-----Original Message-----
From: ietf-dkim-bounces(_at_)mipassoc(_dot_)org [mailto:ietf-dkim-
bounces(_at_)mipassoc(_dot_)org] On Behalf Of hector
Sent: Sunday, November 01, 2009 7:44 PM
To: John Levine
Cc: barryleiba(_at_)computer(_dot_)org; ietf-dkim(_at_)mipassoc(_dot_)org
Subject: Re: [ietf-dkim] Interesting Dupe Signatures
But a body hash is calculated per signature because it might have a
different c14n parsing. So the ideal optimization would be to reduce
the body hashing to unique c= c14n types. Given a ridiculous multiple
signatures case:
DKIM-Signature: .... c=relaxed/relaxed; // dupe
DKIM-Signature: .... c=relaxed/relaxed; // dupe
DKIM-Signature: .... c=relaxed/relaxed; // dupe
DKIM-Signature: .... c=simple/relaxed; // other signer
DKIM-Signature: .... c=relaxed/relaxed; // other signer
You need two header and one body canonicalizations in that example. And that
presumes there's no "l=", which creates another dimension in the matrix of
canonicalizations you need to run.
I've had a lot of success doing this sort of common factoring work in my
implementation, though I sadly have no data about how much computation work it
really saves.
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