Revert minSdkVersion to 21 to fix Robolectric tests.

FIXME: Desugaring ConcurrentHashMap.newKeySet() requires
desugar_jdk_libs version 2, which requires bumping the Android Gradle
plugin version. This seems to have broken Gradle Witness.

.gitlab-ci.yml

@@ -104,3 +104,12 @@ mailbox integration test:
   script:
     - (cd briar-mailbox; git fetch; git reset --hard origin/main)
     - MAILBOX_INTEGRATION_TESTS=true ./gradlew --info mailbox-integration-tests:test
+
+db_performance_comparison_test:
+  extends: .base-test
+  stage: optional_tests
+  script:
+    - OPTIONAL_TESTS=org.briarproject.bramble.db.H2SqliteDatabasePerformanceComparisonTest ./gradlew --info -Djava.security.egd=file:/dev/urandom :bramble-core:test --tests H2SqliteDatabasePerformanceComparisonTest
+  rules:
+    - when: manual
+

bramble-android/.gitignore

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

bramble-android/build.gradle

@@ -11,6 +11,8 @@ android {
 	}
 
 	defaultConfig {
+		// FIXME: sqlite-jdbc-crypt uses __register_atfork which is only available on API >= 23.
+		//  We might be able to solve this by recompiling (or asking upstream to recompile)
 		minSdkVersion 21
 		targetSdkVersion 33
 		versionCode 10506
@@ -37,6 +39,7 @@ android {
 
 configurations {
 	tor
+	sqliteJdbcCrypt
 }
 
 dependencies {
@@ -57,6 +60,8 @@ dependencies {
 	tor "org.briarproject:obfs4proxy-android:$obfs4proxy_version"
 	tor "org.briarproject:snowflake-android:$snowflake_version"
 
+	sqliteJdbcCrypt "io.github.willena:sqlite-jdbc:$sqlite_jdbc_crypt_version"
+
 	annotationProcessor "com.google.dagger:dagger-compiler:$dagger_version"
 
 	compileOnly 'javax.annotation:jsr250-api:1.0'
@@ -69,26 +74,50 @@ dependencies {
 	testImplementation "org.jmock:jmock-imposters:$jmock_version"
 }
 
-def torLibsDir = 'src/main/jniLibs'
+def jniLibsDir = 'src/main/jniLibs'
 
-task cleanTorBinaries {
+task cleanJniLibs {
-	outputs.dir torLibsDir
+	inputs.dir jniLibsDir
+	outputs.dir jniLibsDir
 	doLast {
-		delete fileTree(torLibsDir)
+		delete fileTree(jniLibsDir).filter { it.name.endsWith('.so') }
 	}
 }
 
-clean.dependsOn cleanTorBinaries
+clean.dependsOn cleanJniLibs
 
-task unpackTorBinaries {
+task unpackJniLibs {
-	outputs.dir torLibsDir
+	outputs.dir jniLibsDir
 	doLast {
+		// Tor
 		copy {
 			from configurations.tor.collect { zipTree(it) }
-			into torLibsDir
+			into jniLibsDir
+		}
+		// sqlite-jdbc-crypt
+		def archMap = [
+				aarch64: 'arm64-v8a',
+				arm    : 'armeabi-v7a',
+				x86    : 'x86',
+				x86_64 : 'x86_64'
+		]
+		configurations.sqliteJdbcCrypt.collect { File artifact ->
+			zipTree(artifact).each { File f ->
+				for (String arch : archMap.keySet()) {
+					if (f.absolutePath.endsWith("/Linux-Android/$arch/libsqlitejdbc.so")) {
+						def archDir = new File(jniLibsDir, archMap.get(arch))
+						archDir.mkdirs()
+						copy {
+							from f
+							into archDir
+						}
+						break
 					}
 				}
-	dependsOn cleanTorBinaries
+			}
+		}
+	}
+	dependsOn cleanJniLibs
 }
 
-preBuild.dependsOn unpackTorBinaries
+preBuild.dependsOn unpackJniLibs

bramble-android/proguard-rules.txt

@@ -6,6 +6,9 @@
 -dontwarn org.h2.**
 -dontnote org.h2.**
 
+# Keep sqlite-jdbc-crypt classes that are loaded via reflection or accessed via JNI
+-keep class org.sqlite.** { *; }
+
 -keep class dagger.** { *; }
 -dontwarn dagger.**
 -dontnote dagger.**

bramble-android/witness.gradle

@@ -18,6 +18,7 @@ dependencyVerification {
             'com.google.j2objc:j2objc-annotations:1.3:j2objc-annotations-1.3.jar:21af30c92267bd6122c0e0b4d20cccb6641a37eaf956c6540ec471d584e64a7b',
             'com.squareup:javapoet:1.13.0:javapoet-1.13.0.jar:4c7517e848a71b36d069d12bb3bf46a70fd4cda3105d822b0ed2e19c00b69291',
             'com.squareup:kotlinpoet:1.11.0:kotlinpoet-1.11.0.jar:2887ada1ca03dd83baa2758640d87e840d1907564db0ef88d2289c868a980492',
+            'io.github.willena:sqlite-jdbc:3.41.2.1:sqlite-jdbc-3.41.2.1.jar:fb60e7137c1791db89240701338d31ca42a0bec5508c1aab1c1131cf885f2309',
             'javax.annotation:jsr250-api:1.0:jsr250-api-1.0.jar:a1a922d0d9b6d183ed3800dfac01d1e1eb159f0e8c6f94736931c1def54a941f',
             'javax.inject:javax.inject:1:javax.inject-1.jar:91c77044a50c481636c32d916fd89c9118a72195390452c81065080f957de7ff',
             'junit:junit:4.13.2:junit-4.13.2.jar:8e495b634469d64fb8acfa3495a065cbacc8a0fff55ce1e31007be4c16dc57d3',

bramble-core/build.gradle

@@ -14,9 +14,9 @@ dependencies {
 	api "org.briarproject:onionwrapper-core:$onionwrapper_version"
 
 	implementation "org.bouncycastle:bcprov-jdk15to18:$bouncy_castle_version"
-	// 2.2.222 includes a precompiled Java 21 class that breaks the jetifier, so it will require
+	//noinspection GradleDependency
-	// a Gradle/AGP upgrade
+	implementation 'com.h2database:h2:1.4.192' // The last version that supports Java 1.6
-	implementation 'com.h2database:h2:2.2.220'
+	implementation "io.github.willena:sqlite-jdbc:$sqlite_jdbc_crypt_version"
 	implementation 'org.bitlet:weupnp:0.1.4'
 	implementation 'net.i2p.crypto:eddsa:0.2.0'
 	implementation 'org.whispersystems:curve25519-java:0.5.0'

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

@@ -413,6 +413,9 @@ interface Database<T> {
 	 */
 	Collection<MessageId> getMessageIds(T txn, GroupId g) throws DbException;
 
+	Collection<String> explainGetMessageIds(T txn, GroupId g)
+			throws DbException;
+
 	/**
 	 * Returns the IDs of any delivered messages in the given group with
 	 * metadata that matches all entries in the given query. If the query is

