Additional Hash Algorithms for OAuth 2.0 PKCE and Proof-of-Possession

This document defines SHA-512 as an additional hash algorithm for OAuth 2.0 Proof Key for Code Exchange (PKCE), mutual-TLS certificate- bound access tokens, and Demonstrating Proof of Possession (DPoP), for use in deployments operating under security policies that prohibit the use of SHA-256, which is otherwise mandated or the only option in these mechanisms.