Factor out recognition of QR code format.

bramble-api/src/main/java/org/briarproject/bramble/api/keyagreement/KeyAgreementConstants.java

@@ -1,18 +1,26 @@
 package org.briarproject.bramble.api.keyagreement;
 
-public interface KeyAgreementConstants {
+import org.briarproject.bramble.api.mailbox.MailboxConstants;
 
-	/**
-	 * The version of the BQP protocol used in beta releases. This version
-	 * number is reserved.
-	 */
-	byte BETA_PROTOCOL_VERSION = 89;
+public interface KeyAgreementConstants {
 
 	/**
 	 * The current version of the BQP protocol.
 	 */
 	byte PROTOCOL_VERSION = 4;
 
+	/**
+	 * The QR code format identifier, used to distinguish BQP QR codes from
+	 * QR codes used for other purposes. See
+	 * {@link MailboxConstants#QR_FORMAT_ID}.
+	 */
+	byte QR_FORMAT_ID = 0;
+
+	/**
+	 * The QR code format version.
+	 */
+	byte QR_FORMAT_VERSION = PROTOCOL_VERSION;
+
 	/**
 	 * The length of the BQP key commitment in bytes.
 	 */

bramble-api/src/main/java/org/briarproject/bramble/api/keyagreement/PayloadParser.java

@@ -7,5 +7,5 @@ import java.io.IOException;
 @NotNullByDefault
 public interface PayloadParser {
 
-	Payload parse(byte[] raw) throws IOException;
+	Payload parse(String payload) throws IOException;
 }

bramble-api/src/main/java/org/briarproject/bramble/api/mailbox/MailboxConstants.java

@@ -1,5 +1,6 @@
 package org.briarproject.bramble.api.mailbox;
 
+import org.briarproject.bramble.api.keyagreement.KeyAgreementConstants;
 import org.briarproject.bramble.api.plugin.TransportId;
 
 import java.util.List;
@@ -19,6 +20,18 @@ public interface MailboxConstants {
 	 */
 	TransportId ID = new TransportId("org.briarproject.bramble.mailbox");
 
+	/**
+	 * The QR code format identifier, used to distinguish mailbox QR codes
+	 * from QR codes used for other purposes. See
+	 * {@link KeyAgreementConstants#QR_FORMAT_ID};
+	 */
+	byte QR_FORMAT_ID = 1;
+
+	/**
+	 * The QR code format version.
+	 */
+	byte QR_FORMAT_VERSION = 0;
+
 	/**
 	 * Mailbox API versions that we support as a client. This is reported to our
 	 * contacts by {@link MailboxUpdateManager}.

bramble-api/src/main/java/org/briarproject/bramble/api/mailbox/MailboxPairingState.java

@@ -1,5 +1,7 @@
 package org.briarproject.bramble.api.mailbox;
 
+import org.briarproject.bramble.api.qrcode.QrCodeClassifier.QrCodeType;
+
 public abstract class MailboxPairingState {
 
 	public abstract static class Pending extends MailboxPairingState {
@@ -29,6 +31,14 @@ public abstract class MailboxPairingState {
 	}
 
 	public static class InvalidQrCode extends MailboxPairingState {
+
+		public final QrCodeType qrCodeType;
+		public final int formatVersion;
+
+		public InvalidQrCode(QrCodeType qrCodeType, int formatVersion) {
+			this.qrCodeType = qrCodeType;
+			this.formatVersion = formatVersion;
+		}
 	}
 
 	public static class MailboxAlreadyPaired extends MailboxPairingState {

bramble-api/src/main/java/org/briarproject/bramble/api/qrcode/QrCodeClassifier.java

@@ -0,0 +1,16 @@
+package org.briarproject.bramble.api.qrcode;
+
+import org.briarproject.bramble.api.Pair;
+import org.briarproject.nullsafety.NotNullByDefault;
+
+@NotNullByDefault
+public interface QrCodeClassifier {
+
+	enum QrCodeType {
+		BQP,
+		MAILBOX,
+		UNKNOWN
+	}
+
+	Pair<QrCodeType, Integer> classifyQrCode(String payload);
+}

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

@@ -3,7 +3,6 @@ package org.briarproject.bramble.util;
 import org.briarproject.bramble.api.FormatException;
 import org.briarproject.nullsafety.NotNullByDefault;
 
-import java.io.UnsupportedEncodingException;
 import java.nio.ByteBuffer;
 import java.nio.charset.CharacterCodingException;
 import java.nio.charset.Charset;
@@ -17,13 +16,18 @@ import javax.annotation.Nullable;
 import static java.nio.charset.CodingErrorAction.IGNORE;
 import static java.util.regex.Pattern.CASE_INSENSITIVE;
 
+@SuppressWarnings("CharsetObjectCanBeUsed")
 @NotNullByDefault
 public class StringUtils {
 
-	private static final Charset UTF_8 = Charset.forName("UTF-8");
-	private static Pattern MAC = Pattern.compile("[0-9a-f]{2}:[0-9a-f]{2}:" +
-					"[0-9a-f]{2}:[0-9a-f]{2}:[0-9a-f]{2}:[0-9a-f]{2}",
-			CASE_INSENSITIVE);
+	public static final Charset UTF_8 = Charset.forName("UTF-8");
+	public static final Charset US_ASCII = Charset.forName("US-ASCII");
+	public static final Charset ISO_8859_1 = Charset.forName("ISO-8859-1");
+
+	private static final Pattern MAC =
+			Pattern.compile("[0-9a-f]{2}:[0-9a-f]{2}:" +
+							"[0-9a-f]{2}:[0-9a-f]{2}:[0-9a-f]{2}:[0-9a-f]{2}",
+					CASE_INSENSITIVE);
 
 	private static final char[] HEX = new char[] {
 			'0', '1', '2', '3', '4', '5', '6', '7',
@@ -45,11 +49,7 @@ public class StringUtils {
 	}
 
 	public static byte[] toUtf8(String s) {
-		try {
-			return s.getBytes("UTF-8");
-		} catch (UnsupportedEncodingException e) {
-			throw new AssertionError(e);
-		}
+		return s.getBytes(UTF_8);
 	}
 
 	public static String fromUtf8(byte[] bytes) {

bramble-core/src/main/java/org/briarproject/bramble/BrambleCoreModule.java

@@ -17,6 +17,7 @@ import org.briarproject.bramble.lifecycle.LifecycleModule;
 import org.briarproject.bramble.mailbox.MailboxModule;
 import org.briarproject.bramble.plugin.PluginModule;
 import org.briarproject.bramble.properties.PropertiesModule;
+import org.briarproject.bramble.qrcode.QrCodeModule;
 import org.briarproject.bramble.record.RecordModule;
 import org.briarproject.bramble.reliability.ReliabilityModule;
 import org.briarproject.bramble.rendezvous.RendezvousModule;
@@ -47,6 +48,7 @@ import dagger.Module;
 		MailboxModule.class,
 		PluginModule.class,
 		PropertiesModule.class,
+		QrCodeModule.class,
 		RecordModule.class,
 		ReliabilityModule.class,
 		RendezvousModule.class,

