PRNG for both sets of parameters
-		byte[] seed = new byte[32];
-		new SecureRandom().nextBytes(seed);
-		// Montgomery ladder multiplier
-		SecureRandom random = new PseudoSecureRandom(seed);
-		ECKeyGenerationParameters montgomeryGeneratorParams =
-				new ECKeyGenerationParameters(montgomeryParameters, random);
-		ECKeyPairGenerator montgomeryGenerator = new ECKeyPairGenerator();
-		montgomeryGenerator.init(montgomeryGeneratorParams);
-		AsymmetricCipherKeyPair montgomeryKeyPair1 =
-				montgomeryGenerator.generateKeyPair();
-		ECPrivateKeyParameters montgomeryPrivate1 =
-				(ECPrivateKeyParameters) montgomeryKeyPair1.getPrivate();
-		ECPublicKeyParameters montgomeryPublic1 =
-				(ECPublicKeyParameters) montgomeryKeyPair1.getPublic();
-		AsymmetricCipherKeyPair montgomeryKeyPair2 =
-				montgomeryGenerator.generateKeyPair();
-		ECPrivateKeyParameters montgomeryPrivate2 =
-				(ECPrivateKeyParameters) montgomeryKeyPair2.getPrivate();
-		ECPublicKeyParameters montgomeryPublic2 =
-				(ECPublicKeyParameters) montgomeryKeyPair2.getPublic();
-		// Default multiplier
-		random = new PseudoSecureRandom(seed);
-		ECKeyGenerationParameters defaultGeneratorParams =
-				new ECKeyGenerationParameters(defaultParameters, random);
-		ECKeyPairGenerator defaultGenerator = new ECKeyPairGenerator();
-		defaultGenerator.init(defaultGeneratorParams);
-		AsymmetricCipherKeyPair defaultKeyPair1 =
-				defaultGenerator.generateKeyPair();
-		ECPrivateKeyParameters defaultPrivate1 =
-				(ECPrivateKeyParameters) defaultKeyPair1.getPrivate();
-		ECPublicKeyParameters defaultPublic1 =
-				(ECPublicKeyParameters) defaultKeyPair1.getPublic();
-		AsymmetricCipherKeyPair defaultKeyPair2 =
-				defaultGenerator.generateKeyPair();
-		ECPrivateKeyParameters defaultPrivate2 =
-				(ECPrivateKeyParameters) defaultKeyPair2.getPrivate();
-		ECPublicKeyParameters defaultPublic2 =
-				(ECPublicKeyParameters) defaultKeyPair2.getPublic();
-		// The key pairs generated with both sets of parameters should be equal
-		assertEquals(montgomeryPrivate1.getD(), defaultPrivate1.getD());
-		assertEquals(montgomeryPublic1.getQ(), defaultPublic1.getQ());
-		assertEquals(montgomeryPrivate2.getD(), defaultPrivate2.getD());
-		assertEquals(montgomeryPublic2.getQ(), defaultPublic2.getQ());
-		// OK, all of the above was just sanity checks - now for the test!
-		ECDHCBasicAgreement agreement = new ECDHCBasicAgreement();
-		agreement.init(montgomeryPrivate1);
-		BigInteger sharedSecretMontgomeryMontgomery =
-				agreement.calculateAgreement(montgomeryPublic2);
-		agreement.init(montgomeryPrivate1);
-		BigInteger sharedSecretMontgomeryDefault =
-				agreement.calculateAgreement(defaultPublic2);
-		agreement.init(defaultPrivate1);
-		BigInteger sharedSecretDefaultMontgomery =
-				agreement.calculateAgreement(montgomeryPublic2);
-		agreement.init(defaultPrivate1);
-		BigInteger sharedSecretDefaultDefault =
-				agreement.calculateAgreement(defaultPublic2);
-		// Shared secrets calculated with different multipliers should be equal
-		assertEquals(sharedSecretMontgomeryMontgomery,
-				sharedSecretMontgomeryDefault);
-		assertEquals(sharedSecretMontgomeryMontgomery,
-				sharedSecretDefaultMontgomery);
-		assertEquals(sharedSecretMontgomeryMontgomery,
-				sharedSecretDefaultDefault);
-	}
-
-	private static ECDomainParameters constantTime(ECDomainParameters in) {
-		ECCurve curve = in.getCurve().configure().setMultiplier(
-				new MontgomeryLadderMultiplier()).create();
-		BigInteger x = in.getG().getAffineXCoord().toBigInteger();
-		BigInteger y = in.getG().getAffineYCoord().toBigInteger();
-		ECPoint g = curve.createPoint(x, y);
-		return new ECDomainParameters(curve, g, in.getN(), in.getH());
-	}
-}

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

@@ -3,30 +3,26 @@ package org.briarproject.bramble.crypto;
 import net.i2p.crypto.eddsa.EdDSASecurityProvider;
 import net.i2p.crypto.eddsa.KeyPairGenerator;
 
-import org.spongycastle.asn1.sec.SECNamedCurves;
-import org.spongycastle.asn1.teletrust.TeleTrusTNamedCurves;
-import org.spongycastle.asn1.x9.X9ECParameters;
-import org.spongycastle.crypto.AsymmetricCipherKeyPair;
-import org.spongycastle.crypto.BasicAgreement;
-import org.spongycastle.crypto.Digest;
-import org.spongycastle.crypto.agreement.ECDHBasicAgreement;
-import org.spongycastle.crypto.agreement.ECDHCBasicAgreement;
-import org.spongycastle.crypto.digests.Blake2bDigest;
-import org.spongycastle.crypto.generators.ECKeyPairGenerator;
-import org.spongycastle.crypto.params.ECDomainParameters;
-import org.spongycastle.crypto.params.ECKeyGenerationParameters;
-import org.spongycastle.crypto.params.ParametersWithRandom;
-import org.spongycastle.crypto.signers.DSADigestSigner;
-import org.spongycastle.crypto.signers.DSAKCalculator;
-import org.spongycastle.crypto.signers.ECDSASigner;
-import org.spongycastle.crypto.signers.HMacDSAKCalculator;
-import org.spongycastle.math.ec.ECCurve;
-import org.spongycastle.math.ec.ECPoint;
-import org.spongycastle.math.ec.MontgomeryLadderMultiplier;
+import org.bouncycastle.asn1.sec.SECNamedCurves;
+import org.bouncycastle.asn1.teletrust.TeleTrusTNamedCurves;
+import org.bouncycastle.asn1.x9.X9ECParameters;
+import org.bouncycastle.crypto.AsymmetricCipherKeyPair;
+import org.bouncycastle.crypto.BasicAgreement;
+import org.bouncycastle.crypto.Digest;
+import org.bouncycastle.crypto.agreement.ECDHBasicAgreement;
+import org.bouncycastle.crypto.agreement.ECDHCBasicAgreement;
+import org.bouncycastle.crypto.digests.Blake2bDigest;
+import org.bouncycastle.crypto.generators.ECKeyPairGenerator;
+import org.bouncycastle.crypto.params.ECDomainParameters;
+import org.bouncycastle.crypto.params.ECKeyGenerationParameters;
+import org.bouncycastle.crypto.params.ParametersWithRandom;
+import org.bouncycastle.crypto.signers.DSADigestSigner;
+import org.bouncycastle.crypto.signers.DSAKCalculator;
+import org.bouncycastle.crypto.signers.ECDSASigner;
+import org.bouncycastle.crypto.signers.HMacDSAKCalculator;
 import org.whispersystems.curve25519.Curve25519;
 import org.whispersystems.curve25519.Curve25519KeyPair;
 
-import java.math.BigInteger;
 import java.security.GeneralSecurityException;
 import java.security.KeyPair;
 import java.security.Provider;
@@ -55,14 +51,12 @@ public class EllipticCurvePerformanceTest {
 		for (String name : SEC_NAMES) {
 			ECDomainParameters params =
 					convertParams(SECNamedCurves.getByName(name));
-			runTest(name + " default", params);
-			runTest(name + " constant", constantTime(params));
+			runTest(name, params);
 		}
 		for (String name : BRAINPOOL_NAMES) {
 			ECDomainParameters params =
 					convertParams(TeleTrusTNamedCurves.getByName(name));
-			runTest(name + " default", params);
-			runTest(name + " constant", constantTime(params));
+			runTest(name, params);
 		}
 		runCurve25519Test();
 		runEd25519Test();
@@ -193,13 +187,4 @@ public class EllipticCurvePerformanceTest {
 		return new ECDomainParameters(in.getCurve(), in.getG(), in.getN(),
 				in.getH());
 	}
-
-	private static ECDomainParameters constantTime(ECDomainParameters in) {
-		ECCurve curve = in.getCurve().configure().setMultiplier(
-				new MontgomeryLadderMultiplier()).create();
-		BigInteger x = in.getG().getAffineXCoord().toBigInteger();
-		BigInteger y = in.getG().getAffineYCoord().toBigInteger();
-		ECPoint g = curve.createPoint(x, y);
-		return new ECDomainParameters(curve, g, in.getN(), in.getH());
-	}
 }

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

@@ -1,11 +1,11 @@
 package org.briarproject.bramble.crypto;
 
+import org.bouncycastle.crypto.CryptoException;
 import org.briarproject.bramble.api.crypto.KeyPair;
 import org.briarproject.bramble.api.crypto.PrivateKey;
 import org.briarproject.bramble.api.crypto.PublicKey;
 import org.briarproject.bramble.test.BrambleTestCase;
 import org.junit.Test;
-import org.spongycastle.crypto.CryptoException;
 
 import java.security.SecureRandom;
 

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

@@ -1,11 +1,11 @@
 package org.briarproject.bramble.crypto;
 
+import org.bouncycastle.crypto.Digest;
+import org.bouncycastle.crypto.digests.Blake2bDigest;
+import org.bouncycastle.crypto.engines.Salsa20Engine;
+import org.bouncycastle.crypto.params.KeyParameter;
+import org.bouncycastle.crypto.params.ParametersWithIV;
 import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
-import org.spongycastle.crypto.Digest;
-import org.spongycastle.crypto.digests.Blake2bDigest;
-import org.spongycastle.crypto.engines.Salsa20Engine;
-import org.spongycastle.crypto.params.KeyParameter;
-import org.spongycastle.crypto.params.ParametersWithIV;
 
 import javax.annotation.concurrent.NotThreadSafe;
 

bramble-core/src/test/java/org/briarproject/bramble/test/TestFeatureFlagModule.java

@@ -26,12 +26,12 @@ public class TestFeatureFlagModule {
 			}
 
 			@Override
-			public boolean shouldEnableConnectViaBluetooth() {
+			public boolean shouldEnableTransferData() {
 				return true;
 			}
 
 			@Override
-			public boolean shouldEnableTransferData() {
+			public boolean shouldEnableShareAppViaOfflineHotspot() {
 				return true;
 			}
 		};

bramble-core/witness.gradle

@@ -15,7 +15,6 @@ dependencyVerification {
         'com.google.guava:listenablefuture:9999.0-empty-to-avoid-conflict-with-guava:listenablefuture-9999.0-empty-to-avoid-conflict-with-guava.jar:b372a037d4230aa57fbeffdef30fd6123f9c0c2db85d0aced00c91b974f33f99',
         'com.google.j2objc:j2objc-annotations:1.1:j2objc-annotations-1.1.jar:2994a7eb78f2710bd3d3bfb639b2c94e219cedac0d4d084d516e78c16dddecf6',
         'com.h2database:h2:1.4.192:h2-1.4.192.jar:225b22e9857235c46c93861410b60b8c81c10dc8985f4faf188985ba5445126c',
-        'com.madgag.spongycastle:core:1.58.0.0:core-1.58.0.0.jar:199617dd5698c5a9312b898c0a4cec7ce9dd8649d07f65d91629f58229d72728',
         'com.squareup:javapoet:1.13.0:javapoet-1.13.0.jar:4c7517e848a71b36d069d12bb3bf46a70fd4cda3105d822b0ed2e19c00b69291',
         'javax.annotation:jsr250-api:1.0:jsr250-api-1.0.jar:a1a922d0d9b6d183ed3800dfac01d1e1eb159f0e8c6f94736931c1def54a941f',
         'javax.inject:javax.inject:1:javax.inject-1.jar:91c77044a50c481636c32d916fd89c9118a72195390452c81065080f957de7ff',
@@ -27,13 +26,14 @@ dependencyVerification {
         'net.ltgt.gradle.incap:incap:0.2:incap-0.2.jar:b625b9806b0f1e4bc7a2e3457119488de3cd57ea20feedd513db070a573a4ffd',
         'org.apache-extras.beanshell:bsh:2.0b6:bsh-2.0b6.jar:a17955976070c0573235ee662f2794a78082758b61accffce8d3f8aedcd91047',
         'org.bitlet:weupnp:0.1.4:weupnp-0.1.4.jar:88df7e6504929d00bdb832863761385c68ab92af945b04f0770b126270a444fb',
+        'org.bouncycastle:bcprov-jdk15on:1.69:bcprov-jdk15on-1.69.jar:e469bd39f936999f256002631003ff022a22951da9d5bd9789c7abfa9763a292',
         'org.briarproject:jtorctl:0.3:jtorctl-0.3.jar:f2939238a097898998432effe93b0334d97a787972ab3a91a8973a1d309fc864',
         'org.checkerframework:checker-compat-qual:2.5.3:checker-compat-qual-2.5.3.jar:d76b9afea61c7c082908023f0cbc1427fab9abd2df915c8b8a3e7a509bccbc6d',
         'org.checkerframework:checker-qual:2.5.2:checker-qual-2.5.2.jar:64b02691c8b9d4e7700f8ee2e742dce7ea2c6e81e662b7522c9ee3bf568c040a',
         'org.codehaus.mojo.signature:java16:1.1:java16-1.1.signature:53799223a2c98dba2d0add810bed76315460df285c69e4f397ae6098f87dd619',
         'org.codehaus.mojo:animal-sniffer-annotations:1.17:animal-sniffer-annotations-1.17.jar:92654f493ecfec52082e76354f0ebf87648dc3d5cec2e3c3cdb947c016747a53',
-        'org.codehaus.mojo:animal-sniffer-ant-tasks:1.16:animal-sniffer-ant-tasks-1.16.jar:890040976fbe2d584619a6a61b1fd2e925b3b5eb342a85eb2762c467c0d64e90',
-        'org.codehaus.mojo:animal-sniffer:1.16:animal-sniffer-1.16.jar:72be8bcc226ba43b937c722a08a07852bfa1b11400089265d5df0ee7b38b1d52',
+        'org.codehaus.mojo:animal-sniffer-ant-tasks:1.20:animal-sniffer-ant-tasks-1.20.jar:bb7d2498144118311d968bb08ff6fae3fc535fb1cb9cca8b8e9ea65b189422ac',
+        'org.codehaus.mojo:animal-sniffer:1.20:animal-sniffer-1.20.jar:80c422523c38db91260c6d78e5ee4b012862ab61cc55020c9e243dd7b5c62249',
         'org.hamcrest:hamcrest-core:2.1:hamcrest-core-2.1.jar:e09109e54a289d88506b9bfec987ddd199f4217c9464132668351b9a4f00bee9',
         'org.hamcrest:hamcrest-library:2.1:hamcrest-library-2.1.jar:b7e2b6895b3b679f0e47b6380fda391b225e9b78505db9d8bdde8d3cc8d52a21',
         'org.hamcrest:hamcrest:2.1:hamcrest-2.1.jar:ba93b2e3a562322ba432f0a1b53addcc55cb188253319a020ed77f824e692050',
@@ -48,8 +48,8 @@ dependencyVerification {
         'org.jmock:jmock-testjar:2.12.0:jmock-testjar-2.12.0.jar:efefbcf6cd294d0e29f0c46eb2a3380d4ca4e1763ff719c69e2f2ac62f564a04',
         'org.jmock:jmock:2.12.0:jmock-2.12.0.jar:266d07314c0cd343c46ff8a55601272de8cf406807caf55e6f313295f83d10be',
         'org.objenesis:objenesis:3.0.1:objenesis-3.0.1.jar:7a8ff780b9ff48415d7c705f60030b0acaa616e7f823c98eede3b63508d4e984',
-        'org.ow2.asm:asm-all:5.2:asm-all-5.2.jar:7fbffbc1db3422e2101689fd88df8384b15817b52b9b2b267b9f6d2511dc198d',
         'org.ow2.asm:asm:7.1:asm-7.1.jar:4ab2fa2b6d2cc9ccb1eaa05ea329c407b47b13ed2915f62f8c4b8cc96258d4de',
+        'org.ow2.asm:asm:9.1:asm-9.1.jar:cda4de455fab48ff0bcb7c48b4639447d4de859a7afc30a094a986f0936beba2',
         'org.whispersystems:curve25519-java:0.5.0:curve25519-java-0.5.0.jar:0aadd43cf01d11e9b58f867b3c4f25c3194e8b0623d1953d32dfbfbee009e38d',
     ]
 }

bramble-java/src/main/java/org/briarproject/bramble/network/JavaNetworkManager.java

@@ -9,16 +9,15 @@ import java.net.Inet4Address;
 import java.net.InetAddress;
 import java.net.NetworkInterface;
 import java.net.SocketException;
-import java.util.Enumeration;
 import java.util.logging.Logger;
 
 import javax.inject.Inject;
 
-import static java.net.NetworkInterface.getNetworkInterfaces;
 import static java.util.Collections.list;
 import static java.util.logging.Level.WARNING;
 import static java.util.logging.Logger.getLogger;
 import static org.briarproject.bramble.util.LogUtils.logException;
+import static org.briarproject.bramble.util.NetworkUtils.getNetworkInterfaces;
 
 @MethodsNotNullByDefault
 @ParametersNotNullByDefault
@@ -35,19 +34,14 @@ class JavaNetworkManager implements NetworkManager {
 	public NetworkStatus getNetworkStatus() {
 		boolean connected = false, hasIpv4 = false, hasIpv6Unicast = false;
 		try {
-			Enumeration<NetworkInterface> interfaces = getNetworkInterfaces();
-			if (interfaces == null) {
-				LOG.info("No network interfaces");
-			} else {
-				for (NetworkInterface i : list(interfaces)) {
-					if (i.isLoopback() || !i.isUp()) continue;
-					for (InetAddress addr : list(i.getInetAddresses())) {
-						connected = true;
-						if (addr instanceof Inet4Address) {
-							hasIpv4 = true;
-						} else if (!addr.isMulticastAddress()) {
-							hasIpv6Unicast = true;
-						}
+			for (NetworkInterface i : getNetworkInterfaces()) {
+				if (i.isLoopback() || !i.isUp()) continue;
+				for (InetAddress addr : list(i.getInetAddresses())) {
+					connected = true;
+					if (addr instanceof Inet4Address) {
+						hasIpv4 = true;
+					} else if (!addr.isMulticastAddress()) {
+						hasIpv6Unicast = true;
 					}
 				}
 			}

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+     d="m 143.67921,23.5571 c -1.59043,2.623831 0.18153,5.574737 2.78461,6.642714 2.69504,1.572445 6.1706,4.987176 9.14793,2.232151 2.23313,-2.039515 0.60129,-5.727894 -2.04109,-6.67035 -3.06433,-1.676733 -6.55172,-5.514807 -9.89145,-2.204515 z M 351.7046,23.12937 c -2.76779,1.960623 -7.06819,2.694997 -8.37782,6.042717 -0.64195,2.73095 1.93572,4.99255 4.58419,4.426453 3.2021,-1.637914 7.05658,-2.8424 9.17849,-5.94769 0.56931,-2.60435 -1.49324,-5.35066 -4.26769,-4.745697 -0.41558,-0.107679 -0.76003,0.03505 -1.11717,0.224217 z m -26.76172,13.17187 c -2.93431,1.708015 -7.32039,1.922759 -8.93076,5.153004 -0.90775,2.654328 1.43202,5.159236 4.12365,4.861044 3.35587,-1.304271 7.31954,-2.112696 9.73662,-5.002268 0.81368,-2.537666 -0.97658,-5.469583 -3.79644,-5.128908 -0.4035,-0.14574 -0.75969,-0.03824 -1.13307,0.117128 z m -155.23633,2.46289 c -1.21948,2.711869 0.75683,5.460507 3.4437,6.14538 2.85847,1.080772 6.66937,4.11785 9.31224,1.23392 2.3151,-2.03652 0.33929,-5.835383 -2.40983,-6.41823 -3.32833,-1.175814 -7.38479,-4.713633 -10.34611,-0.96107 z m 127.27344,7.61719 c -3.12289,1.309174 -7.49226,0.970678 -9.49244,3.970097 -1.23184,2.518748 0.7727,5.298264 3.48037,5.339749 3.48706,-0.907308 7.56742,-1.1128 10.30314,-3.739116 1.11397,-2.422222 -0.31199,-5.546068 -3.1516,-5.551016 -0.3827,-0.195662 -0.75023,-0.126964 -1.13947,-0.01971 z m -97.49023,1.54492 c -2.22858,1.461838 -2.68005,4.865948 -0.27553,6.376909 2.5869,1.470583 5.91459,1.954941 8.83971,2.495346 2.78485,0.332188 4.74603,-2.479173 3.89118,-5.048668 -2.04264,-3.279676 -6.47206,-2.73364 -9.71704,-4.089227 -0.91277,0.08855 -1.82555,0.177093 -2.73832,0.26564 z m 68.51367,4.50782 c -3.27623,0.788856 -7.46081,-0.187875 -9.93635,2.381992 -1.64972,2.268076 -0.15709,5.353662 2.50432,5.86185 3.61172,-0.292365 7.71764,0.09072 10.84009,-2.093962 1.46245,-2.227649 0.52336,-5.531725 -2.28478,-5.959415 -0.34949,-0.249225 -0.72211,-0.239347 -1.12328,-0.190465 z m -39.44922,1.41796 c -1.93309,1.83595 -1.76537,5.266611 0.87081,6.321491 2.80857,0.988807 6.17065,0.846733 9.1444,0.861366 2.79909,-0.172766 4.22635,-3.289835 2.92376,-5.664738 -2.60365,-2.851635 -6.84699,-1.541752 -10.29251,-2.269899 -0.88215,0.250593 -1.76431,0.501187 -2.64646,0.75178 z"
+     style="color:#000000;font-style:normal;font-variant:normal;font-weight:normal;font-stretch:normal;font-size:medium;line-height:normal;font-family:sans-serif;text-indent:0;text-align:start;text-decoration:none;text-decoration-line:none;text-decoration-style:solid;text-decoration-color:#000000;letter-spacing:normal;word-spacing:normal;text-transform:none;writing-mode:lr-tb;direction:ltr;baseline-shift:baseline;text-anchor:start;white-space:normal;clip-rule:nonzero;display:inline;overflow:visible;visibility:visible;opacity:1;isolation:auto;mix-blend-mode:normal;color-interpolation:sRGB;color-interpolation-filters:linearRGB;solid-color:#000000;solid-opacity:1;fill:#0a3d91;fill-opacity:1;fill-rule:evenodd;stroke:none;stroke-width:7.55;stroke-linecap:round;stroke-linejoin:round;stroke-miterlimit:4;stroke-dasharray:7.55, 22.65;stroke-dashoffset:0;stroke-opacity:1;color-rendering:auto;image-rendering:auto;shape-rendering:auto;text-rendering:auto;enable-background:accumulate" />
+  <path
+     d="m 252.50083,112.08988 11.6563,-11.45156 -17.12592,-19.790888 0.0193,25.792048 -9.14185,-9.24454 -3.12531,3.09064 11.5214,11.58063 -11.49773,11.30756 c 3.03061,3.05593 0,0 3.03061,3.05593 l 9.18921,-8.97308 c 0.0443,4.73517 0.004,27.16515 0.004,27.16515 l 17.10224,-20.77257 z m -1.07721,-19.570428 6.79869,7.863838 -6.79869,6.63278 z m -0.0237,40.027828 0.0237,-15.39623 6.89338,6.9879 z"
+     id="path1536"
+     style="display:inline;opacity:1;fill:#ffffff;fill-opacity:1;stroke:none;stroke-width:0.254891"
+     sodipodi:nodetypes="ccccccccccccccccccccc" />
 </svg>

briar-android/build.gradle

@@ -26,8 +26,8 @@ android {
 	defaultConfig {
 		minSdkVersion 16
 		targetSdkVersion 30
-		versionCode 10306
-		versionName "1.3.6"
+		versionCode 10308
+		versionName "1.3.8"
 		applicationId "org.briarproject.briar.android"
 
 		vectorDrawables.useSupportLibrary = true
@@ -110,7 +110,7 @@ dependencies {
 
 	implementation 'info.guardianproject.panic:panic:1.0'
 	implementation 'info.guardianproject.trustedintents:trustedintents:0.2'
-	implementation 'de.hdodenhof:circleimageview:3.0.1'
+	implementation 'de.hdodenhof:circleimageview:3.1.0'
 	implementation 'com.google.zxing:core:3.3.3'  // newer version need minSdk 24
 	implementation 'uk.co.samuelwall:material-tap-target-prompt:3.3.0'
 	implementation 'com.vanniktech:emoji-google:0.6.0' // newer versions need minSdk 21
@@ -121,6 +121,7 @@ dependencies {
 		exclude group: 'com.android.support'
 		exclude module: 'disklrucache' // when there's no disk cache, we can't accidentally use it
 	}
+	implementation 'org.nanohttpd:nanohttpd:2.3.1'
 
 	annotationProcessor "com.google.dagger:dagger-compiler:$dagger_version"
 	annotationProcessor "com.github.bumptech.glide:compiler:$glideVersion"

briar-android/src/androidTestScreenshot/java/org/briarproject/briar/android/BriarUiTestComponent.java

@@ -3,6 +3,7 @@ package org.briarproject.briar.android;
 import org.briarproject.bramble.BrambleAndroidModule;
 import org.briarproject.bramble.BrambleCoreModule;
 import org.briarproject.bramble.account.BriarAccountModule;
+import org.briarproject.bramble.plugin.file.RemovableDriveModule;
 import org.briarproject.bramble.system.ClockModule;
 import org.briarproject.briar.BriarCoreModule;
 import org.briarproject.briar.android.attachment.AttachmentModule;
@@ -20,6 +21,7 @@ import dagger.Component;
 		AttachmentModule.class,
 		ClockModule.class,
 		MediaModule.class,
+		RemovableDriveModule.class,
 		BriarCoreModule.class,
 		BrambleAndroidModule.class,
 		BriarAccountModule.class,

briar-android/src/main/AndroidManifest.xml

@@ -18,6 +18,7 @@
 
 	<uses-permission android:name="android.permission.ACCESS_NETWORK_STATE" />
 	<uses-permission android:name="android.permission.ACCESS_WIFI_STATE" />
+	<uses-permission android:name="android.permission.CHANGE_WIFI_STATE" />
 	<uses-permission android:name="android.permission.BLUETOOTH" />
 	<uses-permission android:name="android.permission.BLUETOOTH_ADMIN" />
 	<uses-permission android:name="android.permission.CAMERA" />
@@ -456,6 +457,22 @@
 			android:label="@string/pending_contact_requests"
 			android:theme="@style/BriarTheme" />
 
