Re: [Cfrg] Not the same thread -> was Re: Rerun: Elliptic Curves - preferred curves around 256bit work factor (ends on March 3rd)

Derek Atkins <derek@ihtfp.com> Thu, 26 February 2015 15:56 UTC

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From: Derek Atkins <derek@ihtfp.com>
To: Mike Hamburg <mike@shiftleft.org>
References: <D1133BAF.5C3D2%paul@marvell.com> <54EE0D4D.2080009@shiftleft.org>
Date: Thu, 26 Feb 2015 10:56:07 -0500
In-Reply-To: <54EE0D4D.2080009@shiftleft.org> (Mike Hamburg's message of "Wed, 25 Feb 2015 09:58:37 -0800")
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Subject: Re: [Cfrg] Not the same thread -> was Re: Rerun: Elliptic Curves - preferred curves around 256bit work factor (ends on March 3rd)
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Mike Hamburg <mike@shiftleft.org> writes:

> Thanks, Paul.
>
> On 3.6GHz Haswell with OpenSSL 1.0.1f:
> RSA-2048: sign 1028us, verify 31us
> Ed448: sign 51us, verify 163us, dh 148us
> Ed480: sign 55us, verify 183us, dh 170us
> E-521: sign 79us, verify 256us, dh 241us

I asked this in the previous thread but it was lost, so I'll ask this
again in this thread: Why are you looking at RSA 2048 for this
comparison?  That's only a 2^112 work factor (C.f. Section 1 of
RFC4492).

If you want a 2^256 work factor you need to go up to RSA 15360.  If you
only want to get to 2^128 then you need to look at RSA 3072.

Let's at least compare apples to apples.

> On 1GHz Cortex A8 with OpenSSL 1.0.1f:
> RSA-2048: sign 39.8ms, verify 1.2ms
> Ed448: sign 0.7ms, verify 1.9ms, dh 1.9ms
>
> On both CPUs, the elliptic curves are slower than RSA for verification, but
> much faster for signing.  The Haswell core is about 5-8x faster for RSA verify,
> and 20x slower for signing.

But at quite different security levels, so it's not telling us anything
useful.  I think Ed448 is more like an RSA-4096 level (or possibly even
larger than that).

> The A8 is more favorable to EC, probably because OpenSSL (or this build of it)
> doesn't use NEON for RSA.  It is only 60% faster for RSA verification, and 57x
> slower for signing.  But client devices don't sign very often.

-derek

> -- Mike
>
> On 02/25/2015 08:47 AM, Paul Lambert wrote:
>
>     Could we please get some discipline on this list to not pollute
>     conversation threads – especially well formed threads asking for poll with
>     random questions, comments and rants.  
>    
>     Paul
>
>     From: Phillip Hallam-Baker <phill@hallambaker.com>
>     Date: Wednesday, February 25, 2015 at 8:22 AM
>     To: Stephen Farrell <stephen.farrell@cs.tcd.ie>
>     Cc: "cfrg@irtf.org" <cfrg@irtf.org>
>     Subject: Re: [Cfrg] Rerun: Elliptic Curves - preferred curves around 256bit
>     work factor (ends on March 3rd)
>
>         Do we have figures for performance of these versus RSA2048?
>        
>         Yes, we get a reversal of the public/private speed advantage on
>         signature. And that in itself is a huge win on the server side 
>        
>         RSA signature verification takes 0.16 ms on a reasonably current
>         machine (signature is 6ms)
>        
>         http://www.cryptopp.com/benchmarks.html
>        
>         How much faster/slower one curve is over another matters much less to
>         me than whether the curve is faster or slower than what I am already
>         using. I am not going to be using P521 or P448 curves on a constrained
>         device, I will go for P255.
>        
>         If we had figures comparing the curve candidates to RSA it would
>         probably be illuminating.
>
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-- 
       Derek Atkins                 617-623-3745
       derek@ihtfp.com             www.ihtfp.com
       Computer and Internet Security Consultant