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

@@ -19,7 +19,6 @@ import java.io.FileInputStream;
 import java.io.FileOutputStream;
 import java.io.IOException;
 import java.io.InputStreamReader;
-import java.nio.charset.Charset;
 import java.util.logging.Logger;
 
 import javax.annotation.Nullable;
@@ -29,6 +28,7 @@ import javax.inject.Inject;
 import static java.util.logging.Level.WARNING;
 import static org.briarproject.bramble.api.crypto.DecryptionResult.INVALID_CIPHERTEXT;
 import static org.briarproject.bramble.util.LogUtils.logException;
+import static org.briarproject.bramble.util.StringUtils.UTF_8;
 import static org.briarproject.bramble.util.StringUtils.fromHexString;
 import static org.briarproject.bramble.util.StringUtils.toHexString;
 
@@ -99,7 +99,7 @@ class AccountManagerImpl implements AccountManager {
 		}
 		try {
 			BufferedReader reader = new BufferedReader(new InputStreamReader(
-					new FileInputStream(f), Charset.forName("UTF-8")));
+					new FileInputStream(f), UTF_8));
 			String key = reader.readLine();
 			reader.close();
 			return key;
@@ -151,7 +151,7 @@ class AccountManagerImpl implements AccountManager {
 	@GuardedBy("stateChangeLock")
 	private void writeDbKeyToFile(String key, File f) throws IOException {
 		FileOutputStream out = new FileOutputStream(f);
-		out.write(key.getBytes(Charset.forName("UTF-8")));
+		out.write(key.getBytes(UTF_8));
 		out.flush();
 		out.close();
 	}

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

@@ -29,7 +29,6 @@ import org.briarproject.nullsafety.NotNullByDefault;
 import org.whispersystems.curve25519.Curve25519;
 import org.whispersystems.curve25519.Curve25519KeyPair;
 
-import java.nio.charset.Charset;
 import java.security.GeneralSecurityException;
 import java.security.NoSuchAlgorithmException;
 import java.security.Provider;
@@ -51,6 +50,7 @@ import static org.briarproject.bramble.api.crypto.DecryptionResult.KEY_STRENGTHE
 import static org.briarproject.bramble.util.ByteUtils.INT_32_BYTES;
 import static org.briarproject.bramble.util.LogUtils.logDuration;
 import static org.briarproject.bramble.util.LogUtils.now;
+import static org.briarproject.bramble.util.StringUtils.US_ASCII;
 
 @NotNullByDefault
 class CryptoComponentImpl implements CryptoComponent {
@@ -460,7 +460,7 @@ class CryptoComponentImpl implements CryptoComponent {
 	@Override
 	public String encodeOnion(byte[] publicKey) {
 		Digest digest = new SHA3Digest(256);
-		byte[] label = ".onion checksum".getBytes(Charset.forName("US-ASCII"));
+		byte[] label = ".onion checksum".getBytes(US_ASCII);
 		digest.update(label, 0, label.length);
 		digest.update(publicKey, 0, publicKey.length);
 		digest.update(ONION_HS_PROTOCOL_VERSION);

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

@@ -39,12 +39,13 @@ import java.io.FileOutputStream;
 import java.io.IOException;
 import java.io.InputStream;
 import java.io.PrintStream;
-import java.nio.charset.Charset;
 import java.security.SecureRandom;
 import java.util.Scanner;
 
 import javax.annotation.concurrent.Immutable;
 
+import static org.briarproject.bramble.util.StringUtils.UTF_8;
+
 @Immutable
 @NotNullByDefault
 public class MessageEncrypter {
@@ -228,7 +229,7 @@ public class MessageEncrypter {
 		PublicKey publicKey =
 				encrypter.getKeyParser().parsePublicKey(keyBytes);
 		String message = readFully(System.in);
-		byte[] plaintext = message.getBytes(Charset.forName("UTF-8"));
+		byte[] plaintext = message.getBytes(UTF_8);
 		byte[] ciphertext = encrypter.encrypt(publicKey, plaintext);
 		System.out.println(AsciiArmour.wrap(ciphertext, LINE_LENGTH));
 	}
@@ -242,7 +243,7 @@ public class MessageEncrypter {
 				encrypter.getKeyParser().parsePrivateKey(keyBytes);
 		byte[] ciphertext = AsciiArmour.unwrap(readFully(System.in));
 		byte[] plaintext = encrypter.decrypt(privateKey, ciphertext);
-		System.out.println(new String(plaintext, Charset.forName("UTF-8")));
+		System.out.println(new String(plaintext, UTF_8));
 	}
 
 	private static String readFully(InputStream in) throws IOException {

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

@@ -1,7 +1,5 @@
 package org.briarproject.bramble.keyagreement;
 
-import org.briarproject.bramble.api.data.BdfReaderFactory;
-import org.briarproject.bramble.api.data.BdfWriterFactory;
 import org.briarproject.bramble.api.keyagreement.KeyAgreementTask;
 import org.briarproject.bramble.api.keyagreement.PayloadEncoder;
 import org.briarproject.bramble.api.keyagreement.PayloadParser;
@@ -19,13 +17,13 @@ public class KeyAgreementModule {
 	}
 
 	@Provides
-	PayloadEncoder providePayloadEncoder(BdfWriterFactory bdfWriterFactory) {
-		return new PayloadEncoderImpl(bdfWriterFactory);
+	PayloadEncoder providePayloadEncoder(PayloadEncoderImpl payloadEncoder) {
+		return payloadEncoder;
 	}
 
 	@Provides
-	PayloadParser providePayloadParser(BdfReaderFactory bdfReaderFactory) {
-		return new PayloadParserImpl(bdfReaderFactory);
+	PayloadParser providePayloadParser(PayloadParserImpl payloadParser) {
+		return payloadParser;
 	}
 
 	@Provides

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

@@ -13,7 +13,8 @@ import java.io.IOException;
 import javax.annotation.concurrent.Immutable;
 import javax.inject.Inject;
 
-import static org.briarproject.bramble.api.keyagreement.KeyAgreementConstants.PROTOCOL_VERSION;
+import static org.briarproject.bramble.api.keyagreement.KeyAgreementConstants.QR_FORMAT_ID;
+import static org.briarproject.bramble.api.keyagreement.KeyAgreementConstants.QR_FORMAT_VERSION;
 
 @Immutable
 @NotNullByDefault
@@ -29,7 +30,8 @@ class PayloadEncoderImpl implements PayloadEncoder {
 	@Override
 	public byte[] encode(Payload p) {
 		ByteArrayOutputStream out = new ByteArrayOutputStream();
-		out.write(PROTOCOL_VERSION);
+		int formatIdAndVersion = (QR_FORMAT_ID << 5) | QR_FORMAT_VERSION;
+		out.write(formatIdAndVersion);
 		BdfWriter w = bdfWriterFactory.createWriter(out);
 		try {
 			w.writeListStart(); // Payload start

