mac.init(MD5_KEY);
    mac.update(input.getBytes(UTF_8));
    assertEquals(knownOutput, HashCode.fromBytes(mac.doFinal()).toString());
    assertEquals(knownOutput, HashCode.fromBytes(mac.doFinal(input.getBytes(UTF_8))).toString());
    assertEquals(knownOutput, Hashing.hmacMd5(MD5_KEY).hashString(input, UTF_8).toString());
    assertEquals(knownOutput, Hashing.hmacMd5(MD5_KEY).hashBytes(input.getBytes(UTF_8)).toString());

    mac.init(MD5_KEY);
    mac.update(input.getBytes(UTF_8));
    assertEquals(knownOutput, HashCode.fromBytes(mac.doFinal()).toString());
    assertEquals(knownOutput, HashCode.fromBytes(mac.doFinal(input.getBytes(UTF_8))).toString());
    assertEquals(knownOutput, Hashing.hmacMd5(MD5_KEY).hashString(input, UTF_8).toString());
    assertEquals(knownOutput, Hashing.hmacMd5(MD5_KEY).hashBytes(input.getBytes(UTF_8)).toString());

     * @return the encrypted data
     */
    public byte[] encrypt(final byte[] data) {
        final Cipher cipher = pollEncryptoCipher();
        byte[] encrypted;
        try {
            encrypted = cipher.doFinal(data);
        } catch (final IllegalBlockSizeException e) {
            throw new IllegalBlockSizeRuntimeException(e);
        } catch (final BadPaddingException e) {
            throw new BadPaddingRuntimeException(e);

        cipher.init(Cipher.DECRYPT_MODE, dataKey);

        int plainDataLength = data.length - KerberosConstants.CHECKSUM_SIZE;
        byte[] plainData = cipher.doFinal(data, KerberosConstants.CHECKSUM_SIZE, plainDataLength);

        byte[] plainDataChecksum = getHmac(plainData, codeHmac);
        if (plainDataChecksum.length >= KerberosConstants.CHECKSUM_SIZE) {

                throw new RuntimeException("Failed to create Mac instance", e);
            }

            mac.update(data, offset, length);
            final byte[] sig = mac.doFinal();
            System.arraycopy(sig, 0, data, offset + SIGNATURE_OFFSET, SIGNATURE_LENGTH);
        } finally {
            this.signingLock.unlock();
        }
    }

    /**
     *

            GCMParameterSpec gcmSpec = new GCMParameterSpec(GCM_TAG_SIZE, iv);
            cipher.init(Cipher.ENCRYPT_MODE, masterKey, gcmSpec);

            // Encrypt
            byte[] ciphertext = cipher.doFinal(plaintextBytes);

            // Combine IV and ciphertext
            byte[] result = new byte[GCM_IV_SIZE + ciphertext.length];
            System.arraycopy(iv, 0, result, 0, GCM_IV_SIZE);

        // Process message (will be encrypted)
        final byte[] output = new byte[cipher.getOutputSize(message.length)];
        int len = cipher.processBytes(message, 0, message.length, output, 0);
        len += cipher.doFinal(output, len);

        // Split ciphertext and authentication tag
        final int tagLength = getAuthTagLength();
        final byte[] ciphertext = new byte[message.length];

            log.debug("Truncated " + Hexdump.toHexString(trunc));
        }

        if ((this.ntlmsspFlags & NtlmFlags.NTLMSSP_NEGOTIATE_KEY_EXCH) != 0) {
            try {
                trunc = this.sealClientHandle.doFinal(trunc);
                if (log.isDebugEnabled()) {
                    log.debug("Encrypted " + Hexdump.toHexString(trunc));
                }
            } catch (final GeneralSecurityException e) {

            for (int i = 0; i < SIGNATURE_LENGTH; i++) {
                data[SIGNATURE_OFFSET + i] = 0;
            }

            mac.update(data, 0, data.length);
            byte[] signature = mac.doFinal();

            // Place signature in data
            System.arraycopy(signature, 0, data, SIGNATURE_OFFSET, SIGNATURE_LENGTH);

            boolean result = digest.verify(data, 0, data.length, 0, msg);

        mac.update(channel.getRemoteInterface().getAddress().getAddress());
        mac.update(ByteBuffer.allocate(8)
            .putLong(channel.getEstablishedTime()).array());
        
        return mac.doFinal();
    }
}