On Wed, Jul 31, 2024 at 11:03:47AM -0500, Orie Steele wrote:
> key_ops is defined to parallel to JWK and web crypto key usage:
> 
> https://www.rfc-editor.org/rfc/rfc9052.html#section-7.1

I think key_ops is just FUBAR.

 
> I think you are asking about derive key (7) and derive bits (8).
> 
> The same questions came up with COSE / JOSE HPKE.
> 
> Which of these operations corresponds to KEMs?... should HPKE use "key_ops"
> that mix both kem and symmetric key operations? ( "derive key" + "encrypt"
> ) ?
> 
> AFAIK, there is no guidance on this, and no registry of key operations
> which is extensible (which could be a good thing).

I think it is whatever permission is required in webcrypto to implement
HPKE. Which does not make any sense any other way.


> The pop use case is a bit more specific, because pop usually means some
> form of nonce signing.

Key_ops works for signing, but not for verification.

 
> I have wondered if JOSE and COSE would benefit from "more fine grained" key
> operation restrictions.

JOSE has "use", which is quite coarse-grained but sensible.
Unfortunately, COSE does not have equivalent.

And more fine-grained restrictions would make sense. E.g., restricting
key to a single family of properly-separated operations (which is
cryptographically kosher thing to do).


> I think a new concept that is not tied to web crypto might yield better
> security properties in the long run.

I think it would lead to better security properties.




-Ilari

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