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

@@ -1,6 +1,7 @@
 package org.briarproject.bramble.keyagreement;
 
 import org.briarproject.bramble.api.FormatException;
+import org.briarproject.bramble.api.Pair;
 import org.briarproject.bramble.api.UnsupportedVersionException;
 import org.briarproject.bramble.api.data.BdfList;
 import org.briarproject.bramble.api.data.BdfReader;
@@ -11,6 +12,8 @@ import org.briarproject.bramble.api.keyagreement.TransportDescriptor;
 import org.briarproject.bramble.api.plugin.BluetoothConstants;
 import org.briarproject.bramble.api.plugin.LanTcpConstants;
 import org.briarproject.bramble.api.plugin.TransportId;
+import org.briarproject.bramble.api.qrcode.QrCodeClassifier;
+import org.briarproject.bramble.api.qrcode.QrCodeClassifier.QrCodeType;
 import org.briarproject.nullsafety.NotNullByDefault;
 
 import java.io.ByteArrayInputStream;
@@ -21,34 +24,41 @@ import java.util.List;
 import javax.annotation.concurrent.Immutable;
 import javax.inject.Inject;
 
-import static org.briarproject.bramble.api.keyagreement.KeyAgreementConstants.BETA_PROTOCOL_VERSION;
 import static org.briarproject.bramble.api.keyagreement.KeyAgreementConstants.COMMIT_LENGTH;
-import static org.briarproject.bramble.api.keyagreement.KeyAgreementConstants.PROTOCOL_VERSION;
+import static org.briarproject.bramble.api.keyagreement.KeyAgreementConstants.QR_FORMAT_VERSION;
 import static org.briarproject.bramble.api.keyagreement.KeyAgreementConstants.TRANSPORT_ID_BLUETOOTH;
 import static org.briarproject.bramble.api.keyagreement.KeyAgreementConstants.TRANSPORT_ID_LAN;
+import static org.briarproject.bramble.api.qrcode.QrCodeClassifier.QrCodeType.BQP;
+import static org.briarproject.bramble.util.StringUtils.ISO_8859_1;
 
 @Immutable
 @NotNullByDefault
 class PayloadParserImpl implements PayloadParser {
 
 	private final BdfReaderFactory bdfReaderFactory;
+	private final QrCodeClassifier qrCodeClassifier;
 
 	@Inject
-	PayloadParserImpl(BdfReaderFactory bdfReaderFactory) {
+	PayloadParserImpl(BdfReaderFactory bdfReaderFactory,
+			QrCodeClassifier qrCodeClassifier) {
 		this.bdfReaderFactory = bdfReaderFactory;
+		this.qrCodeClassifier = qrCodeClassifier;
 	}
 
 	@Override
-	public Payload parse(byte[] raw) throws IOException {
-		ByteArrayInputStream in = new ByteArrayInputStream(raw);
-		// First byte: the protocol version
-		int protocolVersion = in.read();
-		if (protocolVersion == -1) throw new FormatException();
-		if (protocolVersion != PROTOCOL_VERSION) {
-			boolean tooOld = protocolVersion < PROTOCOL_VERSION ||
-					protocolVersion == BETA_PROTOCOL_VERSION;
+	public Payload parse(String payloadString) throws IOException {
+		Pair<QrCodeType, Integer> typeAndVersion =
+				qrCodeClassifier.classifyQrCode(payloadString);
+		if (typeAndVersion.getFirst() != BQP) throw new FormatException();
+		int formatVersion = typeAndVersion.getSecond();
+		if (formatVersion != QR_FORMAT_VERSION) {
+			boolean tooOld = formatVersion < QR_FORMAT_VERSION;
 			throw new UnsupportedVersionException(tooOld);
 		}
+		byte[] raw = payloadString.getBytes(ISO_8859_1);
+		ByteArrayInputStream in = new ByteArrayInputStream(raw);
+		// First byte: the format identifier and version (already parsed)
+		if (in.read() == -1) throw new AssertionError();
 		// The rest of the payload is a BDF list with one or more elements
 		BdfReader r = bdfReaderFactory.createReader(in);
 		BdfList payload = r.readList();

bramble-core/src/main/java/org/briarproject/bramble/mailbox/MailboxPairingTaskFactoryImpl.java

@@ -6,6 +6,7 @@ import org.briarproject.bramble.api.event.EventExecutor;
 import org.briarproject.bramble.api.mailbox.MailboxPairingTask;
 import org.briarproject.bramble.api.mailbox.MailboxSettingsManager;
 import org.briarproject.bramble.api.mailbox.MailboxUpdateManager;
+import org.briarproject.bramble.api.qrcode.QrCodeClassifier;
 import org.briarproject.bramble.api.system.Clock;
 import org.briarproject.nullsafety.NotNullByDefault;
 
@@ -25,6 +26,7 @@ class MailboxPairingTaskFactoryImpl implements MailboxPairingTaskFactory {
 	private final MailboxApi api;
 	private final MailboxSettingsManager mailboxSettingsManager;
 	private final MailboxUpdateManager mailboxUpdateManager;
+	private final QrCodeClassifier qrCodeClassifier;
 
 	@Inject
 	MailboxPairingTaskFactoryImpl(
@@ -34,7 +36,8 @@ class MailboxPairingTaskFactoryImpl implements MailboxPairingTaskFactory {
 			Clock clock,
 			MailboxApi api,
 			MailboxSettingsManager mailboxSettingsManager,
-			MailboxUpdateManager mailboxUpdateManager) {
+			MailboxUpdateManager mailboxUpdateManager,
+			QrCodeClassifier qrCodeClassifier) {
 		this.eventExecutor = eventExecutor;
 		this.db = db;
 		this.crypto = crypto;
@@ -42,12 +45,13 @@ class MailboxPairingTaskFactoryImpl implements MailboxPairingTaskFactory {
 		this.api = api;
 		this.mailboxSettingsManager = mailboxSettingsManager;
 		this.mailboxUpdateManager = mailboxUpdateManager;
+		this.qrCodeClassifier = qrCodeClassifier;
 	}
 
 	@Override
 	public MailboxPairingTask createPairingTask(String qrCodePayload) {
 		return new MailboxPairingTaskImpl(qrCodePayload, eventExecutor, db,
 				crypto, clock, api, mailboxSettingsManager,
-				mailboxUpdateManager);
+				mailboxUpdateManager, qrCodeClassifier);
 	}
 }

bramble-core/src/main/java/org/briarproject/bramble/mailbox/MailboxPairingTaskImpl.java

@@ -2,6 +2,7 @@ package org.briarproject.bramble.mailbox;
 
 import org.briarproject.bramble.api.Consumer;
 import org.briarproject.bramble.api.FormatException;
+import org.briarproject.bramble.api.Pair;
 import org.briarproject.bramble.api.contact.Contact;
 import org.briarproject.bramble.api.crypto.CryptoComponent;
 import org.briarproject.bramble.api.db.DatabaseComponent;
@@ -14,13 +15,14 @@ import org.briarproject.bramble.api.mailbox.MailboxProperties;
 import org.briarproject.bramble.api.mailbox.MailboxSettingsManager;
 import org.briarproject.bramble.api.mailbox.MailboxUpdate;
 import org.briarproject.bramble.api.mailbox.MailboxUpdateManager;
+import org.briarproject.bramble.api.qrcode.QrCodeClassifier;
+import org.briarproject.bramble.api.qrcode.QrCodeClassifier.QrCodeType;
 import org.briarproject.bramble.api.system.Clock;
 import org.briarproject.bramble.mailbox.MailboxApi.ApiException;
 import org.briarproject.bramble.mailbox.MailboxApi.MailboxAlreadyPairedException;
 import org.briarproject.nullsafety.NotNullByDefault;
 
 import java.io.IOException;
-import java.nio.charset.Charset;
 import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.List;
@@ -32,7 +34,10 @@ import javax.annotation.concurrent.ThreadSafe;
 
 import static java.util.logging.Level.WARNING;
 import static java.util.logging.Logger.getLogger;
+import static org.briarproject.bramble.api.mailbox.MailboxConstants.QR_FORMAT_VERSION;
+import static org.briarproject.bramble.api.qrcode.QrCodeClassifier.QrCodeType.MAILBOX;
 import static org.briarproject.bramble.util.LogUtils.logException;
+import static org.briarproject.bramble.util.StringUtils.ISO_8859_1;
 
