I’ve written a concise Internet-Draft on proof-of-possession for JWTs with John Bradley and Hannes Tschofenig. Quoting from the abstract:
This specification defines how to express a declaration in a JSON Web Token (JWT) that the presenter of the JWT possesses a particular key and that the recipient can cryptographically confirm proof-of-possession of the key by the presenter. This property is also sometimes described as the presenter being a holder-of-key.
This specification intentionally does not specify the means of communicating the proof-of-possession JWT, nor the messages used to exercise the proof key, as these are necessarily application-specific. Rather, this specification defines a proof-of-possession JWT data structure to be used by other specifications that do define those things.
The specification is available at:
An HTML formatted version is available at: