This specification describes how to declare in a JSON Web Token (JWT) that the presenter of the JWT possesses a particular proof-ofpossession key and how the recipient can cryptographically confirm proof of possession of the key by the presenter. Being able to prove possession of a key is also sometimes described as the presenter being a holder-of-key.
RFC 7800-2016 history
2016RFC 7800-2016 Proof-of-Possession Key Semantics for JSON Web Tokens (JWTs)