 @ThreadSafe
 @NotNullByDefault
@@ -40,9 +45,6 @@ class MailboxPairingTaskImpl implements MailboxPairingTask {
 
 	private final static Logger LOG =
 			getLogger(MailboxPairingTaskImpl.class.getName());
-	@SuppressWarnings("CharsetObjectCanBeUsed") // Requires minSdkVersion >= 19
-	private static final Charset ISO_8859_1 = Charset.forName("ISO-8859-1");
-	private static final int VERSION_REQUIRED = 32;
 
 	private final String payload;
 	private final Executor eventExecutor;
@@ -52,6 +54,7 @@ class MailboxPairingTaskImpl implements MailboxPairingTask {
 	private final MailboxApi api;
 	private final MailboxSettingsManager mailboxSettingsManager;
 	private final MailboxUpdateManager mailboxUpdateManager;
+	private final QrCodeClassifier qrCodeClassifier;
 	private final long timeStarted;
 
 	private final Object lock = new Object();
@@ -69,7 +72,8 @@ class MailboxPairingTaskImpl implements MailboxPairingTask {
 			Clock clock,
 			MailboxApi api,
 			MailboxSettingsManager mailboxSettingsManager,
-			MailboxUpdateManager mailboxUpdateManager) {
+			MailboxUpdateManager mailboxUpdateManager,
+			QrCodeClassifier qrCodeClassifier) {
 		this.payload = payload;
 		this.eventExecutor = eventExecutor;
 		this.db = db;
@@ -78,6 +82,7 @@ class MailboxPairingTaskImpl implements MailboxPairingTask {
 		this.api = api;
 		this.mailboxSettingsManager = mailboxSettingsManager;
 		this.mailboxUpdateManager = mailboxUpdateManager;
+		this.qrCodeClassifier = qrCodeClassifier;
 		timeStarted = clock.currentTimeMillis();
 		state = new MailboxPairingState.QrCodeReceived(timeStarted);
 	}
@@ -101,10 +106,20 @@ class MailboxPairingTaskImpl implements MailboxPairingTask {
 
 	@Override
 	public void run() {
+		Pair<QrCodeType, Integer> typeAndVersion =
+				qrCodeClassifier.classifyQrCode(payload);
+		QrCodeType qrCodeType = typeAndVersion.getFirst();
+		int formatVersion = typeAndVersion.getSecond();
+		if (qrCodeType != MAILBOX || formatVersion != QR_FORMAT_VERSION) {
+			setState(new MailboxPairingState.InvalidQrCode(qrCodeType,
+					formatVersion));
+			return;
+		}
 		try {
 			pairMailbox();
 		} catch (FormatException e) {
-			onMailboxError(e, new MailboxPairingState.InvalidQrCode());
+			onMailboxError(e, new MailboxPairingState.InvalidQrCode(qrCodeType,
+					formatVersion));
 		} catch (MailboxAlreadyPairedException e) {
 			onMailboxError(e, new MailboxPairingState.MailboxAlreadyPaired());
 		} catch (IOException e) {
@@ -169,14 +184,6 @@ class MailboxPairingTaskImpl implements MailboxPairingTask {
 			}
 			throw new FormatException();
 		}
-		int version = bytes[0] & 0xFF;
-		if (version != VERSION_REQUIRED) {
-			if (LOG.isLoggable(WARNING)) {
-				LOG.warning("QR code has not version " + VERSION_REQUIRED +
-						": " + version);
-			}
-			throw new FormatException();
-		}
 		LOG.info("QR code is valid");
 		byte[] onionPubKey = Arrays.copyOfRange(bytes, 1, 33);
 		String onion = crypto.encodeOnion(onionPubKey);

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

@@ -46,7 +46,6 @@ import java.io.OutputStream;
 import java.net.InetSocketAddress;
 import java.net.ServerSocket;
 import java.net.Socket;
-import java.nio.charset.Charset;
 import java.util.ArrayList;
 import java.util.Collection;
 import java.util.List;
@@ -100,6 +99,7 @@ import static org.briarproject.bramble.util.IoUtils.copyAndClose;
 import static org.briarproject.bramble.util.IoUtils.tryToClose;
 import static org.briarproject.bramble.util.LogUtils.logException;
 import static org.briarproject.bramble.util.PrivacyUtils.scrubOnion;
+import static org.briarproject.bramble.util.StringUtils.UTF_8;
 import static org.briarproject.bramble.util.StringUtils.isNullOrEmpty;
 
 @MethodsNotNullByDefault
@@ -419,9 +419,7 @@ abstract class TorPlugin implements DuplexPlugin, EventHandler, EventListener {
 		append(strb, "ClientTransportPlugin meek_lite exec", obfs4Path);
 		String snowflakePath = getSnowflakeExecutableFile().getAbsolutePath();
 		append(strb, "ClientTransportPlugin snowflake exec", snowflakePath);
-		//noinspection CharsetObjectCanBeUsed
-		return new ByteArrayInputStream(
-				strb.toString().getBytes(Charset.forName("UTF-8")));
+		return new ByteArrayInputStream(strb.toString().getBytes(UTF_8));
 	}
 
 	private void listFiles(File f) {

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

@@ -7,7 +7,7 @@ import net.i2p.crypto.eddsa.spec.EdDSAPrivateKeySpec;
 import org.bouncycastle.util.encoders.Base64;
 import org.briarproject.bramble.api.crypto.CryptoComponent;
 
-import java.nio.charset.Charset;
+import static org.briarproject.bramble.util.StringUtils.US_ASCII;
 
 class TorRendezvousCryptoImpl implements TorRendezvousCrypto {
 
@@ -31,6 +31,6 @@ class TorRendezvousCryptoImpl implements TorRendezvousCrypto {
 		EdDSAPrivateKeySpec spec = new EdDSAPrivateKeySpec(seed, CURVE_SPEC);
 		byte[] hash = spec.getH();
 		byte[] base64 = Base64.encode(hash);
-		return "ED25519-V3:" + new String(base64, Charset.forName("US-ASCII"));
+		return "ED25519-V3:" + new String(base64, US_ASCII);
 	}
 }

bramble-core/src/main/java/org/briarproject/bramble/qrcode/QrCodeClassifierImpl.java

