Re: [Cfrg] ECC desiderata

"Blumenthal, Uri - 0668 - MITLL" <uri@ll.mit.edu> Fri, 08 August 2014 18:16 UTC

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Subject: Re: [Cfrg] ECC desiderata
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On Aug 8, 2014, at 14:07 , Bodo Moeller <bmoeller@acm.org> wrote:
> D. J. Bernstein <djb@cr.yp.to>to>:
> Curves with cofactor 1 obviously score so badly on these axes---without
> having any compensating advantages---that I think they should be taken
> off the table.
> 
> The speed advantages are pretty compelling, but I don't agree that curves with cofactor 1 don't have *any* compensating advantages.
> 
> As the example of TLS with its protocol flaws shows (see the unknown key-share attacks in https://secure-resumption.com/tlsauth.pdf), it is possible to end up in a situation in which public-key validation *does* matter; it's easier to get right with cofactor 1.  Using a cryptographic scheme that normally has no need for this can turn into a disadvantage, unless you "redundantly" do such checks anyway.

+1

I'd much rather deal with cofactor 1 curves.