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

@@ -24,7 +24,7 @@ public class DatabaseModule {
 	@Singleton
 	Database<Connection> provideDatabase(DatabaseConfig config,
 			MessageFactory messageFactory, Clock clock) {
-		return new H2Database(config, messageFactory, clock);
+		return new SqliteDatabase(config, messageFactory, clock);
 	}
 
 	@Provides

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

@@ -4,14 +4,16 @@ class DatabaseTypes {
 
 	private final String hashType, secretType, binaryType;
 	private final String counterType, stringType;
+	private final String explainCommand; // FIXME: Remove
 
 	public DatabaseTypes(String hashType, String secretType, String binaryType,
-			String counterType, String stringType) {
+			String counterType, String stringType, String explainCommand) {
 		this.hashType = hashType;
 		this.secretType = secretType;
 		this.binaryType = binaryType;
 		this.counterType = counterType;
 		this.stringType = stringType;
+		this.explainCommand = explainCommand;
 	}
 
 	/**
@@ -22,6 +24,7 @@ class DatabaseTypes {
 	 * <li> _BINARY
 	 * <li> _COUNTER
 	 * <li> _STRING
+	 * <li> _EXPLAIN
 	 */
 	String replaceTypes(String s) {
 		s = s.replaceAll("_HASH", hashType);
@@ -29,6 +32,7 @@ class DatabaseTypes {
 		s = s.replaceAll("_BINARY", binaryType);
 		s = s.replaceAll("_COUNTER", counterType);
 		s = s.replaceAll("_STRING", stringType);
+		s = s.replaceAll("_EXPLAIN", explainCommand);
 		return s;
 	}
 }

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

@@ -38,11 +38,14 @@ class H2Database extends JdbcDatabase {
 
 	private static final String HASH_TYPE = "BINARY(32)";
 	private static final String SECRET_TYPE = "BINARY(32)";
-	private static final String BINARY_TYPE = "BINARY VARYING";
+	private static final String BINARY_TYPE = "BINARY";
-	private static final String COUNTER_TYPE = "INT NOT NULL AUTO_INCREMENT";
+	private static final String COUNTER_TYPE =
+			"INT NOT NULL AUTO_INCREMENT PRIMARY KEY";
 	private static final String STRING_TYPE = "VARCHAR";
+	private static final String EXPLAIN_COMMAND = "EXPLAIN";
 	private static final DatabaseTypes dbTypes = new DatabaseTypes(HASH_TYPE,
-			SECRET_TYPE, BINARY_TYPE, COUNTER_TYPE, STRING_TYPE);
+			SECRET_TYPE, BINARY_TYPE, COUNTER_TYPE, STRING_TYPE,
+			EXPLAIN_COMMAND);
 
 	private final DatabaseConfig config;
 	private final String url;
@@ -57,7 +60,8 @@ class H2Database extends JdbcDatabase {
 		this.config = config;
 		File dir = config.getDatabaseDirectory();
 		String path = new File(dir, "db").getAbsolutePath();
-		url = "jdbc:h2:split:" + path + ";CIPHER=AES;WRITE_DELAY=0";
+		url = "jdbc:h2:split:" + path + ";CIPHER=AES;MULTI_THREADED=1"
+				+ ";WRITE_DELAY=0";
 	}
 
 	@Override
@@ -72,7 +76,7 @@ class H2Database extends JdbcDatabase {
 		boolean reopen = isNonEmptyDirectory(dir);
 		if (LOG.isLoggable(INFO)) LOG.info("Reopening DB: " + reopen);
 		if (!reopen && dir.mkdirs()) LOG.info("Created database directory");
-		super.open("org.h2.Driver", reopen, key, listener);
+		super.open("org.h2.Driver", reopen, false, key, listener);
 		if (LOG.isLoggable(INFO)) {
 			LOG.info("Contents of account directory after opening DB:");
 			logFileOrDir(LOG, INFO, dir.getParentFile());

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

@@ -38,11 +38,13 @@ class HyperSqlDatabase extends JdbcDatabase {
 	private static final String HASH_TYPE = "BINARY(32)";
 	private static final String SECRET_TYPE = "BINARY(32)";
 	private static final String BINARY_TYPE = "BINARY";
-	private static final String COUNTER_TYPE =
+	private static final String COUNTER_TYPE = "INTEGER NOT NULL"
-			"INTEGER NOT NULL GENERATED ALWAYS AS IDENTITY(START WITH 1)";
+			+ " PRIMARY KEY GENERATED ALWAYS AS IDENTITY(START WITH 1)";
 	private static final String STRING_TYPE = "VARCHAR";
+	private static final String EXPLAIN_COMMAND = "EXPLAIN PLAN FOR";
 	private static final DatabaseTypes dbTypes = new DatabaseTypes(HASH_TYPE,
-			SECRET_TYPE, BINARY_TYPE, COUNTER_TYPE, STRING_TYPE);
+			SECRET_TYPE, BINARY_TYPE, COUNTER_TYPE, STRING_TYPE,
+			EXPLAIN_COMMAND);
 
 	private final DatabaseConfig config;
 	private final String url;
@@ -70,7 +72,7 @@ class HyperSqlDatabase extends JdbcDatabase {
 		boolean reopen = isNonEmptyDirectory(dir);
 		if (LOG.isLoggable(INFO)) LOG.info("Reopening DB: " + reopen);
 		if (!reopen && dir.mkdirs()) LOG.info("Created database directory");
-		super.open("org.hsqldb.jdbc.JDBCDriver", reopen, key, listener);
+		super.open("org.hsqldb.jdbc.JDBCDriver", reopen, true, key, listener);
 		return reopen;
 	}
 

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

@@ -117,7 +117,7 @@ abstract class JdbcDatabase implements Database<Connection> {
 			"CREATE TABLE settings"
 					+ " (namespace _STRING NOT NULL,"
 					+ " settingKey _STRING NOT NULL,"
-					+ " settingValue _STRING NOT NULL,"
+					+ " value _STRING NOT NULL,"
 					+ " PRIMARY KEY (namespace, settingKey))";
 
