I’ll ask more people to weigh in on this thread so we can resolve the issue.
Should we:
1. support only the seed private key representation for COSE and JOSE?
2. support both the expanded and seed private key representations for COSE
and JOSE?
Please give the reasons for your choice.
-- Mike (writing as a COSE
chair)
From: Orie <[email protected]>
Sent: Wednesday, April 2, 2025 6:09 PM
To: Ilari Liusvaara <[email protected]>
Cc: [email protected]; [email protected]
Subject: [COSE] Re: [jose] Re: Re: Re: Re: Do COSE and JOSE need both "priv"
and "seed"?
Inline:
On Wed, Apr 2, 2025 at 9:10 AM Ilari Liusvaara
<[email protected]<mailto:[email protected]>> wrote:
On Wed, Apr 02, 2025 at 10:45:25AM +0200, Filip Skokan wrote:
>
> I think the AKP definition of having seed/priv/pub is fine, but I'd say
> that the individual uses of this key type could decide whether to
> exclusively use "seed" (e.g. ML-DSA), or "priv" (e.g. SLH-DSA). Does that
> make sense? I'm not convinced.
I think that exclusively using "seed" does not make sense, and is not
currently allowed.
Not correct.
Specifically, it is legal to use "seed" and "pub", and to expand to "priv"
internally, see the example generated for the draft, and also this text:
https://datatracker.ietf.org/doc/html/draft-ietf-cose-dilithium-06#name-ml-dsa-private-keys
```
When both "seed" and "priv" are present, the "seed" parameter MUST expand to
the "priv" parameter.
When "priv" is present, "seed" SHOULD be present to enable validation of the
private key expansion process.
Validation and expansion of private keys might be skipped in constrained
environments.
```
What is currently allowed is algorithm exclusively uisng "priv" (e.g.,
COSE-HPKE/JOSE-HPKE) or using both "seed" and "priv" (e.g., ML-DSA).
Not true, see above.
If an algorithm has no meaningful expanded format (e.g., HPKE with
X-Wing, Ed25519 or Ed448), it uses "priv" exclusively.
Correct, we added your text, and it applies generically to all AKP:
https://datatracker.ietf.org/doc/html/draft-ietf-cose-dilithium-06#section-3-5
-Ilari
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