[ietf-dkim] Collection of use cases for SSP requirements

[Charles Lindsey]

On Fri, 17 Nov 2006 12:27:43 -0000, Wietse Venema <wietse at porcupine.org>  
wrote:

> Hallam-Baker, Phillip:
>> FOR DKIM BASE:
>> We have three possible outcomes: Definitely Genuine, Definitely
>> Fake and Undetermined
>>
>> [We can if people think there is value further break down
>> Undetermined according to probability but bear with me]
>
> My understanding is that DKIM-base can produce only two results:
> signature verification succeeds or signature verification fails.
> I may be mistaken, but it seems to me that expanding these two
> results into >2 involves information outside DKIM-base.

No, there is a lot more than that.

There is 'signature absent'
          'signature present but invalid'
For failed signatures there is
          'the failure was in the header/the body/both'
For good signatures there is
          'the headers that were signed were the ones expected to be signed'
          'the length of the body was longer than the l-tag said'

Which of these are relevant to automatic decision making, and which only  
for forensics, is a question for imploementors of verifiers. Experience  
may show that all sorts of unexpected scams can be caught by looking for  
obscure cases.

-- 
Charles H. Lindsey ---------At Home, doing my own thing------------------------
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   Web: http://www.cs.man.ac.uk/~chl
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