@@ -0,0 +1,42 @@
+package org.briarproject.bramble.qrcode;
+
+import org.briarproject.bramble.api.Pair;
+import org.briarproject.bramble.api.keyagreement.KeyAgreementConstants;
+import org.briarproject.bramble.api.mailbox.MailboxConstants;
+import org.briarproject.bramble.api.qrcode.QrCodeClassifier;
+import org.briarproject.nullsafety.NotNullByDefault;
+
+import javax.annotation.concurrent.Immutable;
+import javax.inject.Inject;
+
+import static org.briarproject.bramble.api.qrcode.QrCodeClassifier.QrCodeType.BQP;
+import static org.briarproject.bramble.api.qrcode.QrCodeClassifier.QrCodeType.MAILBOX;
+import static org.briarproject.bramble.api.qrcode.QrCodeClassifier.QrCodeType.UNKNOWN;
+import static org.briarproject.bramble.util.StringUtils.ISO_8859_1;
+
+@Immutable
+@NotNullByDefault
+class QrCodeClassifierImpl implements QrCodeClassifier {
+
+	@Inject
+	QrCodeClassifierImpl() {
+	}
+
+	@Override
+	public Pair<QrCodeType, Integer> classifyQrCode(String payload) {
+		byte[] bytes = payload.getBytes(ISO_8859_1);
+		if (bytes.length == 0) return new Pair<>(UNKNOWN, 0);
+		// If this is a Bramble QR code then the first byte encodes the
+		// format ID (3 bits) and version (5 bits)
+		int formatIdAndVersion = bytes[0] & 0xFF;
+		int formatId = formatIdAndVersion >> 5;
+		int formatVersion = formatIdAndVersion & 0x1F;
+		if (formatId == KeyAgreementConstants.QR_FORMAT_ID) {
+			return new Pair<>(BQP, formatVersion);
+		}
+		if (formatId == MailboxConstants.QR_FORMAT_ID) {
+			return new Pair<>(MAILBOX, formatVersion);
+		}
+		return new Pair<>(UNKNOWN, 0);
+	}
+}

bramble-core/src/main/java/org/briarproject/bramble/qrcode/QrCodeModule.java

@@ -0,0 +1,16 @@
+package org.briarproject.bramble.qrcode;
+
+import org.briarproject.bramble.api.qrcode.QrCodeClassifier;
+
+import dagger.Module;
+import dagger.Provides;
+
+@Module
+public class QrCodeModule {
+
+	@Provides
+	QrCodeClassifier provideQrCodeClassifier(
+			QrCodeClassifierImpl qrCodeClassifier) {
+		return qrCodeClassifier;
+	}
+}

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

@@ -20,7 +20,6 @@ import java.io.FileInputStream;
 import java.io.FileOutputStream;
 import java.io.IOException;
 import java.io.InputStreamReader;
-import java.nio.charset.Charset;
 
 import javax.annotation.Nullable;
 
@@ -34,6 +33,7 @@ import static org.briarproject.bramble.test.TestUtils.getIdentity;
 import static org.briarproject.bramble.test.TestUtils.getRandomBytes;
 import static org.briarproject.bramble.test.TestUtils.getSecretKey;
 import static org.briarproject.bramble.test.TestUtils.getTestDirectory;
+import static org.briarproject.bramble.util.StringUtils.UTF_8;
 import static org.briarproject.bramble.util.StringUtils.getRandomString;
 import static org.briarproject.bramble.util.StringUtils.toHexString;
 import static org.junit.Assert.assertArrayEquals;
@@ -342,7 +342,7 @@ public class AccountManagerImplTest extends BrambleMockTestCase {
 	private void storeDatabaseKey(File f, String hex) throws IOException {
 		f.getParentFile().mkdirs();
 		FileOutputStream out = new FileOutputStream(f);
-		out.write(hex.getBytes(Charset.forName("UTF-8")));
+		out.write(hex.getBytes(UTF_8));
 		out.flush();
 		out.close();
 	}
@@ -350,7 +350,7 @@ public class AccountManagerImplTest extends BrambleMockTestCase {
 	@Nullable
 	private String loadDatabaseKey(File f) throws IOException {
 		BufferedReader reader = new BufferedReader(new InputStreamReader(
-				new FileInputStream(f), Charset.forName("UTF-8")));
+				new FileInputStream(f), UTF_8));
 		String hex = reader.readLine();
 		reader.close();
 		return hex;

bramble-core/src/test/java/org/briarproject/bramble/keyagreement/PayloadParserImplTest.java

@@ -2,21 +2,26 @@ package org.briarproject.bramble.keyagreement;
 
 import org.briarproject.bramble.api.Bytes;
 import org.briarproject.bramble.api.FormatException;
+import org.briarproject.bramble.api.Pair;
 import org.briarproject.bramble.api.UnsupportedVersionException;
 import org.briarproject.bramble.api.data.BdfList;
 import org.briarproject.bramble.api.data.BdfReader;
 import org.briarproject.bramble.api.data.BdfReaderFactory;
 import org.briarproject.bramble.api.keyagreement.Payload;
+import org.briarproject.bramble.api.qrcode.QrCodeClassifier;
+import org.briarproject.bramble.api.qrcode.QrCodeClassifier.QrCodeType;
 import org.briarproject.bramble.test.BrambleMockTestCase;
 import org.jmock.Expectations;
 import org.junit.Test;
 
 import java.io.ByteArrayInputStream;
 
-import static org.briarproject.bramble.api.keyagreement.KeyAgreementConstants.BETA_PROTOCOL_VERSION;
 import static org.briarproject.bramble.api.keyagreement.KeyAgreementConstants.COMMIT_LENGTH;
-import static org.briarproject.bramble.api.keyagreement.KeyAgreementConstants.PROTOCOL_VERSION;
+import static org.briarproject.bramble.api.keyagreement.KeyAgreementConstants.QR_FORMAT_VERSION;
+import static org.briarproject.bramble.api.qrcode.QrCodeClassifier.QrCodeType.BQP;
+import static org.briarproject.bramble.api.qrcode.QrCodeClassifier.QrCodeType.MAILBOX;
 import static org.briarproject.bramble.test.TestUtils.getRandomBytes;
+import static org.briarproject.bramble.util.StringUtils.getRandomString;
 import static org.junit.Assert.assertArrayEquals;
 import static org.junit.Assert.assertFalse;
 import static org.junit.Assert.assertTrue;
@@ -26,32 +31,29 @@ public class PayloadParserImplTest extends BrambleMockTestCase {
 
 	private final BdfReaderFactory bdfReaderFactory =
 			context.mock(BdfReaderFactory.class);
+	private final QrCodeClassifier qrCodeClassifier =
+			context.mock(QrCodeClassifier.class);
 	private final BdfReader bdfReader = context.mock(BdfReader.class);
 
+	private final String payload = getRandomString(123);
+
 	private final PayloadParserImpl payloadParser =
-			new PayloadParserImpl(bdfReaderFactory);
+			new PayloadParserImpl(bdfReaderFactory, qrCodeClassifier);
 
 	@Test(expected = FormatException.class)
-	public void testThrowsFormatExceptionIfPayloadIsEmpty() throws Exception {
-		payloadParser.parse(new byte[0]);
+	public void testThrowsFormatExceptionForWrongQrCodeType() throws Exception {
+		expectClassifyQrCode(payload, MAILBOX, QR_FORMAT_VERSION);
+
+		payloadParser.parse(payload);
 	}
 
 	@Test
 	public void testThrowsUnsupportedVersionExceptionForOldVersion()
 			throws Exception {
-		try {
-			payloadParser.parse(new byte[] {PROTOCOL_VERSION - 1});
-			fail();
-		} catch (UnsupportedVersionException e) {
-			assertTrue(e.isTooOld());
-		}
-	}
+		expectClassifyQrCode(payload, BQP, QR_FORMAT_VERSION - 1);
 
