Re: [CFRG] Symmetric SPAKE2
Filippo Valsorda <filippo@ml.filippo.io> Mon, 21 June 2021 15:58 UTC
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Date: Mon, 21 Jun 2021 17:57:24 +0200
From: Filippo Valsorda <filippo@ml.filippo.io>
To: Watson Ladd <watsonbladd@gmail.com>
Cc: CFRG <cfrg@irtf.org>, Brian Warner <warner@lothar.com>, "Hao, Feng" <Feng.Hao@warwick.ac.uk>, Mike Hamburg <mike@shiftleft.org>, Benjamin Kaduk <kaduk@mit.edu>
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Subject: Re: [CFRG] Symmetric SPAKE2
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2021-04-27 06:04 GMT+02:00 Watson Ladd <watsonbladd@gmail.com <mailto:watsonbladd%40gmail.com>>: > On Mon, Apr 26, 2021 at 6:20 PM Filippo Valsorda <filippo@ml.filippo.io <mailto:filippo%40ml.filippo.io>> wrote: > > > > Hi all, > > > > I am trying to figure out the properties of symmetric SPAKE2, where there is no > > ordering and M = N. > > > > The only note I can find in draft-irtf-cfrg-spake2-18 is this in Section 5. > > > > In addition M and N may be equal to have a symmetric variant. The > > security of these variants is examined in [MNVAR]. This variant may > > not be suitable for protocols that require the messages to be > > exchanged symmetrically and do not know the exact identity of the > > parties before the flow begins. > > > > https://tools.ietf.org/html/draft-irtf-cfrg-spake2-18#section-5 > > > > I interpret "these variants" as the ones with M = N, and "This variant" as the > > "Per-User M and N" one, meaning this paragraph is saying that you can't do > > per-user M and N if M = N, which tracks. > > > > However, the spec is hardcoding M and N to different values, so it doesn't > > actually seem to allow M = N variants at all. Should that be addressed? > > "These variants" is supposed to be M=N where you pick the point or the > per user one. Should the spec provide fixed points for M = N, or a recommendation to use the provided N (or M) on both sides? It feels important for interoperability.
- [CFRG] Symmetric SPAKE2 Filippo Valsorda
- Re: [CFRG] Symmetric SPAKE2 Watson Ladd
- Re: [CFRG] Symmetric SPAKE2 Filippo Valsorda