Schannel is the security package (SP) and authentication package (AP) for the following protocols:

• DTLS 1.0 and 2.0

• SSL 2.0 and 3.0

• TLS 1.0, 1.1, 1.2, and 1.3

Schannel previously supported the Private Communication Technology (PCT) protocol version 1, but it appears that Microsoft has removed support for PCT 1 at some point. The use of PCT 1 may still be found in other Microsoft technologies such as the Microsoft Message Queuing (MSMQ) Directory Service Protocol.

• Functions

Microsoft provides lots of documentation on MSDN for using schannel for authenticating client and server applications; though, they do not provide any documentation on the message types for package calls. The message types that schannel supports is provided here. Lsa Whisperer currently provides experimental support for some of these as schannel commands.

Commands marked with an asterisk require the client to be trusted. The LookupCert command may also be alternatively called through the SpCallPackagePassthrough function. Oddly, the PurgeCache command was only available to untrusted callers and was removed from schannel after originally being available since at least NT 5.2.