[147196] in cryptography@c2.net mail archive
Re: [Cryptography] PRISM-Proofing and PRISM-Hardening
daemon@ATHENA.MIT.EDU (Viktor Dukhovni)
Tue Sep 17 18:05:54 2013
X-Original-To: cryptography@metzdowd.com
Date: Tue, 17 Sep 2013 21:31:21 +0000
From: Viktor Dukhovni <cryptography@dukhovni.org>
To: cryptography@metzdowd.com
In-Reply-To: <20130917170112.42537010@jabberwock.cb.piermont.com>
Reply-To: cryptography@metzdowd.com
Errors-To: cryptography-bounces+crypto.discuss=bloom-picayune.mit.edu@metzdowd.com
On Tue, Sep 17, 2013 at 05:01:12PM -0400, Perry E. Metzger wrote:
> (Note that this assumes no cryptographic breakthroughs like doing
> discrete logs over prime fields easily or (completely theoretical
> since we don't really know how to do it) sabotage of the elliptic
> curve system in use.)
>
> Given that many real organizations have hundreds of front end
> machines sharing RSA private keys, theft of RSA keys may very well be
> much easier in many cases than broader forms of sabotage.
There is also I suspect a lot of software with compiled-in EDH
primes (RFC 5114 or other). Without breaking EDH generally, perhaps
they have better precomputation attacks that were effective against
the more popular groups.
I would certainly recommend that each server generate its own EDH
parameters, and change them from time to time. Sadly when choosing
between a 1024-bit or a 2048-bit EDH prime you get one of
interoperability or best-practice security but not both.
And indeed the FUD around the NIST EC curves is rather unfortunate.
Is secp256r1 better or worse than 1024-bit EDH?
--
Viktor.
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