The Hashed Token SASL Mechanism

This document specifies the family of Hashed Token SASL mechanisms which enable a proof-of-possession-based authentication scheme and are meant to be used for quick re-authentication of a previous session. The Hashed Token SASL mechanism's authentication sequence consists of only one round-trip. The usage of short-lived, exclusively ephemeral hashed tokens is achieving the single round- trip property. The SASL mechanism specified herin further provides hash agility, mutual authentication and is secured by channel binding.