On the specific question of encoding the encapsulated keys -- It would be a
mistake to encode these as keys.  The HPKE spec deliberately treats these
as opaque byte strings to preserve agility with regard to the KEM.  In
DHKEM, the encapsulated value is a serialized public key, but that is not
true more generally.

--RLB

On Thu, Sep 22, 2022 at 8:34 AM AJITOMI Daisuke <[email protected]> wrote:

> Hi folks,
>
> I've heard that the JOSE WG is considered to be restarted.
>
> Currently, during some discussions on "Use of HPKE with COSE''[1] in the
> COSE WG, the topic of how to represent HPKE public keys has been
> raised[2][3]. Specifically, it concerns whether encapsulated keys
> (ephemeral **sender** public keys) for HPKE should be represented by
> COSE_Key (binary version of JWK) or not and I am of the opinion that it is
> not necessary to express them in COSE_Key.
>
> On the other hand, however, I'm thinking it would be better to have a
> standardized way and format for publishing **recipient** public keys for
> HPKE. In particular, I believe that if we can express them in very popular
> JWK format and publish them via developer-friendly jwks_uri endpoints the
> use of HPKE on the application layer will be facilitated.
>
> Would this topic be inside the scope of the new JOSE WG planned to be
> re-chartered?
>
> I would like to hear from the experts on this mailing list.
>
> Best regards,
> Ajitomi, Daisuke
>
> [1] https://www.ietf.org/archive/id/draft-ietf-cose-hpke-02.html
> [2] https://mailarchive.ietf.org/arch/msg/cose/kI10B-xaIUFTeN2lZNXKsgYBMSs
> [3] https://mailarchive.ietf.org/arch/msg/cose/Rg_AAtgOL4p9SdlXHyL8-0HSrI8
> _______________________________________________
> jose mailing list
> [email protected]
> https://www.ietf.org/mailman/listinfo/jose
>
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