Re: [OAUTH-WG] JWT: add "iss" and "aud" to Reserved Header Parameter Names in JWE

[Dick Hardt <[e-mail]>]

Yes, there could be privacy issues, and we can describe that as a
consideration in the specification. It is not an issue in my use case.


On Wed, May 29, 2013 at 8:23 AM, Anthony Nadalin <[e-mail]>wrote:

>  So there could be privacy issues on why I would not want the ISS or AUD
> outside the encrypted payload****
>
> ** **
>
> *From:* [e-mail] [mailto:[e-mail]] *On Behalf
> Of *Dick Hardt
> *Sent:* Tuesday, May 28, 2013 9:34 AM
> *To:* O Auth WG
> *Subject:* Re: [OAUTH-WG] JWT: add "iss" and "aud" to Reserved Header
> Parameter Names in JWE****
>
> ** **
>
> Following up on this topic ... ****
>
> ** **
>
> On Wed, May 1, 2013 at 2:12 PM, Dick Hardt <[e-mail]> wrote:**
> **
>
> "iss" and "aud" would be optional parameters in a JWE. These parameters
> are in the payload, but since it is encrypted, the payload must be
> decrypted before they can be read. Some times knowing these parameters is
> required to be able to decrypt the payload …
>
> These would be additions to 9.3.1 in the JWT specification.
>
> Why "iss" is needed:
>
> Bob and Charlie each gave Alice a KID and a symmetric key to use to verify
> and decrypt tokens from them.
>
> The App and Alice share keys so Alice knows it is the App.
>
> The User authorizes Bob to give the App a token (which authorizes the App
> to do something)
>
> The App gives the token to Alice.
>
> Since Alice indirectly received the token,  the only way for Alice to know
> who sent the token, is to look at the KID as the "iss" claim is encrypted.
> If the "kid" values are GUIDs, then Alice can just look up the "kid" and
> retrieve the associated symmetric key, and then decrypt and verify the
> token and THEN see who sent it. If there is a collision in KID values (Bon
> and Charlie gave the same KID for different keys), then Alice will not know
> which symmetric key to use.
>
> Why "aud" is needed:
>
> Dave gives a KID and symmetric key to Ellen, and Frank gives a KID and
> symmetric key to Gwen.
>
> Ellen and Gwen trust each other and know how to talk to each other. Gwen
> does not know Dave. Ellen does not know Frank
>
> The App and Gwen share keys so Gwen knows it is the App.
>
> The User authorizes Dave to give the App a token
>
> Dave gives the token to Gwen (Dave does not have a relationship with Ellen)
>
> Gwen now has a token that Ellen can decrypt and verify, but has no method
> for knowing that Ellen can do that. The "aud" property would allow Gwen to
> give the token to Ellen to decrypt and verify.****
>
>
>
> ****
>
> ** **
>
> --
> -- Dick ****
>



-- 
-- Dick