}
    }


    /**
     * This constructor used to instance a SigningDigest object for
     * 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.