+		<activity
+			android:name=".android.hotspot.HotspotActivity"
+			android:label="@string/hotspot_title"
+			android:theme="@style/BriarTheme" />
+
+		<activity
+			android:name=".android.contact.connect.ConnectViaBluetoothActivity"
+			android:exported="false"
+			android:label="@string/connect_via_bluetooth_title"
+			android:parentActivityName="org.briarproject.briar.android.conversation.ConversationActivity"
+			android:theme="@style/BriarTheme">
+			<meta-data
+				android:name="android.support.PARENT_ACTIVITY"
+				android:value="org.briarproject.briar.android.conversation.ConversationActivity" />
+		</activity>
+
 	</application>
 
 	<queries>

briar-android/src/main/assets/hotspot.html

@@ -0,0 +1,103 @@
+<html>
+<head>
+    <meta content="text/html;charset=utf-8" http-equiv="Content-Type">
+    <meta name="viewport" content="width=device-width, initial-scale=1.0">
+    <style>
+        body {
+            background-color: #F2F2F2;
+            font-family: Roboto,Arial,Helvetica,sans-serif;
+            font-size: 14px;
+            margin: 0;
+            height: 100%;
+        }
+        div#top {
+            background-color: #FFFFFF;
+            padding: 16px;
+        }
+        div#bottom {
+            padding: 16px 32px;
+            margin-top: 12px;
+        }
+        a.button {
+            background-color: #82C91E;
+            width: 100%;
+            display: block;
+            box-sizing: border-box;
+            padding: 12px 32px !important;
+            border: 1px solid transparent;
+            border-radius: 2px;
+            color: #000000 !important;
+            cursor: pointer;
+            font-weight: 500;
+            text-decoration: none;
+            text-transform: uppercase;
+            text-align: center;
+            margin: 20px auto 20px auto;
+        }
+        ol {
+            list-style: none;
+            counter-reset: briar-counter;
+            padding-left: 40px;
+        }
+        ol li {
+            counter-increment: briar-counter;
+            margin-bottom: 2em;
+        }
+        ol li::before {
+            content: counter(briar-counter);
+            background-color: #82C91E;
+            color: #000000 !important;
+            font-weight: bold;
+            border-radius: 70px;
+            width: 24px;
+            height: 24px;
+            line-height: 24px;
+            text-align: center;
+            position: absolute;
+            left: 32px;
+        }
+
+    </style>
+</head>
+<body>
+
+<div id="top">
+    <svg style="width:156px;height:47px;" viewBox="0 0 778 235">
+        <path style="fill:#87c214"
+              d="m 64.900391,0 c -9.7,0 -17.701172,7.9992183 -17.701172,17.699219 v 22.5 h 43.601562 v -22.5 C 90.800781,7.9992183 82.899219,0 73.199219,0 Z m 96.999999,0 c -9.7,0 -17.70117,7.9992183 -17.70117,17.699219 V 137.19922 h 43.60156 V 17.699219 C 187.80078,7.9992183 179.89922,0 170.19922,0 Z M 47.199219,97.800781 V 217.30078 c 0,9.7 7.901172,17.69922 17.701172,17.69922 h 8.298828 c 9.7,0 17.701172,-7.99922 17.701172,-17.69922 V 97.800781 Z m 97.000001,96.999999 v 22.5 c 0,9.7 8.00117,17.69922 17.70117,17.69922 h 8.29883 c 9.7,0 17.70117,-7.99922 17.70117,-17.69922 v -22.5 z"/>
+        <path style="fill:#95d220"
+              d="M 17.699219,47.199219 C 7.9992186,47.199219 0,55.100391 0,64.900391 v 8.298828 c 0,9.7 7.8992186,17.701172 17.699219,17.701172 H 137.19922 V 47.199219 Z m 177.101561,0 v 43.701172 h 22.5 c 9.7,0 17.69922,-7.901172 17.69922,-17.701172 v -8.298828 c 0,-9.8 -7.99922,-17.701172 -17.69922,-17.701172 z M 17.699219,144.19922 C 7.9992186,144.19922 0,152.10039 0,161.90039 v 8.29883 c 0,9.7 7.8992186,17.70117 17.699219,17.70117 h 22.5 v -43.70117 z m 80.101562,0 v 43.70117 H 217.30078 c 9.7,0 17.69922,-8.00117 17.69922,-17.70117 v -8.29883 c 0,-9.8 -7.99922,-17.70117 -17.69922,-17.70117 z"/>
+        <path d="M 301,60.564864 V 174.43514 h 53.31362 c 25.13729,0 38.31622,-12.58548 38.31622,-32.27441 0,-12.78766 -5.88,-22.32687 -17.63776,-27.60431 v -0.20217 c 8.91968,-5.48043 12.77339,-12.38249 12.77339,-23.140374 0,-16.238294 -11.14945,-30.648991 -34.66495,-30.648991 z m 110.68683,0 V 174.43514 h 13.37598 v -45.67022 l -1.41529,-1.41926 h 26.95811 c 15.00127,0 23.51842,5.27428 28.99185,17.04704 l 14.1887,30.04244 h 15.00139 l -16.82503,-35.52128 c -3.64896,-7.91617 -9.52848,-12.99064 -14.79921,-15.22341 v -0.20216 c 12.36593,-3.24765 22.70429,-14.41228 22.70429,-29.229734 0,-22.530633 -17.43208,-33.693671 -38.31224,-33.693671 z m 111.08726,0 V 174.43514 h 13.37992 V 60.564864 Z m 78.65821,0 -50.07469,113.870276 h 14.59701 l 12.16287,-27.40213 -0.60656,-1.41926 h 62.2336 l -0.60655,1.41926 12.16286,27.40213 h 14.59701 L 615.62098,60.564864 Z m 79.463,0 V 174.43514 h 13.37994 v -45.67022 l -1.41927,-1.41926 h 26.96209 c 15.00128,0 23.51842,5.27428 28.99185,17.04704 l 14.1887,30.04244 H 778 l -16.82503,-35.52128 c -3.64895,-7.91617 -9.52851,-12.99064 -14.79921,-15.22341 v -0.20216 c 12.36591,-3.24765 22.70427,-14.41228 22.70427,-29.229734 0,-22.530633 -17.43209,-33.693671 -38.31223,-33.693671 z M 312.96068,73.147961 h 38.72057 c 14.59584,0 22.29593,5.887175 22.29593,18.065895 0,10.148944 -6.07834,18.268094 -22.29593,18.268094 h -38.72057 l 1.41927,-1.41927 V 74.571187 Z m 110.68684,0 h 37.90786 c 13.78495,0 24.32519,5.684988 24.52791,20.908395 0,12.178724 -9.52687,20.702244 -25.94718,20.702244 h -36.48859 l 1.41529,-1.41927 V 74.571187 Z m 269.00626,0 h 37.90788 c 13.98769,0 24.53187,5.684988 24.53187,20.908395 0,12.178724 -9.52688,20.702244 -25.94718,20.702244 h -36.49257 l 1.41927,-1.41927 V 74.571187 Z m -83.92693,1.423226 h 0.20615 l 3.44509,11.366019 20.06794,45.670224 1.41924,1.41926 h -50.07071 l 1.41926,-1.41926 20.06793,-45.670224 z M 312.96068,122.06505 h 41.35294 c 16.82575,0 24.53189,7.71398 24.53189,20.09568 0,12.58468 -7.09797,19.69131 -24.53189,19.69131 h -41.35294 l 1.41927,-1.42322 v -36.94055 z"/>
+    </svg>
+
+    <h2 id="download_title">Download Briar 1.2.20</h2>
+
+    <span id="download_intro">Someone nearby shared Briar with you.</span>
+
+    <a href="/app.apk" class="button">
+        <svg aria-hidden="true"
+             style="width:24px;height:24px;margin-right:6px;vertical-align:middle;"
+             viewBox="0 0 24 24">
+            <path fill="currentColor" d="M5,20H19V18H5M19,9H15V3H9V9H5L12,16L19,9Z"/>
+        </svg>
+        <span id="download_button">Download Briar</span>
+    </a>
+
+    <span id="download_outro">After the download is complete, open the downloaded file and install it.</span>
+</div>
+
+<div id="bottom">
+    <h3 id="troubleshooting_title">Troubleshooting</h3>
+    <ol>
+        <li id="troubleshooting_1">If you can't download the app, try it with a different web
+            browser app.
+        </li>
+        <li id="troubleshooting_2">To install the downloaded app,
+            you might need to allow your browser to install unknown apps.
+            We recommend to undo that after successful installation.
+        </li>
+    </ol>
+</div>
+
+</body>
+</html>

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

@@ -35,7 +35,13 @@ import org.briarproject.briar.BriarCoreEagerSingletons;
 import org.briarproject.briar.BriarCoreModule;
 import org.briarproject.briar.android.attachment.AttachmentModule;
 import org.briarproject.briar.android.attachment.media.MediaModule;
+import org.briarproject.briar.android.contact.connect.BluetoothIntroFragment;
 import org.briarproject.briar.android.conversation.glide.BriarModelLoader;
+import org.briarproject.briar.android.hotspot.AbstractTabsFragment;
+import org.briarproject.briar.android.hotspot.FallbackFragment;
+import org.briarproject.briar.android.hotspot.HotspotIntroFragment;
+import org.briarproject.briar.android.hotspot.ManualHotspotFragment;
+import org.briarproject.briar.android.hotspot.QrHotspotFragment;
 import org.briarproject.briar.android.logging.CachingLogHandler;
 import org.briarproject.briar.android.login.SignInReminderReceiver;
 import org.briarproject.briar.android.removabledrive.ChooserFragment;
@@ -216,9 +222,21 @@ public interface AndroidComponent
 
 	void inject(NotificationsFragment notificationsFragment);
 
+	void inject(HotspotIntroFragment hotspotIntroFragment);
+
+	void inject(AbstractTabsFragment abstractTabsFragment);
+
+	void inject(QrHotspotFragment qrHotspotFragment);
+
+	void inject(ManualHotspotFragment manualHotspotFragment);
+
+	void inject(FallbackFragment fallbackFragment);
+
 	void inject(ChooserFragment chooserFragment);
 
 	void inject(SendFragment sendFragment);
 
 	void inject(ReceiveFragment receiveFragment);
+
+	void inject(BluetoothIntroFragment bluetoothIntroFragment);
 }

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

@@ -30,6 +30,7 @@ import org.briarproject.bramble.util.StringUtils;
 import org.briarproject.briar.R;
 import org.briarproject.briar.android.conversation.ConversationActivity;
 import org.briarproject.briar.android.forum.ForumActivity;
+import org.briarproject.briar.android.hotspot.HotspotActivity;
 import org.briarproject.briar.android.login.SignInReminderReceiver;
 import org.briarproject.briar.android.navdrawer.NavDrawerActivity;
 import org.briarproject.briar.android.privategroup.conversation.GroupActivity;
@@ -63,9 +64,11 @@ import static android.app.Notification.DEFAULT_SOUND;
 import static android.app.Notification.DEFAULT_VIBRATE;
 import static android.app.NotificationManager.IMPORTANCE_DEFAULT;
 import static android.app.NotificationManager.IMPORTANCE_LOW;
+import static android.app.PendingIntent.getActivity;
 import static android.content.Context.NOTIFICATION_SERVICE;
 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_SINGLE_TOP;
 import static android.os.Build.VERSION.SDK_INT;
 import static androidx.core.app.NotificationCompat.CATEGORY_MESSAGE;
 import static androidx.core.app.NotificationCompat.CATEGORY_SERVICE;
@@ -274,7 +277,7 @@ class AndroidNotificationManagerImpl implements AndroidNotificationManager,
 		b.setWhen(0); // Don't show the time
 		b.setOngoing(true);
 		Intent i = new Intent(appContext, SplashScreenActivity.class);
-		b.setContentIntent(PendingIntent.getActivity(appContext, 0, i, 0));
+		b.setContentIntent(getActivity(appContext, 0, i, 0));
 		if (SDK_INT >= 21) {
 			b.setCategory(CATEGORY_SERVICE);
 			b.setVisibility(VISIBILITY_SECRET);
@@ -619,13 +622,11 @@ class AndroidNotificationManagerImpl implements AndroidNotificationManager,
 	public void showSignInNotification() {
 		if (blockSignInReminder) return;
 		if (SDK_INT >= 26) {
-			NotificationChannel channel =
-					new NotificationChannel(REMINDER_CHANNEL_ID, appContext
-							.getString(
-									R.string.reminder_notification_channel_title),
-							IMPORTANCE_LOW);
-			channel.setLockscreenVisibility(
-					NotificationCompat.VISIBILITY_SECRET);
+			NotificationChannel channel = new NotificationChannel(
+					REMINDER_CHANNEL_ID, appContext
+					.getString(R.string.reminder_notification_channel_title),
+					IMPORTANCE_LOW);
+			channel.setLockscreenVisibility(VISIBILITY_SECRET);
 			notificationManager.createNotificationChannel(channel);
 		}
 
@@ -652,7 +653,7 @@ class AndroidNotificationManagerImpl implements AndroidNotificationManager,
 
 		Intent i = new Intent(appContext, SplashScreenActivity.class);
 		i.setFlags(FLAG_ACTIVITY_NEW_TASK | FLAG_ACTIVITY_CLEAR_TOP);
-		b.setContentIntent(PendingIntent.getActivity(appContext, 0, i, 0));
+		b.setContentIntent(getActivity(appContext, 0, i, 0));
 
 		notificationManager.notify(REMINDER_NOTIFICATION_ID, b.build());
 	}
@@ -720,4 +721,40 @@ class AndroidNotificationManagerImpl implements AndroidNotificationManager,
 	public void unblockAllBlogPostNotifications() {
 		androidExecutor.runOnUiThread((Runnable) () -> blockBlogs = false);
 	}
+
+	@Override
+	public void showHotspotNotification() {
+		if (SDK_INT >= 26) {
+			String channelTitle = appContext
+					.getString(R.string.hotspot_notification_channel_title);
+			NotificationChannel channel = new NotificationChannel(
+					HOTSPOT_CHANNEL_ID, channelTitle, IMPORTANCE_LOW);
+			channel.setLockscreenVisibility(VISIBILITY_SECRET);
+			notificationManager.createNotificationChannel(channel);
+		}
+		BriarNotificationBuilder b =
+				new BriarNotificationBuilder(appContext, HOTSPOT_CHANNEL_ID);
+		b.setSmallIcon(R.drawable.notification_hotspot);
+		b.setColorRes(R.color.briar_brand_green);
+		b.setContentTitle(
+				appContext.getText(R.string.hotspot_notification_title));
+		b.setNotificationCategory(CATEGORY_SERVICE);
+		b.setOngoing(true);
+		b.setShowWhen(true);
+
+		String actionTitle =
+				appContext.getString(R.string.hotspot_button_stop_sharing);
+		Intent i = new Intent(appContext, HotspotActivity.class);
+		i.addFlags(FLAG_ACTIVITY_SINGLE_TOP);
+		i.setAction(ACTION_STOP_HOTSPOT);
+		PendingIntent actionIntent = getActivity(appContext, 0, i, 0);
+		int icon = SDK_INT >= 21 ? R.drawable.ic_portable_wifi_off : 0;
+		b.addAction(icon, actionTitle, actionIntent);
+		notificationManager.notify(HOTSPOT_NOTIFICATION_ID, b.build());
+	}
+
+	@Override
+	public void clearHotspotNotification() {
+		notificationManager.cancel(HOTSPOT_NOTIFICATION_ID);
+	}
 }

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

@@ -35,7 +35,9 @@ import org.briarproject.briar.android.account.SetupModule;
 import org.briarproject.briar.android.blog.BlogModule;
 import org.briarproject.briar.android.contact.ContactListModule;
 import org.briarproject.briar.android.contact.add.nearby.AddNearbyContactModule;
+import org.briarproject.briar.android.contact.connect.ConnectViaBluetoothModule;
 import org.briarproject.briar.android.forum.ForumModule;
+import org.briarproject.briar.android.hotspot.HotspotModule;
 import org.briarproject.briar.android.introduction.IntroductionModule;
 import org.briarproject.briar.android.logging.LoggingModule;
 import org.briarproject.briar.android.login.LoginModule;
@@ -88,12 +90,14 @@ import static org.briarproject.briar.android.TestingConstants.IS_DEBUG_BUILD;
 		DevReportModule.class,
 		ContactListModule.class,
 		IntroductionModule.class,
+		ConnectViaBluetoothModule.class,
 		// below need to be within same scope as ViewModelProvider.Factory
 		BlogModule.class,
 		ForumModule.class,
 		GroupListModule.class,
 		GroupConversationModule.class,
 		SharingModule.class,
+		HotspotModule.class,
 		TransferDataModule.class,
 })
 public class AppModule {
@@ -310,12 +314,12 @@ public class AppModule {
 			}
 
 			@Override
-			public boolean shouldEnableConnectViaBluetooth() {
+			public boolean shouldEnableTransferData() {
 				return IS_DEBUG_BUILD;
 			}
 
 			@Override
-			public boolean shouldEnableTransferData() {
+			public boolean shouldEnableShareAppViaOfflineHotspot() {
 				return IS_DEBUG_BUILD;
 			}
 		};

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

@@ -28,8 +28,8 @@ 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;
 import org.briarproject.briar.android.contact.add.remote.PendingContactListActivity;
+import org.briarproject.briar.android.contact.connect.ConnectViaBluetoothActivity;
 import org.briarproject.briar.android.conversation.AliasDialogFragment;
-import org.briarproject.briar.android.conversation.BluetoothConnecterDialogFragment;
 import org.briarproject.briar.android.conversation.ConversationActivity;
 import org.briarproject.briar.android.conversation.ConversationSettingsDialog;
 import org.briarproject.briar.android.conversation.ImageActivity;
@@ -38,6 +38,7 @@ import org.briarproject.briar.android.forum.CreateForumActivity;
 import org.briarproject.briar.android.forum.ForumActivity;
 import org.briarproject.briar.android.forum.ForumListFragment;
 import org.briarproject.briar.android.fragment.ScreenFilterDialogFragment;
+import org.briarproject.briar.android.hotspot.HotspotActivity;
 import org.briarproject.briar.android.introduction.ContactChooserFragment;
 import org.briarproject.briar.android.introduction.IntroductionActivity;
 import org.briarproject.briar.android.introduction.IntroductionMessageFragment;
@@ -177,6 +178,8 @@ public interface ActivityComponent {
 
 	void inject(CrashReportActivity crashReportActivity);
 
+	void inject(HotspotActivity hotspotActivity);
+
 	void inject(RemovableDriveActivity activity);
 
 	// Fragments
@@ -235,9 +238,6 @@ public interface ActivityComponent {
 
 	void inject(ConversationSettingsDialog dialog);
 
-	void inject(
-			BluetoothConnecterDialogFragment bluetoothConnecterDialogFragment);
-
 	void inject(RssFeedImportFragment fragment);
 
 	void inject(RssFeedManageFragment fragment);
@@ -245,4 +245,6 @@ public interface ActivityComponent {
 	void inject(RssFeedImportFailedDialogFragment fragment);
 
 	void inject(RssFeedDeleteFeedDialogFragment fragment);
+
+	void inject(ConnectViaBluetoothActivity connectViaBluetoothActivity);
 }

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

@@ -46,6 +46,7 @@ import static java.util.logging.Level.INFO;
 import static java.util.logging.Logger.getLogger;
 import static org.briarproject.briar.android.TestingConstants.PREVENT_SCREENSHOTS;
 import static org.briarproject.briar.android.util.UiUtils.hideSoftKeyboard;
+import static org.briarproject.briar.android.util.UiUtils.showFragment;
 
 /**
  * Warning: Some activities don't extend {@link BaseActivity}.
@@ -177,13 +178,7 @@ public abstract class BaseActivity extends AppCompatActivity
 
 	public void showNextFragment(BaseFragment f) {
 		if (!getLifecycle().getCurrentState().isAtLeast(STARTED)) return;
-		getSupportFragmentManager().beginTransaction()
-				.setCustomAnimations(R.anim.step_next_in,
-						R.anim.step_previous_out, R.anim.step_previous_in,
-						R.anim.step_next_out)
-				.replace(R.id.fragmentContainer, f, f.getUniqueTag())
-				.addToBackStack(f.getUniqueTag())
-				.commit();
+		showFragment(getSupportFragmentManager(), f, f.getUniqueTag());
 	}
 
 	protected boolean isFragmentAdded(String fragmentTag) {

briar-android/src/main/java/org/briarproject/briar/android/blog/BlogPostItem.java

@@ -1,10 +1,10 @@
 package org.briarproject.briar.android.blog;
 
 import org.briarproject.bramble.api.identity.Author;
-import org.briarproject.briar.api.identity.AuthorInfo;
 import org.briarproject.bramble.api.sync.GroupId;
 import org.briarproject.bramble.api.sync.MessageId;
 import org.briarproject.briar.api.blog.BlogPostHeader;
+import org.briarproject.briar.api.identity.AuthorInfo;
 
 import javax.annotation.Nullable;
 import javax.annotation.concurrent.NotThreadSafe;
@@ -50,7 +50,7 @@ public class BlogPostItem implements Comparable<BlogPostItem> {
 		return text;
 	}
 
-	public boolean isRssFeed() {
+	boolean isRssFeed() {
 		return header.isRssFeed();
 	}
 

briar-android/src/main/java/org/briarproject/briar/android/blog/BlogPostViewHolder.java

@@ -20,6 +20,7 @@ import androidx.annotation.UiThread;
 import androidx.core.view.ViewCompat;
 import androidx.recyclerview.widget.RecyclerView;
 
+import static android.os.Build.VERSION.SDK_INT;
 import static android.view.View.GONE;
 import static android.view.View.VISIBLE;
 import static org.briarproject.briar.android.activity.BriarActivity.GROUP_ID;
@@ -44,6 +45,7 @@ class BlogPostViewHolder extends RecyclerView.ViewHolder {
 	private final TextView text;
 	private final ViewGroup commentContainer;
 	private final boolean fullText, authorClickable;
+	private final int padding;
 
 	private final OnBlogPostClickListener listener;
 
@@ -61,6 +63,8 @@ class BlogPostViewHolder extends RecyclerView.ViewHolder {
 		reblogButton = v.findViewById(R.id.commentView);
 		text = v.findViewById(R.id.textView);
 		commentContainer = v.findViewById(R.id.commentContainer);
+		padding = ctx.getResources()
+				.getDimensionPixelSize(R.dimen.listitem_vertical_margin);
 	}
 
 	void hideReblogButton() {
@@ -129,6 +133,12 @@ class BlogPostViewHolder extends RecyclerView.ViewHolder {
 		} else {
 			reblogger.setVisibility(GONE);
 		}
+
+		// Apply Android 4 padding fix after setting up author/reblogger views
+		if (SDK_INT < 21) {
+			reblogger.setPadding(padding, padding, padding, padding);
+			author.setPadding(padding, padding, padding, padding);
+		}
 	}
 
 	private void onBindComment(BlogCommentItem item, boolean authorClickable) {

briar-android/src/main/java/org/briarproject/briar/android/blog/RssFeedActivity.java

@@ -57,8 +57,12 @@ public class RssFeedActivity extends BriarActivity
 				onBackPressed();
 			}
 		} else if (result == FAILED) {
+			String url = viewModel.getUrlFailedImport();
+			if (url == null) {
+				throw new AssertionError();
+			}
 			RssFeedImportFailedDialogFragment dialog =
-					RssFeedImportFailedDialogFragment.newInstance();
+					RssFeedImportFailedDialogFragment.newInstance(url);
 			dialog.show(getSupportFragmentManager(),
 					RssFeedImportFailedDialogFragment.TAG);
 		} else if (result == EXISTS) {

briar-android/src/main/java/org/briarproject/briar/android/blog/RssFeedImportFailedDialogFragment.java

@@ -25,8 +25,15 @@ public class RssFeedImportFailedDialogFragment extends DialogFragment {
 	ViewModelProvider.Factory viewModelFactory;
 	private RssFeedViewModel viewModel;
 
-	static RssFeedImportFailedDialogFragment newInstance() {
-		return new RssFeedImportFailedDialogFragment();
+	private static final String ARG_URL = "url";
+
+	static RssFeedImportFailedDialogFragment newInstance(String retryUrl) {
+		Bundle args = new Bundle();
+		args.putString(ARG_URL, retryUrl);
+		RssFeedImportFailedDialogFragment f =
+				new RssFeedImportFailedDialogFragment();
+		f.setArguments(args);
+		return f;
 	}
 
 	@Override
@@ -45,8 +52,8 @@ public class RssFeedImportFailedDialogFragment extends DialogFragment {
 						R.style.BriarDialogTheme);
 		builder.setMessage(R.string.blogs_rss_feeds_import_error);
 		builder.setNegativeButton(R.string.cancel, null);
-		builder.setPositiveButton(R.string.try_again_button,
-				(dialog, which) -> viewModel.retryImportFeed());
+		builder.setPositiveButton(R.string.try_again_button, (dialog, which) ->
+				viewModel.importFeed(requireArguments().getString(ARG_URL)));
 
 		return builder.create();
 	}

briar-android/src/main/java/org/briarproject/briar/android/blog/RssFeedManageFragment.java

@@ -20,7 +20,6 @@ import org.briarproject.briar.api.feed.Feed;
 import javax.annotation.Nullable;
 import javax.inject.Inject;
 
-import androidx.annotation.NonNull;
 import androidx.lifecycle.ViewModelProvider;
 import androidx.recyclerview.widget.LinearLayoutManager;
 

briar-android/src/main/java/org/briarproject/briar/android/blog/RssFeedViewModel.java

@@ -159,11 +159,9 @@ class RssFeedViewModel extends DbViewModel {
 		});
 	}
 
-	void retryImportFeed() {
-		if (urlFailedImport == null) {
-			throw new AssertionError();
-		}
-		importFeed(urlFailedImport);
+	@Nullable
+	String getUrlFailedImport() {
+		return urlFailedImport;
 	}
 
 	private boolean exists(String url) {

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

@@ -53,6 +53,7 @@ import org.briarproject.briar.android.contact.add.nearby.AddContactState.Contact
 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.util.QrCodeUtils;
 import org.briarproject.briar.android.viewmodel.LiveEvent;
 import org.briarproject.briar.android.viewmodel.MutableLiveEvent;
 

briar-android/src/main/java/org/briarproject/briar/android/contact/add/remote/LinkExchangeFragment.java

