Re: [Cfrg] Efficient side channel resistance for X25519..

Henry de Valence <ietf@hdevalence.ca> Mon, 11 November 2019 22:17 UTC

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References: <CAMm+LwiB6cpcnb_gpfXueU-A5w=jJ-4U5hhH_xkH5ERx1budoQ@mail.gmail.com> <20191109190705.j4b7chrjfev3lwig@positron.jfet.org> <CAMm+LwhRA3zTMdMM0U-qbC47i80LF8PyN9hX3bzVy_kddHisCw@mail.gmail.com> <810C31990B57ED40B2062BA10D43FBF501E82D65@XMB116CNC.rim.net>
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From: Henry de Valence <ietf@hdevalence.ca>
Date: Mon, 11 Nov 2019 14:16:53 -0800
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To: Dan Brown <danibrown@blackberry.com>
Cc: "phill@hallambaker.com" <phill@hallambaker.com>, "rsw@jfet.org" <rsw@jfet.org>, "mike@shiftleft.org" <mike@shiftleft.org>, "cfrg@irtf.org" <cfrg@irtf.org>
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Subject: Re: [Cfrg] Efficient side channel resistance for X25519..
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On Sun, Nov 10, 2019 at 6:56 AM Dan Brown <danibrown@blackberry.com>; wrote:
>
> Recovering y at end of Montgomery ladder is something I heard about from Scott Vanstone, so it is likely published.

Section 4.3 of https://arxiv.org/pdf/1703.01863.pdf may be helpful.

Cheers,
Henry