* 
         * If signing is not active, the SecuritySignature field of the SMB Header for all messages sent, except
         * the SMB_COM_SESSION_SETUP_ANDX Response (section 2.2.4.53.2), MUST be set to
         * 0x0000000000000000. For the SMB_COM_SESSION_SETUP_ANDX Response, the SecuritySignature
         * field of the SMB Header SHOULD<226> be set to the SecuritySignature received in the

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;
     * The first 8 bytes of this are placed in the signature field.
     *
     * @param data
     *            The data.
     * @param offset

    static final int A         = 0x0001;
    static final int NS        = 0x0002;
    static final int NULL      = 0x000a;

    static final int HEADER_LENGTH = 12;

    // header field offsets
    static final int OPCODE_OFFSET = 2;
    static final int QUESTION_OFFSET = 4;
    static final int ANSWER_OFFSET = 6;
    static final int AUTHORITY_OFFSET = 8;
    static final int ADDITIONAL_OFFSET = 10;

    static final byte SMB_COM_NT_TRANSACT_SECONDARY = (byte)0xA1;
    static final byte SMB_COM_NT_CREATE_ANDX     = (byte)0xA2;

    /*
     * Some fields specify the offset from the beginning of the header. This
     * field should be used for calculating that. This would likely be zero
     * but an implemantation that encorporates the transport header(for
     * efficiency) might use a different initial bufferIndex. For example,

     */
    @Override
    public synchronized void sign ( byte[] data, int offset, int length, CommonServerMessageBlock request, CommonServerMessageBlock response ) {
        this.digest.reset();

        // zero out signature field
        int index = offset + SIGNATURE_OFFSET;
        for ( int i = 0; i < SIGNATURE_LENGTH; i++ )
            data[ index + i ] = 0;

        // set signed flag

                }
                break;
            case 4:
                // Let's ignore this for now
                break;
            default:
                throw new PACDecodingException("Invalid field in kerberos ticket");
            }
        }
    }


    public byte getApOptions () {
        return this.apOptions;
    }


    public KerberosTicket getTicket () {

            }

            /*
             * no point in calling readParameterWordsWireFormat if there are no more
             * parameter words. besides, win98 doesn't return "OptionalSupport" field
             */

            if ( this.wordCount > 2 ) {
                readParameterWordsWireFormat(buffer, bufferIndex + 4);

                /*

 * accounts. SIDs are commonly represented using a textual format such as
 * <tt>S-1-5-21-1496946806-2192648263-3843101252-1029</tt> but they may
 * also be resolved to yield the name of the associated Windows account
 * such as <tt>Administrators</tt> or <tt>MYDOM\alice</tt>.
 * <p>
 * Consider the following output of <tt>examples/SidLookup.java</tt>:
 * <pre>