leo leo - 2 months ago 14
reST (reStructuredText) Question

What is the difference between JSON Web Signature (JWS) and JSON Web Token (JWT)?

I've been coding a restful service in Java. This is what I've understood till now (correct me if i'm wrong):

Token authorization is done using JSON Web Tokens (JWT) which have three parts: the header, the payload, and the secret (shared between the client and the server).

I understood this concept and stumbled over JSON Web Signature (JWS) while reading about JWT.

JWS also is an encoded entity similar to JWT having a header, payload, and a shared secret.

Question: What is the difference between the two concepts, namely JWT and JWS? And if they are alike technically, then what's the difference in their implementation?

This is the first time I'm working with token based auth, so it's possible I've misunderstood the concept altogether.

P.S. I learned about JWS while browsing through the examples on this website.

Thanks :)

Answer

JWT actually uses JWS for its signature, from the spec:

JSON Web Token (JWT) is a compact, URL-safe means of representing claims to be transferred between two parties. The claims in a JWT are encoded as a JavaScript Object Notation (JSON) object that is used as the payload of a JSON Web Signature (JWS) structure or as the plaintext of a JSON Web Encryption (JWE) structure, enabling the claims to be digitally signed or MACed and/or encrypted.

So a JWT is a JWS structure with a JSON object as the payload. Some optional keys (or claims) have been defined such as iss, aud, exp etc.

This also means that its integrity protection is not just limited to shared secrets but public/private key cryptography can also be used.