[Cfrg] Side channel effectiveness against P256?

Dan Brown <dbrown@certicom.com> Thu, 24 July 2014 19:54 UTC

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From: Dan Brown <dbrown@certicom.com>
To: "D. J. Bernstein" <djb@cr.yp.to>
Thread-Topic: Side channel effectiveness against P256?
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Date: Thu, 24 Jul 2014 19:54:42 +0000
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Subject: [Cfrg] Side channel effectiveness against P256?
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‎Dan,

Forgot to ask yesterday: is the side channel on naive P256 you described in the CFRG meeting exploitable against ECDHE over Internet via timing?‎ If not, when is it exploitable? Eg,by timing 256 key re-uses on a local network only? By another process in the same machine? I really don't know this area. Should we recommend against such settings rather than just relying on side channel countermeasures for P256? 

Best regards, 

-- Dan

PS Sorry if you already answered this in your talk‎.