 	private static final String CREATE_LOCAL_AUTHORS =
@@ -143,8 +143,7 @@ abstract class JdbcDatabase implements Database<Connection> {
 					+ " handshakePublicKey _BINARY," // Null if key is unknown
 					+ " localAuthorId _HASH NOT NULL,"
 					+ " verified BOOLEAN NOT NULL,"
-					+ " syncVersions _BINARY DEFAULT X'00' NOT NULL,"
+					+ " syncVersions _BINARY DEFAULT x'00' NOT NULL,"
-					+ " PRIMARY KEY (contactId),"
 					+ " FOREIGN KEY (localAuthorId)"
 					+ " REFERENCES localAuthors (authorId)"
 					+ " ON DELETE CASCADE)";
@@ -161,7 +160,7 @@ abstract class JdbcDatabase implements Database<Connection> {
 			"CREATE TABLE groupMetadata"
 					+ " (groupId _HASH NOT NULL,"
 					+ " metaKey _STRING NOT NULL,"
-					+ " metaValue _BINARY NOT NULL,"
+					+ " value _BINARY NOT NULL,"
 					+ " PRIMARY KEY (groupId, metaKey),"
 					+ " FOREIGN KEY (groupId)"
 					+ " REFERENCES groups (groupId)"
@@ -206,7 +205,7 @@ abstract class JdbcDatabase implements Database<Connection> {
 					+ " groupId _HASH NOT NULL," // Denormalised
 					+ " state INT NOT NULL," // Denormalised
 					+ " metaKey _STRING NOT NULL,"
-					+ " metaValue _BINARY NOT NULL,"
+					+ " value _BINARY NOT NULL,"
 					+ " PRIMARY KEY (messageId, metaKey),"
 					+ " FOREIGN KEY (messageId)"
 					+ " REFERENCES messages (messageId)"
@@ -295,11 +294,11 @@ abstract class JdbcDatabase implements Database<Connection> {
 					+ " active BOOLEAN NOT NULL,"
 					+ " rootKey _SECRET," // Null for rotation keys
 					+ " alice BOOLEAN," // Null for rotation keys
-					+ " PRIMARY KEY (transportId, keySetId),"
+					// FIXME: Primary key has changed, migration needed
 					+ " FOREIGN KEY (transportId)"
 					+ " REFERENCES transports (transportId)"
 					+ " ON DELETE CASCADE,"
-					+ " UNIQUE (keySetId),"
+					// FIXME: Unique constraint removed, migration needed
 					+ " FOREIGN KEY (contactId)"
 					+ " REFERENCES contacts (contactId)"
 					+ " ON DELETE CASCADE,"
@@ -358,6 +357,85 @@ abstract class JdbcDatabase implements Database<Connection> {
 			"CREATE INDEX IF NOT EXISTS messagesByCleanupDeadline"
 					+ " ON messages (cleanupDeadline)";
 
+	// FIXME: Migration needs to add new index
+	private static final String INDEX_OUTGOING_KEYS_BY_TRANSPORT_ID_KEY_SET_ID =
+			"CREATE INDEX IF NOT EXISTS outgoingKeysByTransportIdKeySetId"
+					+ " ON outgoingKeys (transportId, keySetId)";
+
+	private static final String FOREIGN_INDEX_CONTACTS_BY_LOCAL_AUTHOR_ID =
+			"CREATE INDEX IF NOT EXISTS contactsByLocalAuthorId"
+					+ " ON contacts (localAuthorId)";
+
+	private static final String FOREIGN_INDEX_GROUP_METADATA_BY_GROUP_ID =
+			"CREATE INDEX IF NOT EXISTS groupMetadataByGroupId"
+					+ " ON groupMetadata (groupId)";
+
+	private static final String FOREIGN_INDEX_GROUP_VISIBILITIES_BY_CONTACT_ID =
+			"CREATE INDEX IF NOT EXISTS groupVisibilitiesByContactId"
+					+ " ON groupVisibilities (contactId)";
+
+	private static final String FOREIGN_INDEX_GROUP_VISIBILITIES_BY_GROUP_ID =
+			"CREATE INDEX IF NOT EXISTS groupVisibilitiesByGroupId"
+					+ " ON groupVisibilities (groupId)";
+
+	private static final String FOREIGN_INDEX_MESSAGES_BY_GROUP_ID =
+			"CREATE INDEX IF NOT EXISTS messagesByGroupId"
+					+ " ON messages (groupId)";
+
+	private static final String FOREIGN_INDEX_MESSAGE_METADATA_BY_MESSAGE_ID =
+			"CREATE INDEX IF NOT EXISTS messageMetadataByMessageId"
+					+ " ON messageMetadata (messageId)";
+
+	private static final String FOREIGN_INDEX_MESSAGE_METADATA_BY_GROUP_ID =
+			"CREATE INDEX IF NOT EXISTS messageMetadataByGroupId"
+					+ " ON messageMetadata (groupId)";
+
+	private static final String FOREIGN_INDEX_MESSAGE_DEPENDENCIES_BY_GROUP_ID =
+			"CREATE INDEX IF NOT EXISTS messageDependenciesByGroupId"
+					+ " ON messageDependencies (groupId)";
+
+	private static final String
+			FOREIGN_INDEX_MESSAGE_DEPENDENCIES_BY_MESSAGE_ID =
+			"CREATE INDEX IF NOT EXISTS messageDependenciesByMessageId"
+					+ " ON messageDependencies (messageId)";
+
+	private static final String FOREIGN_INDEX_OFFERS_BY_CONTACT_ID =
+			"CREATE INDEX IF NOT EXISTS offersByContactId"
+					+ " ON offers (contactId)";
+
+	private static final String FOREIGN_INDEX_STATUSES_BY_MESSAGE_ID =
+			"CREATE INDEX IF NOT EXISTS statusesByMessageId"
+					+ " ON statuses (messageId)";
+
+	private static final String FOREIGN_INDEX_STATUSES_BY_CONTACT_ID =
+			"CREATE INDEX IF NOT EXISTS statusesByContactId"
+					+ " ON statuses (contactId)";
+
+	private static final String FOREIGN_INDEX_STATUSES_BY_GROUP_ID =
+			"CREATE INDEX IF NOT EXISTS statusesByGroupId"
+					+ " ON statuses (groupId)";
+
+	private static final String FOREIGN_INDEX_OUTGOING_KEYS_BY_TRANSPORT_ID =
+			"CREATE INDEX IF NOT EXISTS outgoingKeysByTransportId"
+					+ " ON outgoingKeys (transportId)";
+
+	private static final String FOREIGN_INDEX_OUTGOING_KEYS_BY_CONTACT_ID =
+			"CREATE INDEX IF NOT EXISTS outgoingKeysByContactId"
+					+ " ON outgoingKeys (contactId)";
+
+	private static final String
+			FOREIGN_INDEX_OUTGOING_KEYS_BY_PENDING_CONTACT_ID =
+			"CREATE INDEX IF NOT EXISTS outgoingKeysByPendingContactId"
+					+ " ON outgoingKeys (pendingContactId)";
+
+	private static final String FOREIGN_INDEX_INCOMING_KEYS_BY_TRANSPORT_ID =
+			"CREATE INDEX IF NOT EXISTS incomingKeysByTransportId"
+					+ " ON incomingKeys (transportId)";
+
+	private static final String FOREIGN_INDEX_INCOMING_KEYS_BY_KEY_SET_ID =
+			"CREATE INDEX IF NOT EXISTS incomingKeysByKeySetId"
+					+ " ON incomingKeys (keySetId)";
+
 	private static final Logger LOG =
 			getLogger(JdbcDatabase.class.getName());
 
@@ -393,6 +471,7 @@ abstract class JdbcDatabase implements Database<Connection> {
 	}
 
 	protected void open(String driverClass, boolean reopen,
+			boolean createForeignKeyIndexes,
 			@SuppressWarnings("unused") SecretKey key,
 			@Nullable MigrationListener listener) throws DbException {
 		// Load the JDBC driver
@@ -419,7 +498,7 @@ abstract class JdbcDatabase implements Database<Connection> {
 			if (LOG.isLoggable(INFO)) {
 				LOG.info("db dirty? " + wasDirtyOnInitialisation);
 			}
-			createIndexes(txn);
+			createIndexes(txn, createForeignKeyIndexes);
 			setDirty(txn, true);
 			commitTransaction(txn);
 		} catch (DbException e) {
@@ -552,7 +631,8 @@ abstract class JdbcDatabase implements Database<Connection> {
 		}
 	}
 
