byte[] dataHmac = getHmac(dataChecksum, codeHmac);
        SecretKeySpec dataKey = new SecretKeySpec(dataHmac, KerberosConstants.RC4_ALGORITHM);

        cipher = Cipher.getInstance(KerberosConstants.RC4_ALGORITHM);
        cipher.init(Cipher.DECRYPT_MODE, dataKey);

        int plainDataLength = data.length - KerberosConstants.CHECKSUM_SIZE;

                dstIndex += 4;
                SMBUtil.writeInt4(0, dst, dstIndex);
                dstIndex += 4; // Reserved
                int dataLen = size8(nc.encode(dst, dstIndex));
                SMBUtil.writeInt2(dataLen, dst, lenOffset);
                dstIndex += dataLen;
            }
        }
        return dstIndex - start;
    }


    /**
     * {@inheritDoc}
     *

                int type = SMBUtil.readInt2(buffer, ncpos);
                int dataLen = SMBUtil.readInt2(buffer, ncpos + 2);
                ncpos += 4;
                ncpos += 4; // Reserved
                NegotiateContextResponse ctx = createContext(type);
                if ( ctx != null ) {
                    ctx.decode(buffer, ncpos, dataLen);
                    contexts[ i ] = ctx;
                }