Re: [Cfrg] draft-black-rpgecc-00-.txt [was: Consensus and a way forward]
Adam Langley <agl@imperialviolet.org> Mon, 01 December 2014 14:17 UTC
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From: Adam Langley <agl@imperialviolet.org>
To: Robert Ransom <rransom.8774@gmail.com>
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Subject: Re: [Cfrg] draft-black-rpgecc-00-.txt [was: Consensus and a way forward]
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On Sun, Nov 30, 2014 at 7:33 PM, Robert Ransom <rransom.8774@gmail.com> wrote: > Third, you appear to be arguing that ECDH operations would not use the > Montgomery curve *isomorphic* to the Edwards curve in your Internet > draft, but use a *different* Montgomery curve (PinkBikeShed) which is > merely *isogenous* to the curve that you are proposing, in order to > reduce the modifications required to make the many existing > independent, interoperable implementations of Curve25519 operate on > your curve. This would *slightly* reduce the technical disadvantage > of your proposal compared to Curve25519, but would clearly not > eliminate it. If you do intend to propose PinkBikeShed for ECDH, > rather than the Montgomery curve isomorphic to the one specified in > your Internet draft, then that needs to be stated explicitly in your > draft. Yes, I agree. The draft should specify the Montgomery curve and the isogeny maps. I also very much hope that the CFRG doesn't just specify curves, but also will provide detailed guidance about their use -- that's also missing from the draft at the moment. > Interesting suggestion. > > Both 89747 and 121665 are 17 bits long (they are between 2^17 and 2^18 > - 1), and 89747 has a slightly greater Hamming weight than 121665 (10 > rather than 9); I would expect any performance improvement on due to > that change in curve parameter to be quite small and only applicable > to a very few implementation strategies. Have you done any > benchmarking to quantify the performance improvement that you are > claiming as a technical benefit of PinkBikeShed? I've not done any benchmarking, it's just a guess. But the Edward's d parameter for the curve isomorphic to Curve25519 isn't 121665, it's +/- 121665/121666 [http://eprint.iacr.org/2007/286.pdf, section 2]. That value doesn't have a small representation so I think that the PinkBikeShed curve does get to use a multiplication by a small constant in place of a multiplication by a large constant. That might be a small help. > Do you believe that that possible performance improvement is a > sufficiently large technical benefit over Curve25519 to outweigh the > technical disadvantages of your proposal that you were aware of at the > time that you submitted it? No. I think the prevalence of Curve25519 alone is enough that the CFRG should adopt it. PinkBikeShed isn't what I want, but it's close and it's something that I can live with in order to move forward. Cheers AGL -- Adam Langley agl@imperialviolet.org https://www.imperialviolet.org
- [Cfrg] Consensus and a way forward Benjamin Black
- Re: [Cfrg] Consensus and a way forward Watson Ladd
- Re: [Cfrg] Consensus and a way forward Joppe Bos
- Re: [Cfrg] Consensus and a way forward Hannes Tschofenig
- Re: [Cfrg] draft-black-rpgecc-00-.txt [was: Conse… Alyssa Rowan
