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Re: [ietf-dkim] SSP acceptance chart

2005-11-05 01:47:10
On Sat, 2005-11-05 at 00:38 -0500, Hector Santos wrote:

And how do to a VERIFIER or SIGNER get this "exposed expressed desire?"  How
does the VERIFIER and and possibly RESIGNER get this information?

The opportunistic scheme is rather simple, so I try fewer words.

As the MDA sees broad-bindings with matching domains, it compiles a list
of these matches.  This list could be simply the domain-names.

 this-bank.com
 that-bank.com
 pay-this.com
 pay-that.com
 this-store.com
 that-store.com

Perhaps these names are stored in a zone or a database. It does not
matter.

When a message is received and there is a domain within the list that
matches a possible originating email-address domain, but the signing-
domain does not match, this should raise an alert on the message.
Instead of 'w=b' there could be an assertion of 'w=p' where such match
failures should be considered possible "phishing" attacks.

The difference is subtle.  An email-address is never expected to
authorize the signing-domain or have a policy.  The signing-domain
asserts the email-address relationship within the signature.

Your chart should not offer hostile treatment when email-addresses don't
match the signing-domain, unless they are on a list.  When they are not
on the list, then the reputation of the signature would simply be
evaluated.  In this case, the signing-domain and email-domain not
matching is fine.  At least the signature provides a valid place to
complain, not the email-address. 

-Doug  

 


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