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Date:      Tue, 17 May 2005 16:18:32 -0700
From:      Colin Percival <cperciva@freebsd.org>
To:        David Schultz <das@freebsd.org>
Cc:        "Drew B. \[Security Expertise/Freelance Security research\]." <d4rkstorm@gmail.com>
Subject:   Re: FreeBSD Security Advisory FreeBSD-SA-05:09.htt [REVISED]
Message-ID:  <428A7BC8.2070405@freebsd.org>
In-Reply-To: <20050517225023.GA55428@VARK.MIT.EDU>
References:  <245f0df105051318564b1ffb6b@mail.gmail.com> <94145.1116037219@critter.freebsd.dk> <20050517225023.GA55428@VARK.MIT.EDU>

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David Schultz wrote:
> Some colleagues and I have a paper in submission that addresses
> the issue of key-dependent control flow, much as you describe.

Care to send me a pre-print?

> If you're willing to wait a day or two, you don't even need to
> have a local account:
> 
> 	http://crypto.stanford.edu/~dabo/abstracts/ssl-timing.html

1. The Boneh-Brumley attack is specific to a particular method of
performing large integer arithmetic (and thus only applies to RSA,
DH, and DSS).  My attack applies to essentially all code -- both
crypto and non-crypto -- although I picked RSA/OpenSSL as a good
demonstration platform.

2. The Boneh-Brumley attack was fixed two years ago.

> I'm just reading Colin's paper now---so as you say, it sounds like
> the punchline is that having a local account buys you a few orders
> of magnitude in attack time.  Kewl.

No.  On hyperthreaded systems which don't run FreeBSD or SCO, having
a local account buys you an attack which would otherwise be impossible.
(Unless you're running a really old version of OpenSSL.)

Colin Percival



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