To explain my comment at the microphone today: Section 8 states:
JWTs use JSON Web Signature (JWS) [JWS<http://tools.ietf.org/html/draft-ietf-oauth-json-web-token-06#ref-JWS>] and JSON Web Encryption (JWE) [JWE<http://tools.ietf.org/html/draft-ietf-oauth-json-web-token-06#ref-JWE>] to sign and/or encrypt the contents of the JWT. I believe it'd be useful to expand upon this to give guidance to those using JWT on what they should do to cryptographically protect it. When should they do nothing? When should they just sign? When should they just encrypt? When should they sign and then encrypt? What security properties does each option provide or not provide? The choices seem to be: 1. No JWS and no JWE - assumes the JWT is protected through some other mechanism or that it doesn't need to be protected 2. JWS - probably OK if confidentiality is not necessary. 3. JWE: Authentication is not provided unless a shared symmetric key is used (if it's asymmetric encryption, only integrity protection will be provided, not authentication). Under what conditions is authentication necessary or not necessary? AES-GCM may not be safe to use with a shared symmetric key (I sent feedback on this to the jose mailing list). draft-ietf-oauth-v2-http-mac for example seems to currently solely use JWE and says "this keying material is a symmetric or asymmetric long-term key established between the resoruce server and authorization server". If it's asymmetric, a JWS seems to also be necessary to authenticate the authorization server as the source of the JWT? 4. JWS then JWE: A recipient who is an attacker/who is compromised could potentially strip off the JWE (making it just a JWS) or strip the JWE and replace it with another JWE to cause confusion about the intended recipient of the JWT and forward it on to another recipient. The presence of the "aud" (Audience) claim seems to protect against this. However, the "aud" claim is optional in JWTs. Thanks, Mike
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