-	@Test
-	public void testThrowsUnsupportedVersionExceptionForBetaVersion()
-			throws Exception {
 		try {
-			payloadParser.parse(new byte[] {BETA_PROTOCOL_VERSION});
+			payloadParser.parse(payload);
 			fail();
 		} catch (UnsupportedVersionException e) {
 			assertTrue(e.isTooOld());
@@ -61,8 +63,10 @@ public class PayloadParserImplTest extends BrambleMockTestCase {
 	@Test
 	public void testThrowsUnsupportedVersionExceptionForNewVersion()
 			throws Exception {
+		expectClassifyQrCode(payload, BQP, QR_FORMAT_VERSION + 1);
+
 		try {
-			payloadParser.parse(new byte[] {PROTOCOL_VERSION + 1});
+			payloadParser.parse(payload);
 			fail();
 		} catch (UnsupportedVersionException e) {
 			assertFalse(e.isTooOld());
@@ -71,6 +75,8 @@ public class PayloadParserImplTest extends BrambleMockTestCase {
 
 	@Test(expected = FormatException.class)
 	public void testThrowsFormatExceptionForEmptyList() throws Exception {
+		expectClassifyQrCode(payload, BQP, QR_FORMAT_VERSION);
+
 		context.checking(new Expectations() {{
 			oneOf(bdfReaderFactory).createReader(
 					with(any(ByteArrayInputStream.class)));
@@ -79,7 +85,7 @@ public class PayloadParserImplTest extends BrambleMockTestCase {
 			will(returnValue(new BdfList()));
 		}});
 
-		payloadParser.parse(new byte[] {PROTOCOL_VERSION});
+		payloadParser.parse(payload);
 	}
 
 	@Test(expected = FormatException.class)
@@ -87,6 +93,8 @@ public class PayloadParserImplTest extends BrambleMockTestCase {
 			throws Exception {
 		byte[] commitment = getRandomBytes(COMMIT_LENGTH);
 
+		expectClassifyQrCode(payload, BQP, QR_FORMAT_VERSION);
+
 		context.checking(new Expectations() {{
 			oneOf(bdfReaderFactory).createReader(
 					with(any(ByteArrayInputStream.class)));
@@ -97,7 +105,7 @@ public class PayloadParserImplTest extends BrambleMockTestCase {
 			will(returnValue(false));
 		}});
 
-		payloadParser.parse(new byte[] {PROTOCOL_VERSION});
+		payloadParser.parse(payload);
 	}
 
 	@Test(expected = FormatException.class)
@@ -105,6 +113,7 @@ public class PayloadParserImplTest extends BrambleMockTestCase {
 			throws Exception {
 		byte[] commitment = getRandomBytes(COMMIT_LENGTH - 1);
 
+		expectClassifyQrCode(payload, BQP, QR_FORMAT_VERSION);
 		context.checking(new Expectations() {{
 			oneOf(bdfReaderFactory).createReader(
 					with(any(ByteArrayInputStream.class)));
@@ -115,7 +124,7 @@ public class PayloadParserImplTest extends BrambleMockTestCase {
 			will(returnValue(true));
 		}});
 
-		payloadParser.parse(new byte[] {PROTOCOL_VERSION});
+		payloadParser.parse(payload);
 	}
 
 	@Test(expected = FormatException.class)
@@ -123,6 +132,7 @@ public class PayloadParserImplTest extends BrambleMockTestCase {
 			throws Exception {
 		byte[] commitment = getRandomBytes(COMMIT_LENGTH + 1);
 
+		expectClassifyQrCode(payload, BQP, QR_FORMAT_VERSION);
 		context.checking(new Expectations() {{
 			oneOf(bdfReaderFactory).createReader(
 					with(any(ByteArrayInputStream.class)));
@@ -133,12 +143,14 @@ public class PayloadParserImplTest extends BrambleMockTestCase {
 			will(returnValue(true));
 		}});
 
-		payloadParser.parse(new byte[] {PROTOCOL_VERSION});
+		payloadParser.parse(payload);
 	}
 
 	@Test
 	public void testAcceptsPayloadWithNoDescriptors() throws Exception {
 		byte[] commitment = getRandomBytes(COMMIT_LENGTH);
+
+		expectClassifyQrCode(payload, BQP, QR_FORMAT_VERSION);
 		context.checking(new Expectations() {{
 			oneOf(bdfReaderFactory).createReader(
 					with(any(ByteArrayInputStream.class)));
@@ -149,8 +161,16 @@ public class PayloadParserImplTest extends BrambleMockTestCase {
 			will(returnValue(true));
 		}});
 
-		Payload p = payloadParser.parse(new byte[] {PROTOCOL_VERSION});
+		Payload p = payloadParser.parse(payload);
 		assertArrayEquals(commitment, p.getCommitment());
 		assertTrue(p.getTransportDescriptors().isEmpty());
 	}
+
+	private void expectClassifyQrCode(String payload, QrCodeType qrCodeType,
+			int formatVersion) {
+		context.checking(new Expectations() {{
+			oneOf(qrCodeClassifier).classifyQrCode(payload);
+			will(returnValue(new Pair<>(qrCodeType, formatVersion)));
+		}});
+	}
 }

bramble-core/src/test/java/org/briarproject/bramble/mailbox/MailboxPairingTaskImplTest.java

@@ -1,5 +1,6 @@
 package org.briarproject.bramble.mailbox;
 
+import org.briarproject.bramble.api.Pair;
 import org.briarproject.bramble.api.contact.Contact;
 import org.briarproject.bramble.api.crypto.CryptoComponent;
 import org.briarproject.bramble.api.db.DatabaseComponent;
@@ -13,6 +14,8 @@ import org.briarproject.bramble.api.mailbox.MailboxSettingsManager;
 import org.briarproject.bramble.api.mailbox.MailboxUpdate;
 import org.briarproject.bramble.api.mailbox.MailboxUpdateManager;
 import org.briarproject.bramble.api.mailbox.MailboxVersion;
+import org.briarproject.bramble.api.qrcode.QrCodeClassifier;
+import org.briarproject.bramble.api.qrcode.QrCodeClassifier.QrCodeType;
 import org.briarproject.bramble.api.system.Clock;
 import org.briarproject.bramble.test.BrambleMockTestCase;
 import org.briarproject.bramble.test.DbExpectations;
@@ -27,6 +30,9 @@ import java.util.concurrent.Executor;
 import java.util.concurrent.atomic.AtomicInteger;
 
 import static java.util.Collections.singletonList;
+import static org.briarproject.bramble.api.mailbox.MailboxConstants.QR_FORMAT_VERSION;
+import static org.briarproject.bramble.api.qrcode.QrCodeClassifier.QrCodeType.BQP;
+import static org.briarproject.bramble.api.qrcode.QrCodeClassifier.QrCodeType.MAILBOX;
 import static org.briarproject.bramble.mailbox.MailboxTestUtils.getQrCodePayload;
 import static org.briarproject.bramble.test.TestUtils.getContact;
 import static org.briarproject.bramble.test.TestUtils.getRandomBytes;
@@ -48,9 +54,8 @@ public class MailboxPairingTaskImplTest extends BrambleMockTestCase {
 			context.mock(MailboxSettingsManager.class);
 	private final MailboxUpdateManager mailboxUpdateManager =
 			context.mock(MailboxUpdateManager.class);
-	private final MailboxPairingTaskFactory factory =
-			new MailboxPairingTaskFactoryImpl(executor, db, crypto, clock, api,
-					mailboxSettingsManager, mailboxUpdateManager);
+	private final QrCodeClassifier qrCodeClassifier =
+			context.mock(QrCodeClassifier.class);
 
 	private final String onion = getRandomString(56);
 	private final byte[] onionBytes = getRandomBytes(32);
@@ -75,23 +80,47 @@ public class MailboxPairingTaskImplTest extends BrambleMockTestCase {
 	}
 
