private extern static int AcquireCredentialsHandle(
     string pszPrincipal,
     string pszPackage,
     int fCredentialUse,
     IntPtr pvLogonID,
     IntPtr pAuthData,
     IntPtr pGetKeyFn,
     IntPtr pvGetKeyArgument,
     ref SecHandle phCredential,
     out SecHandle ptsExpiry
 );

 static extern int InitializeSecurityContext(
     ref SecHandle phCredential,
     IntPtr phContext,
     string pszTargetName,
     int fContextReq,
     int Reserved1,
     int TargetDataRep,
     IntPtr pInput,
     int Reserved2,
     out SecHandle phNewContext,
     out SecBufferDesc pOutput,
     out int pfContextAttr,
     out SecHandle ptsExpiry);

 private static extern int ImpersonateSecurityContext__(SecHandle phContext);

 public static extern int FreeCredentialsHandle(ref SecHandle phCredential);

 public static extern int AcquireCredentialsHandle(string pszPrincipal, string pszPackage, uint fCredentialUse,
     IntPtr pvLogonID, IntPtr pAuthData, IntPtr pGetKeyFn,
     IntPtr pvGetKeyArgument, ref SecHandle phCredential,
     ref long ptsExpiry);

		private void CloseClientCredentials()
		{
			if (!_clientCredentials.IsInvalid)
			{
				FreeCredentialsHandle(ref _clientCredentials);
				_clientCredentials = new SecHandle();
			}
		}

		static extern int DeleteSecurityContext(ref SecHandle phContext); //PCtxtHandle

		static extern int InitializeSecurityContext(
			ref SecHandle phCredential,//PCredHandle
			ref SecHandle phContext, //PCtxtHandle
			string pszTargetName,
			int fContextReq,
			int Reserved1,
			int TargetDataRep,
			ref SecBufferDesc SecBufferDesc, //PSecBufferDesc SecBufferDesc
			int Reserved2,
			out SecHandle phNewContext, //PCtxtHandle
			ref SecBufferDesc pOutput, //PSecBufferDesc SecBufferDesc
			out uint pfContextAttr, //managed ulong == 64 bits!!!
			out SecInteger ptsExpiry //PTimeStamp
		);

 private static extern int FreeCredentialsHandle(
     ref SecHandle phCredential
 );

        /// <summary>
        /// Calls DeleteSecurityContext SSPI API function.
        /// Ignores all possible returned errors.
        /// </summary>
        /// <param name="phContext">Security context being deleted.</param>
        public static void DeleteSecurityContext(SecHandle phContext)
        {
            if (_isNT)
                DeleteSecurityContext_NT(phContext);
            else
                DeleteSecurityContext__(phContext);

            phContext.dwLower = 0;
            phContext.dwUpper = 0;
        }

 private static extern int VerifySignature__(SecHandle phContext,
     ref SecBufferDescNative pMessage, int MessageSeqNo,
     ref int pfQOP);

 private static extern int RevertSecurityContext__(SecHandle phContext);

 private static extern int QuerySecurityContextToken__(SecHandle phContext, out IntPtr phToken);

 private static extern int QueryContextAttributes__(SecHandle phContext,
     int ulAttribute, ref SecPkgContext_Sizes pBuffer);

 private static extern int MakeSignature__(SecHandle phContext, int fQOP, 
     ref SecBufferDescNative pMessage, int MessageSeqNo);

 private static extern int InitializeSecurityContext__(SecHandle phCredential,
     SecHandle phContext, string pszTargetName, int fContextReq, int Reserved1,
     int TargetDataRep, ref SecBufferDescNative pInput, int Reserved2, SecHandle phNewContext,
     ref SecBufferDescNative pOutput, ref int pfContextAttr, ref Int64 ptsExpiry);

 private static extern int DeleteSecurityContext(
     ref SecHandle phContext
 );

        /// <summary>
        /// Calls FreeCredentialsHandle SSPI API function.
        /// Ignores all possible returned errors.
        /// </summary>
        /// <param name="credHandle">Credential handle being freed.</param>
        public static void FreeCredentialsHandle(SecHandle credHandle)
        {
            if (_isNT)
                FreeCredentialsHandle_NT(credHandle);
            else
                FreeCredentialsHandle__(credHandle);

            credHandle.dwLower = 0;
            credHandle.dwUpper = 0;
        }

		static extern int AcquireCredentialsHandle(
			string pszPrincipal, //SEC_CHAR*
			string pszPackage, //SEC_CHAR* //"Kerberos","NTLM","Negotiative"
			int fCredentialUse,
			IntPtr PAuthenticationID,//_LUID AuthenticationID,//pvLogonID, //PLUID
			IntPtr pAuthData,//PVOID
			int pGetKeyFn, //SEC_GET_KEY_FN
			IntPtr pvGetKeyArgument, //PVOID
			out SecHandle phCredential, //SecHandle //PCtxtHandle ref
			out SecInteger ptsExpiry //PTimeStamp //TimeStamp ref
		);

        /// <summary>
        /// Duplicates a security token for another process.
        /// </summary>
        /// <param name="phContext">Security context handle.</param>
        /// <param name="remoteProcessId">The identifier of the remote process.</param>
        /// <returns>The handle of security token for another process.</returns>
        public static IntPtr CloneSecurityToken(SecHandle phContext, int remoteProcessId)
        {
            int result = 0;

            // get the security token
            IntPtr phToken = IntPtr.Zero;
            if (_isNT)
                result = QuerySecurityContextToken_NT(phContext, out phToken);
            else
                result = QuerySecurityContextToken__(phContext, out phToken);

            if (result != SspiApi.SEC_E_OK)
                throw GenuineExceptions.Get_Windows_SspiError(result);

            try
            {
                return CloneSecurityToken(phToken, remoteProcessId);
            }
            finally
            {
                // close security token
                CloseHandle(phToken);
            }
        }