[ietf-dkim] Attempted text for x= with DSN considerations

[Scott Kitterman]

Because if we put that in the spec then we've effectively gotten rid of x= 
because no one would use it then and that's what he wants perhaps?

Scott K

On 04/19/2006 18:54, Bill.Oxley at cox.com wrote:
> Why would a verifyer refuse a message that had a value for x=?
>  "Verifiers MAY support checking of x= values or may refuse to
>         accept messages with the x= tag."
> thanks,
> Bill
>
>
> -----Original Message-----
> From: ietf-dkim-bounces at mipassoc.org on behalf of Douglas Otis
> Sent: Wed 4/19/2006 6:01 PM
> To: Stephen Farrell
> Cc: ietf-dkim
> Subject: Re: [ietf-dkim] Attempted text for x= with DSN considerations
>
> Proposed:
>
> x=     Signature Expiration (plain-text, OPTIONAL, default is
>         no expiration). The format is the same as the "t=" tag,
>         represented as an absolute date, not as a time delta from the
>         signing timestamp.
>
>         Verifiers who support x= should consider a signature invalid
>         when the [received] time at the verifier is past the
>         expiration date.  Verifiers that do not support x= and
>         forward messages, may refuse acceptance of messages
>         when the x= tag is present to avoid causing DSNs.
>
>         When a signature becomes invalid, and is not accepted by a
>         subsequent MTA, a mechanism to rate-limit initial senders
>         may be required to control the level of DSNs.  If a signature
>         is initially found invalid for this reason, then normal rules
>         apply, so the signature SHOULD be treated the same as if
>         cryptographic checking had failed, or as if the public key
>         could not be retrieved.
>
>         Verifiers should not assume that there is any particular
>         relationship between the x= value and the life cycle of a
>         public key.  Signers MAY include an x= value at their
>         discretion.
>
>         Verifiers MAY support checking of x= values or may refuse to
>         accept messages with the x= tag.  The value is expressed as
>         an unsigned integer in decimal ASCII, with the same constraints
>         on the value in the "t=" tag.  The value of the "x=" tag MUST
>         be greater than the value of the "t=" tag, if both are present.
>
>
>             INFORMATIVE NOTES:
>             1) Messages with invalid signatures or x= parameters
>                may be rejected by subsequent MTAs.
>             2) When the signer has no reason to include any
>                particular value, then this tag is better omitted.
>             3) There is no particular reason to include values far
>                into the future, e.g. if it expected that a verifier
>                might not see the message for a long time. In such
>                cases omitting x= will probably be better.
>
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