On 4. Jun 2023, at 08:22, AJITOMI Daisuke <[email protected]> wrote:
>
> > Trivial to add (assign AEAD-Value 7).
>
> The AEAD-Value for Export-Only is 0xffff. I think AEAD-Value 7 cannot be
> assigned. Am I wrong?
So I’d amend my little formula to
AEAD-Identifier = AEAD-Value == 7 ? 0xFFFF : AEAD-Value + 1
or
AEAD-Identifier = AEAD-Value == 0 ? 0xFFFF : AEAD-Value
…or some such.
> > Don’t do that, then.
>
> Indeed. It may not be something to worry about too much :-)
>
> > Indeed. 2 bytes extra. As will be any a-la-carte approach.
>
> a-la-carte approach registers only one alg (HPKE-v1-Base). The
> smallest-length number can be assigned to it.
Not following — how do you get agility with a single value? The bits need to
be somewhere.
> > Can you explain this point?
>
> The current draft utilizes the algorithm IDs (kem_id, kdf_id, aead_id) of
> HPKE as they are. They are passed directly from the higher-level application
> to the HPKE library, so there is no need for a conversion process like your
> proposed alg_id => {kem_id, kdf_id, aead_id}.
But that process is trivial.
(And the combinations that get a lot of use are specific numbers that
implementers will remember, such as 1024 for
DHKEM(P-256,HKDF-SHA256)/HKDF-SHA256/AES-128-GCM.)
Grüße, Carsten
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