On Jun 15, 2011, at 3:50 PM, Daniel Kahn Gillmor wrote:

> On 06/15/2011 03:10 PM, David Shaw wrote:
>> That said I'd probably suggest notations for this, even though 0x40 exists 
>> in the standard.  0x40 signatures are a bit of a leftover tail in the 
>> standard, and are not well specified (0x40 sigclass - is it a binary 
>> signature?  a text signature?).  Using notations also gives you more 
>> flexibility since you can do key=value stuff and specify different 
>> variations on timestamp signatures.
> 
> Note that if you do decide to use a notation for this, you should mark
> the relevant notation subpacket as "critical", so that the signature is
> not interpreted by an unwitting implementation as meaning something
> other than the specific declaration:

I'm not sure I agree with that.  Essentially, this notation is a way for a user 
to say "This is what I mean by this signature".  Meaning and intent is 
difficult for GnuPG to divine :)

In practice, the critical flag tells GnuPG to reject the signature (mark it as 
invalid) if it doesn't know about the notation.  Why does GnuPG need to know 
about this notation?  Or more specifically, what should GnuPG do differently 
for a timestamp-only signature compared to a regular signature?

I'm not against the user deciding to mark the notation as critical if he 
chooses to do so.  I just wouldn't have it automatically and always critical.  
Unless I'm misunderstanding your point, I don't see that the semantics of a 
timestamp notation require that.

David


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