Re: [TLS] Testing consensus for adding curve25519 to the EC named curve registry

Douglas Stebila <stebila@qut.edu.au> Mon, 09 September 2013 23:40 UTC

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From: Douglas Stebila <stebila@qut.edu.au>
To: Nick Mathewson <nickm@torproject.org>
Date: Tue, 10 Sep 2013 09:40:34 +1000
Thread-Topic: [TLS] Testing consensus for adding curve25519 to the EC named curve registry
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Subject: Re: [TLS] Testing consensus for adding curve25519 to the EC named curve registry
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On 2013/09/10, at 02:18, Nick Mathewson <nickm@torproject.org>; wrote:

> On Mon, Sep 9, 2013 at 7:12 AM, Douglas Stebila <stebila@qut.edu.au>; wrote:
> [...]
>> - The curve parameters were generated "verifiably at random", meaning a seed was chosen, and then the curve parameters a and b were generated by hashing the seed a pre-determined number of times using SHA-1.  (Appendix 4 of http://csrc.nist.gov/groups/ST/toolkit/documents/dss/NISTReCur.pdf, or Section 3.1.3.1 of SEC1 http://secg.org, or ANSI X9.62)
> 
> A possibly foolish question, but I couldn't find the answer in any of
> the documents you listed:
> 
> Is it documented how the seeds were chosen?

I haven't found any information on how the seeds were chosen.  The earliest reference I have listing the seeds is a September 1998 draft of ANSI X9.62, a copy of which is available here: https://github.com/ANSSI-FR/parsifal/blob/master/docs/tls/X9-62-1998--ECDSA.pdf, but this provides no reason for the choice of seeds.  Maybe there's someone from X9F on this mailing list who has some historical insight?

Douglas