[openpgp] Re: session key length with SEIPDv2

[Daniel Kahn Gillmor <[e-mail]>]

On Wed 2024-10-09 17:24:57 +0200, Falko Strenzke wrote:
> I think we agree already on the MUST for the producer. The question
> that remains is whether there should be an equivalent MUST for the
> consumer. I think the main question is how well readers of RFC 9580
> will be aware of the errata. I have no experience with that, but my
> guess would be that it might not have the same reach as RFC 9580. That
> is what my concerns about a strict rule for the consumer are based on.
> How do you see this?

The text that i proposed does not put a MUST on the consumer.  For the
record, i proposed:

    When producing a message using SEIPD v2 with corresponding PKESKs
    or SKESKs, The length of the session key MUST equal the key size of
    the symmetric algorithm used in the encryption container.

    When handling a message that uses SEIPD v2, if the session key size
    does not equal the key size of the symmetric algorithm used in the
    encryption container, the consuming implementation SHOULD warn that
    the message is malformed, and MAY decline to decrypt the message.

Regards,

        --dkg