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Re: [TLS] Require deterministic ECDSA

Joseph Birr-Pixton <jpixton@gmail.com> Sat, 23 January 2016 19:59 UTC

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Date: Sat, 23 Jan 2016 19:59:15 +0000
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From: Joseph Birr-Pixton <jpixton@gmail.com>
To: Jacob Maskiewicz <jmaskiew@eng.ucsd.edu>
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Subject: Re: [TLS] Require deterministic ECDSA
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Hi,

The other benefit is being able to test that a critical code path
produces the correct answers. With randomised k, this is not really
possible. For instance, you can choose k with the top bit clear
without any obvious or externally-testable effects, except effectively
publishing your long-term private key after a large number of
signatures[1].

Given the history of these things, I would perhaps challenge the
assumption that all TLS stacks will have a bug-free, thread-safe,
fork-safe, high quality, uncompromised, backdoor-free, unbiased random
number generator :)

Cheers,
Joe

[1]: http://people.rennes.inria.fr/Jean-Christophe.Zapalowicz/papers/asiacrypt2014.pdf

On 23 January 2016 at 19:27, Jacob Maskiewicz <jmaskiew@eng.ucsd.edu> wrote:
> The main argument I see from the RFC for deterministic ECDSA is computing k
> on systems without high quality entropy sources. But any system running a
> TLS stack is already going to have a high quality entropy source for
> client/server randoms and IVs and such, so what's the benefit of
> deterministic ECDSA here?
>
> -Jake M
>
> On Jan 23, 2016 11:13 AM, "Joseph Birr-Pixton" <jpixton@gmail.com> wrote:
>>
>> Hi,
>>
>> I'd like to propose that TLS1.3 mandates RFC6979 deterministic ECDSA.
>>
>> For discussion, here's a pull request with possible language:
>>
>> https://github.com/tlswg/tls13-spec/pull/406
>>
>> Cheers,
>> Joe
>>
>> _______________________________________________
>> TLS mailing list
>> TLS@ietf.org
>> https://www.ietf.org/mailman/listinfo/tls

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