IETF Specifications for Microsoft Digest SSP
HTTP Authentication: Basic and Digest Access Authentication (RFC 2617) is available at https://www.ietf.org/rfc/rfc2617.txt.
Using Digest as a SASL Mechanism Internet draft is available at https://www.ietf.org/rfc/rfc2831.txt.
For additional information on SASL, also see the Simple Authentication and Security Layer specification (RFC 2222) available at https://www.ietf.org/rfc/rfc2222.txt.