private int updates;
    private int signSequence;

    /**
     * Constructs a new signing digest with the specified MAC signing key.
     *
     * @param macSigningKey the MAC signing key for message authentication
     * @param bypass whether to bypass MAC signing
     * @throws SmbException if MD5 algorithm is not available
     */

        // Using a key with a known value for reproducibility
        SecretKeySpec key = new SecretKeySpec(new byte[16], "ARCFOUR");
        byte[] mac = PacMac.calculateMacArcfourHMACMD5(3, key, TEST_DATA);
        assertNotNull(mac);
        assertEquals(16, mac.length);

        // Test with a different key usage
        byte[] mac2 = PacMac.calculateMacArcfourHMACMD5(9, key, TEST_DATA);
        assertNotNull(mac2);

        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()) {

   * @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

 * message integrity and authenticity using MAC (Message Authentication Code) algorithms.
 *
 * @author mbechler
 */
public interface SMBSigningDigest {

    /**
     * Performs MAC signing of the SMB. This is done as follows.
     * The signature field of the SMB is overwritten with the sequence number;
     * The MD5 digest of the MAC signing key + the entire SMB is taken;

    /**
     * Retrieves the MAC address of the remote network interface. Samba returns all zeros.
     *
     * @param tc
     *            context to use
     *
     * @return the MAC address as an array of six bytes
     * @throws UnknownHostException
     *             if the host cannot be resolved to
     *             determine the MAC address.
     */

            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() {

	return plaintext, err
}

// MAC generates the checksum of the given req.Message using the key
// with the req.Name at the KMS.
func (k *KMS) MAC(ctx context.Context, req *MACRequest) ([]byte, error) {
	if req.Name == "" {
		req.Name = k.DefaultKey
	}

	start := time.Now()
	mac, err := k.conn.MAC(ctx, req)
	k.updateMetrics(err, time.Since(start))

	return mac, err
}

     * 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) {