 	@Test
-	public void testInvalidQrCode() {
-		MailboxPairingTask task1 = createPairingTask(getRandomString(42));
-		task1.run();
-		task1.addObserver(state ->
+	public void testInvalidQrCodeType() {
+		String payload = getRandomString(65);
+		MailboxPairingTask task = createPairingTask(payload);
+
+		expectClassifyQrCode(payload, BQP, QR_FORMAT_VERSION);
+
+		task.run();
+		task.addObserver(state ->
 				assertTrue(state instanceof MailboxPairingState.InvalidQrCode)
 		);
+	}
 
-		String goodLength = "00" + getRandomString(63);
-		MailboxPairingTask task2 = createPairingTask(goodLength);
-		task2.run();
-		task2.addObserver(state ->
+	@Test
+	public void testInvalidQrCodeVersion() {
+		String payload = getRandomString(65);
+		MailboxPairingTask task = createPairingTask(payload);
+
+		expectClassifyQrCode(payload, MAILBOX, QR_FORMAT_VERSION + 1);
+
+		task.run();
+		task.addObserver(state ->
+				assertTrue(state instanceof MailboxPairingState.InvalidQrCode)
+		);
+	}
+
+	@Test
+	public void testInvalidQrCodeLength() {
+		String payload = getRandomString(42);
+		MailboxPairingTask task = createPairingTask(payload);
+
+		expectClassifyQrCode(payload, MAILBOX, QR_FORMAT_VERSION);
+
+		task.run();
+		task.addObserver(state ->
 				assertTrue(state instanceof MailboxPairingState.InvalidQrCode)
 		);
 	}
 
 	@Test
 	public void testSuccessfulPairing() throws Exception {
+		expectClassifyQrCode(validPayload, MAILBOX, QR_FORMAT_VERSION);
 		context.checking(new Expectations() {{
 			oneOf(crypto).encodeOnion(onionBytes);
 			will(returnValue(onion));
@@ -156,6 +185,7 @@ public class MailboxPairingTaskImplTest extends BrambleMockTestCase {
 
 	private void testApiException(Exception e,
 			Class<? extends MailboxPairingState> s) throws Exception {
+		expectClassifyQrCode(validPayload, MAILBOX, QR_FORMAT_VERSION);
 		context.checking(new Expectations() {{
 			oneOf(crypto).encodeOnion(onionBytes);
 			will(returnValue(onion));
@@ -170,6 +200,7 @@ public class MailboxPairingTaskImplTest extends BrambleMockTestCase {
 
 	@Test
 	public void testDbException() throws Exception {
+		expectClassifyQrCode(validPayload, MAILBOX, QR_FORMAT_VERSION);
 		context.checking(new Expectations() {{
 			oneOf(crypto).encodeOnion(onionBytes);
 			will(returnValue(onion));
@@ -206,6 +237,16 @@ public class MailboxPairingTaskImplTest extends BrambleMockTestCase {
 			will(returnValue(time));
 		}});
 
-		return factory.createPairingTask(qrCodePayload);
+		return new MailboxPairingTaskImpl(qrCodePayload, executor, db,
+				crypto, clock, api, mailboxSettingsManager,
+				mailboxUpdateManager, qrCodeClassifier);
+	}
+
+	private void expectClassifyQrCode(String payload, QrCodeType qrCodeType,
+			int formatVersion) {
+		context.checking(new Expectations() {{
+			oneOf(qrCodeClassifier).classifyQrCode(payload);
+			will(returnValue(new Pair<>(qrCodeType, formatVersion)));
+		}});
 	}
 }

bramble-core/src/test/java/org/briarproject/bramble/mailbox/MailboxTestUtils.java

@@ -3,7 +3,6 @@ package org.briarproject.bramble.mailbox;
 import org.briarproject.bramble.api.WeakSingletonProvider;
 
 import java.nio.ByteBuffer;
-import java.nio.charset.Charset;
 
 import javax.annotation.Nonnull;
 import javax.net.SocketFactory;
@@ -11,20 +10,24 @@ import javax.net.SocketFactory;
 import okhttp3.OkHttpClient;
 
 import static java.util.concurrent.TimeUnit.MILLISECONDS;
+import static org.briarproject.bramble.api.mailbox.MailboxConstants.QR_FORMAT_ID;
+import static org.briarproject.bramble.api.mailbox.MailboxConstants.QR_FORMAT_VERSION;
 import static org.briarproject.bramble.test.TestUtils.getRandomId;
+import static org.briarproject.bramble.util.StringUtils.ISO_8859_1;
 
 class MailboxTestUtils {
 
 	static String getQrCodePayload(byte[] onionBytes, byte[] setupToken) {
+		int formatIdAndVersion = (QR_FORMAT_ID << 5) | QR_FORMAT_VERSION;
 		byte[] payloadBytes = ByteBuffer.allocate(65)
-				.put((byte) 32) // 1
+				.put((byte) formatIdAndVersion) // 1
 				.put(onionBytes) // 32
 				.put(setupToken) // 32
 				.array();
-		//noinspection CharsetObjectCanBeUsed
-		return new String(payloadBytes, Charset.forName("ISO-8859-1"));
+		return new String(payloadBytes, ISO_8859_1);
 	}
 
+	// Used by mailbox integration tests
 	static String getQrCodePayload(byte[] setupToken) {
 		return getQrCodePayload(getRandomId(), setupToken);
 	}

bramble-core/src/test/java/org/briarproject/bramble/qrcode/QrCodeClassifierImplTest.java

