// Create new Mac instance for thread safety without blocking other operations
            Mac mac;
            try {
                mac = createMacInstance();
            } catch (GeneralSecurityException e) {
                log.error("Failed to create Mac instance for signing", e);
                throw new RuntimeException("Failed to create Mac instance", e);
            }

        final byte[] seqBytes = new byte[4];
        SMBUtil.writeInt4(seqNum, seqBytes, 0);

        final MessageDigest mac = Crypto.getHMACT64(sk);
        mac.update(seqBytes); // sequence
        mac.update(data); // data
        final byte[] dgst = mac.digest();
        byte[] trunc = new byte[8];
        System.arraycopy(dgst, 0, trunc, 0, 8);

        if (log.isDebugEnabled()) {

      Providers.setProviderList(providers);
    }
  }

  public void testMultipleUpdates() throws Exception {
    Mac mac = Mac.getInstance("HmacSHA1");
    mac.init(SHA1_KEY);
    mac.update("hello".getBytes(UTF_8));
    mac.update("world".getBytes(UTF_8));

    assertEquals(
        HashCode.fromBytes(mac.doFinal()),
        Hashing.hmacSha1(SHA1_KEY)
            .newHasher()
            .putString("hello", UTF_8)

   * @throws IllegalArgumentException if the given key is inappropriate for initializing this MAC
   * @since 20.0
   */
  public static HashFunction hmacMd5(Key key) {
    return new MacHashFunction("HmacMD5", key, hmacToString("hmacMd5", key));
  }

  /**
   * Returns a hash function implementing the Message Authentication Code (MAC) algorithm, using the

        System.arraycopy(name.getBytes("US-ASCII"), 0, src, srcIndex + 13, 16);
        src[srcIndex + 28] = 0x00; // hex code
        src[srcIndex + 29] = 0x04; // flags
        // MAC address (6 bytes)
        byte[] mac = new byte[6];
        System.arraycopy(mac, 0, src, srcIndex + 31, 6);
        // Stats (6 bytes)
        byte[] stats = new byte[6];
        System.arraycopy(stats, 0, src, srcIndex + 37, 6);

   * @throws IllegalArgumentException if the given key is inappropriate for initializing this MAC
   * @since 20.0
   */
  public static HashFunction hmacMd5(Key key) {
    return new MacHashFunction("HmacMD5", key, hmacToString("hmacMd5", key));
  }

  /**
   * Returns a hash function implementing the Message Authentication Code (MAC) algorithm, using the

            Mac mac = Mac.getInstance("HmacSHA256");
            mac.init(new SecretKeySpec(sessionKey, "HmacSHA256"));

            // Zero signature field for calculation
            Arrays.fill(data, SIGNATURE_OFFSET, SIGNATURE_OFFSET + SIGNATURE_LENGTH, (byte) 0);
            mac.update(data, 0, data.length);
            byte[] validSig = mac.doFinal();

        Key macKey = new SecretKeySpec(key.clone(), KerberosConstants.HMAC_ALGORITHM);
        Mac mac = Mac.getInstance(KerberosConstants.HMAC_ALGORITHM);
        mac.init(macKey);
        return mac.doFinal(data);
    }

    /**
     * Returns the user's Kerberos realm.
     *
     * @return the user realm
     */
    public String getUserRealm() {

        Mac mac = Mac.getInstance("HmacSHA256");
        SecretKeySpec keySpec = new SecretKeySpec(sessionKey, "HmacSHA256");
        mac.init(keySpec);
        
        // Include channel-specific data
        mac.update(channel.getLocalInterface().getAddress().getAddress());
        mac.update(channel.getRemoteInterface().getAddress().getAddress());
        mac.update(ByteBuffer.allocate(8)

     * signing/verifying SMB using kerberos session key.
     * The MAC Key = concat(Session Key, Digest of Challenge);
     * Because of Kerberos Authentication don't have challenge,
     * The MAC Key = Session Key
     *
     * @param macSigningKey
     *            The MAC key used to sign or verify SMB.
     */
    public SMB1SigningDigest(final byte[] macSigningKey) {