- Re: [Cfrg] Consensus and a way forward Ilari Liusvaara
- Re: [Cfrg] draft-black-rpgecc-00-.txt [was: Conse… Adam Langley
- Re: [Cfrg] draft-black-rpgecc-00-.txt [was: Conse… Alyssa Rowan
- Re: [Cfrg] draft-black-rpgecc-00-.txt [was: Conse… Mike Hamburg
- Re: [Cfrg] draft-black-rpgecc-00-.txt [was: Conse… Alyssa Rowan
- Re: [Cfrg] Consensus and a way forward Paterson, Kenny
- Re: [Cfrg] Consensus and a way forward Paterson, Kenny
- Re: [Cfrg] Consensus and a way forward Paterson, Kenny
- Re: [Cfrg] draft-black-rpgecc-00-.txt [was: Conse… Benjamin Black
- Re: [Cfrg] draft-black-rpgecc-00-.txt [was: Conse… Alexey Melnikov
- Re: [Cfrg] draft-black-rpgecc-00-.txt [was: Conse… Michael Hamburg
- Re: [Cfrg] draft-black-rpgecc-00-.txt [was: Conse… Benjamin Black
- Re: [Cfrg] draft-black-rpgecc-00-.txt [was: Conse… Alyssa Rowan
- Re: [Cfrg] draft-black-rpgecc-00-.txt [was: Conse… Robert Ransom
- Re: [Cfrg] draft-black-rpgecc-00-.txt [was: Conse… Adam Langley
- Re: [Cfrg] Consensus and a way forward Lochter, Manfred
- Re: [Cfrg] draft-black-rpgecc-00-.txt [was: Conse… Ilari Liusvaara
- Re: [Cfrg] draft-black-rpgecc-00-.txt [was: Conse… Robert Ransom
- Re: [Cfrg] draft-black-rpgecc-00-.txt [was: Conse… Benjamin Black
- Re: [Cfrg] draft-black-rpgecc-00-.txt [was: Conse… Watson Ladd
- Re: [Cfrg] draft-black-rpgecc-00-.txt [was: Conse… Tony Arcieri
- Re: [Cfrg] draft-black-rpgecc-00-.txt [was: Conse… Benjamin Black
- Re: [Cfrg] draft-black-rpgecc-00-.txt [was: Conse… Alyssa Rowan
- Re: [Cfrg] draft-black-rpgecc-00-.txt [was: Conse… D. J. Bernstein
- Re: [Cfrg] draft-black-rpgecc-00-.txt [was: Conse… Robert Ransom
- Re: [Cfrg] draft-black-rpgecc-00-.txt [was: Conse… Benjamin Black
- Re: [Cfrg] draft-black-rpgecc-00-.txt [was: Conse… Watson Ladd
- Re: [Cfrg] draft-black-rpgecc-00-.txt [was: Conse… Paterson, Kenny
- Re: [Cfrg] draft-black-rpgecc-00-.txt [was: Conse… Alyssa Rowan
- Re: [Cfrg] draft-black-rpgecc-00-.txt [was: Conse… Watson Ladd
- Re: [Cfrg] draft-black-rpgecc-00-.txt [was: Conse… Benjamin Black
- Re: [Cfrg] draft-black-rpgecc-00-.txt [was: Conse… Robert Ransom
- Re: [Cfrg] draft-black-rpgecc-00-.txt [was: Conse… Paul Hoffman
- Re: [Cfrg] draft-black-rpgecc-00-.txt [was: Conse… Alexey Melnikov
- Re: [Cfrg] draft-black-rpgecc-00-.txt [was: Conse… Paterson, Kenny
- Re: [Cfrg] draft-black-rpgecc-00-.txt [was: Conse… Alexey Melnikov
- Re: [Cfrg] draft-black-rpgecc-00-.txt [was: Conse… Watson Ladd
- Re: [Cfrg] draft-black-rpgecc-00-.txt [was: Conse… Paterson, Kenny
- Re: [Cfrg] draft-black-rpgecc-00-.txt [was: Conse… Harry Halpin
- Re: [Cfrg] draft-black-rpgecc-00-.txt [was: Conse… Paul Hoffman
- Re: [Cfrg] draft-black-rpgecc-00-.txt [was: Conse… Watson Ladd
- Re: [Cfrg] draft-black-rpgecc-00-.txt [was: Conse… Tanja Lange
- Re: [Cfrg] draft-black-rpgecc-00-.txt [was: Conse… Salz, Rich
- Re: [Cfrg] draft-black-rpgecc-00-.txt [was: Conse… Tony Arcieri
- Re: [Cfrg] Mishandling twist attacks D. J. Bernstein
- Re: [Cfrg] draft-black-rpgecc-00-.txt [was: Conse… Paterson, Kenny
- Re: [Cfrg] draft-black-rpgecc-00-.txt [was: Conse… Tanja Lange
- Re: [Cfrg] Mishandling twist attacks Paterson, Kenny
- Re: [Cfrg] Mishandling twist attacks D. J. Bernstein
- Re: [Cfrg] Mishandling twist attacks Salz, Rich
- Re: [Cfrg] Mishandling twist attacks Stephen Farrell
- Re: [Cfrg] Mishandling twist attacks Adam Back