[ietf-dkim] RFC4871bis - whether to drop -- x: Signature expiration

[Charles Lindsey]

On Sat, 30 May 2009 18:12:47 +0100, Dave CROCKER <dhc at dcrocker.net> wrote:

> This note is intended to anchor a discussion thread for discusses one of  
> those
> features, namely:
>
>
>>    DKIM-Signature Header tags
>>
>>      x: Signature expiration
>>
>> Expiration is a fairly common feature in signing specifications. But
>> DK and DKIM are different in that the public key is not distributed to
>> others, it's always under the control of the signer. Does this add
>> anything that removing the DNS TXT record doesn't do? Is it used? Is
>> it necessary?

OTOH, there might well be other applications, built on top of DKIM for as  
yet totally unforeseen purposes, which might need to specify other (longer  
term) means of establishing the public key, and for such applications the  
x tag might well be needed.

There is nothing inherent in the basic DKIM protocol that would prevent  
such extensions in the future, so do not close them off prematurely.

I know of (at least) 3 different and mutually incompatible systems for  
signing headers in regular use, and DKIM is merely the latest of them. I  
would not like to see people to be forced to invent fourth and fifth  
systems, just because DKIM has painted itself into some unnecessary corner.

-- 
Charles H. Lindsey ---------At Home, doing my own thing------------------------
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