-	private void createIndexes(Connection txn) throws DbException {
+	private void createIndexes(Connection txn, boolean createForeignKeyIndexes)
+			throws DbException {
 		Statement s = null;
 		try {
 			s = txn.createStatement();
@@ -564,6 +644,31 @@ abstract class JdbcDatabase implements Database<Connection> {
 			s.executeUpdate(INDEX_STATUSES_BY_CONTACT_ID_TIMESTAMP);
 			s.executeUpdate(INDEX_STATUSES_BY_CONTACT_ID_TX_COUNT_TIMESTAMP);
 			s.executeUpdate(INDEX_MESSAGES_BY_CLEANUP_DEADLINE);
+			s.executeUpdate(INDEX_OUTGOING_KEYS_BY_TRANSPORT_ID_KEY_SET_ID);
+			// Some DB implementations automatically create indexes on columns
+			// that are foreign keys, others don't
+			if (createForeignKeyIndexes) {
+				s.executeUpdate(FOREIGN_INDEX_CONTACTS_BY_LOCAL_AUTHOR_ID);
+				s.executeUpdate(FOREIGN_INDEX_GROUP_METADATA_BY_GROUP_ID);
+				s.executeUpdate(FOREIGN_INDEX_GROUP_VISIBILITIES_BY_CONTACT_ID);
+				s.executeUpdate(FOREIGN_INDEX_GROUP_VISIBILITIES_BY_GROUP_ID);
+				s.executeUpdate(FOREIGN_INDEX_MESSAGES_BY_GROUP_ID);
+				s.executeUpdate(FOREIGN_INDEX_MESSAGE_METADATA_BY_MESSAGE_ID);
+				s.executeUpdate(FOREIGN_INDEX_MESSAGE_METADATA_BY_GROUP_ID);
+				s.executeUpdate(FOREIGN_INDEX_MESSAGE_DEPENDENCIES_BY_GROUP_ID);
+				s.executeUpdate(
+						FOREIGN_INDEX_MESSAGE_DEPENDENCIES_BY_MESSAGE_ID);
+				s.executeUpdate(FOREIGN_INDEX_OFFERS_BY_CONTACT_ID);
+				s.executeUpdate(FOREIGN_INDEX_STATUSES_BY_MESSAGE_ID);
+				s.executeUpdate(FOREIGN_INDEX_STATUSES_BY_CONTACT_ID);
+				s.executeUpdate(FOREIGN_INDEX_STATUSES_BY_GROUP_ID);
+				s.executeUpdate(FOREIGN_INDEX_OUTGOING_KEYS_BY_TRANSPORT_ID);
+				s.executeUpdate(FOREIGN_INDEX_OUTGOING_KEYS_BY_CONTACT_ID);
+				s.executeUpdate(
+						FOREIGN_INDEX_OUTGOING_KEYS_BY_PENDING_CONTACT_ID);
+				s.executeUpdate(FOREIGN_INDEX_INCOMING_KEYS_BY_TRANSPORT_ID);
+				s.executeUpdate(FOREIGN_INDEX_INCOMING_KEYS_BY_KEY_SET_ID);
+			}
 			s.close();
 		} catch (SQLException e) {
 			tryToClose(s, LOG, WARNING);
@@ -1914,6 +2019,38 @@ abstract class JdbcDatabase implements Database<Connection> {
 		}
 	}
 
+	@Override
+	public Collection<String> explainGetMessageIds(Connection txn, GroupId g)
+			throws DbException {
+		PreparedStatement ps = null;
+		ResultSet rs = null;
+		try {
+			String sql = dbTypes.replaceTypes("_EXPLAIN SELECT messageId"
+					+ " FROM messages"
+					+ " WHERE groupId = ? AND state = ?");
+			ps = txn.prepareStatement(sql);
+			ps.setBytes(1, g.getBytes());
+			ps.setInt(2, DELIVERED.getValue());
+			rs = ps.executeQuery();
+			int cols = rs.getMetaData().getColumnCount();
+			List<String> explanation = new ArrayList<>();
+			while (rs.next()) {
+				StringBuilder sb = new StringBuilder();
+				for (int i = 1; i <= cols; i++) {
+					sb.append(rs.getString(i)).append(' ');
+				}
+				explanation.add(sb.toString());
+			}
+			rs.close();
+			ps.close();
+			return explanation;
+		} catch (SQLException e) {
+			tryToClose(rs, LOG, WARNING);
+			tryToClose(ps, LOG, WARNING);
+			throw new DbException(e);
+		}
+	}
+
 	@Override
 	public Collection<MessageId> getMessageIds(Connection txn, GroupId g,
 			Metadata query) throws DbException {
@@ -1926,7 +2063,7 @@ abstract class JdbcDatabase implements Database<Connection> {
 			Set<MessageId> intersection = null;
 			String sql = "SELECT messageId FROM messageMetadata"
 					+ " WHERE groupId = ? AND state = ?"
-					+ " AND metaKey = ? AND metaValue = ?";
+					+ " AND metaKey = ? AND value = ?";
 			for (Entry<String, byte[]> e : query.entrySet()) {
 				ps = txn.prepareStatement(sql);
 				ps.setBytes(1, g.getBytes());
@@ -1982,7 +2119,7 @@ abstract class JdbcDatabase implements Database<Connection> {
 		PreparedStatement ps = null;
 		ResultSet rs = null;
 		try {
-			String sql = "SELECT messageId, metaKey, metaValue"
+			String sql = "SELECT messageId, metaKey, value"
 					+ " FROM messageMetadata"
 					+ " WHERE groupId = ? AND state = ?";
 			ps = txn.prepareStatement(sql);
@@ -2027,7 +2164,7 @@ abstract class JdbcDatabase implements Database<Connection> {
 		PreparedStatement ps = null;
 		ResultSet rs = null;
 		try {
-			String sql = "SELECT metaKey, metaValue FROM groupMetadata"
+			String sql = "SELECT metaKey, value FROM groupMetadata"
 					+ " WHERE groupId = ?";
 			ps = txn.prepareStatement(sql);
 			ps.setBytes(1, g.getBytes());
@@ -2050,7 +2187,7 @@ abstract class JdbcDatabase implements Database<Connection> {
 		PreparedStatement ps = null;
 		ResultSet rs = null;
 		try {
-			String sql = "SELECT metaKey, metaValue FROM messageMetadata"
+			String sql = "SELECT metaKey, value FROM messageMetadata"
 					+ " WHERE state = ? AND messageId = ?";
 			ps = txn.prepareStatement(sql);
 			ps.setInt(1, DELIVERED.getValue());
@@ -2074,7 +2211,7 @@ abstract class JdbcDatabase implements Database<Connection> {
 		PreparedStatement ps = null;
 		ResultSet rs = null;
 		try {
-			String sql = "SELECT metaKey, metaValue FROM messageMetadata"
+			String sql = "SELECT metaKey, value FROM messageMetadata"
 					+ " WHERE (state = ? OR state = ?)"
 					+ " AND messageId = ?";
 			ps = txn.prepareStatement(sql);
@@ -2597,6 +2734,9 @@ abstract class JdbcDatabase implements Database<Connection> {
 			PublicKey publicKey = new AgreementPublicKey(rs.getBytes(1));
 			String alias = rs.getString(2);
 			long timestamp = rs.getLong(3);
+			if (rs.next()) throw new DbStateException();
+			rs.close();
+			ps.close();
 			return new PendingContact(p, publicKey, alias, timestamp);
 		} catch (SQLException e) {
 			tryToClose(rs, LOG, WARNING);
@@ -2678,7 +2818,7 @@ abstract class JdbcDatabase implements Database<Connection> {
 		PreparedStatement ps = null;
 		ResultSet rs = null;
 		try {
-			String sql = "SELECT settingKey, settingValue FROM settings"
+			String sql = "SELECT settingKey, value FROM settings"
 					+ " WHERE namespace = ?";
 			ps = txn.prepareStatement(sql);
 			ps.setString(1, namespace);
@@ -2914,8 +3054,7 @@ abstract class JdbcDatabase implements Database<Connection> {
 					g.getBytes(), meta, "groupMetadata", "groupId");
 			if (added.isEmpty()) return;
 			// Insert any keys that don't already exist
-			String sql = "INSERT INTO groupMetadata"
+			String sql = "INSERT INTO groupMetadata (groupId, metaKey, value)"
-					+ " (groupId, metaKey, metaValue)"
 					+ " VALUES (?, ?, ?)";
 			ps = txn.prepareStatement(sql);
 			ps.setBytes(1, g.getBytes());
@@ -2958,7 +3097,7 @@ abstract class JdbcDatabase implements Database<Connection> {
 			ps.close();
 			// Insert any keys that don't already exist
 			sql = "INSERT INTO messageMetadata"
-					+ " (messageId, groupId, state, metaKey, metaValue)"
+					+ " (messageId, groupId, state, metaKey, value)"
 					+ " VALUES (?, ?, ?, ?, ?)";
 			ps = txn.prepareStatement(sql);
 			ps.setBytes(1, m.getBytes());
@@ -3017,7 +3156,7 @@ abstract class JdbcDatabase implements Database<Connection> {
 			}
 			if (notRemoved.isEmpty()) return Collections.emptyMap();
 			// Update any keys that already exist
-			String sql = "UPDATE " + tableName + " SET metaValue = ?"
+			String sql = "UPDATE " + tableName + " SET value = ?"
 					+ " WHERE " + columnName + " = ? AND metaKey = ?";
 			ps = txn.prepareStatement(sql);
 			ps.setBytes(2, id);
@@ -3054,7 +3193,7 @@ abstract class JdbcDatabase implements Database<Connection> {
 		PreparedStatement ps = null;
 		try {
 			// Update any settings that already exist
-			String sql = "UPDATE settings SET settingValue = ?"
+			String sql = "UPDATE settings SET value = ?"
 					+ " WHERE namespace = ? AND settingKey = ?";
 			ps = txn.prepareStatement(sql);
 			for (Entry<String, String> e : s.entrySet()) {
@@ -3070,7 +3209,7 @@ abstract class JdbcDatabase implements Database<Connection> {
 				if (rows > 1) throw new DbStateException();
 			}
 			// Insert any settings that don't already exist
-			sql = "INSERT INTO settings (namespace, settingKey, settingValue)"
+			sql = "INSERT INTO settings (namespace, settingKey, value)"
 					+ " VALUES (?, ?, ?)";
 			ps = txn.prepareStatement(sql);
 			int updateIndex = 0, inserted = 0;