@@ -59,7 +59,7 @@ public class LinkExchangeFragment extends BaseFragment
 	@Override
 	public void injectFragment(ActivityComponent component) {
 		component.inject(this);
-		viewModel = new ViewModelProvider(getActivity(), viewModelFactory)
+		viewModel = new ViewModelProvider(requireActivity(), viewModelFactory)
 				.get(AddContactViewModel.class);
 	}
 

briar-android/src/main/java/org/briarproject/briar/android/contact/connect/BluetoothConditionManager.java

@@ -0,0 +1,87 @@
+package org.briarproject.briar.android.contact.connect;
+
+import android.app.Activity;
+import android.content.Context;
+
+import org.briarproject.briar.R;
+
+import androidx.activity.result.ActivityResultLauncher;
+import androidx.annotation.Nullable;
+import androidx.annotation.UiThread;
+import androidx.appcompat.app.AlertDialog;
+
+import static android.Manifest.permission.ACCESS_FINE_LOCATION;
+import static android.os.Build.VERSION.SDK_INT;
+import static androidx.core.app.ActivityCompat.shouldShowRequestPermissionRationale;
+import static org.briarproject.briar.android.util.UiUtils.getGoToSettingsListener;
+import static org.briarproject.briar.android.util.UiUtils.isLocationEnabled;
+import static org.briarproject.briar.android.util.UiUtils.showLocationDialog;
+
+class BluetoothConditionManager {
+
+	private enum Permission {
+		UNKNOWN, GRANTED, SHOW_RATIONALE, PERMANENTLY_DENIED
+	}
+
+	private Permission locationPermission = Permission.UNKNOWN;
+
+	/**
+	 * Call this when the using activity or fragment starts,
+	 * because permissions might have changed while it was stopped.
+	 */
+	void reset() {
+		locationPermission = Permission.UNKNOWN;
+	}
+
+	@UiThread
+	void onLocationPermissionResult(Activity activity,
+			@Nullable Boolean result) {
+		if (result != null && result) {
+			locationPermission = Permission.GRANTED;
+		} else if (shouldShowRequestPermissionRationale(activity,
+				ACCESS_FINE_LOCATION)) {
+			locationPermission = Permission.SHOW_RATIONALE;
+		} else {
+			locationPermission = Permission.PERMANENTLY_DENIED;
+		}
+	}
+
+	boolean areRequirementsFulfilled(Context ctx,
+			ActivityResultLauncher<String> permissionRequest,
+			Runnable onLocationDenied) {
+		boolean permissionGranted =
+				SDK_INT < 23 || locationPermission == Permission.GRANTED;
+		boolean locationEnabled = isLocationEnabled(ctx);
+		if (permissionGranted && locationEnabled) return true;
+
+		if (locationPermission == Permission.PERMANENTLY_DENIED) {
+			showDenialDialog(ctx, onLocationDenied);
+		} else if (locationPermission == Permission.SHOW_RATIONALE) {
+			showRationale(ctx, permissionRequest);
+		} else if (!locationEnabled) {
+			showLocationDialog(ctx);
+		}
+		return false;
+	}
+
+	private void showDenialDialog(Context ctx, Runnable onLocationDenied) {
+		new AlertDialog.Builder(ctx, R.style.BriarDialogTheme)
+				.setTitle(R.string.permission_location_title)
+				.setMessage(R.string.permission_location_denied_body)
+				.setPositiveButton(R.string.ok, getGoToSettingsListener(ctx))
+				.setNegativeButton(R.string.cancel, (v, d) ->
+						onLocationDenied.run())
+				.show();
+	}
+
+	private void showRationale(Context ctx,
+			ActivityResultLauncher<String> permissionRequest) {
+		new AlertDialog.Builder(ctx, R.style.BriarDialogTheme)
+				.setTitle(R.string.permission_location_title)
+				.setMessage(R.string.permission_location_request_body)
+				.setPositiveButton(R.string.ok, (dialog, which) ->
+						permissionRequest.launch(ACCESS_FINE_LOCATION))
+				.show();
+	}
+
+}

briar-android/src/main/java/org/briarproject/briar/android/contact/connect/BluetoothIntroFragment.java

@@ -0,0 +1,109 @@
+package org.briarproject.briar.android.contact.connect;
+
+import android.app.Activity;
+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 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.util.ActivityLaunchers.RequestBluetoothDiscoverable;
+
+import javax.inject.Inject;
+
+import androidx.activity.result.ActivityResultLauncher;
+import androidx.activity.result.contract.ActivityResultContracts.RequestPermission;
+import androidx.annotation.Nullable;
+import androidx.fragment.app.Fragment;
+import androidx.lifecycle.ViewModelProvider;
+
+import static android.Manifest.permission.ACCESS_FINE_LOCATION;
+import static android.widget.Toast.LENGTH_LONG;
+import static org.briarproject.briar.android.AppModule.getAndroidComponent;
+
+@MethodsNotNullByDefault
+@ParametersNotNullByDefault
+public class BluetoothIntroFragment extends Fragment {
+
+	final static String TAG = BluetoothIntroFragment.class.getName();
+
+	@Inject
+	ViewModelProvider.Factory viewModelFactory;
+
+	private final BluetoothConditionManager conditionManager =
+			new BluetoothConditionManager();
+	private ConnectViaBluetoothViewModel viewModel;
+
+	private final ActivityResultLauncher<Integer> bluetoothDiscoverableRequest =
+			registerForActivityResult(new RequestBluetoothDiscoverable(),
+					this::onBluetoothDiscoverable);
+	private final ActivityResultLauncher<String> permissionRequest =
+			registerForActivityResult(new RequestPermission(),
+					this::onPermissionRequestResult);
+
+	@Override
+	public void onAttach(Context context) {
+		super.onAttach(context);
+		getAndroidComponent(requireContext()).inject(this);
+		viewModel = new ViewModelProvider(requireActivity(), viewModelFactory)
+				.get(ConnectViaBluetoothViewModel.class);
+	}
+
+	@Override
+	public View onCreateView(LayoutInflater inflater,
+			@Nullable ViewGroup container,
+			@Nullable Bundle savedInstanceState) {
+		return inflater
+				.inflate(R.layout.fragment_bluetooth_intro, container, false);
+	}
+
+	@Override
+	public void onViewCreated(View view, @Nullable Bundle savedInstanceState) {
+		Button startButton = view.findViewById(R.id.startButton);
+		startButton.setOnClickListener(this::onStartClicked);
+	}
+
+	@Override
+	public void onStart() {
+		super.onStart();
+		conditionManager.reset();
+	}
+
+	private void onStartClicked(View v) {
+		if (viewModel.shouldStartFlow()) {
+			// The dialog starts a permission request which comes back as true
+			// if the permission is already granted.
+			// So we can use the request as a generic entry point
+			// to the whole flow.
+			permissionRequest.launch(ACCESS_FINE_LOCATION);
+		}
+	}
+
+	private void onPermissionRequestResult(@Nullable Boolean result) {
+		Activity a = requireActivity();
+		// update permission result in BluetoothConnecter
+		conditionManager.onLocationPermissionResult(a, result);
+		// what to do when the user denies granting the location permission
+		Runnable onLocationPermissionDenied = () -> Toast.makeText(
+				requireContext(),
+				R.string.connect_via_bluetooth_no_location_permission,
+				LENGTH_LONG).show();
+		// if requirements are fulfilled, request Bluetooth discoverability
+		if (conditionManager.areRequirementsFulfilled(a, permissionRequest,
+				onLocationPermissionDenied)) {
+			bluetoothDiscoverableRequest.launch(120); // for 2min
+		}
+	}
+
+	private void onBluetoothDiscoverable(@Nullable Boolean result) {
+		if (result != null && result) {
+			viewModel.onBluetoothDiscoverable();
+		}
+	}
+
+}

briar-android/src/main/java/org/briarproject/briar/android/contact/connect/BluetoothProgressFragment.java

@@ -0,0 +1,29 @@
+package org.briarproject.briar.android.contact.connect;
+
+import android.os.Bundle;
+import android.view.LayoutInflater;
+import android.view.View;
+import android.view.ViewGroup;
+
+import org.briarproject.bramble.api.nullsafety.MethodsNotNullByDefault;
+import org.briarproject.bramble.api.nullsafety.ParametersNotNullByDefault;
+import org.briarproject.briar.R;
+
+import androidx.annotation.Nullable;
+import androidx.fragment.app.Fragment;
+
+@MethodsNotNullByDefault
+@ParametersNotNullByDefault
+public class BluetoothProgressFragment extends Fragment {
+
+	final static String TAG = BluetoothProgressFragment.class.getName();
+
+	@Override
+	public View onCreateView(LayoutInflater inflater,
+			@Nullable ViewGroup container,
+			@Nullable Bundle savedInstanceState) {
+		return inflater
+				.inflate(R.layout.fragment_bluetooth_progress, container, false);
+	}
+
+}

briar-android/src/main/java/org/briarproject/briar/android/contact/connect/ConnectViaBluetoothActivity.java

@@ -0,0 +1,98 @@
+package org.briarproject.briar.android.contact.connect;
+
+import android.content.Intent;
+import android.os.Bundle;
+import android.view.MenuItem;
+import android.widget.Toast;
+
+import org.briarproject.bramble.api.contact.ContactId;
+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 javax.inject.Inject;
+
+import androidx.annotation.NonNull;
+import androidx.annotation.Nullable;
+import androidx.fragment.app.Fragment;
+import androidx.lifecycle.ViewModelProvider;
+
+import static android.widget.Toast.LENGTH_LONG;
+import static java.util.Objects.requireNonNull;
+import static org.briarproject.briar.android.conversation.ConversationActivity.CONTACT_ID;
+import static org.briarproject.briar.android.util.UiUtils.showFragment;
+
+@MethodsNotNullByDefault
+@ParametersNotNullByDefault
+public class ConnectViaBluetoothActivity extends BriarActivity {
+
+	@Inject
+	ViewModelProvider.Factory viewModelFactory;
+
+	private ConnectViaBluetoothViewModel viewModel;
+
+	@Override
+	public void injectActivity(ActivityComponent component) {
+		component.inject(this);
+
+		viewModel = new ViewModelProvider(this, viewModelFactory)
+				.get(ConnectViaBluetoothViewModel.class);
+	}
+
+	@Override
+	public void onCreate(@Nullable Bundle savedInstanceState) {
+		super.onCreate(savedInstanceState);
+
+		Intent intent = requireNonNull(getIntent());
+		int contactId = intent.getIntExtra(CONTACT_ID, -1);
+		if (contactId == -1) throw new IllegalArgumentException("ContactId");
+		viewModel.setContactId(new ContactId(contactId));
+
+		setContentView(R.layout.activity_fragment_container);
+
+		viewModel.getState().observeEvent(this, this::onStateChanged);
+
+		if (savedInstanceState == null) {
+			Fragment f = new BluetoothIntroFragment();
+			String tag = BluetoothIntroFragment.TAG;
+			getSupportFragmentManager().beginTransaction()
+					.replace(R.id.fragmentContainer, f, tag)
+					.commitNow();
+		}
+	}
+
+	@Override
+	public void onStart() {
+		super.onStart();
+		viewModel.reset();
+	}
+
+	@Override
+	public boolean onOptionsItemSelected(@NonNull MenuItem item) {
+		if (item.getItemId() == android.R.id.home) {
+			onBackPressed();
+			return true;
+		}
+		return super.onOptionsItemSelected(item);
+	}
+
+	private void onStateChanged(ConnectViaBluetoothState state) {
+		if (state instanceof ConnectViaBluetoothState.Connecting) {
+			Fragment f = new BluetoothProgressFragment();
+			String tag = BluetoothProgressFragment.TAG;
+			showFragment(getSupportFragmentManager(), f, tag, false);
+		} else if (state instanceof ConnectViaBluetoothState.Success) {
+			Toast.makeText(this, R.string.connect_via_bluetooth_success,
+					LENGTH_LONG).show();
+			supportFinishAfterTransition();
+		} else if (state instanceof ConnectViaBluetoothState.Error) {
+			Toast.makeText(this,
+					((ConnectViaBluetoothState.Error) state).errorRes,
+					LENGTH_LONG).show();
+			supportFinishAfterTransition();
+		} else throw new AssertionError();
+	}
+
+}

briar-android/src/main/java/org/briarproject/briar/android/contact/connect/ConnectViaBluetoothModule.java

@@ -0,0 +1,19 @@
+package org.briarproject.briar.android.contact.connect;
+
+import org.briarproject.briar.android.viewmodel.ViewModelKey;
+
+import androidx.lifecycle.ViewModel;
+import dagger.Binds;
+import dagger.Module;
+import dagger.multibindings.IntoMap;
+
+@Module
+public abstract class ConnectViaBluetoothModule {
+
+	@Binds
+	@IntoMap
+	@ViewModelKey(ConnectViaBluetoothViewModel.class)
+	abstract ViewModel bindContactListViewModel(
+			ConnectViaBluetoothViewModel connectViaBluetoothViewModel);
+
+}

briar-android/src/main/java/org/briarproject/briar/android/contact/connect/ConnectViaBluetoothState.java

@@ -0,0 +1,23 @@
+package org.briarproject.briar.android.contact.connect;
+
+import androidx.annotation.StringRes;
+
+abstract class ConnectViaBluetoothState {
+
+	static class Connecting extends ConnectViaBluetoothState {
+	}
+
+	static class Success extends ConnectViaBluetoothState {
+	}
+
+	static class Error extends ConnectViaBluetoothState {
+		@StringRes
+		final int errorRes;
+
+		Error(@StringRes int errorRes) {
+			this.errorRes = errorRes;
+		}
+	}
+
+}
+

briar-android/src/main/java/org/briarproject/briar/android/contact/connect/ConnectViaBluetoothViewModel.java

@@ -1,19 +1,20 @@
-package org.briarproject.briar.android.conversation;
+package org.briarproject.briar.android.contact.connect;
 
-import android.app.Activity;
 import android.app.Application;
 import android.bluetooth.BluetoothAdapter;
-import android.content.Context;
-import android.widget.Toast;
 
 import org.briarproject.bramble.api.connection.ConnectionManager;
 import org.briarproject.bramble.api.connection.ConnectionRegistry;
 import org.briarproject.bramble.api.contact.ContactId;
+import org.briarproject.bramble.api.db.DatabaseExecutor;
 import org.briarproject.bramble.api.db.DbException;
+import org.briarproject.bramble.api.db.TransactionManager;
 import org.briarproject.bramble.api.event.Event;
 import org.briarproject.bramble.api.event.EventBus;
 import org.briarproject.bramble.api.event.EventListener;
 import org.briarproject.bramble.api.lifecycle.IoExecutor;
+import org.briarproject.bramble.api.lifecycle.LifecycleManager;
+import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
 import org.briarproject.bramble.api.plugin.PluginManager;
 import org.briarproject.bramble.api.plugin.duplex.DuplexTransportConnection;
 import org.briarproject.bramble.api.plugin.event.ConnectionOpenedEvent;
@@ -21,23 +22,22 @@ import org.briarproject.bramble.api.properties.TransportPropertyManager;
 import org.briarproject.bramble.api.system.AndroidExecutor;
 import org.briarproject.bramble.plugin.bluetooth.BluetoothPlugin;
 import org.briarproject.briar.R;
-import org.briarproject.briar.android.contact.ContactItem;
+import org.briarproject.briar.android.contact.connect.ConnectViaBluetoothState.Connecting;
+import org.briarproject.briar.android.contact.connect.ConnectViaBluetoothState.Success;
+import org.briarproject.briar.android.viewmodel.DbViewModel;
+import org.briarproject.briar.android.viewmodel.LiveEvent;
+import org.briarproject.briar.android.viewmodel.MutableLiveEvent;
 
 import java.util.concurrent.Executor;
 import java.util.logging.Logger;
 
+import javax.annotation.Nullable;
 import javax.inject.Inject;
 
-import androidx.activity.result.ActivityResultLauncher;
 import androidx.annotation.NonNull;
-import androidx.annotation.Nullable;
-import androidx.annotation.StringRes;
 import androidx.annotation.UiThread;
-import androidx.appcompat.app.AlertDialog;
 
-import static android.Manifest.permission.ACCESS_FINE_LOCATION;
-import static android.os.Build.VERSION.SDK_INT;
-import static androidx.core.app.ActivityCompat.shouldShowRequestPermissionRationale;
+import static java.util.Objects.requireNonNull;
 import static java.util.concurrent.TimeUnit.SECONDS;
 import static java.util.logging.Level.WARNING;
 import static java.util.logging.Logger.getLogger;
@@ -46,48 +46,50 @@ import static org.briarproject.bramble.api.plugin.BluetoothConstants.PROP_UUID;
 import static org.briarproject.bramble.api.plugin.Plugin.State.ACTIVE;
 import static org.briarproject.bramble.util.LogUtils.logException;
 import static org.briarproject.bramble.util.StringUtils.isNullOrEmpty;
-import static org.briarproject.briar.android.util.UiUtils.getGoToSettingsListener;
-import static org.briarproject.briar.android.util.UiUtils.isLocationEnabled;
-import static org.briarproject.briar.android.util.UiUtils.showLocationDialog;
 
-class BluetoothConnecter implements EventListener {
+@UiThread
+@NotNullByDefault
+class ConnectViaBluetoothViewModel extends DbViewModel implements
+		EventListener {
 
-	private final Logger LOG = getLogger(BluetoothConnecter.class.getName());
+	private final Logger LOG =
+			getLogger(ConnectViaBluetoothViewModel.class.getName());
 
 	private final long BT_ACTIVE_TIMEOUT = SECONDS.toMillis(5);
 
-	private enum Permission {
-		UNKNOWN, GRANTED, SHOW_RATIONALE, PERMANENTLY_DENIED
-	}
-
-	private final Application app;
 	private final PluginManager pluginManager;
 	private final Executor ioExecutor;
-	private final AndroidExecutor androidExecutor;
 	private final ConnectionRegistry connectionRegistry;
+	@Nullable
 	private final BluetoothAdapter bt = BluetoothAdapter.getDefaultAdapter();
 	private final EventBus eventBus;
 	private final TransportPropertyManager transportPropertyManager;
 	private final ConnectionManager connectionManager;
 
+	@Nullable
 	private volatile BluetoothPlugin bluetoothPlugin;
-
-	private Permission locationPermission = Permission.UNKNOWN;
+	@Nullable
 	private ContactId contactId = null;
 
+	private final MutableLiveEvent<ConnectViaBluetoothState> state =
+			new MutableLiveEvent<>();
+
 	@Inject
-	BluetoothConnecter(Application app,
+	ConnectViaBluetoothViewModel(
+			Application app,
+			@DatabaseExecutor Executor dbExecutor,
+			LifecycleManager lifecycleManager,
+			TransactionManager db,
+			AndroidExecutor androidExecutor,
 			PluginManager pluginManager,
 			@IoExecutor Executor ioExecutor,
-			AndroidExecutor androidExecutor,
 			ConnectionRegistry connectionRegistry,
 			EventBus eventBus,
 			TransportPropertyManager transportPropertyManager,
 			ConnectionManager connectionManager) {
-		this.app = app;
+		super(app, dbExecutor, lifecycleManager, db, androidExecutor);
 		this.pluginManager = pluginManager;
 		this.ioExecutor = ioExecutor;
-		this.androidExecutor = androidExecutor;
 		this.bluetoothPlugin = (BluetoothPlugin) pluginManager.getPlugin(ID);
 		this.connectionRegistry = connectionRegistry;
 		this.eventBus = eventBus;
@@ -95,20 +97,22 @@ class BluetoothConnecter implements EventListener {
 		this.connectionManager = connectionManager;
 	}
 
-	boolean isConnectedViaBluetooth(ContactId contactId) {
-		return connectionRegistry.isConnected(contactId, ID);
-	}
-
-	boolean isDiscovering() {
-		return bluetoothPlugin.isDiscovering();
+	@Override
+	protected void onCleared() {
+		stopConnecting();
 	}
 
 	/**
-	 * Call this when the using activity or fragment starts,
-	 * because permissions might have changed while it was stopped.
+	 * Set this as soon as it becomes available.
+	 */
+	void setContactId(ContactId contactId) {
+		this.contactId = contactId;
+	}
+
+	/**
+	 * Call this when the using activity or fragment starts.
 	 */
 	void reset() {
-		locationPermission = Permission.UNKNOWN;
 		// When this class is instantiated before we are logged in
 		// (like when returning to a killed activity), bluetoothPlugin would be
 		// null and we consider bluetooth not supported. So reset here.
@@ -116,94 +120,52 @@ class BluetoothConnecter implements EventListener {
 	}
 
 	@UiThread
-	void onLocationPermissionResult(Activity activity,
-			@Nullable Boolean result) {
-		if (result != null && result) {
-			locationPermission = Permission.GRANTED;
-		} else if (shouldShowRequestPermissionRationale(activity,
-				ACCESS_FINE_LOCATION)) {
-			locationPermission = Permission.SHOW_RATIONALE;
-		} else {
-			locationPermission = Permission.PERMANENTLY_DENIED;
+	boolean shouldStartFlow() {
+		if (isBluetoothNotSupported()) {
+			state.setEvent(new ConnectViaBluetoothState.Error(
+					R.string.bt_plugin_status_inactive));
+			return false;
+		} else if (isConnectedViaBluetooth()) {
+			state.setEvent(new Success());
+			return false;
+		} else if (isDiscovering()) {
+			state.setEvent(new ConnectViaBluetoothState.Error(
+					R.string.connect_via_bluetooth_already_discovering));
+			return false;
 		}
+		return true;
 	}
 
-	boolean isBluetoothNotSupported() {
+	private boolean isBluetoothNotSupported() {
 		return bt == null || bluetoothPlugin == null;
 	}
 
-	boolean areRequirementsFulfilled(Context ctx,
-			ActivityResultLauncher<String> permissionRequest,
-			Runnable onLocationDenied) {
-		boolean permissionGranted =
-				SDK_INT < 23 || locationPermission == Permission.GRANTED;
-		boolean locationEnabled = isLocationEnabled(ctx);
-		if (permissionGranted && locationEnabled) return true;
-
-		if (locationPermission == Permission.PERMANENTLY_DENIED) {
-			showDenialDialog(ctx, onLocationDenied);
-		} else if (locationPermission == Permission.SHOW_RATIONALE) {
-			showRationale(ctx, permissionRequest);
-		} else if (!locationEnabled) {
-			showLocationDialog(ctx);
-		}
-		return false;
+	private boolean isDiscovering() {
+		// we should not be calling this if isBluetoothNotSupported() is true
+		return requireNonNull(bluetoothPlugin).isDiscovering();
 	}
 
-	private void showDenialDialog(Context ctx, Runnable onLocationDenied) {
-		new AlertDialog.Builder(ctx, R.style.BriarDialogTheme)
-				.setTitle(R.string.permission_location_title)
-				.setMessage(R.string.permission_location_denied_body)
-				.setPositiveButton(R.string.ok, getGoToSettingsListener(ctx))
-				.setNegativeButton(R.string.cancel, (v, d) ->
-						onLocationDenied.run())
-				.show();
-	}
-
-	private void showRationale(Context ctx,
-			ActivityResultLauncher<String> permissionRequest) {
-		new AlertDialog.Builder(ctx, R.style.BriarDialogTheme)
-				.setTitle(R.string.permission_location_title)
-				.setMessage(R.string.permission_location_request_body)
-				.setPositiveButton(R.string.ok, (dialog, which) ->
-						permissionRequest.launch(ACCESS_FINE_LOCATION))
-				.show();
+	private boolean isConnectedViaBluetooth() {
+		return connectionRegistry.isConnected(requireNonNull(contactId), ID);
 	}
 
 	@UiThread
-	void onBluetoothDiscoverable(ContactItem contact) {
-		contactId = contact.getContact().getId();
-		connect();
-	}
+	void onBluetoothDiscoverable() {
+		ContactId contactId = requireNonNull(this.contactId);
+		BluetoothPlugin bluetoothPlugin = requireNonNull(this.bluetoothPlugin);
 
-	@UiThread
-	@Override
-	public void eventOccurred(@NonNull Event e) {
-		if (e instanceof ConnectionOpenedEvent) {
-			ConnectionOpenedEvent c = (ConnectionOpenedEvent) e;
-			if (c.getContactId().equals(contactId) && c.isIncoming() &&
-					c.getTransportId() == ID) {
-				if (bluetoothPlugin != null) {
-					bluetoothPlugin.stopDiscoverAndConnect();
-				}
-				LOG.info("Contact connected to us");
-				showToast(R.string.toast_connect_via_bluetooth_success);
-			}
-		}
-	}
+		state.setEvent(new Connecting());
 
-	private void connect() {
 		bluetoothPlugin.disablePolling();
 		pluginManager.setPluginEnabled(ID, true);
-
 		ioExecutor.execute(() -> {
 			try {
 				if (!waitForBluetoothActive()) {
-					showToast(R.string.bt_plugin_status_inactive);
+					state.postEvent(new ConnectViaBluetoothState.Error(
+							R.string.bt_plugin_status_inactive));
 					LOG.warning("Bluetooth plugin didn't become active");
 					return;
 				}
-				showToast(R.string.toast_connect_via_bluetooth_start);
 				eventBus.addListener(this);
 				try {
 					String uuid = null;
@@ -226,7 +188,7 @@ class BluetoothConnecter implements EventListener {
 						LOG.info("Could connect, handling connection");
 						connectionManager
 								.manageOutgoingConnection(contactId, ID, conn);
-						showToast(R.string.toast_connect_via_bluetooth_success);
+						state.postEvent(new Success());
 					}
 				} finally {
 					eventBus.removeListener(this);
@@ -237,8 +199,23 @@ class BluetoothConnecter implements EventListener {
 		});
 	}
 
+	@UiThread
+	@Override
+	public void eventOccurred(@NonNull Event e) {
+		if (e instanceof ConnectionOpenedEvent) {
+			ConnectionOpenedEvent c = (ConnectionOpenedEvent) e;
+			if (c.getContactId().equals(contactId) && c.isIncoming() &&
+					c.getTransportId() == ID) {
+				stopConnecting();
+				LOG.info("Contact connected to us");
+				state.postEvent(new Success());
+			}
+		}
+	}
+
 	@IoExecutor
 	private boolean waitForBluetoothActive() {
+		BluetoothPlugin bluetoothPlugin = requireNonNull(this.bluetoothPlugin);
 		long left = BT_ACTIVE_TIMEOUT;
 		final long sleep = 250;
 		try {
@@ -264,9 +241,9 @@ class BluetoothConnecter implements EventListener {
 		final long sleep = 250;
 		try {
 			while (left > 0) {
-				if (isConnectedViaBluetooth(contactId)) {
+				if (isConnectedViaBluetooth()) {
 					LOG.info("Failed to connect, but contact connected");
-					// no Toast needed here, as it gets shown when
+					// no success state needed here, as it gets shown when
 					// ConnectionOpenedEvent is received
 					return;
 				}
@@ -277,13 +254,19 @@ class BluetoothConnecter implements EventListener {
 			Thread.currentThread().interrupt();
 		}
 		LOG.warning("Failed to connect");
-		showToast(R.string.toast_connect_via_bluetooth_error);
+		state.postEvent(new ConnectViaBluetoothState.Error(
+				R.string.connect_via_bluetooth_error));
 	}
 
