> On Fri, Jul 14, 2006 at 10:55:28PM -0400, [email protected] wrote:
> > In fact, the best you can do here is to reduce the effective bandwidth
> > the signal can have, as Shannon showed quite clearly.
>
> Yes.
>
> > And even 20 years ago, the guys who did the original DoD Orange Book
> > requirements understood this - they didn't make a requirement that covert
> > channels (both timing and other) be totally closed down, they only made
> > a requirement that for higher security configurations the bandwidth of
> > the channel be reduced below a specified level...
>
> Why I think it's trivial to guarantee the closure of the seccomp side
> channel timing attack even on a very fast internet by simply
> introducing the random delay, is that below a certain sampling
> frequency you won't be able to extract data from the latencies of the
> cache. The max length of the random noise has to be >= of what it
> takes to refill the whole cache. Then you won't know if it was a
> cache
You won't know for sure... but. Let t be time takes to reload the
cache. Let your random noise be in <0, t> interval. According to you,
that would be okay. IT IS NOT.
If the original delay was long, and your generator returned t,
attacker sees 2*t. He can be _sure_ delay was long now.
If the delay was short, and your generator returns 0, attacker sees 0,
and _knows_ delay was short. (Chance that generator produces 0 or t is
small, but non zero).
Even if you do random noise in <0, 2*t) interval, I'll be able to
gather some statistics.
Pavel
Thanks, Sharp!
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to [email protected]
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
[Index of Archives]
[Kernel Newbies]
[Netfilter]
[Bugtraq]
[Photo]
[Stuff]
[Gimp]
[Yosemite News]
[MIPS Linux]
[ARM Linux]
[Linux Security]
[Linux RAID]
[Video 4 Linux]
[Linux for the blind]
[Linux Resources]