@@ -0,0 +1,70 @@
+package org.briarproject.bramble.qrcode;
+
+import org.briarproject.bramble.api.Pair;
+import org.briarproject.bramble.api.keyagreement.KeyAgreementConstants;
+import org.briarproject.bramble.api.mailbox.MailboxConstants;
+import org.briarproject.bramble.api.qrcode.QrCodeClassifier;
+import org.briarproject.bramble.api.qrcode.QrCodeClassifier.QrCodeType;
+import org.briarproject.bramble.test.BrambleTestCase;
+import org.junit.Test;
+
+import static org.briarproject.bramble.api.qrcode.QrCodeClassifier.QrCodeType.BQP;
+import static org.briarproject.bramble.api.qrcode.QrCodeClassifier.QrCodeType.MAILBOX;
+import static org.briarproject.bramble.api.qrcode.QrCodeClassifier.QrCodeType.UNKNOWN;
+import static org.briarproject.bramble.test.TestUtils.getRandomBytes;
+import static org.briarproject.bramble.util.StringUtils.ISO_8859_1;
+import static org.junit.Assert.assertEquals;
+
+public class QrCodeClassifierImplTest extends BrambleTestCase {
+
+	private final QrCodeClassifier classifier = new QrCodeClassifierImpl();
+
+	@Test
+	public void testClassifiesEmptyStringAsUnknown() {
+		Pair<QrCodeType, Integer> result = classifier.classifyQrCode("");
+		assertEquals(UNKNOWN, result.getFirst());
+		assertEquals(0, result.getSecond().intValue());
+	}
+
+	@Test
+	public void testClassifiesKeyAgreement() {
+		byte[] payloadBytes = getRandomBytes(123);
+		for (int version = 0; version < 32; version++) {
+			int typeAndVersion =
+					(KeyAgreementConstants.QR_FORMAT_ID << 5) | version;
+			payloadBytes[0] = (byte) typeAndVersion;
+			String payload = new String(payloadBytes, ISO_8859_1);
+			Pair<QrCodeType, Integer> result =
+					classifier.classifyQrCode(payload);
+			assertEquals(BQP, result.getFirst());
+			assertEquals(version, result.getSecond().intValue());
+		}
+	}
+
+	@Test
+	public void testClassifiesMailbox() {
+		byte[] payloadBytes = getRandomBytes(123);
+		for (int version = 0; version < 32; version++) {
+			int typeAndVersion =
+					(MailboxConstants.QR_FORMAT_ID << 5) | version;
+			payloadBytes[0] = (byte) typeAndVersion;
+			String payload = new String(payloadBytes, ISO_8859_1);
+			Pair<QrCodeType, Integer> result =
+					classifier.classifyQrCode(payload);
+			assertEquals(MAILBOX, result.getFirst());
+			assertEquals(version, result.getSecond().intValue());
+		}
+	}
+
+	@Test
+	public void testClassifiesUnknownFormatIdAsUnknown() {
+		byte[] payloadBytes = getRandomBytes(123);
+		int unknownFormatId = MailboxConstants.QR_FORMAT_ID + 1;
+		int typeAndVersion = unknownFormatId << 5;
+		payloadBytes[0] = (byte) typeAndVersion;
+		String payload = new String(payloadBytes, ISO_8859_1);
+		Pair<QrCodeType, Integer> result = classifier.classifyQrCode(payload);
+		assertEquals(UNKNOWN, result.getFirst());
+		assertEquals(0, result.getSecond().intValue());
+	}
+}

bramble-java/src/main/java/org/briarproject/bramble/plugin/modem/ModemImpl.java

@@ -12,7 +12,6 @@ import java.io.InputStream;
 import java.io.OutputStream;
 import java.nio.ByteBuffer;
 import java.nio.charset.CharacterCodingException;
-import java.nio.charset.Charset;
 import java.nio.charset.CharsetDecoder;
 import java.util.concurrent.Executor;
 import java.util.concurrent.Semaphore;
@@ -33,6 +32,7 @@ import static java.util.logging.Level.WARNING;
 import static jssc.SerialPort.PURGE_RXCLEAR;
 import static jssc.SerialPort.PURGE_TXCLEAR;
 import static org.briarproject.bramble.util.LogUtils.logException;
+import static org.briarproject.bramble.util.StringUtils.US_ASCII;
 
 @MethodsNotNullByDefault
 @ParametersNotNullByDefault
@@ -41,7 +41,6 @@ class ModemImpl implements Modem, WriteHandler, SerialPortEventListener {
 	private static final Logger LOG =
 			Logger.getLogger(ModemImpl.class.getName());
 
-	private static final Charset US_ASCII = Charset.forName("US-ASCII");
 	private static final int MAX_LINE_LENGTH = 256;
 	private static final int[] BAUD_RATES = {
 		256000, 128000, 115200, 57600, 38400, 19200, 14400, 9600, 4800, 1200

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

@@ -60,7 +60,6 @@ import org.briarproject.briar.android.viewmodel.MutableLiveEvent;
 import org.briarproject.nullsafety.NotNullByDefault;
 
 import java.io.IOException;
-import java.nio.charset.Charset;
 import java.util.concurrent.Executor;
 import java.util.logging.Logger;
 
@@ -85,6 +84,7 @@ 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.LogUtils.logException;
+import static org.briarproject.bramble.util.StringUtils.ISO_8859_1;
 import static org.briarproject.briar.android.contact.add.nearby.AddNearbyContactPermissionManager.areEssentialPermissionsGranted;
 import static org.briarproject.briar.android.contact.add.nearby.AddNearbyContactViewModel.BluetoothDecision.NO_ADAPTER;
 import static org.briarproject.briar.android.contact.add.nearby.AddNearbyContactViewModel.BluetoothDecision.REFUSED;
@@ -126,9 +126,6 @@ class AddNearbyContactViewModel extends AndroidViewModel
 		REFUSED
 	}
 
-	@SuppressWarnings("CharsetObjectCanBeUsed") // Requires minSdkVersion >= 19
-	private static final Charset ISO_8859_1 = Charset.forName("ISO-8859-1");
-
 	private final EventBus eventBus;
 	private final AndroidExecutor androidExecutor;
 	private final Executor ioExecutor;
@@ -446,10 +443,7 @@ class AddNearbyContactViewModel extends AndroidViewModel
 		// Ignore results until the KeyAgreementTask is ready
 		if (!gotLocalPayload || gotRemotePayload || currentTask == null) return;
 		try {
-			byte[] payloadBytes = result.getText().getBytes(ISO_8859_1);
-			if (LOG.isLoggable(INFO))
-				LOG.info("Remote payload is " + payloadBytes.length + " bytes");
-			Payload remotePayload = payloadParser.parse(payloadBytes);
+			Payload remotePayload = payloadParser.parse(result.getText());
 			gotRemotePayload = true;
 			currentTask.connectAndRunProtocol(remotePayload);
 			state.postValue(new AddContactState.QrCodeScanned());

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

@@ -436,7 +436,7 @@ class HotspotManager {
 	}
 
 	private static String createWifiLoginString(String ssid, String password) {
-		// https://en.wikipedia.org/wiki/QR_code#WiFi_network_login
+		// https://en.wikipedia.org/wiki/QR_code#Joining_a_Wi%E2%80%91Fi_network
 		// do not remove the dangling ';', it can cause problems to omit it
 		return "WIFI:S:" + ssid + ";T:WPA;P:" + password + ";;";
 	}

briar-android/src/main/java/org/briarproject/briar/android/qrcode/QrCodeDecoder.java

@@ -41,7 +41,6 @@ public class QrCodeDecoder implements PreviewConsumer, PreviewCallback {
 	private final ResultCallback callback;
 
 	private Camera camera = null;
-	private int cameraIndex = 0;
 
 	public QrCodeDecoder(AndroidExecutor androidExecutor,
 			@IoExecutor Executor ioExecutor, ResultCallback callback) {
@@ -53,14 +52,12 @@ public class QrCodeDecoder implements PreviewConsumer, PreviewCallback {
 	@Override
 	public void start(Camera camera, int cameraIndex) {
 		this.camera = camera;
-		this.cameraIndex = cameraIndex;
 		askForPreviewFrame();
 	}
 
 	@Override
 	public void stop() {
 		camera = null;
-		cameraIndex = 0;
 	}
 
 	@UiThread