[ietf-dkim] IDNs, was Proposed new charter

[Dave CROCKER]

On 3/3/2010 10:32 PM, Eliot Lear wrote:
> Certainly. In a nut shell, the problem is at the implementation end
> between the MUA and the signer. The common signers out there will only
> do so for certain domains, and they will generally only do so, based on
> the From: line. Here is where the confusion sets in. If an MUA sees an
> address, such as the following:

Confusion, indeed.  In what way is the From: line relevant to DKIM, other than 
being part of the header field hash?

I believe we are not in any way implying any changes to the hashing algorithm, 
since DKIM does not do field-specific processing.  (For example, it cannot know 
all of the possible address header fields.)


> From: Eliot Lear =?iso-8859-1?Q?<lear at klapsm=FChle.ch>?=
>
> When the signer sees this, it could upgrade to get klapsmühle.ch, and
> then check the punycode version of that. Things get more confused in
> EAI, because there 8-bit MIME floating around. If you sign 8-bit MIME
> and a downgrade occurs, the game is over, and the signature is invalidated.

Ahh, well, the DKIM specification does not provide text that guides selection of 
the d= value.

So, yes, the signer might have differential signing practices based on the From: 
field, but that's outside the scope of the specification.

What am I missing?

d/
-- 

   Dave Crocker
   Brandenburg InternetWorking
   bbiw.net