-	private void showToast(@StringRes int res) {
-		androidExecutor.runOnUiThread(() ->
-				Toast.makeText(app, res, Toast.LENGTH_LONG).show()
-		);
+	private void stopConnecting() {
+		BluetoothPlugin bluetoothPlugin = this.bluetoothPlugin;
+		if (bluetoothPlugin != null) {
+			bluetoothPlugin.stopDiscoverAndConnect();
+		}
+	}
+
+	LiveEvent<ConnectViaBluetoothState> getState() {
+		return state;
 	}
 
 }

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

@@ -1,151 +0,0 @@
-package org.briarproject.briar.android.conversation;
-
-import android.app.Activity;
-import android.app.Dialog;
-import android.content.Context;
-import android.os.Bundle;
-import android.view.View;
-import android.widget.Button;
-import android.widget.Toast;
-
-import org.briarproject.bramble.api.contact.ContactId;
-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.BaseActivity;
-import org.briarproject.briar.android.contact.ContactItem;
-import org.briarproject.briar.android.util.ActivityLaunchers.RequestBluetoothDiscoverable;
-
-import javax.inject.Inject;
-
-import androidx.activity.result.ActivityResultLauncher;
-import androidx.activity.result.contract.ActivityResultContracts.RequestPermission;
-import androidx.annotation.Nullable;
-import androidx.annotation.StringRes;
-import androidx.appcompat.app.AlertDialog;
-import androidx.fragment.app.DialogFragment;
-import androidx.lifecycle.ViewModelProvider;
-
-import static android.Manifest.permission.ACCESS_FINE_LOCATION;
-import static android.content.DialogInterface.BUTTON_POSITIVE;
-import static android.widget.Toast.LENGTH_LONG;
-import static java.util.Objects.requireNonNull;
-
-@MethodsNotNullByDefault
-@ParametersNotNullByDefault
-public class BluetoothConnecterDialogFragment extends DialogFragment {
-
-	final static String TAG = BluetoothConnecterDialogFragment.class.getName();
-
-	@Inject
-	ViewModelProvider.Factory viewModelFactory;
-
-	private ConversationViewModel viewModel;
-	private BluetoothConnecter bluetoothConnecter;
-
-	private final ActivityResultLauncher<Integer> bluetoothDiscoverableRequest =
-			registerForActivityResult(new RequestBluetoothDiscoverable(),
-					this::onBluetoothDiscoverable);
-	private final ActivityResultLauncher<String> permissionRequest =
-			registerForActivityResult(new RequestPermission(),
-					this::onPermissionRequestResult);
-
-	@Override
-	public void onAttach(Context ctx) {
-		super.onAttach(ctx);
-		((BaseActivity) requireActivity()).getActivityComponent().inject(this);
-		viewModel = new ViewModelProvider(requireActivity(), viewModelFactory)
-				.get(ConversationViewModel.class);
-		bluetoothConnecter = viewModel.getBluetoothConnecter();
-	}
-
-	@Override
-	public Dialog onCreateDialog(@Nullable Bundle savedInstanceState) {
-		Context ctx = requireContext();
-		return new AlertDialog.Builder(ctx, R.style.BriarDialogTheme)
-				.setTitle(R.string.dialog_title_connect_via_bluetooth)
-				.setMessage(R.string.dialog_message_connect_via_bluetooth)
-				// actual listener gets set in onResume()
-				.setPositiveButton(R.string.start, null)
-				.setNegativeButton(R.string.cancel, null)
-				.setCancelable(false) // keep it open until dismissed
-				.create();
-	}
-
-	@Override
-	public void onStart() {
-		super.onStart();
-		bluetoothConnecter.reset();
-		if (bluetoothConnecter.isBluetoothNotSupported()) {
-			showToast(R.string.toast_connect_via_bluetooth_error);
-			dismiss();
-			return;
-		}
-		// MenuItem only gets enabled after contactItem has loaded
-		ContactItem contact =
-				requireNonNull(viewModel.getContactItem().getValue());
-		ContactId contactId = contact.getContact().getId();
-		if (bluetoothConnecter.isConnectedViaBluetooth(contactId)) {
-			showToast(R.string.toast_connect_via_bluetooth_success);
-			dismiss();
-			return;
-		}
-		if (bluetoothConnecter.isDiscovering()) {
-			showToast(R.string.toast_connect_via_bluetooth_already_discovering);
-			dismiss();
-		}
-	}
-
-	@Override
-	public void onResume() {
-		super.onResume();
-		// Set the click listener for the START button here
-		// to prevent it from automatically dismissing the dialog.
-		// The dialog is shown in onStart(), so we set the listener here later.
-		AlertDialog dialog = (AlertDialog) getDialog();
-		Button positiveButton = dialog.getButton(BUTTON_POSITIVE);
-		positiveButton.setOnClickListener(this::onStartClicked);
-	}
-
-	private void onStartClicked(View v) {
-		// The dialog starts a permission request which comes back as true
-		// if the permission is already granted.
-		// So we can use the request as a generic entry point to the whole flow.
-		permissionRequest.launch(ACCESS_FINE_LOCATION);
-	}
-
-	private void onPermissionRequestResult(@Nullable Boolean result) {
-		Activity a = requireActivity();
-		// update permission result in BluetoothConnecter
-		bluetoothConnecter.onLocationPermissionResult(a, result);
-		// what to do when the user denies granting the location permission
-		Runnable onLocationPermissionDenied = () -> {
-			Toast.makeText(requireContext(),
-					R.string.toast_connect_via_bluetooth_no_location_permission,
-					LENGTH_LONG).show();
-			dismiss();
-		};
-		// if requirements are fulfilled, request Bluetooth discoverability
-		if (bluetoothConnecter.areRequirementsFulfilled(a, permissionRequest,
-				onLocationPermissionDenied)) {
-			bluetoothDiscoverableRequest.launch(120); // for 2min
-		}
-	}
-
-	private void onBluetoothDiscoverable(@Nullable Boolean result) {
-		if (result != null && result) {
-			// MenuItem only gets enabled after contactItem has loaded
-			ContactItem contact =
-					requireNonNull(viewModel.getContactItem().getValue());
-			bluetoothConnecter.onBluetoothDiscoverable(contact);
-			dismiss();
-		} else {
-			showToast(R.string.toast_connect_via_bluetooth_not_discoverable);
-		}
-	}
-
-	private void showToast(@StringRes int stringRes) {
-		Toast.makeText(requireContext(), stringRes, LENGTH_LONG).show();
-	}
-
-}

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

@@ -48,6 +48,7 @@ import org.briarproject.briar.android.activity.BriarActivity;
 import org.briarproject.briar.android.attachment.AttachmentItem;
 import org.briarproject.briar.android.attachment.AttachmentRetriever;
 import org.briarproject.briar.android.blog.BlogActivity;
+import org.briarproject.briar.android.contact.connect.ConnectViaBluetoothActivity;
 import org.briarproject.briar.android.conversation.ConversationVisitor.AttachmentCache;
 import org.briarproject.briar.android.conversation.ConversationVisitor.TextCache;
 import org.briarproject.briar.android.forum.ForumActivity;
@@ -104,7 +105,6 @@ import androidx.appcompat.widget.Toolbar;
 import androidx.core.app.ActivityCompat;
 import androidx.core.app.ActivityOptionsCompat;
 import androidx.core.content.ContextCompat;
-import androidx.fragment.app.FragmentManager;
 import androidx.lifecycle.LiveData;
 import androidx.lifecycle.Observer;
 import androidx.lifecycle.ViewModelProvider;
@@ -379,9 +379,6 @@ public class ConversationActivity extends BriarActivity
 						this::showIntroductionOnboarding);
 			}
 		});
-		if (!featureFlags.shouldEnableConnectViaBluetooth()) {
-			menu.findItem(R.id.action_connect_via_bluetooth).setVisible(false);
-		}
 		// Transfer Data feature only supported on API 19+
 		if (SDK_INT >= 19 && featureFlags.shouldEnableTransferData()) {
 			menu.findItem(R.id.action_transfer_data).setVisible(true);
@@ -422,9 +419,9 @@ public class ConversationActivity extends BriarActivity
 			onAutoDeleteTimerNoticeClicked();
 			return true;
 		} else if (itemId == R.id.action_connect_via_bluetooth) {
-			FragmentManager fm = getSupportFragmentManager();
-			new BluetoothConnecterDialogFragment().show(fm,
-					BluetoothConnecterDialogFragment.TAG);
+			Intent intent = new Intent(this, ConnectViaBluetoothActivity.class);
+			intent.putExtra(CONTACT_ID, contactId.getInt());
+			startActivity(intent);
 			return true;
 		} else if (itemId == R.id.action_transfer_data) {
 			Intent intent = new Intent(this, RemovableDriveActivity.class);

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

@@ -101,7 +101,6 @@ public class ConversationViewModel extends DbViewModel
 	private final AttachmentCreator attachmentCreator;
 	private final AutoDeleteManager autoDeleteManager;
 	private final ConversationManager conversationManager;
-	private final BluetoothConnecter bluetoothConnecter;
 
 	@Nullable
 	private ContactId contactId = null;
@@ -140,8 +139,7 @@ public class ConversationViewModel extends DbViewModel
 			AttachmentRetriever attachmentRetriever,
 			AttachmentCreator attachmentCreator,
 			AutoDeleteManager autoDeleteManager,
-			ConversationManager conversationManager,
-			BluetoothConnecter bluetoothConnecter) {
+			ConversationManager conversationManager) {
 		super(application, dbExecutor, lifecycleManager, db, androidExecutor);
 		this.db = db;
 		this.eventBus = eventBus;
@@ -154,7 +152,6 @@ public class ConversationViewModel extends DbViewModel
 		this.attachmentCreator = attachmentCreator;
 		this.autoDeleteManager = autoDeleteManager;
 		this.conversationManager = conversationManager;
-		this.bluetoothConnecter = bluetoothConnecter;
 		messagingGroupId = map(contactItem, c ->
 				messagingManager.getContactGroup(c.getContact()).getId());
 		eventBus.addListener(this);
@@ -414,10 +411,6 @@ public class ConversationViewModel extends DbViewModel
 		return attachmentRetriever;
 	}
 
-	BluetoothConnecter getBluetoothConnecter() {
-		return bluetoothConnecter;
-	}
-
 	LiveData<ContactItem> getContactItem() {
 		return contactItem;
 	}

briar-android/src/main/java/org/briarproject/briar/android/fragment/ErrorFragment.java

@@ -17,7 +17,7 @@ import androidx.annotation.Nullable;
 @ParametersNotNullByDefault
 public class ErrorFragment extends BaseFragment {
 
-	private static final String TAG = ErrorFragment.class.getName();
+	public static final String TAG = ErrorFragment.class.getName();
 
 	private static final String ERROR_MSG = "errorMessage";
 
@@ -40,8 +40,7 @@ public class ErrorFragment extends BaseFragment {
 	public void onCreate(@Nullable Bundle savedInstanceState) {
 		super.onCreate(savedInstanceState);
 
-		Bundle args = getArguments();
-		if (args == null) throw new AssertionError();
+		Bundle args = requireArguments();
 		errorMessage = args.getString(ERROR_MSG);
 	}
 

briar-android/src/main/java/org/briarproject/briar/android/fragment/FinalFragment.java

@@ -7,7 +7,6 @@ import android.view.View;
 import android.view.ViewGroup;
 import android.widget.Button;
 import android.widget.ImageView;
-import android.widget.ScrollView;
 import android.widget.TextView;
 
 import org.briarproject.bramble.api.nullsafety.MethodsNotNullByDefault;
@@ -22,9 +21,11 @@ import androidx.annotation.StringRes;
 import androidx.appcompat.app.ActionBar;
 import androidx.appcompat.app.AppCompatActivity;
 import androidx.core.widget.ImageViewCompat;
+import androidx.core.widget.NestedScrollView;
 import androidx.fragment.app.Fragment;
 
 import static android.view.View.FOCUS_DOWN;
+import static android.view.View.GONE;
 
 /**
  * A fragment to be used at the end of a user flow
@@ -58,7 +59,7 @@ public class FinalFragment extends Fragment {
 		return f;
 	}
 
-	private ScrollView scrollView;
+	private NestedScrollView scrollView;
 	protected Button buttonView;
 
 	@Nullable
@@ -69,7 +70,7 @@ public class FinalFragment extends Fragment {
 		View v = inflater
 				.inflate(R.layout.fragment_final, container, false);
 
-		scrollView = (ScrollView) v;
+		scrollView = (NestedScrollView) v;
 		ImageView iconView = v.findViewById(R.id.iconView);
 		TextView titleView = v.findViewById(R.id.titleView);
 		TextView textView = v.findViewById(R.id.textView);
@@ -81,7 +82,12 @@ public class FinalFragment extends Fragment {
 		int color = getResources().getColor(args.getInt(ARG_ICON_TINT));
 		ColorStateList tint = ColorStateList.valueOf(color);
 		ImageViewCompat.setImageTintList(iconView, tint);
-		textView.setText(args.getInt(ARG_TEXT));
+		int textRes = args.getInt(ARG_TEXT);
+		if (textRes == 0) {
+			textView.setVisibility(GONE);
+		} else {
+			textView.setText(textRes);
+		}
 
 		buttonView.setOnClickListener(view -> onBackButtonPressed());
 

briar-android/src/main/java/org/briarproject/briar/android/hotspot/AbstractConditionManager.java

@@ -0,0 +1,84 @@
+package org.briarproject.briar.android.hotspot;
+
+import android.content.Context;
+import android.content.DialogInterface;
+import android.net.wifi.WifiManager;
+
+import org.briarproject.briar.R;
+
+import androidx.annotation.StringRes;
+import androidx.appcompat.app.AlertDialog;
+import androidx.core.util.Consumer;
+import androidx.fragment.app.FragmentActivity;
+
+import static android.content.Context.WIFI_SERVICE;
+
+/**
+ * Abstract base class for the ConditionManagers that ensure that the conditions
+ * to open a hotspot are fulfilled. There are different extensions of this for
+ * API levels lower than 29 and 29+.
+ */
+abstract class AbstractConditionManager {
+
+	enum Permission {
+		UNKNOWN, GRANTED, SHOW_RATIONALE, PERMANENTLY_DENIED
+	}
+
+	protected final Consumer<Boolean> permissionUpdateCallback;
+	protected FragmentActivity ctx;
+	WifiManager wifiManager;
+
+	AbstractConditionManager(Consumer<Boolean> permissionUpdateCallback) {
+		this.permissionUpdateCallback = permissionUpdateCallback;
+	}
+
+	/**
+	 * Pass a FragmentActivity context here during `onCreateView()`.
+	 */
+	void init(FragmentActivity ctx) {
+		this.ctx = ctx;
+		this.wifiManager = (WifiManager) ctx.getApplicationContext()
+				.getSystemService(WIFI_SERVICE);
+	}
+
+	/**
+	 * Call this during onStart() in the fragment where the ConditionManager
+	 * is used.
+	 */
+	abstract void onStart();
+
+	/**
+	 * Check if all required conditions are met such that the hotspot can be
+	 * started. If any precondition is not met yet, bring up relevant dialogs
+	 * asking the user to grant relevant permissions or take relevant actions.
+	 *
+	 * @return true if conditions are fulfilled and flow can continue.
+	 */
+	abstract boolean checkAndRequestConditions();
+
+	void showDenialDialog(FragmentActivity ctx,
+			@StringRes int title, @StringRes int body,
+			DialogInterface.OnClickListener onOkClicked, Runnable onDismiss) {
+		AlertDialog.Builder builder = new AlertDialog.Builder(ctx);
+		builder.setTitle(title);
+		builder.setMessage(body);
+		builder.setPositiveButton(R.string.ok, onOkClicked);
+		builder.setNegativeButton(R.string.cancel,
+				(dialog, which) -> ctx.supportFinishAfterTransition());
+		builder.setOnDismissListener(dialog -> onDismiss.run());
+		builder.show();
+	}
+
+	void showRationale(Context ctx, @StringRes int title,
+			@StringRes int body, Runnable onContinueClicked,
+			Runnable onDismiss) {
+		AlertDialog.Builder builder = new AlertDialog.Builder(ctx);
+		builder.setTitle(title);
+		builder.setMessage(body);
+		builder.setNeutralButton(R.string.continue_button,
+				(dialog, which) -> onContinueClicked.run());
+		builder.setOnDismissListener(dialog -> onDismiss.run());
+		builder.show();
+	}
+
+}

briar-android/src/main/java/org/briarproject/briar/android/hotspot/AbstractTabsFragment.java

@@ -0,0 +1,143 @@
+package org.briarproject.briar.android.hotspot;
+
+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.Button;
+import android.widget.TextView;
+
+import com.google.android.material.tabs.TabLayout;
+import com.google.android.material.tabs.TabLayoutMediator;
+
+import org.briarproject.bramble.api.nullsafety.MethodsNotNullByDefault;
+import org.briarproject.bramble.api.nullsafety.ParametersNotNullByDefault;
+import org.briarproject.briar.R;
+
+import javax.inject.Inject;
+
+import androidx.annotation.CallSuper;
+import androidx.annotation.Nullable;
+import androidx.fragment.app.Fragment;
+import androidx.lifecycle.ViewModelProvider;
+import androidx.viewpager2.adapter.FragmentStateAdapter;
+import androidx.viewpager2.widget.ViewPager2;
+
+import static androidx.core.app.ActivityCompat.finishAfterTransition;
+import static org.briarproject.briar.android.AppModule.getAndroidComponent;
+import static org.briarproject.briar.android.util.UiUtils.showFragment;
+
+@MethodsNotNullByDefault
+@ParametersNotNullByDefault
+public abstract class AbstractTabsFragment extends Fragment {
+
+	static String ARG_FOR_WIFI_CONNECT = "forWifiConnect";
+
+	@Inject
+	ViewModelProvider.Factory viewModelFactory;
+
+	protected HotspotViewModel viewModel;
+
+	protected Button stopButton;
+	protected Button connectedButton;
+	protected TextView connectedView;
+
+	@Override
+	public void onAttach(Context context) {
+		super.onAttach(context);
+		getAndroidComponent(requireContext()).inject(this);
+		viewModel = new ViewModelProvider(requireActivity(), viewModelFactory)
+				.get(HotspotViewModel.class);
+	}
+
+	@Override
+	public View onCreateView(LayoutInflater inflater,
+			@Nullable ViewGroup container,
+			@Nullable Bundle savedInstanceState) {
+		setHasOptionsMenu(true);
+		return inflater
+				.inflate(R.layout.fragment_hotspot_tabs, container, false);
+	}
+
+	@Override
+	@CallSuper
+	public void onViewCreated(View view, @Nullable Bundle savedInstanceState) {
+		TabAdapter tabAdapter = new TabAdapter(this);
+		ViewPager2 viewPager = view.findViewById(R.id.pager);
+		viewPager.setAdapter(tabAdapter);
+		TabLayout tabLayout = view.findViewById(R.id.tabLayout);
+		new TabLayoutMediator(tabLayout, viewPager, (tab, position) -> {
+			// tabs are set in XML, but are just dummies that don't get added
+			if (position == 0) {
+				tab.setText(R.string.hotspot_tab_manual);
+				tab.setIcon(R.drawable.forum_item_create_white);
+			} else if (position == 1) {
+				tab.setText(R.string.qr_code);
+				tab.setIcon(R.drawable.ic_qr_code);
+			} else throw new AssertionError();
+		}).attach();
+
+		stopButton = view.findViewById(R.id.stopButton);
+		stopButton.setOnClickListener(v -> {
+			// also clears hotspot
+			finishAfterTransition(requireActivity());
+		});
+		connectedButton = view.findViewById(R.id.connectedButton);
+		connectedView = view.findViewById(R.id.connectedView);
+		viewModel.getPeersConnectedEvent()
+				.observe(getViewLifecycleOwner(), this::onPeerConnected);
+	}
+
+	@Override
+	public void onCreateOptionsMenu(Menu menu, MenuInflater inflater) {
+		inflater.inflate(R.menu.hotspot_help_action, menu);
+		super.onCreateOptionsMenu(menu, inflater);
+	}
+
+	@Override
+	public boolean onOptionsItemSelected(MenuItem item) {
+		if (item.getItemId() == R.id.action_help) {
+			Fragment f = new HotspotHelpFragment();
+			String tag = HotspotHelpFragment.TAG;
+			showFragment(getParentFragmentManager(), f, tag);
+			return true;
+		}
+		return super.onOptionsItemSelected(item);
+	}
+
+	protected abstract Fragment getFirstFragment();
+
+	protected abstract Fragment getSecondFragment();
+
+	private class TabAdapter extends FragmentStateAdapter {
+		private TabAdapter(Fragment fragment) {
+			super(fragment);
+		}
+
+		@Override
+		public Fragment createFragment(int position) {
+			if (position == 0) return getFirstFragment();
+			if (position == 1) return getSecondFragment();
+			throw new AssertionError();
+		}
+
+		@Override
+		public int getItemCount() {
+			return 2;
+		}
+	}
+
+	private void onPeerConnected(int peers) {
+		if (peers == 0) {
+			connectedView.setText(R.string.hotspot_no_peers_connected);
+		} else {
+			connectedView.setText(getResources().getQuantityString(
+					R.plurals.hotspot_peers_connected, peers, peers));
+		}
+	}
+
+}

briar-android/src/main/java/org/briarproject/briar/android/hotspot/ConditionManager.java

@@ -0,0 +1,83 @@
+package org.briarproject.briar.android.hotspot;
+
+import android.content.Intent;
+import android.provider.Settings;
+
+import org.briarproject.briar.R;
+
+import java.util.logging.Logger;
+
+import androidx.activity.result.ActivityResultCaller;
+import androidx.activity.result.ActivityResultLauncher;
+import androidx.activity.result.contract.ActivityResultContracts.StartActivityForResult;
+import androidx.core.util.Consumer;
+
+import static java.util.logging.Level.INFO;
+import static java.util.logging.Logger.getLogger;
+
+/**
+ * This class ensures that the conditions to open a hotspot are fulfilled on
+ * API levels < 29.
+ * <p>
+ * As soon as {@link #checkAndRequestConditions()} returns true,
+ * all conditions are fulfilled.
+ */
+class ConditionManager extends AbstractConditionManager {
+
+	private static final Logger LOG =
+			getLogger(ConditionManager.class.getName());
+
+	private final ActivityResultLauncher<Intent> wifiRequest;
+
+	ConditionManager(ActivityResultCaller arc,
+			Consumer<Boolean> permissionUpdateCallback) {
+		super(permissionUpdateCallback);
+		wifiRequest = arc.registerForActivityResult(
+				new StartActivityForResult(),
+				result -> permissionUpdateCallback
+						.accept(wifiManager.isWifiEnabled()));
+	}
+
+	@Override
+	void onStart() {
+		// nothing to do here
+	}
+
+	private boolean areEssentialPermissionsGranted() {
+		if (LOG.isLoggable(INFO)) {
+			LOG.info(String.format("areEssentialPermissionsGranted(): " +
+							"wifiManager.isWifiEnabled()? %b",
+					wifiManager.isWifiEnabled()));
+		}
+		return wifiManager.isWifiEnabled();
+	}
+
+	@Override
+	boolean checkAndRequestConditions() {
+		if (areEssentialPermissionsGranted()) return true;
+
+		if (!wifiManager.isWifiEnabled()) {
+			// Try enabling the Wifi and return true if that seems to have been
+			// successful, i.e. "Wifi is either already in the requested state, or
+			// in progress toward the requested state".
+			if (wifiManager.setWifiEnabled(true)) {
+				LOG.info("Enabled wifi");
+				return true;
+			}
+
+			// Wifi is not enabled and we can't seem to enable it, so ask the user
+			// to enable it for us.
+			showRationale(ctx, R.string.wifi_settings_title,
+					R.string.wifi_settings_request_enable_body,
+					this::requestEnableWiFi,
+					() -> permissionUpdateCallback.accept(false));
+		}
+
+		return false;
+	}
+
+	private void requestEnableWiFi() {
+		wifiRequest.launch(new Intent(Settings.ACTION_WIFI_SETTINGS));
+	}
+
+}

briar-android/src/main/java/org/briarproject/briar/android/hotspot/ConditionManager29.java

