[ietf-dkim] Re: signature construct

[Douglas Otis]

On Oct 14, 2005, at 2:06 PM, Dave Crocker wrote:

>
>
>> I agree with this point.  What's important to me, though, is that  
>> we be able to tell the difference between a failed signature  
>> (because the body was changed) and a bogus signature (something  
>> signed with the wrong key, or something made to look like a sig  
>> that's not).
>>
>
> This is the sort of goal that seems entirely reasonable, but might  
> not be.  It's worth exploring exactly how much sophistication and  
> subtlety is needed, for the functionality DKIM is seeking to provide.
>
> As I understand it, the goal is to determine a domain that is  
> willing to assert responsibility for the message.
>
> That's a positive goal.  It only applies if the signature  
> validates.  If validation fails, for any reason, then we do not  
> have an accountable domain.
>
>
> It sounds as if the distinction you want to draw is useful for some  
> sort of additional goal:

The signature header may include both a body hash and perhaps even a  
future salty RCPT TO hash.  Failure to validate the hash in the first  
case would be useful when attempting to understand the cause.  This  
would have greater significances during the first few years of  
deployment.  Extending this mechanism as a means to mitigate some  
other checks for example, may be made easier when following this  
approach.

-Doug