Access control using proof-of-possession token

A client computing device may obtain access to protected resources with a proof-of-possession (Pop) token. The client computing device may request an access token from an authorization server via an application server. The request may include key material (e.g., token binding type, key, and key parameters) that the client computing device possesses or has access to, such as a public key of an asymmetric public/private key pair. In some embodiments, the public key may be a confirmation (CNF) key, which may be added to the access token and JWT signed by the authorization server. The private key may be retained by the client, who may then use the PoP token to prove possession of the private key.