[deathanatos]

Forgive me if I don't find your own blog a decent citation. Re-reading your first article a bit closer, I can see how you might interpret it, I think (and perhaps I was not charitable enough during my first read), but I still think it is perilously close to mixing JWS being a concrete serialization of a JWT (this is correct) with JWS being a JWT (this is not).

JWS is simply a format that contains a signature for an arbitrary (that is, not always JWT) payload. See the "typ" header in the JWS RFC (in fact, see the entire RFC)[1]; were a JWS always a JWT, we would have no need for "typ". In fact, the RFC for JWS never mentions JWT in the normative parts of the standard — it is only ever mentioned during examples, since JWT is perhaps the primary consumer of the JWS standard. It calls this out, explicitly:

> While the first three examples all represent JSON Web Tokens (JWTs) [JWT], the payload can be any octet sequence

JWT is the concrete thing in that it is a JSON document encoding a set of claims, and comes either signed (wrapped in a JWS) or encrypted (wrapped in a JWE). JWT's RFC[2] states this fairly directly:

> The claims in a JWT are encoded as a 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

While I see what you're getting at with "JWT is an abstract concept" — that you need to wrap a JWT inside a JWS or a JWE — that does not mean that all JWSs are JWTs, and while the text can certainly be interpreted as "you must wrap a JWT in either a JWS or a JWE", I feel it toes the line too close to "all JWS's are JWTS", particularly at, "A signed JWT is known as a JWS". Having a JWS doesn't imply that it is a JWT; for example, the ACME protocol uses JWS, but not JWT. The distinction here is subtle, but important, I feel.[3]

> HMAC is not recommended - as it will be symmetric key. In fact you will find more details in the above link...

Not recommended by who? For what reasons?

Your article never mentions HMAC AFAICT (it mentions MAC in the process of describing JWS, but no further). And yes, use of HMAC implies a symmetric key, but that isn't necessarily insecure: it just means that anything that wishes to validate JWTs signed with that key must have the key to do so, and thus, must be trusted with that key. If you have a single service (say, an "auth" service) that is responsible for validating JWTs, this works fine, and is a great tradeoff for the additional complexity that signing w/ RSA keys brings. E.g.,

1.

  client  -- login --> auth_service
         <--  JWT  --

2.

       client  -- JWT+cmd --> foo_service
                                          -- is this JWT valid? --> auth_service
                                         <--      yes, it is    --
              <-- success --

Here, the HMAC key only needs to reside on the auth service, so it is reasonably well contained. The tradeoff, of course, is that we need to make a network request to auth service to validate JWTs, but we don't need to deal with RSA. For some setups, this is perfectly acceptable. (Swapping out RSA keys directly here results in no more or less "secret" stuff on any given node.)

The big advantage to RSA keys, of course, is that any service can verify JWTs without being able to issue them, but if you want to swap out the secret (the private key), you'll need to touch a lot more places, or have some infrastructure to distribute the public key.

[1]: https://tools.ietf.org/html/rfc7515#section-4.1.9

[2]: https://tools.ietf.org/html/rfc7519

[3]: Doubly so since I feel there is a lot of ill-will towards JWT, and many misconceptions about it. It's a good format, IMO, but the messaging around it needs to be crystal clear if people are going to ever stop fearing and start understanding it.

[prabaths]

Okay - rereading your comments - looks like you have misinterpreted this one.

"A signed JWT is known as a JWS (JSON Web Signature) and an encrypted JWT is known as a JWE (JSON Web Encryption)"

This is a correct statement. This does not mean JWS is a JWT all the time.

This is well highlighted in the blog link I shared with you: https://medium.facilelogin.com/jwt-jws-and-jwe-for-not-so-du...

"Yes, you read it correctly, the payload of a JWS necessarily need not to be JSON - if you’d like it can be XML too."

[prabaths]

Well I am not quite clear from your comment how you interpret. This is my point - as also rightly in the JWT RFC.

"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 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 integrity protected with a Message Authentication Code (MAC) and/or encrypted."

"JWTs are always represented using the JWS Compact Serialization or the JWE Compact Serialization."

A JWT will only exist as a JWS or JWE. It does not exist by itself - its an abstract concept.

Regarding HMAC - its not recommended for the context of this article. It's not a recommended approach to do authentication with shared keys is in a distributed environment.