Re: x86 MSRs - example program

Matthias Urlichs (smurf@work.smurf.noris.de)
2 Mar 1997 01:33:59 +0100

In linux.dev.kernel, article <m0w0aqh-000A8LC@cerebro>,
mlehmann@hildesheim.sgh-net.de (Marc Lehmann) writes:
>
> ON the other hand... security hole????? how????????
>
Cryptography. If you know exactly how long a given algorithm takes for
different inputs, you can sometimes infer clues about the secret key.

It's highly unlikely that anybody ever tries to do that kind of thing to
exploit security weaknesses on a Linux box, but you never know...

IMHO, we should have a bit in the securelevel variable which controls
userspace read access to the cycle counter. Assuming that the securelevel
variable ever becomes a bitmap. ;-)

-- 
Weirdness is the best defense

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