Re: [jose] Do we have actual normative text which curves are allowed / standard for ECDH-ES in JOSE?

Carsten Bormann <cabo@tzi.org> Wed, 04 November 2020 08:57 UTC

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From: Carsten Bormann <cabo@tzi.org>
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Date: Wed, 4 Nov 2020 09:57:28 +0100
Cc: Vladimir Dzhuvinov <vladimir@connect2id.com>, "Hamad, Samer K" <samer.k.hamad@chase.com>, "Voss, Ray" <ray.voss@jpmorgan.com>, "jose@ietf.org" <jose@ietf.org>
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To: Filip Skokan <panva.ip@gmail.com>
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Subject: Re: [jose] Do we have actual normative text which curves are allowed / standard for ECDH-ES in JOSE?
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The JSON Web Key Elliptic Curve registry just lists the curves:

https://www.iana.org/assignments/jose/jose.xhtml#web-key-elliptic-curve

In COSE we have a registry "COSE Elliptic Curves”:

https://www.iana.org/assignments/cose/cose.xhtml#elliptic-curves

This actually has a column “description” that contains some more information about where these curves are supposed to be used.

Grüße, Carsten



> On 2020-11-03, at 22:50, Filip Skokan <panva.ip@gmail.com> wrote:
> 
> Hi Vladimir,
> 
> I kinda got the same question from someone a couple days ago and could pinpoint a clear normative answer.
> 
> We have https://tools.ietf.org/html/rfc7520 that shows ECDH-ES with P-384 and P-256. In not having any normative text around these curves being allowed or P-521 being disallowed I always assumed all original three are fair use for ECDH-ES (and its composite KW variants).
> 
> We also have https://tools.ietf.org/html/rfc8037 which specifically mentions X25519 and X448 OKP subtypes to be usable for ECDH-ES (and its composite KW variants).
> 
> Then we have the JOSE registration of EC secp256k1 curve which specifically mentions that the curve is NOT released for ECDH in that document.
> 
> So, 
> 
> EC P-256
> EC P-384
> EC P-521
> OKP X25519
> OKP X448
> 
> S pozdravem,
> Filip Skokan
> 
> 
> On Tue, 3 Nov 2020 at 22:40, Vladimir Dzhuvinov <vladimir@connect2id.com> wrote:
> Today we received the question why the Nimbus JOSE+JWT lib supports the
> EC curves it does for ECDH (P-256, P-384, P-512) and I couldn't find any
> normative text or reference in the JWA spec to explain this.
> 
> https://tools.ietf.org/html/rfc7518#section-4.6
> 
> 
> We also looked at the IANA registry for hints:
> 
> https://www.iana.org/assignments/jose/jose.xhtml
> 
> 
> Contrast this with the JWS ECDSA, where the curves to go with the ESxxx
> algs are specced:
> 
> https://tools.ietf.org/html/rfc7518#section-3.4
> 
> 
> Can someone help here? :)
> 
> 
> Thanks,
> 
> Vladimir
> 
> -- 
> Vladimir Dzhuvinov
> 
> 
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