@@ -0,0 +1,136 @@
+package org.briarproject.briar.android.hotspot;
+
+import android.content.Intent;
+import android.provider.Settings;
+
+import org.briarproject.briar.R;
+
+import java.util.logging.Logger;
+
+import androidx.activity.result.ActivityResultCaller;
+import androidx.activity.result.ActivityResultLauncher;
+import androidx.activity.result.contract.ActivityResultContracts.RequestPermission;
+import androidx.activity.result.contract.ActivityResultContracts.StartActivityForResult;
+import androidx.annotation.Nullable;
+import androidx.annotation.RequiresApi;
+import androidx.core.util.Consumer;
+
+import static android.Manifest.permission.ACCESS_FINE_LOCATION;
+import static androidx.core.app.ActivityCompat.shouldShowRequestPermissionRationale;
+import static java.lang.Boolean.TRUE;
+import static java.util.logging.Level.INFO;
+import static java.util.logging.Logger.getLogger;
+import static org.briarproject.briar.android.util.UiUtils.getGoToSettingsListener;
+
+/**
+ * This class ensures that the conditions to open a hotspot are fulfilled on
+ * API levels >= 29.
+ * <p>
+ * As soon as {@link #checkAndRequestConditions()} returns true,
+ * all conditions are fulfilled.
+ */
+@RequiresApi(29)
+class ConditionManager29 extends AbstractConditionManager {
+
+	private static final Logger LOG =
+			getLogger(ConditionManager29.class.getName());
+
+	private Permission locationPermission = Permission.UNKNOWN;
+
+	private final ActivityResultLauncher<String> locationRequest;
+	private final ActivityResultLauncher<Intent> wifiRequest;
+
+	ConditionManager29(ActivityResultCaller arc,
+			Consumer<Boolean> permissionUpdateCallback) {
+		super(permissionUpdateCallback);
+		locationRequest = arc.registerForActivityResult(
+				new RequestPermission(), granted -> {
+					onRequestPermissionResult(granted);
+					permissionUpdateCallback.accept(TRUE.equals(granted));
+				});
+		wifiRequest = arc.registerForActivityResult(
+				new StartActivityForResult(),
+				result -> permissionUpdateCallback
+						.accept(wifiManager.isWifiEnabled())
+		);
+	}
+
+	@Override
+	void onStart() {
+		locationPermission = Permission.UNKNOWN;
+	}
+
+	private boolean areEssentialPermissionsGranted() {
+		boolean isWifiEnabled = wifiManager.isWifiEnabled();
+		if (LOG.isLoggable(INFO)) {
+			LOG.info(String.format("areEssentialPermissionsGranted(): " +
+							"locationPermission? %s, " +
+							"wifiManager.isWifiEnabled()? %b",
+					locationPermission, isWifiEnabled));
+		}
+		return locationPermission == Permission.GRANTED && isWifiEnabled;
+	}
+
+	@Override
+	boolean checkAndRequestConditions() {
+		if (areEssentialPermissionsGranted()) return true;
+
+		if (locationPermission == Permission.UNKNOWN) {
+			locationRequest.launch(ACCESS_FINE_LOCATION);
+			return false;
+		}
+
+		// If the location permission has been permanently denied, ask the
+		// user to change the setting
+		if (locationPermission == Permission.PERMANENTLY_DENIED) {
+			showDenialDialog(ctx, R.string.permission_location_title,
+					R.string.permission_hotspot_location_denied_body,
+					getGoToSettingsListener(ctx),
+					() -> permissionUpdateCallback.accept(false));
+			return false;
+		}
+
+		// Should we show the rationale for location permission?
+		if (locationPermission == Permission.SHOW_RATIONALE) {
+			showRationale(ctx, R.string.permission_location_title,
+					R.string.permission_hotspot_location_request_body,
+					this::requestPermissions,
+					() -> permissionUpdateCallback.accept(false));
+			return false;
+		}
+
+		// If Wifi is not enabled, we show the rationale for enabling Wifi?
+		if (!wifiManager.isWifiEnabled()) {
+			showRationale(ctx, R.string.wifi_settings_title,
+					R.string.wifi_settings_request_enable_body,
+					this::requestEnableWiFi,
+					() -> permissionUpdateCallback.accept(false));
+			return false;
+		}
+
+		// we shouldn't usually reach this point, but if we do, return false
+		// anyway to force a recheck. Maybe some condition changed in the
+		// meantime.
+		return false;
+	}
+
+	private void onRequestPermissionResult(@Nullable Boolean granted) {
+		if (granted != null && granted) {
+			locationPermission = Permission.GRANTED;
+		} else if (shouldShowRequestPermissionRationale(ctx,
+				ACCESS_FINE_LOCATION)) {
+			locationPermission = Permission.SHOW_RATIONALE;
+		} else {
+			locationPermission = Permission.PERMANENTLY_DENIED;
+		}
+	}
+
+	private void requestPermissions() {
+		locationRequest.launch(ACCESS_FINE_LOCATION);
+	}
+
+	private void requestEnableWiFi() {
+		wifiRequest.launch(new Intent(Settings.Panel.ACTION_WIFI));
+	}
+
+}

briar-android/src/main/java/org/briarproject/briar/android/hotspot/FallbackFragment.java

@@ -0,0 +1,127 @@
+package org.briarproject.briar.android.hotspot;
+
+import android.content.Context;
+import android.content.Intent;
+import android.content.pm.ResolveInfo;
+import android.net.Uri;
+import android.os.Bundle;
+import android.view.LayoutInflater;
+import android.view.View;
+import android.view.ViewGroup;
+import android.widget.Button;
+import android.widget.ProgressBar;
+
+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 org.briarproject.briar.android.util.ActivityLaunchers.CreateDocumentAdvanced;
+
+import java.util.List;
+
+import javax.inject.Inject;
+
+import androidx.activity.result.ActivityResultLauncher;
+import androidx.annotation.Nullable;
+import androidx.fragment.app.FragmentActivity;
+import androidx.lifecycle.ViewModelProvider;
+
+import static android.content.Intent.ACTION_SEND;
+import static android.content.Intent.EXTRA_STREAM;
+import static android.content.Intent.FLAG_GRANT_READ_URI_PERMISSION;
+import static android.content.pm.PackageManager.MATCH_DEFAULT_ONLY;
+import static android.os.Build.VERSION.SDK_INT;
+import static android.view.View.INVISIBLE;
+import static android.view.View.VISIBLE;
+import static androidx.transition.TransitionManager.beginDelayedTransition;
+import static org.briarproject.briar.android.AppModule.getAndroidComponent;
+import static org.briarproject.briar.android.hotspot.HotspotViewModel.getApkFileName;
+
+@MethodsNotNullByDefault
+@ParametersNotNullByDefault
+public class FallbackFragment extends BaseFragment {
+
+	public static final String TAG = FallbackFragment.class.getName();
+
+	@Inject
+	ViewModelProvider.Factory viewModelFactory;
+
+	private HotspotViewModel viewModel;
+	private final ActivityResultLauncher<String> launcher =
+			registerForActivityResult(new CreateDocumentAdvanced(),
+					this::onDocumentCreated);
+	private Button fallbackButton;
+	private ProgressBar progressBar;
+
+	@Override
+	public String getUniqueTag() {
+		return TAG;
+	}
+
+	@Override
+	public void onAttach(Context context) {
+		super.onAttach(context);
+		FragmentActivity activity = requireActivity();
+		getAndroidComponent(activity).inject(this);
+		viewModel = new ViewModelProvider(activity, viewModelFactory)
+				.get(HotspotViewModel.class);
+	}
+
+	@Nullable
+	@Override
+	public View onCreateView(LayoutInflater inflater,
+			@Nullable ViewGroup container,
+			@Nullable Bundle savedInstanceState) {
+		return inflater
+				.inflate(R.layout.fragment_hotspot_fallback, container, false);
+	}
+
+	@Override
+	public void onViewCreated(View v, @Nullable Bundle savedInstanceState) {
+		super.onViewCreated(v, savedInstanceState);
+
+		fallbackButton = v.findViewById(R.id.fallbackButton);
+		progressBar = v.findViewById(R.id.progressBar);
+		fallbackButton.setOnClickListener(view -> {
+			beginDelayedTransition((ViewGroup) v);
+			fallbackButton.setVisibility(INVISIBLE);
+			progressBar.setVisibility(VISIBLE);
+
+			if (SDK_INT >= 19) launcher.launch(getApkFileName());
+			else viewModel.exportApk();
+		});
+		viewModel.getSavedApkToUri().observeEvent(this, this::shareUri);
+	}
+
+	private void onDocumentCreated(@Nullable Uri uri) {
+		showButton();
+		if (uri != null) viewModel.exportApk(uri);
+	}
+
+	private void showButton() {
+		beginDelayedTransition((ViewGroup) requireView());
+		fallbackButton.setVisibility(VISIBLE);
+		progressBar.setVisibility(INVISIBLE);
+	}
+
+	void shareUri(Uri uri) {
+		Intent i = new Intent(ACTION_SEND);
+		i.putExtra(EXTRA_STREAM, uri);
+		i.setType("*/*"); // gives us all sharing options
+		i.addFlags(FLAG_GRANT_READ_URI_PERMISSION);
+		Context ctx = requireContext();
+		if (SDK_INT <= 19) {
+			// Workaround for Android bug:
+			// ctx.grantUriPermission also needed for Android 4
+			List<ResolveInfo> resInfoList = ctx.getPackageManager()
+					.queryIntentActivities(i, MATCH_DEFAULT_ONLY);
+			for (ResolveInfo resolveInfo : resInfoList) {
+				String packageName = resolveInfo.activityInfo.packageName;
+				ctx.grantUriPermission(packageName, uri,
+						FLAG_GRANT_READ_URI_PERMISSION);
+			}
+		}
+		startActivity(Intent.createChooser(i, null));
+	}
+
+}

briar-android/src/main/java/org/briarproject/briar/android/hotspot/HotspotActivity.java

@@ -0,0 +1,143 @@
+package org.briarproject.briar.android.hotspot;
+
+import android.content.Intent;
+import android.os.Bundle;
+import android.view.MenuItem;
+
+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.fragment.BaseFragment.BaseFragmentListener;
+import org.briarproject.briar.android.hotspot.HotspotState.HotspotError;
+import org.briarproject.briar.android.hotspot.HotspotState.HotspotStarted;
+
+import javax.annotation.Nullable;
+import javax.inject.Inject;
+
+import androidx.appcompat.app.ActionBar;
+import androidx.fragment.app.Fragment;
+import androidx.fragment.app.FragmentManager;
+import androidx.lifecycle.ViewModelProvider;
+
+import static org.briarproject.briar.android.util.UiUtils.showFragment;
+import static org.briarproject.briar.api.android.AndroidNotificationManager.ACTION_STOP_HOTSPOT;
+
+@MethodsNotNullByDefault
+@ParametersNotNullByDefault
+public class HotspotActivity extends BriarActivity
+		implements BaseFragmentListener {
+
+	@Inject
+	ViewModelProvider.Factory viewModelFactory;
+
+	private HotspotViewModel viewModel;
+
+	@Override
+	public void injectActivity(ActivityComponent component) {
+		component.inject(this);
+		viewModel = new ViewModelProvider(this, viewModelFactory)
+				.get(HotspotViewModel.class);
+	}
+
+	@Override
+	public void onCreate(@Nullable Bundle savedInstanceState) {
+		super.onCreate(savedInstanceState);
+		setContentView(R.layout.activity_fragment_container);
+
+		ActionBar ab = getSupportActionBar();
+		if (ab != null) {
+			ab.setDisplayHomeAsUpEnabled(true);
+		}
+
+		FragmentManager fm = getSupportFragmentManager();
+		viewModel.getState().observe(this, hotspotState -> {
+			if (hotspotState instanceof HotspotStarted) {
+				HotspotStarted started = (HotspotStarted) hotspotState;
+				String tag = HotspotFragment.TAG;
+				// check if fragment is already added
+				// to not lose state on configuration changes
+				if (fm.findFragmentByTag(tag) == null) {
+					if (started.wasNotYetConsumed()) {
+						started.consume();
+						showFragment(fm, new HotspotFragment(), tag);
+					}
+				}
+			} else if (hotspotState instanceof HotspotError) {
+				HotspotError error = (HotspotError) hotspotState;
+				showErrorFragment(error.getError());
+			}
+		});
+
+		if (savedInstanceState == null) {
+			// If there is no saved instance state, just start with the intro fragment.
+			fm.beginTransaction()
+					.replace(R.id.fragmentContainer, new HotspotIntroFragment(),
+							HotspotIntroFragment.TAG)
+					.commit();
+		} else if (viewModel.getState().getValue() == null) {
+			// If there is saved instance state, then there's either been an
+			// configuration change like rotated device or the activity has been
+			// destroyed and is now being re-created.
+			// In the latter case, the view model will have been destroyed, too.
+			// The activity can only have been destroyed if the user navigated
+			// away from the HotspotActivity which is nothing we
+			// intend to support, so we want to detect that and start from scratch
+			// in this case. We need to clean up existing fragments in order not
+			// to stack new fragments on top of old ones.
+
+			// If it is a configuration change and we moved past the intro
+			// fragment already, then the view model state will be != null,
+			// hence we can use this check for null to determine the destroyed
+			// activity. It can also be null if the user has not pressed
+			// "start sharing" yet, but in that case it won't harm to start from
+			// scratch.
+
+			Fragment current = fm.findFragmentById(R.id.fragmentContainer);
+			if (current instanceof HotspotIntroFragment) {
+				// If the currently displayed fragment is the intro fragment,
+				// there's nothing we need to do.
+				return;
+			}
+
+			// Remove everything from the back stack.
+			fm.popBackStackImmediate(null,
+					FragmentManager.POP_BACK_STACK_INCLUSIVE);
+
+			// Start fresh with the intro fragment.
+			fm.beginTransaction()
+					.replace(R.id.fragmentContainer, new HotspotIntroFragment(),
+							HotspotIntroFragment.TAG)
+					.commit();
+		}
+	}
+
+	private void showErrorFragment(String error) {
+		FragmentManager fm = getSupportFragmentManager();
+		String tag = HotspotErrorFragment.TAG;
+		if (fm.findFragmentByTag(tag) == null) {
+			Fragment f = HotspotErrorFragment.newInstance(error);
+			showFragment(fm, f, tag, false);
+		}
+	}
+
+	@Override
+	public boolean onOptionsItemSelected(MenuItem item) {
+		if (item.getItemId() == android.R.id.home) {
+			onBackPressed();
+			return true;
+		}
+		return super.onOptionsItemSelected(item);
+	}
+
+	@Override
+	protected void onNewIntent(Intent intent) {
+		super.onNewIntent(intent);
+		if (ACTION_STOP_HOTSPOT.equals(intent.getAction())) {
+			// also closes hotspot
+			supportFinishAfterTransition();
+		}
+	}
+
+}

briar-android/src/main/java/org/briarproject/briar/android/hotspot/HotspotErrorFragment.java

@@ -0,0 +1,78 @@
+package org.briarproject.briar.android.hotspot;
+
+import android.os.Bundle;
+import android.view.LayoutInflater;
+import android.view.View;
+import android.view.ViewGroup;
+import android.widget.Button;
+import android.widget.TextView;
+
+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.inject.Inject;
+
+import androidx.annotation.Nullable;
+import androidx.lifecycle.ViewModelProvider;
+
+import static org.briarproject.briar.android.util.UiUtils.triggerFeedback;
+
+
+@MethodsNotNullByDefault
+@ParametersNotNullByDefault
+public class HotspotErrorFragment extends BaseFragment {
+
+	public static final String TAG = HotspotErrorFragment.class.getName();
+
+	@Inject
+	ViewModelProvider.Factory viewModelFactory;
+
+	private static final String ERROR_MSG = "errorMessage";
+
+	public static HotspotErrorFragment newInstance(String message) {
+		HotspotErrorFragment f = new HotspotErrorFragment();
+		Bundle args = new Bundle();
+		args.putString(ERROR_MSG, message);
+		f.setArguments(args);
+		return f;
+	}
+
+	private String errorMessage;
+
+	@Override
+	public String getUniqueTag() {
+		return TAG;
+	}
+
+	@Override
+	public void onCreate(@Nullable Bundle savedInstanceState) {
+		super.onCreate(savedInstanceState);
+
+		Bundle args = requireArguments();
+		errorMessage = args.getString(ERROR_MSG);
+	}
+
+	@Nullable
+	@Override
+	public View onCreateView(LayoutInflater inflater,
+			@Nullable ViewGroup container,
+			@Nullable Bundle savedInstanceState) {
+		requireActivity().setTitle(R.string.error);
+		return inflater
+				.inflate(R.layout.fragment_hotspot_error, container, false);
+	}
+
+	@Override
+	public void onViewCreated(View v, @Nullable Bundle savedInstanceState) {
+		super.onViewCreated(v, savedInstanceState);
+		TextView msg = v.findViewById(R.id.errorMessageDetail);
+		msg.setText(errorMessage);
+
+		Button feedbackButton = v.findViewById(R.id.feedbackButton);
+		feedbackButton.setOnClickListener(
+				button -> triggerFeedback(requireContext(), errorMessage));
+	}
+
+}

briar-android/src/main/java/org/briarproject/briar/android/hotspot/HotspotFragment.java

@@ -0,0 +1,42 @@
+package org.briarproject.briar.android.hotspot;
+
+import android.os.Bundle;
+import android.view.View;
+
+import org.briarproject.bramble.api.nullsafety.MethodsNotNullByDefault;
+import org.briarproject.bramble.api.nullsafety.ParametersNotNullByDefault;
+
+import androidx.annotation.Nullable;
+import androidx.fragment.app.Fragment;
+
+import static org.briarproject.briar.android.util.UiUtils.showFragment;
+
+@MethodsNotNullByDefault
+@ParametersNotNullByDefault
+public class HotspotFragment extends AbstractTabsFragment {
+
+	public final static String TAG = HotspotFragment.class.getName();
+
+	@Override
+	public void onViewCreated(View view, @Nullable Bundle savedInstanceState) {
+		super.onViewCreated(view, savedInstanceState);
+		connectedButton.setOnClickListener(v -> showNextFragment());
+	}
+
+	@Override
+	protected Fragment getFirstFragment() {
+		return ManualHotspotFragment.newInstance(true);
+	}
+
+	@Override
+	protected Fragment getSecondFragment() {
+		return QrHotspotFragment.newInstance(true);
+	}
+
+	private void showNextFragment() {
+		Fragment f = new WebsiteFragment();
+		String tag = WebsiteFragment.TAG;
+		showFragment(getParentFragmentManager(), f, tag);
+	}
+
+}

briar-android/src/main/java/org/briarproject/briar/android/hotspot/HotspotHelpFragment.java

@@ -0,0 +1,29 @@
+package org.briarproject.briar.android.hotspot;
+
+import android.os.Bundle;
+import android.view.LayoutInflater;
+import android.view.View;
+import android.view.ViewGroup;
+
+import org.briarproject.bramble.api.nullsafety.MethodsNotNullByDefault;
+import org.briarproject.bramble.api.nullsafety.ParametersNotNullByDefault;
+import org.briarproject.briar.R;
+
+import androidx.annotation.Nullable;
+import androidx.fragment.app.Fragment;
+
+@MethodsNotNullByDefault
+@ParametersNotNullByDefault
+public class HotspotHelpFragment extends Fragment {
+
+	public final static String TAG = HotspotHelpFragment.class.getName();
+
+	@Override
+	public View onCreateView(LayoutInflater inflater,
+			@Nullable ViewGroup container,
+			@Nullable Bundle savedInstanceState) {
+		return inflater
+				.inflate(R.layout.fragment_hotspot_help, container, false);
+	}
+
+}

briar-android/src/main/java/org/briarproject/briar/android/hotspot/HotspotIntroFragment.java

@@ -0,0 +1,133 @@
+package org.briarproject.briar.android.hotspot;
+
+import android.content.Context;
+import android.content.pm.ApplicationInfo;
+import android.content.pm.PackageManager;
+import android.os.Bundle;
+import android.view.LayoutInflater;
+import android.view.View;
+import android.view.ViewGroup;
+import android.widget.Button;
+import android.widget.ProgressBar;
+import android.widget.ScrollView;
+import android.widget.TextView;
+
+import com.google.android.material.snackbar.Snackbar;
+
+import org.briarproject.bramble.api.nullsafety.MethodsNotNullByDefault;
+import org.briarproject.bramble.api.nullsafety.ParametersNotNullByDefault;
+import org.briarproject.briar.R;
+
+import javax.inject.Inject;
+
+import androidx.annotation.Nullable;
+import androidx.fragment.app.Fragment;
+import androidx.fragment.app.FragmentActivity;
+import androidx.lifecycle.ViewModelProvider;
+
+import static android.content.pm.ApplicationInfo.FLAG_TEST_ONLY;
+import static android.os.Build.VERSION.SDK_INT;
+import static android.view.View.FOCUS_DOWN;
+import static android.view.View.INVISIBLE;
+import static android.view.View.VISIBLE;
+import static androidx.transition.TransitionManager.beginDelayedTransition;
+import static com.google.android.material.snackbar.BaseTransientBottomBar.LENGTH_LONG;
+import static org.briarproject.briar.android.AppModule.getAndroidComponent;
+
+@MethodsNotNullByDefault
+@ParametersNotNullByDefault
+public class HotspotIntroFragment extends Fragment {
+
+	public final static String TAG = HotspotIntroFragment.class.getName();
+
+	@Inject
+	ViewModelProvider.Factory viewModelFactory;
+
+	private HotspotViewModel viewModel;
+
+	private Button startButton;
+	private ProgressBar progressBar;
+	private TextView progressTextView;
+	private ScrollView scrollView;
+
+	private final AbstractConditionManager conditionManager = SDK_INT < 29 ?
+			new ConditionManager(this, this::onPermissionUpdate) :
+			new ConditionManager29(this, this::onPermissionUpdate);
+
+	@Override
+	public void onAttach(Context context) {
+		super.onAttach(context);
+		FragmentActivity activity = requireActivity();
+		getAndroidComponent(activity).inject(this);
+		viewModel = new ViewModelProvider(activity, viewModelFactory)
+				.get(HotspotViewModel.class);
+	}
+
+	@Override
+	public View onCreateView(LayoutInflater inflater,
+			@Nullable ViewGroup container,
+			@Nullable Bundle savedInstanceState) {
+		View v = inflater
+				.inflate(R.layout.fragment_hotspot_intro, container, false);
+
+		startButton = v.findViewById(R.id.startButton);
+		progressBar = v.findViewById(R.id.progressBar);
+		progressTextView = v.findViewById(R.id.progressTextView);
+		scrollView = v.findViewById(R.id.scrollView);
+
+		startButton.setOnClickListener(this::onButtonClick);
+
+		conditionManager.init(requireActivity());
+
+		return v;
+	}
+
+	@Override
+	public void onStart() {
+		super.onStart();
+		conditionManager.onStart();
+		// Scroll down in case the screen is small, so the button is visible
+		scrollView.post(() -> scrollView.fullScroll(FOCUS_DOWN));
+	}
+
+	private void onButtonClick(View view) {
+		startButton.setEnabled(false);
+		startHotspotIfConditionsFulfilled();
+	}
+
+	private void startHotspotIfConditionsFulfilled() {
+		if (conditionManager.checkAndRequestConditions()) {
+			showInstallWarningIfNeeded();
+			beginDelayedTransition((ViewGroup) requireView());
+			startButton.setVisibility(INVISIBLE);
+			progressBar.setVisibility(VISIBLE);
+			progressTextView.setVisibility(VISIBLE);
+			viewModel.startHotspot();
+		}
+	}
+
+	private void onPermissionUpdate(boolean recheckPermissions) {
+		startButton.setEnabled(true);
+		if (recheckPermissions) {
+			startHotspotIfConditionsFulfilled();
+		}
+	}
+
+	private void showInstallWarningIfNeeded() {
+		Context ctx = requireContext();
+		ApplicationInfo applicationInfo;
+		try {
+			applicationInfo = ctx.getPackageManager()
+					.getApplicationInfo(ctx.getPackageName(), 0);
+		} catch (PackageManager.NameNotFoundException e) {
+			throw new AssertionError(e);
+		}
+		// test only apps can not be installed
+		if ((applicationInfo.flags & FLAG_TEST_ONLY) == FLAG_TEST_ONLY) {
+			int color = getResources().getColor(R.color.briar_red_500);
+			Snackbar.make(requireView(), R.string.hotspot_flag_test,
+					LENGTH_LONG).setBackgroundTint(color).show();
+		}
+	}
+
+}

briar-android/src/main/java/org/briarproject/briar/android/hotspot/HotspotManager.java

