"HTTP/1.0", includes the specification for a Basic Access Authentication scheme. This document also provides the specification for HTTP's authentication framework, the original Basic authentication scheme and a scheme based on cryptographic hashes, referred to as "Digest Access Authentication".

A method and system...to integrate the Kerberos security mechanism into the message flow of the signaling operation under the Session Initiation Protocol to allow a SIP client and a SIP proxy to authenticate each other. When the SIP proxy receives an request message, such an INVITE request, from the SIP client, it responds with a challenge message indicating that authentication based on Kerberos is required. In response, the SIP client sends a second request message with a proxy authorization header containing authentication data, including a Kerberos server ticket for the Proxy, to allow the proxy to authenticate the client's user.