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Re: [Cfrg] Elliptic Curves - poll on specific curve around 256bit work factor (ends on February 23rd)

Phillip Hallam-Baker <phill@hallambaker.com> Fri, 20 February 2015 06:09 UTC

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Date: Fri, 20 Feb 2015 01:09:56 -0500
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From: Phillip Hallam-Baker <phill@hallambaker.com>
To: Alexey Melnikov <alexey.melnikov@isode.com>
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Subject: Re: [Cfrg] Elliptic Curves - poll on specific curve around 256bit work factor (ends on February 23rd)
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On Wed, Feb 18, 2015 at 5:51 AM, Alexey Melnikov <alexey.melnikov@isode.com>
wrote:

> CFRG chairs are starting another poll:
>
> Q3: (For people who want CFRG to recommend a curve at 256bit level) Is
> bandwidth cost of going to p521 worth the speed win over primes closer to
> 512 bits?
>

No, and I rather object to the phrasing.

The issue has never been the bandwidth of 9 extra bits. Its that it is an
odd size. Going down a bit from 256 to 255 is much easier than going up a
step.

Speed isn't much of a concern as this is going to be used for the long term
trust framework and as a backup algorithm.

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