@@ -0,0 +1,453 @@
+package org.briarproject.briar.android.hotspot;
+
+import android.annotation.SuppressLint;
+import android.app.Application;
+import android.content.Context;
+import android.graphics.Bitmap;
+import android.net.wifi.WifiManager;
+import android.net.wifi.p2p.WifiP2pConfig;
+import android.net.wifi.p2p.WifiP2pGroup;
+import android.net.wifi.p2p.WifiP2pManager;
+import android.net.wifi.p2p.WifiP2pManager.ActionListener;
+import android.net.wifi.p2p.WifiP2pManager.GroupInfoListener;
+import android.os.Handler;
+import android.os.PowerManager;
+import android.util.DisplayMetrics;
+
+import org.briarproject.bramble.api.db.DatabaseExecutor;
+import org.briarproject.bramble.api.db.DbException;
+import org.briarproject.bramble.api.lifecycle.IoExecutor;
+import org.briarproject.bramble.api.nullsafety.MethodsNotNullByDefault;
+import org.briarproject.bramble.api.nullsafety.ParametersNotNullByDefault;
+import org.briarproject.bramble.api.settings.Settings;
+import org.briarproject.bramble.api.settings.SettingsManager;
+import org.briarproject.bramble.api.system.AndroidExecutor;
+import org.briarproject.briar.R;
+import org.briarproject.briar.android.hotspot.HotspotState.NetworkConfig;
+import org.briarproject.briar.android.util.QrCodeUtils;
+
+import java.security.SecureRandom;
+import java.util.concurrent.Executor;
+import java.util.logging.Logger;
+
+import javax.inject.Inject;
+
+import androidx.annotation.Nullable;
+import androidx.annotation.RequiresApi;
+import androidx.annotation.UiThread;
+
+import static android.content.Context.POWER_SERVICE;
+import static android.content.Context.WIFI_P2P_SERVICE;
+import static android.content.Context.WIFI_SERVICE;
+import static android.net.wifi.WifiManager.WIFI_MODE_FULL;
+import static android.net.wifi.WifiManager.WIFI_MODE_FULL_HIGH_PERF;
+import static android.net.wifi.p2p.WifiP2pConfig.GROUP_OWNER_BAND_2GHZ;
+import static android.net.wifi.p2p.WifiP2pManager.BUSY;
+import static android.net.wifi.p2p.WifiP2pManager.ERROR;
+import static android.net.wifi.p2p.WifiP2pManager.NO_SERVICE_REQUESTS;
+import static android.net.wifi.p2p.WifiP2pManager.P2P_UNSUPPORTED;
+import static android.os.Build.VERSION.SDK_INT;
+import static android.os.PowerManager.FULL_WAKE_LOCK;
+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.briar.android.util.QrCodeUtils.HOTSPOT_QRCODE_FACTOR;
+import static org.briarproject.briar.android.util.UiUtils.handleException;
+
+@MethodsNotNullByDefault
+@ParametersNotNullByDefault
+class HotspotManager {
+
+	interface HotspotListener {
+		@UiThread
+		void onStartingHotspot();
+
+		@IoExecutor
+		void onHotspotStarted(NetworkConfig networkConfig);
+
+		@UiThread
+		void onPeersUpdated(int peers);
+
+		@UiThread
+		void onHotspotError(String error);
+	}
+
+	private static final Logger LOG = getLogger(HotspotManager.class.getName());
+
+	private static final int MAX_FRAMEWORK_ATTEMPTS = 5;
+	private static final int MAX_GROUP_INFO_ATTEMPTS = 5;
+	private static final int RETRY_DELAY_MILLIS = 1000;
+	private static final String HOTSPOT_NAMESPACE = "hotspot";
+	private static final String HOTSPOT_KEY_SSID = "ssid";
+	private static final String HOTSPOT_KEY_PASS = "pass";
+
+	private final Context ctx;
+	@DatabaseExecutor
+	private final Executor dbExecutor;
+	@IoExecutor
+	private final Executor ioExecutor;
+	private final AndroidExecutor androidExecutor;
+	private final SettingsManager settingsManager;
+	private final SecureRandom random;
+	private final WifiManager wifiManager;
+	private final WifiP2pManager wifiP2pManager;
+	private final PowerManager powerManager;
+	private final Handler handler;
+	private final String lockTag;
+
+	private HotspotListener listener;
+	private WifiManager.WifiLock wifiLock;
+	private PowerManager.WakeLock wakeLock;
+	private WifiP2pManager.Channel channel;
+	@Nullable
+	@RequiresApi(29)
+	private volatile NetworkConfig savedNetworkConfig = null;
+
+	@Inject
+	HotspotManager(Application ctx,
+			@DatabaseExecutor Executor dbExecutor,
+			@IoExecutor Executor ioExecutor,
+			AndroidExecutor androidExecutor,
+			SettingsManager settingsManager,
+			SecureRandom random) {
+		this.ctx = ctx.getApplicationContext();
+		this.dbExecutor = dbExecutor;
+		this.ioExecutor = ioExecutor;
+		this.androidExecutor = androidExecutor;
+		this.settingsManager = settingsManager;
+		this.random = random;
+		wifiManager = (WifiManager) ctx.getApplicationContext()
+				.getSystemService(WIFI_SERVICE);
+		wifiP2pManager =
+				(WifiP2pManager) ctx.getSystemService(WIFI_P2P_SERVICE);
+		powerManager = (PowerManager) ctx.getSystemService(POWER_SERVICE);
+		handler = new Handler(ctx.getMainLooper());
+		lockTag = ctx.getPackageName() + ":app-sharing-hotspot";
+	}
+
+	void setHotspotListener(HotspotListener listener) {
+		this.listener = listener;
+	}
+
+	@UiThread
+	void startWifiP2pHotspot() {
+		if (wifiP2pManager == null) {
+			listener.onHotspotError(
+					ctx.getString(R.string.hotspot_error_no_wifi_direct));
+			return;
+		}
+		listener.onStartingHotspot();
+		acquireLocks();
+		startWifiP2pFramework(1);
+	}
+
+	/**
+	 * As soon as Wifi is enabled, we try starting the WifiP2p framework.
+	 * If Wifi has just been enabled, it is possible that will fail. If that
+	 * happens we try again for MAX_FRAMEWORK_ATTEMPTS times after a delay of
+	 * RETRY_DELAY_MILLIS after each attempt.
+	 * <p>
+	 * Rationale: it can take a few milliseconds for WifiP2p to become available
+	 * after enabling Wifi. Depending on the API level it is possible to check this
+	 * using {@link WifiP2pManager#requestP2pState} or register a BroadcastReceiver
+	 * on the WIFI_P2P_STATE_CHANGED_ACTION to get notified when WifiP2p is really
+	 * available. Trying to implement a solution that works reliably using these
+	 * checks turned out to be a long rabbit-hole with lots of corner cases and
+	 * workarounds for specific situations.
+	 * Instead we now rely on this trial-and-error approach of just starting
+	 * the framework and retrying if it fails.
+	 * <p>
+	 * We'll realize that the framework is busy when the ActionListener passed
+	 * to {@link WifiP2pManager#createGroup} is called with onFailure(BUSY)
+	 */
+	@UiThread
+	private void startWifiP2pFramework(int attempt) {
+		if (LOG.isLoggable(INFO)) {
+			LOG.info("startWifiP2pFramework attempt: " + attempt);
+		}
+		/*
+		 * It is important that we call WifiP2pManager#initialize again
+		 * for every attempt to starting the framework because otherwise,
+		 * createGroup() will continue to fail with a BUSY state.
+		 */
+		channel = wifiP2pManager.initialize(ctx, ctx.getMainLooper(), null);
+		if (channel == null) {
+			releaseHotspotWithError(
+					ctx.getString(R.string.hotspot_error_no_wifi_direct));
+			return;
+		}
+
+		ActionListener listener = new ActionListener() {
+			@Override
+			// Callback for wifiP2pManager#createGroup() during startWifiP2pHotspot()
+			public void onSuccess() {
+				requestGroupInfo(1);
+			}
+
+			@Override
+			// Callback for wifiP2pManager#createGroup() during startWifiP2pHotspot()
+			public void onFailure(int reason) {
+				if (LOG.isLoggable(INFO)) {
+					LOG.info("onFailure: " + reason);
+				}
+				if (reason == BUSY) {
+					// WifiP2p not ready yet or hotspot already running
+					restartWifiP2pFramework(attempt);
+				} else if (reason == P2P_UNSUPPORTED) {
+					releaseHotspotWithError(ctx.getString(
+							R.string.hotspot_error_start_callback_failed,
+							"p2p unsupported"));
+				} else if (reason == ERROR) {
+					releaseHotspotWithError(ctx.getString(
+							R.string.hotspot_error_start_callback_failed,
+							"p2p error"));
+				} else if (reason == NO_SERVICE_REQUESTS) {
+					releaseHotspotWithError(ctx.getString(
+							R.string.hotspot_error_start_callback_failed,
+							"no service requests"));
+				} else {
+					// all cases covered, in doubt set to error
+					releaseHotspotWithError(ctx.getString(
+							R.string.hotspot_error_start_callback_failed_unknown,
+							reason));
+				}
+			}
+		};
+
+		try {
+			if (SDK_INT >= 29) {
+				Runnable createGroup = () -> {
+					NetworkConfig c = requireNonNull(savedNetworkConfig);
+					WifiP2pConfig config = new WifiP2pConfig.Builder()
+							.setGroupOperatingBand(GROUP_OWNER_BAND_2GHZ)
+							.setNetworkName(c.ssid)
+							.setPassphrase(c.password)
+							.build();
+					wifiP2pManager.createGroup(channel, config, listener);
+				};
+				if (savedNetworkConfig == null) {
+					// load savedNetworkConfig before starting hotspot
+					dbExecutor.execute(() -> {
+						loadSavedNetworkConfig();
+						androidExecutor.runOnUiThread(createGroup);
+					});
+				} else {
+					// savedNetworkConfig was already loaded, create group now
+					createGroup.run();
+				}
+			} else {
+				wifiP2pManager.createGroup(channel, listener);
+			}
+		} catch (SecurityException e) {
+			// this should never happen, because we request permissions before
+			throw new AssertionError(e);
+		}
+	}
+
+	@UiThread
+	private void restartWifiP2pFramework(int attempt) {
+		LOG.info("retrying to start WifiP2p framework");
+		if (attempt < MAX_FRAMEWORK_ATTEMPTS) {
+			if (SDK_INT >= 27 && channel != null) channel.close();
+			channel = null;
+			handler.postDelayed(() -> startWifiP2pFramework(attempt + 1),
+					RETRY_DELAY_MILLIS);
+		} else {
+			releaseHotspotWithError(
+					ctx.getString(R.string.hotspot_error_framework_busy));
+		}
+	}
+
+	@UiThread
+	void stopWifiP2pHotspot() {
+		if (channel == null) return;
+		wifiP2pManager.removeGroup(channel, new ActionListener() {
+			@Override
+			public void onSuccess() {
+				closeChannelAndReleaseLocks();
+			}
+
+			@Override
+			public void onFailure(int reason) {
+				// not propagating back error
+				if (LOG.isLoggable(WARNING)) {
+					LOG.warning("Error removing Wifi P2P group: " + reason);
+				}
+				closeChannelAndReleaseLocks();
+			}
+		});
+	}
+
+	@SuppressLint("WakelockTimeout")
+	private void acquireLocks() {
+		// FLAG_KEEP_SCREEN_ON is not respected on some Huawei devices.
+		wakeLock = powerManager.newWakeLock(FULL_WAKE_LOCK, lockTag);
+		wakeLock.acquire();
+		// WIFI_MODE_FULL has no effect on API >= 29
+		int lockType =
+				SDK_INT >= 29 ? WIFI_MODE_FULL_HIGH_PERF : WIFI_MODE_FULL;
+		wifiLock = wifiManager.createWifiLock(lockType, lockTag);
+		wifiLock.acquire();
+	}
+
+	@UiThread
+	private void releaseHotspotWithError(String error) {
+		listener.onHotspotError(error);
+		closeChannelAndReleaseLocks();
+	}
+
+	@UiThread
+	private void closeChannelAndReleaseLocks() {
+		if (SDK_INT >= 27 && channel != null) channel.close();
+		channel = null;
+		if (wakeLock.isHeld()) wakeLock.release();
+		if (wifiLock.isHeld()) wifiLock.release();
+	}
+
+	@UiThread
+	private void requestGroupInfo(int attempt) {
+		if (LOG.isLoggable(INFO)) {
+			LOG.info("requestGroupInfo attempt: " + attempt);
+		}
+		GroupInfoListener groupListener = group -> {
+			boolean valid = isGroupValid(group);
+			// If the group is valid, set the hotspot to started. If we don't
+			// have any attempts left, we try what we got
+			if (valid || attempt >= MAX_GROUP_INFO_ATTEMPTS) {
+				onHotspotStarted(group);
+			} else {
+				retryRequestingGroupInfo(attempt);
+			}
+		};
+		try {
+			if (channel == null) return;
+			wifiP2pManager.requestGroupInfo(channel, groupListener);
+		} catch (SecurityException e) {
+			// this should never happen, because we request permissions before
+			throw new AssertionError(e);
+		}
+	}
+
+	@UiThread
+	private void onHotspotStarted(WifiP2pGroup group) {
+		DisplayMetrics dm = ctx.getResources().getDisplayMetrics();
+		ioExecutor.execute(() -> {
+			String content = createWifiLoginString(group.getNetworkName(),
+					group.getPassphrase());
+			Bitmap qrCode = QrCodeUtils.createQrCode(
+					(int) (dm.heightPixels * HOTSPOT_QRCODE_FACTOR), content);
+			NetworkConfig config = new NetworkConfig(group.getNetworkName(),
+					group.getPassphrase(), qrCode);
+			listener.onHotspotStarted(config);
+		});
+		requestGroupInfoForConnection();
+	}
+
+	private boolean isGroupValid(@Nullable WifiP2pGroup group) {
+		if (group == null) {
+			LOG.info("group is null");
+			return false;
+		} else if (!group.getNetworkName().startsWith("DIRECT-")) {
+			LOG.info("received networkName without prefix 'DIRECT-'");
+			return false;
+		} else if (SDK_INT >= 29) {
+			// if we get here, the savedNetworkConfig must have a value
+			String networkName = requireNonNull(savedNetworkConfig).ssid;
+			if (!networkName.equals(group.getNetworkName())) {
+				LOG.info("expected networkName does not match received one");
+				return false;
+			}
+		}
+		return true;
+	}
+
+	@UiThread
+	private void retryRequestingGroupInfo(int attempt) {
+		LOG.info("retrying to request group info");
+		// On some devices we need to wait for the group info to become available
+		if (attempt < MAX_GROUP_INFO_ATTEMPTS) {
+			handler.postDelayed(() -> requestGroupInfo(attempt + 1),
+					RETRY_DELAY_MILLIS);
+		} else {
+			releaseHotspotWithError(ctx.getString(
+					R.string.hotspot_error_start_callback_no_group_info));
+		}
+	}
+
+	@UiThread
+	private void requestGroupInfoForConnection() {
+		LOG.info("requestGroupInfo for connection");
+		GroupInfoListener groupListener = group -> {
+			if (group != null) {
+				listener.onPeersUpdated(group.getClientList().size());
+			}
+			handler.postDelayed(this::requestGroupInfoForConnection,
+					RETRY_DELAY_MILLIS);
+		};
+		try {
+			if (channel == null) return;
+			wifiP2pManager.requestGroupInfo(channel, groupListener);
+		} catch (SecurityException e) {
+			throw new AssertionError(e);
+		}
+	}
+
+	/**
+	 * Store persistent Wi-Fi SSID and passphrase in Settings to improve UX
+	 * so that users don't have to change them when attempting to connect.
+	 * Works only on API 29 and above.
+	 */
+	@RequiresApi(29)
+	@DatabaseExecutor
+	private void loadSavedNetworkConfig() {
+		try {
+			Settings settings = settingsManager.getSettings(HOTSPOT_NAMESPACE);
+			String ssid = settings.get(HOTSPOT_KEY_SSID);
+			String pass = settings.get(HOTSPOT_KEY_PASS);
+			if (ssid == null || pass == null) {
+				ssid = getSsid();
+				pass = getPassword();
+				settings.put(HOTSPOT_KEY_SSID, ssid);
+				settings.put(HOTSPOT_KEY_PASS, pass);
+				settingsManager.mergeSettings(settings, HOTSPOT_NAMESPACE);
+			}
+			savedNetworkConfig = new NetworkConfig(ssid, pass, null);
+		} catch (DbException e) {
+			handleException(ctx, androidExecutor, LOG, e);
+			// probably never happens, but if lets use non-persistent data
+			String ssid = getSsid();
+			String pass = getPassword();
+			savedNetworkConfig = new NetworkConfig(ssid, pass, null);
+		}
+	}
+
+	@RequiresApi(29)
+	private String getSsid() {
+		return "DIRECT-" + getRandomString(2) + "-" +
+				getRandomString(10);
+	}
+
+	@RequiresApi(29)
+	private String getPassword() {
+		return getRandomString(8);
+	}
+
+	private static String createWifiLoginString(String ssid, String password) {
+		// https://en.wikipedia.org/wiki/QR_code#WiFi_network_login
+		// do not remove the dangling ';', it can cause problems to omit it
+		return "WIFI:S:" + ssid + ";T:WPA;P:" + password + ";;";
+	}
+
+	// exclude chars that are easy to confuse: 0 (O), 5 (S), 1 l (I)
+	private static final String chars = "2346789abcdefghijkmnopqrstuvwxyz";
+
+	private String getRandomString(int length) {
+		char[] c = new char[length];
+		for (int i = 0; i < length; i++) {
+			c[i] = chars.charAt(random.nextInt(chars.length()));
+		}
+		return new String(c);
+	}
+
+}

briar-android/src/main/java/org/briarproject/briar/android/hotspot/HotspotModule.java

@@ -0,0 +1,18 @@
+package org.briarproject.briar.android.hotspot;
+
+import org.briarproject.briar.android.viewmodel.ViewModelKey;
+
+import androidx.lifecycle.ViewModel;
+import dagger.Binds;
+import dagger.Module;
+import dagger.multibindings.IntoMap;
+
+@Module
+public interface HotspotModule {
+
+	@Binds
+	@IntoMap
+	@ViewModelKey(HotspotViewModel.class)
+	ViewModel bindHotspotViewModel(HotspotViewModel hotspotViewModel);
+
+}

briar-android/src/main/java/org/briarproject/briar/android/hotspot/HotspotState.java

@@ -0,0 +1,88 @@
+package org.briarproject.briar.android.hotspot;
+
+import android.graphics.Bitmap;
+
+import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
+
+import androidx.annotation.Nullable;
+import androidx.annotation.UiThread;
+
+@NotNullByDefault
+abstract class HotspotState {
+
+	static class StartingHotspot extends HotspotState {
+	}
+
+	static class NetworkConfig {
+		final String ssid, password;
+		@Nullable
+		final Bitmap qrCode;
+
+		NetworkConfig(String ssid, String password, @Nullable Bitmap qrCode) {
+			this.ssid = ssid;
+			this.password = password;
+			this.qrCode = qrCode;
+		}
+	}
+
+	static class WebsiteConfig {
+		final String url;
+		@Nullable
+		final Bitmap qrCode;
+
+		WebsiteConfig(String url, @Nullable Bitmap qrCode) {
+			this.url = url;
+			this.qrCode = qrCode;
+		}
+	}
+
+	static class HotspotStarted extends HotspotState {
+		private final NetworkConfig networkConfig;
+		private final WebsiteConfig websiteConfig;
+		// 'consumed' is set to true once this state triggered a UI change, i.e.
+		// moving to the next fragment.
+		private boolean consumed = false;
+
+		HotspotStarted(NetworkConfig networkConfig,
+				WebsiteConfig websiteConfig) {
+			this.networkConfig = networkConfig;
+			this.websiteConfig = websiteConfig;
+		}
+
+		NetworkConfig getNetworkConfig() {
+			return networkConfig;
+		}
+
+		WebsiteConfig getWebsiteConfig() {
+			return websiteConfig;
+		}
+
+		@UiThread
+		boolean wasNotYetConsumed() {
+			return !consumed;
+		}
+
+		/**
+		 * Mark this state as consumed, i.e. the UI has already done something
+		 * as a result of the state changing to this. This can be used in order
+		 * to not repeat actions such as showing fragments on rotation changes.
+		 */
+		@UiThread
+		void consume() {
+			consumed = true;
+		}
+	}
+
+	static class HotspotError extends HotspotState {
+		private final String error;
+
+		HotspotError(String error) {
+			this.error = error;
+		}
+
+		String getError() {
+			return error;
+		}
+	}
+
+}

briar-android/src/main/java/org/briarproject/briar/android/hotspot/HotspotViewModel.java

@@ -0,0 +1,224 @@
+package org.briarproject.briar.android.hotspot;
+
+import android.app.Application;
+import android.net.Uri;
+
+import org.briarproject.bramble.api.db.DatabaseExecutor;
+import org.briarproject.bramble.api.db.TransactionManager;
+import org.briarproject.bramble.api.lifecycle.IoExecutor;
+import org.briarproject.bramble.api.lifecycle.LifecycleManager;
+import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
+import org.briarproject.bramble.api.system.AndroidExecutor;
+import org.briarproject.briar.R;
+import org.briarproject.briar.android.hotspot.HotspotManager.HotspotListener;
+import org.briarproject.briar.android.hotspot.HotspotState.HotspotError;
+import org.briarproject.briar.android.hotspot.HotspotState.HotspotStarted;
+import org.briarproject.briar.android.hotspot.HotspotState.NetworkConfig;
+import org.briarproject.briar.android.hotspot.HotspotState.StartingHotspot;
+import org.briarproject.briar.android.hotspot.HotspotState.WebsiteConfig;
+import org.briarproject.briar.android.hotspot.WebServerManager.WebServerListener;
+import org.briarproject.briar.android.viewmodel.DbViewModel;
+import org.briarproject.briar.android.viewmodel.LiveEvent;
+import org.briarproject.briar.android.viewmodel.MutableLiveEvent;
+import org.briarproject.briar.api.android.AndroidNotificationManager;
+
+import java.io.File;
+import java.io.FileInputStream;
+import java.io.FileNotFoundException;
+import java.io.FileOutputStream;
+import java.io.IOException;
+import java.io.OutputStream;
+import java.util.concurrent.Executor;
+import java.util.logging.Logger;
+
+import javax.inject.Inject;
+
+import androidx.annotation.Nullable;
+import androidx.annotation.UiThread;
+import androidx.lifecycle.LiveData;
+import androidx.lifecycle.MutableLiveData;
+
+import static android.os.Build.VERSION.SDK_INT;
+import static android.os.Environment.DIRECTORY_DOWNLOADS;
+import static android.os.Environment.getExternalStoragePublicDirectory;
+import static java.util.Objects.requireNonNull;
+import static java.util.logging.Level.WARNING;
+import static java.util.logging.Logger.getLogger;
+import static org.briarproject.bramble.util.IoUtils.copyAndClose;
+import static org.briarproject.briar.BuildConfig.DEBUG;
+import static org.briarproject.briar.BuildConfig.VERSION_NAME;
+
+@NotNullByDefault
+class HotspotViewModel extends DbViewModel
+		implements HotspotListener, WebServerListener {
+
+	private static final Logger LOG =
+			getLogger(HotspotViewModel.class.getName());
+
+	@IoExecutor
+	private final Executor ioExecutor;
+	private final AndroidNotificationManager notificationManager;
+	private final HotspotManager hotspotManager;
+	private final WebServerManager webServerManager;
+
+	private final MutableLiveData<HotspotState> state =
+			new MutableLiveData<>();
+	private final MutableLiveData<Integer> peersConnected =
+			new MutableLiveData<>();
+	private final MutableLiveEvent<Uri> savedApkToUri =
+			new MutableLiveEvent<>();
+
+	@Nullable
+	// Field to temporarily store the network config received via onHotspotStarted()
+	// in order to post it along with a HotspotStarted status
+	private volatile NetworkConfig networkConfig;
+
+	@Inject
+	HotspotViewModel(Application app,
+			@DatabaseExecutor Executor dbExecutor,
+			LifecycleManager lifecycleManager,
+			TransactionManager db,
+			AndroidExecutor androidExecutor,
+			@IoExecutor Executor ioExecutor,
+			HotspotManager hotspotManager,
+			WebServerManager webServerManager,
+			AndroidNotificationManager notificationManager) {
+		super(app, dbExecutor, lifecycleManager, db, androidExecutor);
+		this.ioExecutor = ioExecutor;
+		this.notificationManager = notificationManager;
+		this.hotspotManager = hotspotManager;
+		this.hotspotManager.setHotspotListener(this);
+		this.webServerManager = webServerManager;
+		this.webServerManager.setListener(this);
+	}
+
+	@UiThread
+	void startHotspot() {
+		HotspotState s = state.getValue();
+		if (s instanceof HotspotStarted) {
+			// This can happen if the user navigates back to intro fragment and
+			// taps 'start sharing' again. In this case, don't try to start the
+			// hotspot again. Instead, just create a new, unconsumed HotspotStarted
+			// event with the same config.
+			HotspotStarted old = (HotspotStarted) s;
+			state.setValue(new HotspotStarted(old.getNetworkConfig(),
+					old.getWebsiteConfig()));
+		} else {
+			hotspotManager.startWifiP2pHotspot();
+			notificationManager.showHotspotNotification();
+		}
+	}
+
+	@UiThread
+	private void stopHotspot() {
+		ioExecutor.execute(webServerManager::stopWebServer);
+		hotspotManager.stopWifiP2pHotspot();
+		notificationManager.clearHotspotNotification();
+	}
+
+	@Override
+	protected void onCleared() {
+		super.onCleared();
+		stopHotspot();
+	}
+
+	@Override
+	public void onStartingHotspot() {
+		state.setValue(new StartingHotspot());
+	}
+
+	@Override
+	@IoExecutor
+	public void onHotspotStarted(NetworkConfig networkConfig) {
+		this.networkConfig = networkConfig;
+		LOG.info("starting webserver");
+		webServerManager.startWebServer();
+	}
+
+	@UiThread
+	@Override
+	public void onPeersUpdated(int peers) {
+		peersConnected.setValue(peers);
+	}
+
+	@Override
+	public void onHotspotError(String error) {
+		if (LOG.isLoggable(WARNING)) {
+			LOG.warning("Hotspot error: " + error);
+		}
+		state.postValue(new HotspotError(error));
+		ioExecutor.execute(webServerManager::stopWebServer);
+		notificationManager.clearHotspotNotification();
+	}
+
+	@Override
+	@IoExecutor
+	public void onWebServerStarted(WebsiteConfig websiteConfig) {
+		NetworkConfig nc = requireNonNull(networkConfig);
+		state.postValue(new HotspotStarted(nc, websiteConfig));
+		networkConfig = null;
+	}
+
+	@Override
+	@IoExecutor
+	public void onWebServerError() {
+		state.postValue(new HotspotError(getApplication()
+				.getString(R.string.hotspot_error_web_server_start)));
+		stopHotspot();
+	}
+
+	void exportApk(Uri uri) {
+		if (SDK_INT < 19) throw new IllegalStateException();
+		try {
+			OutputStream out = getApplication().getContentResolver()
+					.openOutputStream(uri, "wt");
+			writeApk(out, uri);
+		} catch (FileNotFoundException e) {
+			handleException(e);
+		}
+	}
+
+	void exportApk() {
+		if (SDK_INT >= 19) throw new IllegalStateException();
+		File path = getExternalStoragePublicDirectory(DIRECTORY_DOWNLOADS);
+		//noinspection ResultOfMethodCallIgnored
+		path.mkdirs();
+		File file = new File(path, getApkFileName());
+		try {
+			OutputStream out = new FileOutputStream(file);
+			writeApk(out, Uri.fromFile(file));
+		} catch (FileNotFoundException e) {
+			handleException(e);
+		}
+	}
+
+	static String getApkFileName() {
+		return "briar" + (DEBUG ? "-debug-" : "-") + VERSION_NAME + ".apk";
+	}
+
+	private void writeApk(OutputStream out, Uri uriToShare) {
+		File apk = new File(getApplication().getPackageCodePath());
+		ioExecutor.execute(() -> {
+			try {
+				FileInputStream in = new FileInputStream(apk);
+				copyAndClose(in, out);
+				savedApkToUri.postEvent(uriToShare);
+			} catch (IOException e) {
+				handleException(e);
+			}
+		});
+	}
+
+	LiveData<HotspotState> getState() {
+		return state;
+	}
+
+	LiveData<Integer> getPeersConnectedEvent() {
+		return peersConnected;
+	}
+
+	LiveEvent<Uri> getSavedApkToUri() {
+		return savedApkToUri;
+	}
+
+}

briar-android/src/main/java/org/briarproject/briar/android/hotspot/ManualHotspotFragment.java

