[openpgp] Re: I-D Action: draft-ietf-openpgp-replacementkey-01.txt

[Daniel Huigens <[e-mail]>]

On Monday, November 4th, 2024 at 13:51, andrewg wrote:
> The imprint is only included in order to ensure that
> automated fallback from a v6 key to a v4 key has exactly the same
> cryptographic strength as going the other way. It is arguable that it is
> already overkill...

Yeah. I personally also don't think the v6->v4 binding is all that
important. I would expect/hope that the primary use of this draft is to
switch from a v4 to a v6 key (identified by a SHA256 fingerprint
already). Even for cases where you care about the reverse somehow,
I don't think the issue with using SHA1 is all that critical.

That being said, I also don't think the imprint is a large burden to
implement, since we (Proton) already have the concept of SHA256-
Fingerprints for v4 keys (for Key Transparency), admittedly for similar
reasons (not having to rely on SHA1 simplifies the security story - but
again, even that I'm not sure really applies here if what we care about
is the v4->v6 transition).

So either way, I'm not strongly opposed to any of the options but having
only the fingerprint seems simplest to me.

Best,
Daniel