Re: [openpgp] To bind or not to bind

[Johannes Roth <[e-mail]>]

On 23.03.2024 04:59, Daniel Kahn Gillmor wrote:
> I would not object to a statement like "Binding a PQC encryption-capable
> subkey into a certificate implies setting Feature Flag 0x08 (SEIPDv2
> support)".  We basically already require implementations to impute
> Feature Flag 0x01 (SEIPDv1 support) even if it is not explicitly set,
> because SED encryption needs to go away.  And an implementation that can
> implement PQC but is incapable of implementing SEIPDv2 would be very
> surprising.  Why not couple them explicitly to move users to the more
> robust format?

A non-SEIPDv2-capable PQC implementation does not seem surprising *if* 
we decide to allow PQC encryption for v4 keys since then you can 
implement it independently from the Crypto Refresh.

We need to consider these two cases:

1) A Crypto Refresh + PQC implementation that uses a v4 PQC certificate 
for backwards compatibility.

2) A v4 + PQC implementation that does not understand SEIPDv2/PKESKv6 
and v6 keys/signatures.

Therefore, explicitly setting only the SEIPDv1 flag should be honored to 
allow implementations of type 2) to state "I understand PQC but I don't 
understand SEIPDv2".

- Johannes


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Johannes Roth
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