@@ -0,0 +1,119 @@
+package org.briarproject.briar.android.hotspot;
+
+import android.content.Context;
+import android.os.Bundle;
+import android.text.SpannableString;
+import android.text.method.LinkMovementMethod;
+import android.text.style.ClickableSpan;
+import android.view.LayoutInflater;
+import android.view.View;
+import android.view.ViewGroup;
+import android.widget.TextView;
+
+import org.briarproject.bramble.api.nullsafety.MethodsNotNullByDefault;
+import org.briarproject.bramble.api.nullsafety.ParametersNotNullByDefault;
+import org.briarproject.briar.R;
+
+import javax.inject.Inject;
+
+import androidx.annotation.Nullable;
+import androidx.core.util.Consumer;
+import androidx.fragment.app.Fragment;
+import androidx.lifecycle.ViewModelProvider;
+import androidx.viewpager2.widget.ViewPager2;
+
+import static android.text.Spanned.SPAN_EXCLUSIVE_EXCLUSIVE;
+import static android.view.View.GONE;
+import static org.briarproject.briar.android.AppModule.getAndroidComponent;
+import static org.briarproject.briar.android.hotspot.AbstractTabsFragment.ARG_FOR_WIFI_CONNECT;
+import static org.briarproject.briar.android.hotspot.HotspotState.HotspotStarted;
+
+@MethodsNotNullByDefault
+@ParametersNotNullByDefault
+public class ManualHotspotFragment extends Fragment {
+
+	public final static String TAG = ManualHotspotFragment.class.getName();
+
+	@Inject
+	ViewModelProvider.Factory viewModelFactory;
+
+	private HotspotViewModel viewModel;
+
+	static ManualHotspotFragment newInstance(boolean forWifiConnect) {
+		ManualHotspotFragment f = new ManualHotspotFragment();
+		Bundle bundle = new Bundle();
+		bundle.putBoolean(ARG_FOR_WIFI_CONNECT, forWifiConnect);
+		f.setArguments(bundle);
+		return f;
+	}
+
+	@Override
+	public void onAttach(Context context) {
+		super.onAttach(context);
+		getAndroidComponent(requireContext()).inject(this);
+		viewModel = new ViewModelProvider(requireActivity(), viewModelFactory)
+				.get(HotspotViewModel.class);
+	}
+
+	@Override
+	public View onCreateView(LayoutInflater inflater,
+			@Nullable ViewGroup container,
+			@Nullable Bundle savedInstanceState) {
+		return inflater
+				.inflate(R.layout.fragment_hotspot_manual, container, false);
+	}
+
+	@Override
+	public void onViewCreated(View v, @Nullable Bundle savedInstanceState) {
+		super.onViewCreated(v, savedInstanceState);
+
+		TextView manualIntroView = v.findViewById(R.id.manualIntroView);
+		TextView ssidLabelView = v.findViewById(R.id.ssidLabelView);
+		TextView ssidView = v.findViewById(R.id.ssidView);
+		TextView passwordView = v.findViewById(R.id.passwordView);
+
+		Consumer<HotspotStarted> consumer;
+		if (requireArguments().getBoolean(ARG_FOR_WIFI_CONNECT)) {
+			linkify(manualIntroView, R.string.hotspot_manual_wifi);
+			ssidLabelView.setText(R.string.hotspot_manual_wifi_ssid);
+			consumer = state -> {
+				ssidView.setText(state.getNetworkConfig().ssid);
+				passwordView.setText(state.getNetworkConfig().password);
+			};
+		} else {
+			linkify(manualIntroView, R.string.hotspot_manual_site);
+			ssidLabelView.setText(R.string.hotspot_manual_site_address);
+			consumer = state -> ssidView.setText(state.getWebsiteConfig().url);
+			v.findViewById(R.id.passwordLabelView).setVisibility(GONE);
+			passwordView.setVisibility(GONE);
+		}
+		viewModel.getState().observe(getViewLifecycleOwner(), state -> {
+			// we only expect to be in this state here
+			if (state instanceof HotspotStarted) {
+				consumer.accept((HotspotStarted) state);
+			}
+		});
+	}
+
+	private void linkify(TextView textView, int resPattern) {
+		String pattern = getString(resPattern);
+		String replacement = getString(R.string.hotspot_scanning_a_qr_code);
+		String text = String.format(pattern, replacement);
+		int start = pattern.indexOf("%s");
+		int end = start + replacement.length();
+		SpannableString spannable = new SpannableString(text);
+		ClickableSpan clickable = new ClickableSpan() {
+
+			@Override
+			public void onClick(View textView) {
+				ViewPager2 pager = requireActivity().findViewById(R.id.pager);
+				pager.setCurrentItem(1);
+			}
+
+		};
+		spannable.setSpan(clickable, start, end, SPAN_EXCLUSIVE_EXCLUSIVE);
+
+		textView.setText(spannable);
+		textView.setMovementMethod(LinkMovementMethod.getInstance());
+	}
+}

briar-android/src/main/java/org/briarproject/briar/android/hotspot/QrHotspotFragment.java

@@ -0,0 +1,86 @@
+package org.briarproject.briar.android.hotspot;
+
+import android.content.Context;
+import android.graphics.Bitmap;
+import android.os.Bundle;
+import android.view.LayoutInflater;
+import android.view.View;
+import android.view.ViewGroup;
+import android.widget.ImageView;
+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.hotspot.HotspotState.HotspotStarted;
+
+import javax.inject.Inject;
+
+import androidx.annotation.Nullable;
+import androidx.fragment.app.Fragment;
+import androidx.lifecycle.ViewModelProvider;
+
+import static org.briarproject.briar.android.AppModule.getAndroidComponent;
+import static org.briarproject.briar.android.hotspot.AbstractTabsFragment.ARG_FOR_WIFI_CONNECT;
+
+@MethodsNotNullByDefault
+@ParametersNotNullByDefault
+public class QrHotspotFragment extends Fragment {
+
+	public final static String TAG = QrHotspotFragment.class.getName();
+
+	@Inject
+	ViewModelProvider.Factory viewModelFactory;
+
+	private HotspotViewModel viewModel;
+
+	static QrHotspotFragment newInstance(boolean forWifiConnect) {
+		QrHotspotFragment f = new QrHotspotFragment();
+		Bundle bundle = new Bundle();
+		bundle.putBoolean(ARG_FOR_WIFI_CONNECT, forWifiConnect);
+		f.setArguments(bundle);
+		return f;
+	}
+
+	@Override
+	public void onAttach(Context context) {
+		super.onAttach(context);
+		getAndroidComponent(requireContext()).inject(this);
+		viewModel = new ViewModelProvider(requireActivity(), viewModelFactory)
+				.get(HotspotViewModel.class);
+	}
+
+	@Override
+	public View onCreateView(LayoutInflater inflater,
+			@Nullable ViewGroup container,
+			@Nullable Bundle savedInstanceState) {
+		View v = inflater
+				.inflate(R.layout.fragment_hotspot_qr, container, false);
+
+		TextView qrIntroView = v.findViewById(R.id.qrIntroView);
+		ImageView qrCodeView = v.findViewById(R.id.qrCodeView);
+
+		boolean forWifi = requireArguments().getBoolean(ARG_FOR_WIFI_CONNECT);
+
+		qrIntroView.setText(forWifi ? R.string.hotspot_qr_wifi :
+				R.string.hotspot_qr_site);
+
+		viewModel.getState().observe(getViewLifecycleOwner(), state -> {
+			if (state instanceof HotspotStarted) {
+				HotspotStarted s = (HotspotStarted) state;
+				Bitmap qrCode = forWifi ? s.getNetworkConfig().qrCode :
+						s.getWebsiteConfig().qrCode;
+				if (qrCode == null) {
+					Toast.makeText(requireContext(), R.string.error,
+							Toast.LENGTH_SHORT).show();
+					qrCodeView.setImageResource(R.drawable.ic_image_broken);
+				} else {
+					qrCodeView.setImageBitmap(qrCode);
+				}
+			}
+		});
+		return v;
+	}
+
+}

briar-android/src/main/java/org/briarproject/briar/android/hotspot/WebServer.java

@@ -0,0 +1,135 @@
+package org.briarproject.briar.android.hotspot;
+
+import android.content.Context;
+
+import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
+import org.briarproject.briar.R;
+import org.jsoup.Jsoup;
+import org.jsoup.nodes.Document;
+
+import java.io.File;
+import java.io.FileInputStream;
+import java.io.FileNotFoundException;
+import java.io.IOException;
+import java.io.InputStream;
+import java.util.logging.Logger;
+import java.util.regex.Matcher;
+import java.util.regex.Pattern;
+
+import androidx.annotation.Nullable;
+import fi.iki.elonen.NanoHTTPD;
+
+import static android.util.Xml.Encoding.UTF_8;
+import static fi.iki.elonen.NanoHTTPD.Response.Status.INTERNAL_ERROR;
+import static fi.iki.elonen.NanoHTTPD.Response.Status.NOT_FOUND;
+import static fi.iki.elonen.NanoHTTPD.Response.Status.OK;
+import static java.util.Objects.requireNonNull;
+import static java.util.logging.Level.WARNING;
+import static java.util.logging.Logger.getLogger;
+import static org.briarproject.bramble.util.LogUtils.logException;
+import static org.briarproject.briar.BuildConfig.VERSION_NAME;
+import static org.briarproject.briar.android.hotspot.HotspotViewModel.getApkFileName;
+
+@NotNullByDefault
+class WebServer extends NanoHTTPD {
+
+	final static int PORT = 9999;
+
+	private static final Logger LOG = getLogger(WebServer.class.getName());
+	private static final String FILE_HTML = "hotspot.html";
+	private static final Pattern REGEX_AGENT =
+			Pattern.compile("Android ([0-9]+)");
+
+	private final Context ctx;
+
+	WebServer(Context ctx) {
+		super(PORT);
+		this.ctx = ctx;
+	}
+
+	@Override
+	public void start() throws IOException {
+		start(NanoHTTPD.SOCKET_READ_TIMEOUT, false);
+	}
+
+	@Override
+	public Response serve(IHTTPSession session) {
+		if (session.getUri().endsWith("favicon.ico")) {
+			return newFixedLengthResponse(NOT_FOUND, MIME_PLAINTEXT,
+					NOT_FOUND.getDescription());
+		}
+		if (session.getUri().endsWith(".apk")) {
+			return serveApk();
+		}
+		Response res;
+		try {
+			String html = getHtml(session.getHeaders().get("user-agent"));
+			res = newFixedLengthResponse(OK, MIME_HTML, html);
+		} catch (Exception e) {
+			logException(LOG, WARNING, e);
+			res = newFixedLengthResponse(INTERNAL_ERROR, MIME_PLAINTEXT,
+					ctx.getString(R.string.hotspot_error_web_server_serve));
+		}
+		return res;
+	}
+
+	private String getHtml(@Nullable String userAgent) throws Exception {
+		Document doc;
+		try (InputStream is = ctx.getAssets().open(FILE_HTML)) {
+			doc = Jsoup.parse(is, UTF_8.name(), "");
+		}
+		String app = ctx.getString(R.string.app_name);
+		String appV = app + " " + VERSION_NAME;
+		String filename = getApkFileName();
+		doc.select("#download_title").first()
+				.text(ctx.getString(R.string.website_download_title, appV));
+		doc.select("#download_intro").first()
+				.text(ctx.getString(R.string.website_download_intro, app));
+		doc.select(".button").first().attr("href", filename);
+		doc.select("#download_button").first()
+				.text(ctx.getString(R.string.website_download_title, app));
+		doc.select("#download_outro").first()
+				.text(ctx.getString(R.string.website_download_outro));
+		doc.select("#troubleshooting_title").first()
+				.text(ctx.getString(R.string.website_troubleshooting_title));
+		doc.select("#troubleshooting_1").first()
+				.text(ctx.getString(R.string.website_troubleshooting_1));
+		doc.select("#troubleshooting_2").first()
+				.text(getUnknownSourcesString(userAgent));
+		return doc.outerHtml();
+	}
+
+	private String getUnknownSourcesString(@Nullable String userAgent) {
+		boolean is8OrHigher = false;
+		if (userAgent != null) {
+			Matcher matcher = REGEX_AGENT.matcher(userAgent);
+			if (matcher.find()) {
+				int androidMajorVersion =
+						Integer.parseInt(requireNonNull(matcher.group(1)));
+				is8OrHigher = androidMajorVersion >= 8;
+			}
+		}
+		return is8OrHigher ?
+				ctx.getString(R.string.website_troubleshooting_2_new) :
+				ctx.getString(R.string.website_troubleshooting_2_old);
+	}
+
+	private Response serveApk() {
+		String mime = "application/vnd.android.package-archive";
+
+		File file = new File(ctx.getPackageCodePath());
+		long fileLen = file.length();
+
+		Response res;
+		try {
+			FileInputStream fis = new FileInputStream(file);
+			res = newFixedLengthResponse(OK, mime, fis, fileLen);
+			res.addHeader("Content-Length", "" + fileLen);
+		} catch (FileNotFoundException e) {
+			logException(LOG, WARNING, e);
+			res = newFixedLengthResponse(NOT_FOUND, MIME_PLAINTEXT,
+					ctx.getString(R.string.hotspot_error_web_server_serve));
+		}
+		return res;
+	}
+}

briar-android/src/main/java/org/briarproject/briar/android/hotspot/WebServerManager.java

@@ -0,0 +1,113 @@
+package org.briarproject.briar.android.hotspot;
+
+import android.app.Application;
+import android.graphics.Bitmap;
+import android.util.DisplayMetrics;
+
+import org.briarproject.bramble.api.lifecycle.IoExecutor;
+import org.briarproject.bramble.api.nullsafety.MethodsNotNullByDefault;
+import org.briarproject.bramble.api.nullsafety.ParametersNotNullByDefault;
+import org.briarproject.briar.android.hotspot.HotspotState.WebsiteConfig;
+import org.briarproject.briar.android.util.QrCodeUtils;
+
+import java.io.IOException;
+import java.net.InetAddress;
+import java.net.InterfaceAddress;
+import java.net.NetworkInterface;
+import java.util.logging.Logger;
+
+import javax.inject.Inject;
+
+import androidx.annotation.Nullable;
+import androidx.annotation.UiThread;
+
+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.util.LogUtils.logException;
+import static org.briarproject.bramble.util.NetworkUtils.getNetworkInterfaces;
+import static org.briarproject.briar.android.hotspot.WebServer.PORT;
+import static org.briarproject.briar.android.util.QrCodeUtils.HOTSPOT_QRCODE_FACTOR;
+
+@MethodsNotNullByDefault
+@ParametersNotNullByDefault
+class WebServerManager {
+
+	interface WebServerListener {
+		@IoExecutor
+		void onWebServerStarted(WebsiteConfig websiteConfig);
+
+		@IoExecutor
+		void onWebServerError();
+	}
+
+	private static final Logger LOG =
+			getLogger(WebServerManager.class.getName());
+
+	private final WebServer webServer;
+	private final DisplayMetrics dm;
+
+	private volatile WebServerListener listener;
+
+	@Inject
+	WebServerManager(Application ctx) {
+		webServer = new WebServer(ctx);
+		dm = ctx.getResources().getDisplayMetrics();
+	}
+
+	@UiThread
+	void setListener(WebServerListener listener) {
+		this.listener = listener;
+	}
+
+	@IoExecutor
+	void startWebServer() {
+		try {
+			webServer.start();
+			onWebServerStarted();
+		} catch (IOException e) {
+			logException(LOG, WARNING, e);
+			listener.onWebServerError();
+		}
+	}
+
+	@IoExecutor
+	private void onWebServerStarted() {
+		String url = "http://192.168.49.1:" + PORT;
+		InetAddress address = getAccessPointAddress();
+		if (address == null) {
+			LOG.info(
+					"Could not find access point address, assuming 192.168.49.1");
+		} else {
+			if (LOG.isLoggable(INFO)) {
+				LOG.info("Access point address " + address.getHostAddress());
+			}
+			url = "http://" + address.getHostAddress() + ":" + PORT;
+		}
+		Bitmap qrCode = QrCodeUtils.createQrCode(
+				(int) (dm.heightPixels * HOTSPOT_QRCODE_FACTOR), url);
+		listener.onWebServerStarted(new WebsiteConfig(url, qrCode));
+	}
+
+	/**
+	 * It is safe to call this more than once and it won't throw.
+	 */
+	@IoExecutor
+	void stopWebServer() {
+		webServer.stop();
+	}
+
+	@Nullable
+	private static InetAddress getAccessPointAddress() {
+		for (NetworkInterface i : getNetworkInterfaces()) {
+			if (i.getName().startsWith("p2p")) {
+				for (InterfaceAddress a : i.getInterfaceAddresses()) {
+					// we consider only IPv4 addresses
+					if (a.getAddress().getAddress().length == 4)
+						return a.getAddress();
+				}
+			}
+		}
+		return null;
+	}
+}

briar-android/src/main/java/org/briarproject/briar/android/hotspot/WebsiteFragment.java

@@ -0,0 +1,36 @@
+package org.briarproject.briar.android.hotspot;
+
+import android.os.Bundle;
+import android.view.View;
+
+import org.briarproject.bramble.api.nullsafety.MethodsNotNullByDefault;
+import org.briarproject.bramble.api.nullsafety.ParametersNotNullByDefault;
+
+import androidx.annotation.Nullable;
+import androidx.fragment.app.Fragment;
+
+import static android.view.View.GONE;
+
+@MethodsNotNullByDefault
+@ParametersNotNullByDefault
+public class WebsiteFragment extends AbstractTabsFragment {
+
+	public final static String TAG = WebsiteFragment.class.getName();
+
+	@Override
+	public void onViewCreated(View view, @Nullable Bundle savedInstanceState) {
+		super.onViewCreated(view, savedInstanceState);
+		connectedButton.setVisibility(GONE);
+	}
+
+	@Override
+	protected Fragment getFirstFragment() {
+		return ManualHotspotFragment.newInstance(false);
+	}
+
+	@Override
+	protected Fragment getSecondFragment() {
+		return QrHotspotFragment.newInstance(false);
+	}
+
+}

briar-android/src/main/java/org/briarproject/briar/android/removabledrive/ChooserFragment.java

@@ -11,6 +11,7 @@ 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.widget.OnboardingFullDialogFragment;
 
 import javax.inject.Inject;
 
@@ -51,6 +52,10 @@ public class ChooserFragment extends Fragment {
 				container, false);
 
 		scrollView = (ScrollView) v;
+
+		Button buttonLearnMore = v.findViewById(R.id.buttonLearnMore);
+		buttonLearnMore.setOnClickListener(e -> showLearnMoreDialog());
+
 		Button sendButton = v.findViewById(R.id.sendButton);
 		sendButton.setOnClickListener(i -> viewModel.startSendData());
 
@@ -75,4 +80,10 @@ public class ChooserFragment extends Fragment {
 		}
 	}
 
+	private void showLearnMoreDialog() {
+		OnboardingFullDialogFragment.newInstance(
+				R.string.removable_drive_menu_title,
+				R.string.removable_drive_explanation
+		).show(getChildFragmentManager(), OnboardingFullDialogFragment.TAG);
+	}
 }

briar-android/src/main/java/org/briarproject/briar/android/reporting/BriarExceptionHandler.java

@@ -2,6 +2,7 @@ package org.briarproject.briar.android.reporting;
 
 import android.app.Application;
 import android.os.Process;
+import android.util.Log;
 
 import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
 import org.briarproject.briar.android.logging.LogEncrypter;
@@ -10,6 +11,7 @@ import java.lang.Thread.UncaughtExceptionHandler;
 
 import javax.inject.Inject;
 
+import static org.briarproject.briar.android.TestingConstants.IS_DEBUG_BUILD;
 import static org.briarproject.briar.android.util.UiUtils.startDevReportActivity;
 
 @NotNullByDefault
@@ -28,13 +30,15 @@ class BriarExceptionHandler implements UncaughtExceptionHandler {
 
 	@Override
 	public void uncaughtException(Thread t, Throwable e) {
+		if (IS_DEBUG_BUILD) Log.w("Uncaught exception", e);
+
 		// encrypt logs to disk before handing over to new process
 		// the intent has limited space, so we can't reliably store them there.
 		byte[] logKey = logEncrypter.encryptLogs();
 
 		// activity runs in its own process, so we can kill the old one
 		startDevReportActivity(app.getApplicationContext(),
-				CrashReportActivity.class, e, appStartTime, logKey);
+				CrashReportActivity.class, e, appStartTime, logKey, null);
 		Process.killProcess(Process.myPid());
 		System.exit(10);
 	}

briar-android/src/main/java/org/briarproject/briar/android/reporting/CrashReportActivity.java

@@ -33,6 +33,7 @@ import static java.util.Objects.requireNonNull;
 public class CrashReportActivity extends BaseActivity
 		implements BaseFragmentListener {
 
+	public static final String EXTRA_INITIAL_COMMENT = "initialComment";
 	public static final String EXTRA_THROWABLE = "throwable";
 	public static final String EXTRA_APP_START_TIME = "appStartTime";
 	public static final String EXTRA_APP_LOGCAT = "logcat";
@@ -55,10 +56,11 @@ public class CrashReportActivity extends BaseActivity
 		setContentView(R.layout.activity_dev_report);
 
 		Intent intent = getIntent();
+		String initialComment = intent.getStringExtra(EXTRA_INITIAL_COMMENT);
 		Throwable t = (Throwable) intent.getSerializableExtra(EXTRA_THROWABLE);
 		long appStartTime = intent.getLongExtra(EXTRA_APP_START_TIME, -1);
 		byte[] logKey = intent.getByteArrayExtra(EXTRA_APP_LOGCAT);
-		viewModel.init(t, appStartTime, logKey);
+		viewModel.init(t, appStartTime, logKey, initialComment);
 		viewModel.getShowReport().observeEvent(this, show -> {
 			if (show) displayFragment(true);
 		});

briar-android/src/main/java/org/briarproject/briar/android/reporting/ReportFormFragment.java

@@ -78,6 +78,9 @@ public class ReportFormFragment extends BaseFragment {
 		list = v.findViewById(R.id.list);
 		progress = v.findViewById(R.id.progress_wheel);
 
+		if (viewModel.getInitialComment() != null)
+			userCommentView.setText(viewModel.getInitialComment());
+
 		if (viewModel.isFeedback()) {
 			includeDebugReport
 					.setText(getString(R.string.include_debug_report_feedback));

briar-android/src/main/java/org/briarproject/briar/android/reporting/ReportViewModel.java

@@ -64,6 +64,8 @@ class ReportViewModel extends AndroidViewModel {
 	private final MutableLiveEvent<Integer> closeReport =
 			new MutableLiveEvent<>();
 	private boolean isFeedback;
+	@Nullable
+	private String initialComment;
 
 	@Inject
 	ReportViewModel(@NonNull Application application,
@@ -80,7 +82,8 @@ class ReportViewModel extends AndroidViewModel {
 	}
 
 	void init(@Nullable Throwable t, long appStartTime,
-			@Nullable byte[] logKey) {
+			@Nullable byte[] logKey, @Nullable String initialComment) {
+		this.initialComment = initialComment;
 		isFeedback = t == null;
 		if (reportData.getValue() == null) new SingleShotAndroidExecutor(() -> {
 			String decryptedLogs;
@@ -103,6 +106,11 @@ class ReportViewModel extends AndroidViewModel {
 		}).start();
 	}
 
+	@Nullable
+	String getInitialComment() {
+		return initialComment;
+	}
+
 	boolean isFeedback() {
 		return isFeedback;
 	}
@@ -140,7 +148,7 @@ class ReportViewModel extends AndroidViewModel {
 
 	/**
 	 * The content of the report that will be loaded after
-	 * {@link #init(Throwable, long, byte[])} was called.
+	 * {@link #init(Throwable, long, byte[], String)} was called.
 	 */
 	LiveData<ReportData> getReportData() {
 		return reportData;

briar-android/src/main/java/org/briarproject/briar/android/settings/SettingsFragment.java

@@ -36,6 +36,7 @@ public class SettingsFragment extends PreferenceFragmentCompat {
 	private static final String PREF_KEY_FEEDBACK = "pref_key_send_feedback";
 	private static final String PREF_KEY_DEV = "pref_key_dev";
 	private static final String PREF_KEY_EXPLODE = "pref_key_explode";
+	private static final String PREF_KEY_SHARE_APP = "pref_key_share_app";
 
 	@Inject
 	ViewModelProvider.Factory viewModelFactory;
@@ -85,6 +86,12 @@ public class SettingsFragment extends PreferenceFragmentCompat {
 			PreferenceGroup dev = requireNonNull(findPreference(PREF_KEY_DEV));
 			dev.setVisible(false);
 		}
+
+		if (!viewModel.shouldEnableShareAppViaOfflineHotspot()) {
+			Preference shareApp =
+					requireNonNull(findPreference(PREF_KEY_SHARE_APP));
+			shareApp.setVisible(false);
+		}
 	}
 
 	@Override

briar-android/src/main/java/org/briarproject/briar/android/settings/SettingsViewModel.java

@@ -262,4 +262,8 @@ class SettingsViewModel extends DbViewModel implements EventListener {
 		return screenLockTimeout;
 	}
 
+	boolean shouldEnableShareAppViaOfflineHotspot() {
+		return featureFlags.shouldEnableShareAppViaOfflineHotspot();
+	}
+
 }

briar-android/src/main/java/org/briarproject/briar/android/util/QrCodeUtils.java

@@ -1,4 +1,4 @@
-package org.briarproject.briar.android.contact.add.nearby;
+package org.briarproject.briar.android.util;
 
 import android.graphics.Bitmap;
 import android.util.DisplayMetrics;
@@ -22,17 +22,23 @@ 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 = getLogger(QrCodeUtils.class.getName());
 
+	public static final double HOTSPOT_QRCODE_FACTOR = 0.35;
+
 	@Nullable
-	static Bitmap createQrCode(DisplayMetrics dm, String input) {
-		int smallestDimen = Math.min(dm.widthPixels, dm.heightPixels);
+	public static Bitmap createQrCode(DisplayMetrics dm, String input) {
+		return createQrCode(Math.min(dm.widthPixels, dm.heightPixels), input);
+	}
+
+	@Nullable
+	public static Bitmap createQrCode(int edgeLen, String input) {
 		try {
 			// Generate QR code
 			BitMatrix encoded = new QRCodeWriter().encode(input, QR_CODE,
-					smallestDimen, smallestDimen);
+					edgeLen, edgeLen);
 			return renderQrCode(encoded);
 		} catch (WriterException e) {
 			logException(LOG, WARNING, e);

briar-android/src/main/java/org/briarproject/briar/android/util/UiUtils.java

@@ -61,6 +61,7 @@ import androidx.core.util.Consumer;
 import androidx.fragment.app.Fragment;
 import androidx.fragment.app.FragmentActivity;
 import androidx.fragment.app.FragmentManager;
+import androidx.fragment.app.FragmentTransaction;
 import androidx.lifecycle.LifecycleOwner;
 import androidx.lifecycle.LiveData;
 import androidx.lifecycle.Observer;
@@ -111,6 +112,7 @@ import static org.briarproject.briar.BuildConfig.APPLICATION_ID;
 import static org.briarproject.briar.android.TestingConstants.EXPIRY_DATE;
 import static org.briarproject.briar.android.reporting.CrashReportActivity.EXTRA_APP_LOGCAT;
 import static org.briarproject.briar.android.reporting.CrashReportActivity.EXTRA_APP_START_TIME;
+import static org.briarproject.briar.android.reporting.CrashReportActivity.EXTRA_INITIAL_COMMENT;
 import static org.briarproject.briar.android.reporting.CrashReportActivity.EXTRA_THROWABLE;
 
