[ietf-dkim] Base issue: multiple linked signatures

[John L]

>> Can you describe the algorithm to distinguish the cases where the original
>> value is fine from the cases where it's not?
>
> You took one line without additional context where I gave an example of users 
> who have processing script to find mail lists based on subject tags.

We all have scripts like that.  What do they have to do with DKIM 
signature validation?

> BTW - Did you notice that we are talking about email cases where message 
> passed through processing system that thought its ok to make modifications
> to the originator's header data before further delivery. So is the question
> you're asking when its ok to make further modifications to the same message?

Actually, that's not at all what I was talking about.  I was asking how a 
recipient system can algorithmically distinguish an upstream modification 
that broke the signature but was "ok" from one that wasn't.

I think that we all agree that if the intermediate system re-signed the 
message and we trust that signature, the message is OK.  But the 
discussion in progress is, as far as I can tell, about messages where an 
intermediate system modified but did not re-sign.

R's,
John