Re: [Cfrg] Point format endian

Damien Miller <djm@mindrot.org> Tue, 27 January 2015 22:01 UTC

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Date: Wed, 28 Jan 2015 09:00:41 +1100
From: Damien Miller <djm@mindrot.org>
To: Derek Atkins <derek@ihtfp.com>
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Cc: Peter Gutmann <pgut001@cs.auckland.ac.nz>, "'cfrg@irtf.org'" <cfrg@irtf.org>
Subject: Re: [Cfrg] Point format endian
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On Tue, 27 Jan 2015, Derek Atkins wrote:

> Stephen Farrell <stephen.farrell@cs.tcd.ie> writes:
> 
> > On 27/01/15 10:34, Peter Gutmann wrote:
> >> The universal standard for crypto bignums is big-endian
> >
> > Hmmm.... sez who? :-)
> 
> PKIX, OpenPGP, OpenSSH, Kerberos, TLS...  Pretty much every existing
> IETF security standard I know of to date encodes numbers in big-endian
> format.

No, OpenSSH uses little endian encoding for X25519 and Ed25519.

We don't care - they are opaque strings as far as our application is
concerned (which is IMO exactly how it should be).

+1 to little endian, for the sake of compatibility with deployed and
tested code.

-d