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

@@ -0,0 +1,117 @@
+package org.briarproject.bramble.db;
+
+import org.briarproject.bramble.api.crypto.SecretKey;
+import org.briarproject.bramble.api.db.DatabaseConfig;
+import org.briarproject.bramble.api.db.DbClosedException;
+import org.briarproject.bramble.api.db.DbException;
+import org.briarproject.bramble.api.db.MigrationListener;
+import org.briarproject.bramble.api.sync.MessageFactory;
+import org.briarproject.bramble.api.system.Clock;
+import org.briarproject.nullsafety.NotNullByDefault;
+import org.sqlite.mc.SQLiteMCSqlCipherConfig;
+
+import java.io.File;
+import java.sql.Connection;
+import java.sql.DriverManager;
+import java.sql.SQLException;
+import java.sql.Statement;
+import java.util.Properties;
+import java.util.logging.Logger;
+
+import javax.annotation.Nullable;
+import javax.inject.Inject;
+
+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.db.JdbcUtils.tryToClose;
+import static org.briarproject.bramble.util.IoUtils.isNonEmptyDirectory;
+
+/**
+ * Contains all the SQLite-specific code for the database.
+ */
+@NotNullByDefault
+class SqliteDatabase extends JdbcDatabase {
+
+	private static final Logger LOG = getLogger(SqliteDatabase.class.getName());
+
+	private static final String HASH_TYPE = "BLOB";
+	private static final String SECRET_TYPE = "BLOB";
+	private static final String BINARY_TYPE = "BLOB";
+	private static final String COUNTER_TYPE =
+			"INTEGER PRIMARY KEY AUTOINCREMENT";
+	private static final String STRING_TYPE = "VARCHAR";
+	private static final String EXPLAIN_COMMAND = "EXPLAIN QUERY PLAN";
+	private static final DatabaseTypes dbTypes = new DatabaseTypes(HASH_TYPE,
+			SECRET_TYPE, BINARY_TYPE, COUNTER_TYPE, STRING_TYPE,
+			EXPLAIN_COMMAND);
+
+	private final DatabaseConfig config;
+	private final String url;
+
+	@Nullable
+	private volatile Properties properties = null;
+
+	@Inject
+	SqliteDatabase(DatabaseConfig config, MessageFactory messageFactory,
+			Clock clock) {
+		super(dbTypes, messageFactory, clock);
+		this.config = config;
+		File dir = config.getDatabaseDirectory();
+		String path = new File(dir, "db").getAbsolutePath();
+		url = "jdbc:sqlite:" + path + "?cipher=sqlcipher";
+	}
+
+	@Override
+	public boolean open(SecretKey key, @Nullable MigrationListener listener)
+			throws DbException {
+		properties = SQLiteMCSqlCipherConfig.getDefault()
+				.withHexKey(key.getBytes())
+				.build()
+				.toProperties();
+		File dir = config.getDatabaseDirectory();
+		boolean reopen = isNonEmptyDirectory(dir);
+		if (LOG.isLoggable(INFO)) LOG.info("Reopening DB: " + reopen);
+		if (!reopen && dir.mkdirs()) LOG.info("Created database directory");
+		super.open("org.sqlite.JDBC", reopen, true, key, listener);
+		return reopen;
+	}
+
+	@Override
+	public void close() throws DbException {
+		Connection c = null;
+		try {
+			c = createConnection();
+			setDirty(c, false);
+			c.close();
+			closeAllConnections();
+		} catch (SQLException e) {
+			tryToClose(c, LOG, WARNING);
+			throw new DbException(e);
+		}
+	}
+
+	@Override
+	protected Connection createConnection() throws DbException, SQLException {
+		Properties properties = this.properties;
+		if (properties == null) throw new DbClosedException();
+		Connection c = DriverManager.getConnection(url, properties);
+		Statement s = null;
+		try {
+			s = c.createStatement();
+			s.execute("PRAGMA foreign_keys = ON");
+			s.execute("PRAGMA secure_delete = ON");
+			s.close();
+		} catch (SQLException e) {
+			tryToClose(s, LOG, WARNING);
+			tryToClose(c, LOG, WARNING);
+			throw new DbException(e);
+		}
+		return c;
+	}
+
+	@Override
+	protected void compactAndClose() throws DbException {
+		close();
+	}
+}

bramble-core/src/test/java/org/briarproject/bramble/db/H2SqliteDatabasePerformanceComparisonTest.java

