Re: [openpgp] SHA3 algorithm ids.

Peter Gutmann <pgut001@cs.auckland.ac.nz> Sun, 09 August 2015 12:45 UTC

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From: Peter Gutmann <pgut001@cs.auckland.ac.nz>
To: Phillip Hallam-Baker <phill@hallambaker.com>, Christoph Anton Mitterer <calestyo@scientia.net>
Thread-Topic: [openpgp] SHA3 algorithm ids.
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Date: Sun, 9 Aug 2015 12:44:58 +0000
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Subject: Re: [openpgp] SHA3 algorithm ids.
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Phillip Hallam-Baker <phill@hallambaker.com>; writes:

>Why is anyone going to move from SHA-2 to SHA-3 ?

There isn't one.  As a result of the SHA-3 competition, we now know that SHA-2
is a lot stronger than people had originally thought (based on its SHA-1
heritage).  So the real winner of the SHA-3 competition was SHA-2.

>For OpenPGP, I think the case for 512 only or 256 and 512 is pretty strong.

The case for -256 only is that it's no worse than -512 but half the size.
This is particularly egregious for things like TLS and SSH, where you have to
use an idiotic-length 64-byte MAC if you want to protect a single-byte
keystroke.  It's less so for PGP and S/MIME where you're not sending a
constant stream of packets all unnecessarily bloated up by 64 bytes, but it's
still pointless.

Peter.