> On Jun 4, 2023, at 12:12 AM, AJITOMI Daisuke <[email protected]> wrote:
> 
> Hi Laurence, Ilari,
> 
> > My proposal is to fully replace the Enc_structure with COSE_KDF_Context in 
> > COSE-HPKE. I am not proposing double protection.
> 
> ...
> 
> Given that there's no need to use it, it's not required by the core spec, and 
> there's the issue, as Ilari has repeatedly pointed out, of not being able to 
> input a meaningful value into SuppPubInfo.keyDataLength,

For multiple recipient COSE-HPKE, it IS It is possible to put a meaningful 
value in for both COSE_KDF_Context. AlgorithmID and 
COSE_KDF_Context.SuppPubInfo.keyDataLength.

Single recipient COSE-HPKE is kind of a degenerate case for this. It doesn’t 
need these values because it is all handled internally, so we can just put 
none/0.

Ironically, it is the COSE standard COSE_Recipient alg -29 in RFC 9053 that has 
the problem mixing in the content encryption algorithm because AES Key Wrap is 
not an AEAD and in the way.

LL


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