[ietf-dkim] New Issue: 4.2 needs new Attack Item: Inconsistent Signature vs Policy Attacks

[Dave Crocker]

> SSP is not necessary if a valid originating address signature is found. 

This has always struck me as an astonishingly powerful observation.

It means that we can have entirely independent lines of discussion.  One for the 
creation and handling of a successful signature.  The other for all other 
scenarios.

In particular, it means that the signature work can be partitioned from the 
non-signature work.  (To anticipate a mis-reading of this comment:  I am not 
saying that the two are not equally important.  Merely that each can receive its 
own focus of effort.)

My reading of the comments about the signature mechanism, versus comments on the 
  SSP mechanism, is that the former tend to represent very narrow, crisp, 
technical details, whereas the latter tend to be far more conceptual.

Given that the signature mechanism was carefully designed to re-use quite a bit 
of well-understood mechanism, it is not surprising that review and revision to 
it can be so crisp.  This tends to permit efficiently understanding the problem 
and usually means efficiently fixing it.

Given that SSP pertains to a topic that has little, if any, Internet-scale 
standardization or operations history, and given that it pertains to 
human/organizational rules, rather than lower-level bit-twiddling, it is also 
not a surprise that discussion about it requires wandering around the concept 
space rather more.

d/
-- 

Dave Crocker
Brandenburg InternetWorking
<http://bbiw.net>