RFC 9970: Connected Identity for Secure Telephone Identity Revisited (STIR)

The Session Initiation Protocol (SIP) Identity header field conveys cryptographic identity information about the originators of SIP requests. However, the Secure Telephone Identity Revisited (STIR) framework provides no means for determining the identity of the called party in a conventional telephone-calling scenario. This document updates prior guidance on the "connected identity" problem to reflect the changes to SIP identity that accompanied STIR. It also considers a revised problem space for connected identity as a means of detecting calls that have been retargeted to a party impersonating the intended destination and preventing the spoofing of mid-dialog or dialog-terminating events by intermediaries or third parties.