----- Original Message -----
From: "Hallam-Baker, Phillip" <[EMAIL PROTECTED]>

> From an administrative point of view it is useful to be able to
> tell the signer 'hey dude' (that's technical speak) 'hey dude if you
> want to verify this signature better get the signature key before
> this date.'
>
>
>     Signature expiration in seconds-since-1970 format
>     as an absolute date, not as a time delta from the signing
>     timestamp. The signature expiration date allows the signer
>     to notify verifiers that distribution of the signing key
>     MAY cease once the expiration date has passed.

Ok.  In short, you are saying don't bother trying to do a Verification
because the odds are good it is will fail, and it does fail, this would be
one reason.

Question: Why limit the signer ability to have DKIM system that keeps the
same selector, creates different x= values depending on message type or
value?

I see that is a pretty powerful option.

If we remove x=, we are left with removing selector.

The result is a guarantee that it will fail based on a NXDOMAIN error.

So it is correct to say:

   Signatures with selectors resulting in NXDOMAIN DNS querys SHOULD NOT
   be considered valid?

I prefer to see a more direct "signal" from the signer that says this
signature is no longer valid.   Are we willing to say NXDOMAIN is sufficient
for this?

How about this in section 5.2:

| 5.2  Select a private-key and corresponding selector information
|
|    ..
|    A signer SHOULD NOT sign with a key that is expected to expire within
|    seven days; that is, when rotating to a new key, signing should
|    immediately commence with the new key and the old key SHOULD be
|    retained for at least seven days before being removed from the key
|    server.

That basically means that x= must be used if there is planned event for
selector removal within 7 days.

--
Hector Santos, Santronics Software, Inc.
http://www.santronics.com








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