nsspi
nsspi is a C and .NET library that provides a managed interface to the Windows SSPI (Security Support Provider Interface) authentication API. It enables developers to integrate Windows Integrated Authentication, including Kerberos, NTLM, and the negotiate meta-package, into custom client and server applications, allowing single sign-on using existing user logon credentials. The library offers raw access to authentication tokens, which can be transmitted over any communication channel such as sockets, remoting, or named pipes. This flexibility lets applications embed authentication directly into their own protocols. Once authentication completes, clients and servers share a security context that supports encrypted and signed message exchange, and servers can perform client impersonation. The latest version, 0.3.1, adds the ability to obtain an IIdentity or WindowsPrincipal object representing the remote connection, enabling servers to query principal properties such as claims. The solution is distributed as a