 @MethodsNotNullByDefault
@@ -137,13 +139,18 @@ public class UiUtils {
 
 	public static void showFragment(FragmentManager fm, Fragment f,
 			@Nullable String tag) {
-		fm.beginTransaction()
+		showFragment(fm, f, tag, true);
+	}
+
+	public static void showFragment(FragmentManager fm, Fragment f,
+			@Nullable String tag, boolean addToBackStack) {
+		FragmentTransaction ta = fm.beginTransaction()
 				.setCustomAnimations(R.anim.step_next_in,
 						R.anim.step_previous_out, R.anim.step_previous_in,
 						R.anim.step_next_out)
-				.replace(R.id.fragmentContainer, f, tag)
-				.addToBackStack(tag)
-				.commit();
+				.replace(R.id.fragmentContainer, f, tag);
+		if (addToBackStack) ta.addToBackStack(tag);
+		ta.commit();
 	}
 
 	public static String getContactDisplayName(Author author,
@@ -410,17 +417,25 @@ public class UiUtils {
 	}
 
 	public static void triggerFeedback(Context ctx) {
-		startDevReportActivity(ctx, FeedbackActivity.class, null, null, null);
+		triggerFeedback(ctx, null);
+	}
+
+	public static void triggerFeedback(Context ctx,
+			@Nullable String initialComment) {
+		startDevReportActivity(ctx, FeedbackActivity.class, null, null, null,
+				initialComment);
 	}
 
 	public static void startDevReportActivity(Context ctx,
 			Class<? extends FragmentActivity> activity, @Nullable Throwable t,
-			@Nullable Long appStartTime, @Nullable byte[] logKey) {
+			@Nullable Long appStartTime, @Nullable byte[] logKey, @Nullable
+			String initialComment) {
 		final Intent dialogIntent = new Intent(ctx, activity);
 		dialogIntent.setFlags(FLAG_ACTIVITY_NEW_TASK);
 		dialogIntent.putExtra(EXTRA_THROWABLE, t);
 		dialogIntent.putExtra(EXTRA_APP_START_TIME, appStartTime);
 		dialogIntent.putExtra(EXTRA_APP_LOGCAT, logKey);
+		dialogIntent.putExtra(EXTRA_INITIAL_COMMENT, initialComment);
 		ctx.startActivity(dialogIntent);
 	}
 
@@ -546,4 +561,5 @@ public class UiUtils {
 		activity.getWindow().setSoftInputMode(SOFT_INPUT_ADJUST_RESIZE |
 				SOFT_INPUT_STATE_HIDDEN);
 	}
+
 }

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

@@ -3,6 +3,7 @@ package org.briarproject.briar.android.view;
 import android.content.Context;
 import android.content.res.TypedArray;
 import android.graphics.Typeface;
+import android.graphics.drawable.Drawable;
 import android.util.AttributeSet;
 import android.view.LayoutInflater;
 import android.widget.ImageView;
@@ -29,6 +30,7 @@ import im.delight.android.identicons.IdenticonDrawable;
 import static android.content.Context.LAYOUT_INFLATER_SERVICE;
 import static android.graphics.Typeface.BOLD;
 import static android.util.TypedValue.COMPLEX_UNIT_PX;
+import static androidx.appcompat.content.res.AppCompatResources.getDrawable;
 import static org.briarproject.briar.android.util.UiUtils.getContactDisplayName;
 import static org.briarproject.briar.android.util.UiUtils.resolveAttribute;
 import static org.briarproject.briar.api.identity.AuthorInfo.Status.NONE;
@@ -177,14 +179,14 @@ public class AuthorView extends ConstraintLayout {
 			case RSS_FEED:
 				avatarIcon.setVisibility(INVISIBLE);
 				date.setVisibility(VISIBLE);
-				avatar.setImageResource(R.drawable.ic_rss_feed);
+				setRssVectorAvatar();
 				setAvatarSize(R.dimen.blogs_avatar_normal_size);
 				setTextSize(authorName, R.dimen.text_size_small);
 				break;
 			case RSS_FEED_REBLOGGED:
 				avatarIcon.setVisibility(INVISIBLE);
 				date.setVisibility(VISIBLE);
-				avatar.setImageResource(R.drawable.ic_rss_feed);
+				setRssVectorAvatar();
 				setAvatarSize(R.dimen.blogs_avatar_comment_size);
 				setTextSize(authorName, R.dimen.text_size_tiny);
 				break;
@@ -204,4 +206,16 @@ public class AuthorView extends ConstraintLayout {
 		v.setTextSize(COMPLEX_UNIT_PX, textSize);
 	}
 
+	/**
+	 * Applies special hack to use AppCompat vector drawable support
+	 * when setting the RSS vector drawable to the avatar view.
+	 * {@link ImageView#setImageResource(int)} is not working as
+	 * {@link CircleImageView} is not using
+	 * {@link androidx.appcompat.widget.AppCompatImageView}.
+	 */
+	private void setRssVectorAvatar() {
+		Drawable d = getDrawable(getContext(), R.drawable.ic_rss_feed);
+		avatar.setImageDrawable(d);
+	}
+
 }

briar-android/src/main/java/org/briarproject/briar/api/android/AndroidNotificationManager.java

@@ -31,6 +31,7 @@ public interface AndroidNotificationManager {
 	int FORUM_POST_NOTIFICATION_ID = 6;
 	int BLOG_POST_NOTIFICATION_ID = 7;
 	int CONTACT_ADDED_NOTIFICATION_ID = 8;
+	int HOTSPOT_NOTIFICATION_ID = 9;
 
 	// Channel IDs
 	String CONTACT_CHANNEL_ID = "contacts";
@@ -42,12 +43,15 @@ public interface AndroidNotificationManager {
 	String ONGOING_CHANNEL_OLD_ID = "zForegroundService";
 	String ONGOING_CHANNEL_ID = "zForegroundService2";
 	String REMINDER_CHANNEL_ID = "zSignInReminder";
+	String HOTSPOT_CHANNEL_ID = "zHotspot";
+
 	// This channel is no longer used - keep the ID so we can remove the
 	// channel from existing installations
 	String FAILURE_CHANNEL_ID = "zStartupFailure";
 
 	// Actions for pending intents
 	String ACTION_DISMISS_REMINDER = "dismissReminder";
+	String ACTION_STOP_HOTSPOT = "stopHotspot";
 
 	Notification getForegroundNotification();
 
@@ -96,4 +100,8 @@ public interface AndroidNotificationManager {
 	void blockAllBlogPostNotifications();
 
 	void unblockAllBlogPostNotifications();
+
+	void showHotspotNotification();
+
+	void clearHotspotNotification();
 }

briar-android/src/main/res/drawable-anydpi-v24/notification_hotspot.xml

@@ -0,0 +1,16 @@
+<vector xmlns:android="http://schemas.android.com/apk/res/android"
+	android:width="24dp"
+	android:height="24dp"
+	android:tint="#FFFFFF"
+	android:viewportWidth="24"
+	android:viewportHeight="24">
+	<group
+		android:scaleX="0.92"
+		android:scaleY="0.92"
+		android:translateX="0.96"
+		android:translateY="0.96">
+		<path
+			android:fillColor="@android:color/white"
+			android:pathData="M12,11c-1.1,0 -2,0.9 -2,2s0.9,2 2,2 2,-0.9 2,-2 -0.9,-2 -2,-2zM18,13c0,-3.31 -2.69,-6 -6,-6s-6,2.69 -6,6c0,2.22 1.21,4.15 3,5.19l1,-1.74c-1.19,-0.7 -2,-1.97 -2,-3.45 0,-2.21 1.79,-4 4,-4s4,1.79 4,4c0,1.48 -0.81,2.75 -2,3.45l1,1.74c1.79,-1.04 3,-2.97 3,-5.19zM12,3C6.48,3 2,7.48 2,13c0,3.7 2.01,6.92 4.99,8.65l1,-1.73C5.61,18.53 4,15.96 4,13c0,-4.42 3.58,-8 8,-8s8,3.58 8,8c0,2.96 -1.61,5.53 -4,6.92l1,1.73c2.99,-1.73 5,-4.95 5,-8.65 0,-5.52 -4.48,-10 -10,-10z" />
+	</group>
+</vector>

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

@@ -0,0 +1,21 @@
+<vector xmlns:android="http://schemas.android.com/apk/res/android"
+	android:width="100dp"
+	android:height="35dp"
+	android:viewportWidth="500"
+	android:viewportHeight="175">
+	<path
+		android:fillColor="?attr/colorControlNormal"
+		android:pathData="m459.809,167.16 l-4.327,-4.334 -7.07,-2.427c-3.888,-1.335 -8.723,-2.996 -10.744,-3.691l-3.674,-1.263 3.524,-0.173c8.242,-0.404 12.988,-4.007 14.336,-10.884 0.796,-4.061 1.129,-17.298 0.83,-33.041 -0.153,-8.084 -0.166,-15.416 -0.028,-16.295 0.138,-0.878 0.535,-2.42 0.883,-3.426 1.222,-3.532 0.34,-11.908 -1.858,-17.631 -0.348,-0.908 -1.934,-4.215 -3.524,-7.35 -4.158,-8.2 -4.505,-8.942 -4.893,-10.484 -0.459,-1.821 -0.212,-5.435 0.463,-6.766 0.666,-1.315 2.157,-2.916 3.246,-3.487 1.299,-0.68 2.616,0.122 4.686,2.855 3.422,4.516 14.001,19.441 15.732,22.193 3.746,5.956 5.956,11.165 7.972,18.788 0.655,2.475 1.885,6.997 2.735,10.05 0.849,3.053 2.714,10.158 4.144,15.79l2.6,10.24 4.65,5.193c2.557,2.856 5.798,6.464 7.2,8.017 1.403,1.553 2.55,2.975 2.55,3.161 0,0.335 -34.5,29.299 -34.899,29.299 -0.115,0 -2.156,-1.95 -4.535,-4.334zM365.944,150.772c-1.258,-0.628 -2.206,-1.379 -2.914,-2.307 -2.089,-2.736 -1.95,2.369 -1.864,-68.482l0.078,-64.039 0.661,-1.235c1.015,-1.898 1.992,-2.911 3.74,-3.879l1.6,-0.886 37.784,-0.08c42.456,-0.089 39.402,-0.248 42.116,2.192 0.875,0.787 1.757,1.959 2.184,2.904 0.713,1.577 0.716,1.638 0.806,14.204l0.09,12.62 -1.798,-0.13c-1.426,-0.103 -2.081,0.007 -3.166,0.532 -2.013,0.974 -3.94,2.899 -5.115,5.108l-1.037,1.95 -0.007,-12.825 -0.007,-12.825h-33.6,-33.6v51.3,51.3h33.599,33.599l0.076,-34.425c0.073,-32.96 0.098,-34.361 0.591,-32.925 0.283,0.825 1.806,3.997 3.383,7.05 5.493,10.626 5.405,9.86 5.396,47.203 -0.007,27.621 -0.124,29.951 -1.662,33.109 -1.071,2.199 -2.711,3.71 -5.058,4.66l-1.674,0.677 -36.168,0.08 -36.168,0.08 -1.864,-0.931zM408.344,145.734c2.871,-1.309 4.458,-3.678 4.43,-6.617 -0.039,-4.116 -3.109,-7.223 -7.136,-7.223 -2.12,0 -3.567,0.609 -5.164,2.172 -2.245,2.198 -2.754,5.439 -1.301,8.287 0.713,1.398 2.521,3.009 3.962,3.53 1.497,0.542 3.84,0.475 5.209,-0.149z" />
+	<path
+		android:fillColor="?attr/colorControlNormal"
+		android:pathData="m39.434,167.16 l4.327,-4.334 7.07,-2.427c3.888,-1.335 8.723,-2.996 10.744,-3.691l3.674,-1.263 -3.524,-0.173c-8.242,-0.404 -12.988,-4.007 -14.336,-10.884 -0.796,-4.061 -1.129,-17.298 -0.83,-33.041 0.153,-8.084 0.166,-15.416 0.028,-16.295 -0.138,-0.878 -0.535,-2.42 -0.883,-3.426 -1.222,-3.532 -0.34,-11.908 1.858,-17.631 0.348,-0.908 1.934,-4.215 3.524,-7.35 4.158,-8.2 4.505,-8.942 4.893,-10.484 0.459,-1.821 0.212,-5.435 -0.463,-6.766 -0.666,-1.315 -2.157,-2.916 -3.246,-3.487 -1.299,-0.68 -2.616,0.122 -4.686,2.855 -3.422,4.516 -14.001,19.441 -15.732,22.193 -3.746,5.956 -5.956,11.165 -7.972,18.788 -0.655,2.475 -1.885,6.997 -2.735,10.05 -0.849,3.053 -2.714,10.158 -4.144,15.79L14.4,125.824 9.75,131.017c-2.557,2.856 -5.798,6.464 -7.2,8.017 -1.403,1.553 -2.55,2.975 -2.55,3.161 0,0.335 34.5,29.299 34.899,29.299 0.115,0 2.156,-1.95 4.535,-4.334zM133.299,150.772c1.258,-0.628 2.206,-1.379 2.914,-2.307 2.089,-2.736 1.95,2.369 1.864,-68.482l-0.078,-64.039 -0.661,-1.235c-1.015,-1.898 -1.992,-2.911 -3.74,-3.879L132,9.944 94.216,9.865c-42.456,-0.089 -39.402,-0.248 -42.116,2.192 -0.875,0.787 -1.757,1.959 -2.184,2.904 -0.713,1.577 -0.716,1.638 -0.806,14.204l-0.09,12.62 1.798,-0.13c1.426,-0.103 2.081,0.007 3.166,0.532 2.013,0.974 3.94,2.899 5.115,5.108l1.037,1.95 0.007,-12.825 0.007,-12.825h33.6,33.6v51.3,51.3L93.752,126.194 60.153,126.194l-0.076,-34.425c-0.073,-32.96 -0.098,-34.361 -0.591,-32.925 -0.283,0.825 -1.806,3.997 -3.383,7.05 -5.493,10.626 -5.405,9.86 -5.396,47.203 0.007,27.621 0.124,29.951 1.662,33.109 1.071,2.199 2.711,3.71 5.058,4.66l1.674,0.677 36.168,0.08 36.168,0.08 1.864,-0.931zM90.9,145.734c-2.871,-1.309 -4.458,-3.678 -4.43,-6.617 0.039,-4.116 3.109,-7.223 7.136,-7.223 2.12,0 3.567,0.609 5.164,2.172 2.245,2.198 2.754,5.439 1.301,8.287 -0.713,1.398 -2.521,3.009 -3.962,3.53 -1.497,0.542 -3.84,0.475 -5.209,-0.149z" />
+	<path
+		android:fillColor="#0a3d91"
+		android:pathData="m247.254,71.979h4.736c13.165,0 23.763,10.599 23.763,23.763v32.175c0,13.165 -10.599,23.763 -23.763,23.763h-4.736c-13.165,0 -23.763,-10.599 -23.763,-23.763V95.743c0,-13.165 10.599,-23.763 23.763,-23.763z" />
+	<path
+		android:fillColor="#0a3d91"
+		android:pathData="m143.679,23.557c-1.59,2.624 0.182,5.575 2.785,6.643 2.695,1.572 6.171,4.987 9.148,2.232 2.233,-2.04 0.601,-5.728 -2.041,-6.67 -3.064,-1.677 -6.552,-5.515 -9.891,-2.205zM351.705,23.129c-2.768,1.961 -7.068,2.695 -8.378,6.043 -0.642,2.731 1.936,4.993 4.584,4.426 3.202,-1.638 7.057,-2.842 9.178,-5.948 0.569,-2.604 -1.493,-5.351 -4.268,-4.746 -0.416,-0.108 -0.76,0.035 -1.117,0.224zM324.943,36.301c-2.934,1.708 -7.32,1.923 -8.931,5.153 -0.908,2.654 1.432,5.159 4.124,4.861 3.356,-1.304 7.32,-2.113 9.737,-5.002 0.814,-2.538 -0.977,-5.47 -3.796,-5.129 -0.403,-0.146 -0.76,-0.038 -1.133,0.117zM169.707,38.764c-1.219,2.712 0.757,5.461 3.444,6.145 2.858,1.081 6.669,4.118 9.312,1.234 2.315,-2.037 0.339,-5.835 -2.41,-6.418 -3.328,-1.176 -7.385,-4.714 -10.346,-0.961zM296.98,46.381c-3.123,1.309 -7.492,0.971 -9.492,3.97 -1.232,2.519 0.773,5.298 3.48,5.34 3.487,-0.907 7.567,-1.113 10.303,-3.739 1.114,-2.422 -0.312,-5.546 -3.152,-5.551 -0.383,-0.196 -0.75,-0.127 -1.139,-0.02zM199.49,47.926c-2.229,1.462 -2.68,4.866 -0.276,6.377 2.587,1.471 5.915,1.955 8.84,2.495 2.785,0.332 4.746,-2.479 3.891,-5.049 -2.043,-3.28 -6.472,-2.734 -9.717,-4.089 -0.913,0.089 -1.826,0.177 -2.738,0.266zM268.003,52.434c-3.276,0.789 -7.461,-0.188 -9.936,2.382 -1.65,2.268 -0.157,5.354 2.504,5.862 3.612,-0.292 7.718,0.091 10.84,-2.094 1.462,-2.228 0.523,-5.532 -2.285,-5.959 -0.349,-0.249 -0.722,-0.239 -1.123,-0.19zM228.554,53.852c-1.933,1.836 -1.765,5.267 0.871,6.321 2.809,0.989 6.171,0.847 9.144,0.861 2.799,-0.173 4.226,-3.29 2.924,-5.665 -2.604,-2.852 -6.847,-1.542 -10.293,-2.27 -0.882,0.251 -1.764,0.501 -2.646,0.752z" />
+	<path
+		android:fillColor="#ffffff"
+		android:pathData="m252.501,112.09 l11.656,-11.452 -17.126,-19.791 0.019,25.792 -9.142,-9.245 -3.125,3.091 11.521,11.581 -11.498,11.308c3.031,3.056 0,0 3.031,3.056l9.189,-8.973c0.044,4.735 0.004,27.165 0.004,27.165l17.102,-20.773zM251.424,92.519 L258.222,100.383 251.424,107.016zM251.4,132.547 L251.424,117.151 258.317,124.139z" />
+</vector>

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

@@ -0,0 +1,10 @@
+<vector xmlns:android="http://schemas.android.com/apk/res/android"
+	android:width="8dp"
+	android:height="8dp"
+	android:tint="?attr/colorControlNormal"
+	android:viewportWidth="24"
+	android:viewportHeight="24">
+	<path
+		android:fillColor="@android:color/white"
+		android:pathData="M12,2C6.47,2 2,6.47 2,12s4.47,10 10,10 10,-4.47 10,-10S17.53,2 12,2z" />
+</vector>

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

@@ -0,0 +1,10 @@
+<vector xmlns:android="http://schemas.android.com/apk/res/android"
+	android:width="24dp"
+	android:height="24dp"
+	android:tint="?attr/colorControlNormal"
+	android:viewportWidth="24"
+	android:viewportHeight="24">
+	<path
+		android:fillColor="@android:color/white"
+		android:pathData="M17.56,14.24c0.28,-0.69 0.44,-1.45 0.44,-2.24 0,-3.31 -2.69,-6 -6,-6 -0.79,0 -1.55,0.16 -2.24,0.44l1.62,1.62c0.2,-0.03 0.41,-0.06 0.62,-0.06 2.21,0 4,1.79 4,4 0,0.21 -0.02,0.42 -0.05,0.63l1.61,1.61zM12,4c4.42,0 8,3.58 8,8 0,1.35 -0.35,2.62 -0.95,3.74l1.47,1.47C21.46,15.69 22,13.91 22,12c0,-5.52 -4.48,-10 -10,-10 -1.91,0 -3.69,0.55 -5.21,1.47l1.46,1.46C9.37,4.34 10.65,4 12,4zM3.27,2.5L2,3.77l2.1,2.1C2.79,7.57 2,9.69 2,12c0,3.7 2.01,6.92 4.99,8.65l1,-1.73C5.61,17.53 4,14.96 4,12c0,-1.76 0.57,-3.38 1.53,-4.69l1.43,1.44C6.36,9.68 6,10.8 6,12c0,2.22 1.21,4.15 3,5.19l1,-1.74c-1.19,-0.7 -2,-1.97 -2,-3.45 0,-0.65 0.17,-1.25 0.44,-1.79l1.58,1.58L10,12c0,1.1 0.9,2 2,2l0.21,-0.02 0.01,0.01 7.51,7.51L21,20.23 4.27,3.5l-1,-1z" />
+</vector>

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

@@ -0,0 +1,40 @@
+<vector xmlns:android="http://schemas.android.com/apk/res/android"
+	android:width="24dp"
+	android:height="24dp"
+	android:tint="?attr/colorControlNormal"
+	android:viewportWidth="24"
+	android:viewportHeight="24">
+	<path
+		android:fillColor="@android:color/white"
+		android:pathData="M3,11h8V3H3V11zM5,5h4v4H5V5z" />
+	<path
+		android:fillColor="@android:color/white"
+		android:pathData="M3,21h8v-8H3V21zM5,15h4v4H5V15z" />
+	<path
+		android:fillColor="@android:color/white"
+		android:pathData="M13,3v8h8V3H13zM19,9h-4V5h4V9z" />
+	<path
+		android:fillColor="@android:color/white"
+		android:pathData="M19,19h2v2h-2z" />
+	<path
+		android:fillColor="@android:color/white"
+		android:pathData="M13,13h2v2h-2z" />
+	<path
+		android:fillColor="@android:color/white"
+		android:pathData="M15,15h2v2h-2z" />
+	<path
+		android:fillColor="@android:color/white"
+		android:pathData="M13,17h2v2h-2z" />
+	<path
+		android:fillColor="@android:color/white"
+		android:pathData="M15,19h2v2h-2z" />
+	<path
+		android:fillColor="@android:color/white"
+		android:pathData="M17,17h2v2h-2z" />
+	<path
+		android:fillColor="@android:color/white"
+		android:pathData="M17,13h2v2h-2z" />
+	<path
+		android:fillColor="@android:color/white"
+		android:pathData="M19,15h2v2h-2z" />
+</vector>

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

@@ -0,0 +1,12 @@
+<vector xmlns:android="http://schemas.android.com/apk/res/android"
+	xmlns:tools="http://schemas.android.com/tools"
+	android:width="24dp"
+	android:height="24dp"
+	android:tint="?android:attr/textColorPrimary"
+	android:viewportWidth="24.0"
+	android:viewportHeight="24.0"
+	tools:ignore="NewApi">
+	<path
+		android:fillColor="#FFFFFFFF"
+		android:pathData="M18,16.08c-0.76,0 -1.44,0.3 -1.96,0.77L8.91,12.7c0.05,-0.23 0.09,-0.46 0.09,-0.7s-0.04,-0.47 -0.09,-0.7l7.05,-4.11c0.54,0.5 1.25,0.81 2.04,0.81 1.66,0 3,-1.34 3,-3s-1.34,-3 -3,-3 -3,1.34 -3,3c0,0.24 0.04,0.47 0.09,0.7L8.04,9.81C7.5,9.31 6.79,9 6,9c-1.66,0 -3,1.34 -3,3s1.34,3 3,3c0.79,0 1.5,-0.31 2.04,-0.81l7.12,4.16c-0.05,0.21 -0.08,0.43 -0.08,0.65 0,1.61 1.31,2.92 2.92,2.92 1.61,0 2.92,-1.31 2.92,-2.92s-1.31,-2.92 -2.92,-2.92z" />
+</vector>

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

@@ -0,0 +1,10 @@
+<vector xmlns:android="http://schemas.android.com/apk/res/android"
+    android:width="24dp"
+    android:height="24dp"
+    android:tint="?attr/colorControlNormal"
+    android:viewportWidth="24"
+    android:viewportHeight="24">
+  <path
+      android:fillColor="@android:color/white"
+      android:pathData="M12,11c-1.1,0 -2,0.9 -2,2s0.9,2 2,2 2,-0.9 2,-2 -0.9,-2 -2,-2zM18,13c0,-3.31 -2.69,-6 -6,-6s-6,2.69 -6,6c0,2.22 1.21,4.15 3,5.19l1,-1.74c-1.19,-0.7 -2,-1.97 -2,-3.45 0,-2.21 1.79,-4 4,-4s4,1.79 4,4c0,1.48 -0.81,2.75 -2,3.45l1,1.74c1.79,-1.04 3,-2.97 3,-5.19zM12,3C6.48,3 2,7.48 2,13c0,3.7 2.01,6.92 4.99,8.65l1,-1.73C5.61,18.53 4,15.96 4,13c0,-4.42 3.58,-8 8,-8s8,3.58 8,8c0,2.96 -1.61,5.53 -4,6.92l1,1.73c2.99,-1.73 5,-4.95 5,-8.65 0,-5.52 -4.48,-10 -10,-10z" />
+</vector>

briar-android/src/main/res/layout/fragment_bluetooth_intro.xml

@@ -0,0 +1,51 @@
+<?xml version="1.0" encoding="utf-8"?>
+<ScrollView xmlns:android="http://schemas.android.com/apk/res/android"
+	xmlns:app="http://schemas.android.com/apk/res-auto"
+	xmlns:tools="http://schemas.android.com/tools"
+	android:layout_width="match_parent"
+	android:layout_height="match_parent"
+	android:fillViewport="true"
+	tools:context=".android.contact.connect.BluetoothIntroFragment">
+
+	<androidx.constraintlayout.widget.ConstraintLayout
+		android:layout_width="match_parent"
+		android:layout_height="wrap_content">
+
+		<androidx.appcompat.widget.AppCompatImageView
+			android:id="@+id/introImageView"
+			android:layout_width="0dp"
+			android:layout_height="0dp"
+			android:layout_margin="16dp"
+			app:layout_constraintBottom_toTopOf="@+id/introTextView"
+			app:layout_constraintEnd_toEndOf="parent"
+			app:layout_constraintHeight_percent="0.2"
+			app:layout_constraintStart_toStartOf="parent"
+			app:layout_constraintTop_toTopOf="parent"
+			app:srcCompat="@drawable/ic_bluetooth" />
+
+		<TextView
+			android:id="@+id/introTextView"
+			android:layout_width="0dp"
+			android:layout_height="wrap_content"
+			android:layout_margin="16dp"
+			android:text="@string/connect_via_bluetooth_intro"
+			app:layout_constraintBottom_toTopOf="@+id/startButton"
+			app:layout_constraintEnd_toEndOf="parent"
+			app:layout_constraintHorizontal_bias="0.5"
+			app:layout_constraintStart_toStartOf="parent"
+			app:layout_constraintTop_toBottomOf="@+id/introImageView" />
+
+		<Button
+			android:id="@+id/startButton"
+			style="@style/BriarButton"
+			android:layout_width="0dp"
+			android:layout_height="wrap_content"
+			android:layout_margin="16dp"
+			android:text="@string/start"
+			app:layout_constraintBottom_toBottomOf="parent"
+			app:layout_constraintEnd_toEndOf="parent"
+			app:layout_constraintStart_toStartOf="parent" />
+
+	</androidx.constraintlayout.widget.ConstraintLayout>
+
+</ScrollView>