Re: [Cfrg] Point format endian (was: Adoption of draft-ladd-spake2 as a RG document)

Peter Gutmann <> Tue, 27 January 2015 11:03 UTC

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From: Peter Gutmann <>
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Thread-Topic: [Cfrg] Point format endian (was: Adoption of draft-ladd-spake2 as a RG document)
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Date: Tue, 27 Jan 2015 11:03:13 +0000
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Subject: Re: [Cfrg] Point format endian (was: Adoption of draft-ladd-spake2 as a RG document)
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Stephen Farrell <> writes:
>On 27/01/15 10:34, Peter Gutmann wrote:
>> The universal standard for crypto bignums is big-endian
>Hmmm.... sez who? :-)

Name any significant IETF (i.e. CFRG-relevant) crypto standard that uses
little-endian bignums.

>But seriously, if in fact this makes little or no difference, which I believe
>is the case, and which I believe you are also arguing, then what is the
>problem with going with the initial coder's choice here?

Because, as I've already pointed out in an earlier message, if the universal
standard is big-endian and the vast majority of your potential user base (via
OpenSSL, not sure about MS CryptoAPI) only does big-endian, then choosing a
format that's not big-endian is a really bad idea.