[ietf-dkim] Revised proposal for specifying syntax and semantics for multiple signatures

[Paul Hoffman]

At 5:27 PM +0100 4/4/06, Stephen Farrell wrote:
>Currently "h=foo" is usable to say "I didn't sign foo cause it
>wasn't there" (or some better wording), effectively meaning
>that if someone adds a foo header field then the sig breaks.
>
>Ought your proposal make reference to this, even if only
>to include a reminder that making use of this feature/trick
>is liable to be problematic if such a field is likely to be
>added by a later MTA/signer?

No, because it doesn't seem related to signing the DKIM-Signature 
header. There is no sensible way to use DKIM-Signature in h= to 
indicate "there will be no future DKIM-Signature headers".

Maybe I'm misunderstanding your question.