[openpgp] Re: Deterministic generation of (symmetric) public key params from private key params

[Justus Winter <[e-mail]>]

Hi Daniel :)

Daniel Huigens <d.huigens=[e-mail]> writes:

> In the meeting last week, Justus noted that folks might want to
> deterministically generate key pairs from the private key material
> (presumably by storing some metadata like the key generation time).
>
> And, the change in draft-ietf-openpgp-persistent-symmetric-keys-00
> complicates this, by no longer storing the hash seed in the private
> key material.
>
> So, you'd have to store some additional algorithm-specific metadata
> from the public key material, namely the fingerprint seed.
>
> Since we didn't have much time for discussion last week, I thought I'd
> ask the wider WG here whether this is a use case people care about,
> and whether this workaround would be sufficient?

I don't understand the motivation for the hash seed in the first place.
Why not derive a mock public key from the secret key, i.e. include
SHA2-256(persistent symmetric key material) in the algorithm-specific
bits of the public key packet?

Best,
Justus