Security Support Provider/Authentication Packages
The Windows operating system supports authentication using security packages that function as both security support providers and as authentication packages. Security packages provide the logon process support services of a Windows authentication package and also provide authentication services to applications by implementing a set of functions that are mapped to the Security Support Provider Interface (SSPI).
A security package that functions as an authentication package and implements the functionality required by SSPI is called a security support provider/authentication package (SSP/AP).
For more information about security packages, see SSP Packages Provided by Microsoft. For information about developing custom SSP/APs, see Custom Security Packages.