public static String receive(
String finalMessageText, ContactModel sender, BinaryTextEncoding encoding)
throws NoSuchAlgorithmException, InvalidKeyException, NoSuchPaddingException,
IllegalBlockSizeException, BadPaddingException, IOException,
InvalidAlgorithmParameterException, InvalidParameterSpecException,
FailedVerificationException, InvalidSessionKeyException {
UserModel user = new Select().from(UserModel.class).executeSingle();
Log.d(TAG, "receive - finalMessageText: " + finalMessageText);
byte[] finalMessageBytes = encoding.decode(finalMessageText);
byte[] integrityPart = Arrays.copyOfRange(finalMessageBytes, 0, INTEGRITY_LENGTH);
byte[] intermediateMessage =
Arrays.copyOfRange(finalMessageBytes, INTEGRITY_LENGTH, finalMessageBytes.length);
Log.d(TAG, "integrityPart: " + encoding.encode(integrityPart));
Log.d(TAG, "intermediateMessage: " + encoding.encode(intermediateMessage));
if (!AsymCrypto.verify(intermediateMessage, integrityPart, sender.getPublicKey()))
throw new FailedVerificationException();
byte[] cipheredBody;
if (intermediateMessage[0] == 'k') {
byte[] cipheredKeyBytes = Arrays.copyOfRange(intermediateMessage, 1, CIPHERED_KEY_LENGTH + 1);
cipheredBody =
Arrays.copyOfRange(
intermediateMessage, CIPHERED_KEY_LENGTH + 1, intermediateMessage.length);
Log.d(TAG, "cipheredKeyBytes: " + encoding.encode(cipheredKeyBytes));
byte[] sessionKeyBytes = AsymCrypto.decrypt(cipheredKeyBytes, user.getPrivateKey());
sender.setSessionKey(KeyHelper.bytesToSecretKey(sessionKeyBytes));
sender.save();
} else {
cipheredBody = Arrays.copyOfRange(intermediateMessage, 1, intermediateMessage.length);
}
Log.d(TAG, "cipheredBody: " + encoding.encode(cipheredBody));
if (!sender.hasValidSessionKey()) {
throw new InvalidSessionKeyException();
}
SecretKey sessionKey = sender.getSessionKey();
byte[] plainBodyBytes = SymCrypto.decrypt(cipheredBody, sessionKey);
return new String(plainBodyBytes);
}
public static String send(String plainBody, ContactModel destination, BinaryTextEncoding encoding)
throws NoSuchAlgorithmException, InvalidKeyException, NoSuchPaddingException,
IllegalBlockSizeException, BadPaddingException, IOException,
InvalidAlgorithmParameterException, InvalidParameterSpecException {
UserModel user = new Select().from(UserModel.class).executeSingle();
boolean includeSymmetricKey = false;
byte[] plainBodyBytes = plainBody.getBytes();
if (!destination.hasValidSessionKey()) {
destination.setSessionKey(KeyHelper.generateSymmetricKey());
destination.save();
includeSymmetricKey = true;
}
SecretKey sessionKey = destination.getSessionKey();
ByteArrayOutputStream messageComposition = new ByteArrayOutputStream();
if (includeSymmetricKey) {
messageComposition.write('k');
byte[] cipheredKey = AsymCrypto.encrypt(sessionKey.getEncoded(), destination.getPublicKey());
Log.d(TAG, "cipheredKey: " + encoding.encode(cipheredKey));
messageComposition.write(cipheredKey);
} else {
messageComposition.write('0');
}
byte[] cipheredBody = SymCrypto.encrypt(plainBodyBytes, sessionKey);
Log.d(TAG, "cipheredBody: " + encoding.encode(cipheredBody));
messageComposition.write(cipheredBody);
byte[] intermediateMessage = messageComposition.toByteArray();
byte[] integrityPart = AsymCrypto.sign(intermediateMessage, user.getPrivateKey());
Log.d(TAG, "intermediateMessage: " + encoding.encode(intermediateMessage));
Log.d(TAG, "integrityPart: " + encoding.encode(integrityPart));
ByteArrayOutputStream finalMessageComposition = new ByteArrayOutputStream();
finalMessageComposition.write(integrityPart);
finalMessageComposition.write(intermediateMessage);
String finalMessage = encoding.encode(finalMessageComposition.toByteArray());
Log.d(TAG, "send - finalMessage: " + finalMessage);
return finalMessage;
}