/** * Construct a group session for sending messages. * * @param senderKeyName The (groupId, senderId, deviceId) tuple. In this case, 'senderId' should be the caller. * @return A SenderKeyDistributionMessage that is individually distributed to each member of the group. */ public SenderKeyDistributionMessage create(SenderKeyName senderKeyName) { lock (GroupCipher.LOCK) { try { SenderKeyRecord senderKeyRecord = senderKeyStore.loadSenderKey(senderKeyName); if (senderKeyRecord.isEmpty()) { senderKeyRecord.setSenderKeyState(KeyHelper.generateSenderKeyId(), 0, KeyHelper.generateSenderKey(), KeyHelper.generateSenderSigningKey()); senderKeyStore.storeSenderKey(senderKeyName, senderKeyRecord); } SenderKeyState state = senderKeyRecord.getSenderKeyState(); return(new SenderKeyDistributionMessage(state.getKeyId(), state.getSenderChainKey().getIteration(), state.getSenderChainKey().getSeed(), state.getSigningKeyPublic())); } catch (InvalidKeyIdException e) { throw new Exception(e.Message); } catch (InvalidKeyException e) { throw new Exception(e.Message); } } }
/** * Decrypt a SenderKey group message. * * @param senderKeyMessageBytes The received ciphertext. * @param callback A callback that is triggered after decryption is complete, * but before the updated session state has been committed to the session * DB. This allows some implementations to store the committed plaintext * to a DB first, in case they are concerned with a crash happening between * the time the session state is updated but before they're able to store * the plaintext to disk. * @return Plaintext * @throws LegacyMessageException * @throws InvalidMessageException * @throws DuplicateMessageException */ public byte[] decrypt(byte[] senderKeyMessageBytes, DecryptionCallback callback) { lock (LOCK) { try { SenderKeyRecord record = senderKeyStore.loadSenderKey(senderKeyId); if (record.isEmpty()) { throw new NoSessionException("No sender key for: " + senderKeyId); } SenderKeyMessage senderKeyMessage = new SenderKeyMessage(senderKeyMessageBytes); SenderKeyState senderKeyState = record.getSenderKeyState(senderKeyMessage.getKeyId()); senderKeyMessage.verifySignature(senderKeyState.getSigningKeyPublic()); SenderMessageKey senderKey = getSenderKey(senderKeyState, senderKeyMessage.getIteration()); byte[] plaintext = getPlainText(senderKey.getIv(), senderKey.getCipherKey(), senderKeyMessage.getCipherText()); callback.handlePlaintext(plaintext); senderKeyStore.storeSenderKey(senderKeyId, record); return(plaintext); } catch (InvalidKeyException e) { throw new InvalidMessageException(e); } catch (InvalidKeyIdException e) { throw new InvalidMessageException(e); } } }