@@ -0,0 +1,37 @@
+package org.briarproject.bramble.db;
+
+import org.briarproject.bramble.api.db.DatabaseConfig;
+import org.briarproject.bramble.api.sync.MessageFactory;
+import org.briarproject.bramble.api.system.Clock;
+import org.junit.BeforeClass;
+
+import java.sql.Connection;
+
+import static org.briarproject.bramble.test.TestUtils.isOptionalTestEnabled;
+import static org.junit.Assume.assumeTrue;
+
+public class H2SqliteDatabasePerformanceComparisonTest
+		extends DatabasePerformanceComparisonTest {
+
+	@BeforeClass
+	public static void setUpClass() {
+		assumeTrue(isOptionalTestEnabled(
+				H2SqliteDatabasePerformanceComparisonTest.class));
+	}
+
+	@Override
+	Database<Connection> createDatabase(boolean conditionA,
+			DatabaseConfig databaseConfig, MessageFactory messageFactory,
+			Clock clock) {
+		if (conditionA) {
+			return new H2Database(databaseConfig, messageFactory, clock);
+		} else {
+			return new SqliteDatabase(databaseConfig, messageFactory, clock);
+		}
+	}
+
+	@Override
+	protected String getTestName() {
+		return getClass().getSimpleName();
+	}
+}

bramble-core/src/test/java/org/briarproject/bramble/db/H2TransactionIsolationTest.java

@@ -23,18 +23,21 @@ public class H2TransactionIsolationTest extends BrambleTestCase {
 
 	private static final String DROP_TABLE = "DROP TABLE foo IF EXISTS";
 	private static final String CREATE_TABLE = "CREATE TABLE foo"
-			+ " (_key INT NOT NULL,"
+			+ " (key INT NOT NULL,"
 			+ " counter INT NOT NULL)";
 	private static final String INSERT_ROW =
-			"INSERT INTO foo (_key, counter) VALUES (1, 123)";
+			"INSERT INTO foo (key, counter) VALUES (1, 123)";
 	private static final String GET_COUNTER =
-			"SELECT counter FROM foo WHERE _key = 1";
+			"SELECT counter FROM foo WHERE key = 1";
 	private static final String SET_COUNTER =
-			"UPDATE foo SET counter = ? WHERE _key = 1";
+			"UPDATE foo SET counter = ? WHERE key = 1";
 
 	private final File testDir = TestUtils.getTestDirectory();
 	private final File db = new File(testDir, "db");
-	private final String url = "jdbc:h2:split:" + db.getAbsolutePath();
+	private final String withMvcc = "jdbc:h2:split:" + db.getAbsolutePath()
+			+ ";MV_STORE=TRUE;MVCC=TRUE";
+	private final String withoutMvcc = "jdbc:h2:split:" + db.getAbsolutePath()
+			+ ";MV_STORE=FALSE;MVCC=FALSE;LOCK_MODE=1";
 
 	@Before
 	public void setUp() throws Exception {
@@ -49,14 +52,14 @@ public class H2TransactionIsolationTest extends BrambleTestCase {
 
 	@Test
 	public void testDoesNotReadUncommittedWritesWithMvcc() throws Exception {
-		Connection connection = openConnection();
+		Connection connection = openConnection(true);
 		try {
 			createTableAndInsertRow(connection);
 		} finally {
 			connection.close();
 		}
 		// Start the first transaction
-		Connection txn1 = openConnection();
+		Connection txn1 = openConnection(true);
 		try {
 			txn1.setAutoCommit(false);
 			// The first transaction should read the initial value
@@ -64,7 +67,7 @@ public class H2TransactionIsolationTest extends BrambleTestCase {
 			// The first transaction updates the value but doesn't commit it
 			assertEquals(1, setCounter(txn1, 234));
 			// Start the second transaction
-			Connection txn2 = openConnection();
+			Connection txn2 = openConnection(true);
 			try {
 				txn2.setAutoCommit(false);
 				// The second transaction should still read the initial value
@@ -83,14 +86,14 @@ public class H2TransactionIsolationTest extends BrambleTestCase {
 
 	@Test
 	public void testLastWriterWinsWithMvcc() throws Exception {
-		Connection connection = openConnection();
+		Connection connection = openConnection(true);
 		try {
 			createTableAndInsertRow(connection);
 		} finally {
 			connection.close();
 		}
 		// Start the first transaction
-		Connection txn1 = openConnection();
+		Connection txn1 = openConnection(true);
 		try {
 			txn1.setAutoCommit(false);
 			// The first transaction should read the initial value
@@ -98,7 +101,7 @@ public class H2TransactionIsolationTest extends BrambleTestCase {
 			// The first transaction updates the value but doesn't commit it
 			assertEquals(1, setCounter(txn1, 234));
 			// Start the second transaction
-			Connection txn2 = openConnection();
+			Connection txn2 = openConnection(true);
 			try {
 				txn2.setAutoCommit(false);
 				// The second transaction should still read the initial value
@@ -116,7 +119,7 @@ public class H2TransactionIsolationTest extends BrambleTestCase {
 			txn1.close();
 		}
 		// The second transaction was the last writer, so it should win
-		connection = openConnection();
+		connection = openConnection(true);
 		try {
 			assertEquals(345, getCounter(connection));
 		} finally {
@@ -126,20 +129,20 @@ public class H2TransactionIsolationTest extends BrambleTestCase {
 
 	@Test
 	public void testLockTimeoutOnRowWithMvcc() throws Exception {
-		Connection connection = openConnection();
+		Connection connection = openConnection(true);
 		try {
 			createTableAndInsertRow(connection);
 		} finally {
 			connection.close();
 		}
 		// Start the first transaction
-		Connection txn1 = openConnection();
+		Connection txn1 = openConnection(true);
 		try {
 			txn1.setAutoCommit(false);
 			// The first transaction should read the initial value
 			assertEquals(123, getCounter(txn1));
 			// Start the second transaction
-			Connection txn2 = openConnection();
+			Connection txn2 = openConnection(true);
 			try {
 				txn2.setAutoCommit(false);
 				// The second transaction should read the initial value
@@ -164,8 +167,84 @@ public class H2TransactionIsolationTest extends BrambleTestCase {
 		}
 	}
 
