/** * Encrypt a message. * * @param paddedPlaintext The plaintext message bytes, optionally padded. * @return Ciphertext. * @throws NoSessionException */ public byte[] encrypt(byte[] paddedPlaintext) { lock (LOCK) { try { SenderKeyRecord record = senderKeyStore.loadSenderKey(senderKeyId); SenderKeyState senderKeyState = record.getSenderKeyState(); SenderMessageKey senderKey = senderKeyState.getSenderChainKey().getSenderMessageKey(); byte[] ciphertext = getCipherText(senderKey.getIv(), senderKey.getCipherKey(), paddedPlaintext); SenderKeyMessage senderKeyMessage = new SenderKeyMessage(senderKeyState.getKeyId(), senderKey.getIteration(), ciphertext, senderKeyState.getSigningKeyPrivate()); senderKeyState.setSenderChainKey(senderKeyState.getSenderChainKey().getNext()); senderKeyStore.storeSenderKey(senderKeyId, record); return senderKeyMessage.serialize(); } catch (InvalidKeyIdException e) { throw new NoSessionException(e); } } }
/** * 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); } } }