Re: [Hash] Charter discussion, round 1

EKR <ekr@networkresonance.com> Thu, 16 June 2005 02:24 UTC

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To: "Jim Schaad" <ietf@augustcellars.com>
Subject: Re: [Hash] Charter discussion, round 1
In-reply-to: Your message of "Tue, 14 Jun 2005 15:43:44 PDT." <20050614224156.A506B830E6@smtp2.pacifier.net>
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Date: Wed, 15 Jun 2005 19:24:36 -0700
From: EKR <ekr@networkresonance.com>
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Jim Schaad <ietf@augustcellars.com>; wrote:
> 1. Is this new hash function we are considering in phase 1 going to be the
> same length as SHA-1 or not?  This would appear to be implied by the goals.
> Would replacement of SHA-1 with SHA-256 intact be considered as reasonable
> in the first phase?

Right. It's important here to distinguish between DSA/ECDSA and RSA.

There's basically no advantage to using a truncated SHA-256 over
straight SHA-256 with RSA. The performance is (of course) the same
and there's plenty of room for a 256-bit hash in a 1024-bit RSA block
(and people using 512-bit deserve what they get). 

So, defining truncated hashes really only makes sense for ECDSA/DSA
and other algorithms with fixed input sizes....

-Ekr

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