Similar to ECDH-ES, JOSE HPKE for traditional algorithms would be using
ephemeral keys. In the proposed use case, the keys will be used for
long-term and will not provide forward-secrecy. It looks like a new mode to
me

In case of Hybrid or pure PQC, the output of KEM encaps will be
non-deterministic and this new mode is not required. It seems adding a new
just for traditional algorithms seems unwarranted.

-Tiru

On Sat, 26 Oct 2024 at 03:09, Orie Steele <[email protected]> wrote:

> Hi Rene,
>
> The current draft is primarily targeting JWE support for HPKE.
>
> That means support for encrypted JWTs (single recipient), and multiple
> recipient interoperability via json serialized JWE.
>
> We're obviously excited about enabling a path to post quantum kems like
> ML-KEM or XWING for JOSE.
>
> The flow you describe sounds like a series of messages, instead of a
> single message with one or more recipients.
>
> That being said, there is potentially some opportunity to share algorithm
> identifiers, public key formats, and possibly adjust the integrated
> encryption or key encryption mode requirements to align more with your use
> case.
>
> There is also COSE HPKE, is support for CBOR a consideration?
>
> Perhaps there is path to ommiting the encapsulated key if specific
> protected header parameters were present... And that could be made to be
> compatible with integrated encryption mode... Or perhaps this is a new JOSE
> HPKE model entirely.
>
> I'll need to read up on CXP, but I'm happy to propose some message
> examples to ground the discussion in the current drafts capabilities.
>
> Regards,
>
> OS
>
>
>
>
>
> On Fri, Oct 25, 2024, 4:18 PM Rene Leveille <rene.leveille=
> [email protected]> wrote:
>
>> Hello JOSE mailing list,
>>
>> As some of you may be aware, the FIDO Alliance has been working on some
>> new specifications for interoperability of credential managers. The 
>> Credential
>> Exchange Protocol
>> <https://fidoalliance.org/specs/cx/cxp-v1.0-wd-20241003.html> (CXP)
>> specifically leverages HPKE (RFC 9180) for the encryption of the credential
>> payload. Seeing as this is a JSON based protocol, the use of
>> draft-ietf-jose-hpke-encrypt
>> <https://datatracker.ietf.org/doc/draft-ietf-jose-hpke-encrypt/> is a
>> logical choice for containing the encrypted payload. To that effect, I am
>> reaching out to make the working group aware of the use case and the
>> importance of the draft for CXP.
>>
>> To this end, i also have questions regarding the draft:
>>
>>    - The protocol will be encrypting multiple payloads using the same
>>    AEAD context. HPKE encryption contexts use a counter as a state for
>>    deriving the nonces. However it seems that the current draft seems
>>    to support only the one shot API of the RFC. Would the authors be open to
>>    adding a sequence key to the schema to support longer lived encryption
>>    contexts?
>>    - In the case of a longer lived context, having the JWE hold the
>>    encapsulated key would be redundant. Would it make sense to have the
>>    encapsulated key be optional when a sequence key is present?
>>
>> Regards,
>>
>> René Léveillé
>> Senior Developer, Security Development
>> [email protected]
>>
>> More than 100,000 businesses trust 1Password to secure their most
>> important information. Try it free.
>> <https://1password.com/teams/pricing/>
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