Ending an SSPI Session
After the client and server have finished communicating, both sides call the DeleteSecurityContext function with their respective context handles. When the client has finished communicating with any server or has finished using the additional credentials passed to the AcquireCredentialsHandle function, the client must call the FreeCredentialsHandle function. When the server is ready to shut down and before unloading the DLL, the server must call DeleteSecurityContext.