Appendix A. Use with Proof-of-Possession Tokens

With bearer tokens such as those defined by OAuth 2.0 Bearer Token Usage [RFC6750], the protected resource will have in its possession the entire secret portion of the token for submission to the introspection service. However, for proof-of-possession style tokens, the protected resource will have only a token identifier used during the request, along with the cryptographic signature on the request. To validate the signature on the request, the protected resource could be able to submit the token identifier to the authorization server's introspection endpoint to obtain the necessary key information needed for that token. The details of this usage are outside the scope of this specification and will be defined in an appropriate companion specification.