-	private Connection openConnection() throws SQLException {
+	@Test
-		return DriverManager.getConnection(url);
+	public void testReadLockTimeoutOnTableWithoutMvcc() throws Exception {
+		Connection connection = openConnection(false);
+		try {
+			createTableAndInsertRow(connection);
+		} finally {
+			connection.close();
+		}
+		// Start the first transaction
+		Connection txn1 = openConnection(false);
+		try {
+			txn1.setAutoCommit(false);
+			// The first transaction should read the initial value
+			assertEquals(123, getCounter(txn1));
+			// Start the second transaction
+			Connection txn2 = openConnection(false);
+			try {
+				txn2.setAutoCommit(false);
+				// The second transaction should read the initial value
+				assertEquals(123, getCounter(txn2));
+				// The first transaction tries to update the value
+				try {
+					setCounter(txn1, 345);
+					fail();
+				} catch (SQLException expected) {
+					// Expected: the table is locked by the second transaction
+				}
+				// Abort the transactions
+				txn1.rollback();
+				txn2.rollback();
+			} finally {
+				txn2.close();
+			}
+		} finally {
+			txn1.close();
+		}
+	}
+
+	@Test
+	public void testWriteLockTimeoutOnTableWithoutMvcc() throws Exception {
+		Connection connection = openConnection(false);
+		try {
+			createTableAndInsertRow(connection);
+		} finally {
+			connection.close();
+		}
+		// Start the first transaction
+		Connection txn1 = openConnection(false);
+		try {
+			txn1.setAutoCommit(false);
+			// The first transaction should read the initial value
+			assertEquals(123, getCounter(txn1));
+			// The first transaction updates the value but doesn't commit yet
+			assertEquals(1, setCounter(txn1, 345));
+			// Start the second transaction
+			Connection txn2 = openConnection(false);
+			try {
+				txn2.setAutoCommit(false);
+				// The second transaction tries to read the value
+				try {
+					getCounter(txn2);
+					fail();
+				} catch (SQLException expected) {
+					// Expected: the table is locked by the first transaction
+				}
+				// Abort the transactions
+				txn1.rollback();
+				txn2.rollback();
+			} finally {
+				txn2.close();
+			}
+		} finally {
+			txn1.close();
+		}
+	}
+
+	private Connection openConnection(boolean mvcc) throws SQLException {
+		return DriverManager.getConnection(mvcc ? withMvcc : withoutMvcc);
 	}
 
 	private void createTableAndInsertRow(Connection c) throws SQLException {

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

@@ -10,14 +10,21 @@ import static org.junit.Assume.assumeTrue;
 
 public class HyperSqlDatabaseTest extends JdbcDatabaseTest {
 
+	@Override
 	@Before
 	public void setUp() {
 		assumeTrue(isCryptoStrengthUnlimited());
+		super.setUp();
 	}
 
 	@Override
 	protected JdbcDatabase createDatabase(DatabaseConfig config,
 			MessageFactory messageFactory, Clock clock) {
-		return new HyperSqlDatabase(config, messageFactory ,clock);
+		return new HyperSqlDatabase(config, messageFactory, clock);
+	}
+
+	@Override
+	public void testExplainGetMessageIds() {
+		// Ugh, HSQLDB can't handle EXPLAIN PLAN FOR in prepared statements
 	}
 }

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

@@ -2500,6 +2500,21 @@ public abstract class JdbcDatabaseTest extends BrambleTestCase {
 		assertEquals(NO_CLEANUP_DEADLINE, db.getNextCleanupDeadline(txn));
 	}
 
+	// FIXME: Remove
+	@Test
+	public void testExplainGetMessageIds() throws Exception {
+		Database<Connection> db = open(false);
+		Connection txn = db.startTransaction();
+		db.addGroup(txn, group);
+		Collection<String> explanation = db.explainGetMessageIds(txn, groupId);
+		db.commitTransaction(txn);
+		db.close();
+
+		System.out.println("getMessageIds(T, GroupId)");
+		for (String line : explanation) System.out.println(line);
+		System.out.println();
+	}
+
 	private Database<Connection> open(boolean resume) throws Exception {
 		return open(resume, new TestMessageFactory(), new SystemClock());
 	}

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

@@ -0,0 +1,25 @@
+package org.briarproject.bramble.db;
+
+import org.briarproject.bramble.api.db.DatabaseConfig;
+import org.briarproject.bramble.api.sync.MessageFactory;
+import org.briarproject.bramble.api.system.Clock;
+import org.junit.Before;
+
+import static org.briarproject.bramble.test.TestUtils.isCryptoStrengthUnlimited;
+import static org.junit.Assume.assumeTrue;
+
+public class SqliteDatabaseTest extends JdbcDatabaseTest {
+
+	@Override
+	@Before
+	public void setUp() {
+		assumeTrue(isCryptoStrengthUnlimited());
+		super.setUp();
+	}
+
+	@Override
+	protected JdbcDatabase createDatabase(DatabaseConfig config,
+			MessageFactory messageFactory, Clock clock) {
+		return new SqliteDatabase(config, messageFactory, clock);
+	}
+}

bramble-core/witness.gradle

@@ -18,12 +18,13 @@ dependencyVerification {
 			'com.google.guava:guava:31.0.1-jre:guava-31.0.1-jre.jar:d5be94d65e87bd219fb3193ad1517baa55a3b88fc91d21cf735826ab5af087b9',
 			'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:1.3:j2objc-annotations-1.3.jar:21af30c92267bd6122c0e0b4d20cccb6641a37eaf956c6540ec471d584e64a7b',
-		    'com.h2database:h2:2.2.220:h2-2.2.220.jar:978ab863018d3f965e38880571c36293ea8b10a8086194159c4d5d20b50f0a57',
+			'com.h2database:h2:1.4.192:h2-1.4.192.jar:225b22e9857235c46c93861410b60b8c81c10dc8985f4faf188985ba5445126c',
 			'com.squareup.okhttp3:mockwebserver:4.10.0:mockwebserver-4.10.0.jar:af29da234e63159d6e0dea43bf8288eea97d71cdf1651a5ee2d6c0d0d4adbf8f',
 			'com.squareup.okhttp3:okhttp:4.10.0:okhttp-4.10.0.jar:7580f14fa1691206e37081ad3f92063b1603b328da0bb316f2fef02e0562e7ec',
 			'com.squareup.okio:okio-jvm:3.0.0:okio-jvm-3.0.0.jar:be64a0cc1f28ea9cd5c970dd7e7557af72c808d738c495b397bf897c9921e907',
 			'com.squareup:javapoet:1.13.0:javapoet-1.13.0.jar:4c7517e848a71b36d069d12bb3bf46a70fd4cda3105d822b0ed2e19c00b69291',
 			'com.squareup:kotlinpoet:1.11.0:kotlinpoet-1.11.0.jar:2887ada1ca03dd83baa2758640d87e840d1907564db0ef88d2289c868a980492',
+			'io.github.willena:sqlite-jdbc:3.41.2.1:sqlite-jdbc-3.41.2.1.jar:fb60e7137c1791db89240701338d31ca42a0bec5508c1aab1c1131cf885f2309',
 			'javax.inject:javax.inject:1:javax.inject-1.jar:91c77044a50c481636c32d916fd89c9118a72195390452c81065080f957de7ff',
 			'junit:junit:4.13.2:junit-4.13.2.jar:8e495b634469d64fb8acfa3495a065cbacc8a0fff55ce1e31007be4c16dc57d3',
 			'net.bytebuddy:byte-buddy:1.9.12:byte-buddy-1.9.12.jar:3688c3d434bebc3edc5516296a2ed0f47b65e451071b4afecad84f902f0efc11',

