Microsoft.Protocols.TestTools.StackSdk.RemoteDesktop.Rdpbcgr.RdpbcgrDecoder.DecryptSendDataIndication C# (CSharp) Method

        private byte[] DecryptSendDataIndication(byte[] userData, SecurityHeaderType securityHeaderType)
        {
            // Parse security header
            int index = 0;
            TS_SECURITY_HEADER header = ParseTsSecurityHeader(userData, ref index, securityHeaderType);

            // If header is absent, data is not encrypted, return directly
            if (null == header)
            {
                return userData;
            }

            // Get remain data with security header removed
            int remainLength = userData.Length - index;
            byte[] remainData = GetBytes(userData, ref index, remainLength);

            // Header is present, but still data is not encrypted, return directly
            bool isEncryptFlagExist = IsFlagExist((UInt16)header.flags,
                (UInt16)TS_SECURITY_HEADER_flags_Values.SEC_ENCRYPT);
            bool isRedirectFlagExist = IsFlagExist((UInt16)header.flags,
                (UInt16)TS_SECURITY_HEADER_flags_Values.SEC_REDIRECTION_PKT);
            if ((!isEncryptFlagExist) && (!isRedirectFlagExist))
            {
                return remainData;
            }

            if (isRedirectFlagExist)
            {
                SecurityHeaderType oldType = securityHeaderType;
                UpdateSecurityHeaderType(ref securityHeaderType);
                if (oldType != securityHeaderType)
                {
                    index = 0;
                    header = ParseTsSecurityHeader(userData, ref index, securityHeaderType);
                    remainLength = userData.Length - index;
                    remainData = GetBytes(userData, ref index, remainLength);
                }
            }

            // Get data signature (Fips/NonFips only)
            byte[] signature;
            switch (securityHeaderType)
            {
                case SecurityHeaderType.NonFips:
                    TS_SECURITY_HEADER1 nonFipsHeader = (TS_SECURITY_HEADER1)header;
                    signature = nonFipsHeader.dataSignature;
                    break;

                case SecurityHeaderType.Fips:
                    TS_SECURITY_HEADER2 fipsHeader = (TS_SECURITY_HEADER2)header;
                    signature = fipsHeader.dataSignature;
                    break;

                case SecurityHeaderType.Basic:
                    signature = null;
                    break;

                case SecurityHeaderType.None:
                    signature = null;
                    break;

                default:
                    throw new FormatException(ConstValue.ERROR_MESSAGE_ENUM_UNRECOGNIZED);
            }

            // Check if "Salted MAC Generation" was used in PDU generation
            bool isSalted = IsFlagExist((UInt16)header.flags,
                (UInt16)TS_SECURITY_HEADER_flags_Values.SEC_SECURE_CHECKSUM);

            // Decryption
            byte[] decryptedData = null;
            if (!clientContext.Decrypt(remainData, signature, isSalted, out decryptedData))
            {
                // If decryption failed
                throw new FormatException(ConstValue.ERROR_MESSAGE_DECRYPTION_FAILED);
            }
            return decryptedData;
        }