Re: [Cfrg] Minimum required work force for additional curve
Simon Josefsson <simon@josefsson.org> Mon, 02 March 2015 11:26 UTC
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From: Simon Josefsson <simon@josefsson.org>
To: Kurt Roeckx <kurt@roeckx.be>
References: <20150226190333.GA12230@roeckx.be>
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Date: Mon, 02 Mar 2015 12:25:55 +0100
In-Reply-To: <20150226190333.GA12230@roeckx.be> (Kurt Roeckx's message of "Thu, 26 Feb 2015 20:03:33 +0100")
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Subject: Re: [Cfrg] Minimum required work force for additional curve
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Kurt Roeckx <kurt@roeckx.be> writes: > Since I think this hasn't been clearly asked and that it might > explain the answer on the other questions asked, I'm guess I'll > just ask it myself: > > Assuming other than the 128 WF curve we only add 1 other curve, > what is the minimum WF it should have? I believe the focus on power-of-two work factor comparisons for asymmetric schemes is harmful. It makes people jump to the conclusion that asymmetric schemes share the commonly-believed property that symmetric schemes have: that adding another bit in the key space doubles the work factor. This focus also leads to confusing "algorithm pairing" ideas. The concept of work factor is useful though. I don't see how humans will ever do > 2^100 operations using today's non-quantum-technology. Thus, to me, a work-factor of 2^100 is sufficient to address our needs. And at that level, I would prefer having multiple options. I could live with recommending Curve25519 and some significantly larger curve like Ed448-Goldilocks if we can't get consensus on anything more reasonable (like two curves at 2^100-2^130 work factor), but it will lead to wasting energy computing the Ed448 operations where cheaper (energy-wise) alternatives would suffice. If we want significantly stronger alternatives to >~2^100 work factor solutions, I would prefer recommending solutions that withstand quantum technology attackers -- I believe there are solutions in that space. /Simon > I'm proposing the following answers, each time 16 bit more: > 144 > 160 > 176 > 192 > 208 > 224 > 240 > 256 > > > Kurt
- [Cfrg] Minimum required work force for additional… Kurt Roeckx
- Re: [Cfrg] Minimum required work force for additi… Michael Hamburg
- Re: [Cfrg] Minimum required work force for additi… Simon Josefsson