briar-android/build.gradle

@@ -21,22 +21,31 @@ android {
 
 	packagingOptions {
 		doNotStrip '**/*.so'
+		jniLibs {
+			// Unpack native libs from the APK rather than using them in-place. We package the
+			// Tor binaries as native libs and need them to be unpacked so we can execute them
+			useLegacyPackaging = true
+		}
 	}
 
 	defaultConfig {
+		// FIXME: sqlite-jdbc-crypt uses __register_atfork which is only available on API >= 23.
+		//  We might be able to solve this by recompiling (or asking upstream to recompile)
 		minSdkVersion 21
 		targetSdkVersion 33
 		versionCode 10506
 		versionName "1.5.6"
 		applicationId "org.briarproject.briar.android"
-		buildConfigField "String", "TorVersion", "\"$tor_version\""
 
 		vectorDrawables.useSupportLibrary = true
+
+		buildConfigField "String", "TorVersion", "\"$tor_version\""
 		buildConfigField "String", "GitHash",
 				"\"${getStdout(['git', 'rev-parse', '--short=7', 'HEAD'], 'No commit hash')}\""
 		def now = (long) (System.currentTimeMillis() / 1000)
 		buildConfigField "Long", "BuildTimestamp",
 				"${getStdout(['git', 'log', '-n', '1', '--format=%ct'], now)}000L"
+
 		testInstrumentationRunner 'org.briarproject.briar.android.BriarTestRunner'
 		testInstrumentationRunnerArguments disableAnalytics: 'true'
 	}
@@ -148,7 +157,7 @@ dependencies {
 
 	compileOnly 'javax.annotation:jsr250-api:1.0'
 
-	coreLibraryDesugaring 'com.android.tools:desugar_jdk_libs_nio:2.0.3'
+	coreLibraryDesugaring 'com.android.tools:desugar_jdk_libs:2.0.3'
 
 	testImplementation project(path: ':bramble-api', configuration: 'testOutput')
 	testImplementation project(path: ':bramble-core', configuration: 'testOutput')

briar-android/proguard-rules.txt

@@ -25,8 +25,9 @@
 -dontnote com.android.org.conscrypt.SSLParametersImpl
 -dontnote org.apache.harmony.xnet.provider.jsse.SSLParametersImpl
 -dontnote sun.security.ssl.SSLContextImpl
--dontwarn org.conscrypt.OpenSSLProvider
+-dontwarn org.bouncycastle.jsse.**
--dontwarn org.conscrypt.Conscrypt
+-dontwarn org.conscrypt.**
+-dontwarn org.openjsse.**
 
 # HTML sanitiser
 -keep class org.jsoup.safety.Whitelist

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

@@ -150,7 +150,8 @@ public class AppModule {
 		//FIXME: StrictMode
 		StrictMode.ThreadPolicy tp = StrictMode.allowThreadDiskReads();
 		StrictMode.allowThreadDiskWrites();
-		File dbDir = app.getApplicationContext().getDir("db", MODE_PRIVATE);
+		File dbDir = app.getApplicationContext().getDir("db_sqlite",
+				MODE_PRIVATE);
 		File keyDir = app.getApplicationContext().getDir("key", MODE_PRIVATE);
 		StrictMode.setThreadPolicy(tp);
 		KeyStrengthener keyStrengthener = SDK_INT >= 23

briar-android/witness.gradle

@@ -87,8 +87,8 @@ dependencyVerification {
 			'androidx.window:window:1.0.0:window-1.0.0.aar:3212985be4127373ca4d0ea7f8b81a250ae2105e924f7940105d067a0f9ac130',
 			'cglib:cglib:3.2.8:cglib-3.2.8.jar:3f64de999ecc5595dc84ca8ff0879d8a34c8623f9ef3c517a53ed59023fcb9db',
 			'com.almworks.sqlite4java:sqlite4java:1.0.392:sqlite4java-1.0.392.jar:243a64470fda0e86a6fddeb0af4c7aa9426ce84e68cbfe18d75ee5da4b7e0b92',
-		    'com.android.tools:desugar_jdk_libs_configuration_nio:2.0.3:desugar_jdk_libs_configuration_nio-2.0.3.jar:1e46fd75ae4db46ae592a17afeda3865321492020847c16ec82b1d2026ed967a',
+			'com.android.tools:desugar_jdk_libs:2.0.3:desugar_jdk_libs-2.0.3.jar:7f4e68385dfe88eba4344ff71912912bdc731806b9b2ce4a12bef9aa6a7d4565',
-		    'com.android.tools:desugar_jdk_libs_nio:2.0.3:desugar_jdk_libs_nio-2.0.3.jar:7f4e68385dfe88eba4344ff71912912bdc731806b9b2ce4a12bef9aa6a7d4565',
+			'com.android.tools:desugar_jdk_libs_configuration:2.0.3:desugar_jdk_libs_configuration-2.0.3.jar:9f834a20ca4e1376522afe7bf523d3f1d5e9ad9bb0214b534ee79cc8481b4fc5',
 			'com.github.bumptech.glide:annotations:4.14.2:annotations-4.14.2.jar:8419bf262be70edeb6b9582b386546be66d2e8659c7aae65fd69a9ede02c4877',
 			'com.github.bumptech.glide:compiler:4.14.2:compiler-4.14.2.jar:315b1325283c3d0cf9bc0599c1ecdb85e5f7863b1aa25991b63d616b13930cb6',
 			'com.github.bumptech.glide:gifdecoder:4.14.2:gifdecoder-4.14.2.aar:d021eee1ac1a036fcdc377b6dc3b218f4a0cc2bc2f096d69b474198b635e8302',

briar-headless/src/main/java/org/briarproject/briar/headless/HeadlessModule.kt

@@ -64,7 +64,7 @@ internal class HeadlessModule(private val appDir: File) {
     @Provides
     @Singleton
     internal fun provideDatabaseConfig(): DatabaseConfig {
-        val dbDir = File(appDir, "db")
+        val dbDir = File(appDir, "db_sqlite")
         val keyDir = File(appDir, "key")
         return HeadlessDatabaseConfig(dbDir, keyDir)
     }

briar-headless/src/test/java/org/briarproject/briar/headless/HeadlessTestModule.kt

@@ -58,7 +58,7 @@ internal class HeadlessTestModule(private val appDir: File) {
     @Provides
     @Singleton
     internal fun provideDatabaseConfig(): DatabaseConfig {
-        val dbDir = File(appDir, "db")
+        val dbDir = File(appDir, "db_sqlite")
         val keyDir = File(appDir, "key")
         return HeadlessDatabaseConfig(dbDir, keyDir)
     }

build.gradle

@@ -38,6 +38,7 @@ buildscript {
 		jmock_version = '2.12.0'
 		mockwebserver_version = '4.10.0'
 		onionwrapper_version = '0.0.5'
+		sqlite_jdbc_crypt_version = '3.41.2.1'
 	}
 	dependencies {
 		classpath 'com.android.tools.build:gradle:7.4.2'