From owner-cvs-src@FreeBSD.ORG  Mon May 16 19:47:42 2005
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To: Colin Percival <cperciva@freebsd.org>
From: "Poul-Henning Kamp" <phk@phk.freebsd.dk>
In-Reply-To: Your message of "Sun, 15 May 2005 16:29:32 EDT."
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Date: Mon, 16 May 2005 21:47:33 +0200
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cc: Jacques Vidrine <nectar@freebsd.org>
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cc: Nate Lawson <nate@root.org>
Subject: Re: cvs commit: src/sys/amd64/amd64 mp_machdep.c
	src/sys/amd64/include cpufunc.h src/sys/i386/i386 mp_machdep.c
	src/sys/i386/include cpufunc.h 
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In message <4287B12C.9080903@freebsd.org>, Colin Percival writes:
>Nate Lawson wrote:
>> Every general-purpose machine has measurable timing side channels.  The
>> question is merely one of bandwidth.
>
>Absolutely.  Most covert channels operate at up to a few kbps; this covert
>channel operates at several Mbps.

Not only that, but the measurement precision is much better than for more
indirect inspection methods like ps(1).

-- 
Poul-Henning Kamp       | UNIX since Zilog Zeus 3.20
phk@FreeBSD.ORG         | TCP/IP since RFC 956
FreeBSD committer       | BSD since 4.3-tahoe    
Never attribute to malice what can adequately be explained by incompetence.