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Posted by Wayne McClaine on 01/04/07 20:25
The Ghost In The Machine wrote:
> In comp.os.linux.advocacy, Wayne McClaine
> <gary.griffith@gmail.com>
> wrote
> on 3 Jan 2007 21:19:22 -0800
> <1167887962.598432.130480@31g2000cwt.googlegroups.com>:
> >
> > Tim Smith wrote:
> >>
> >> This depends on what you mean by "broke". In particular, do you
> >> consider a successful brute force attack a break? With its mere 40-bit
> >> key length, and weak algorithms, CSS falls fairly quickly to a brute
> >> force attack, in about 2^25 steps.
> >
> > Any encrypted cipher can be "foiled" by brute force - you're just
> > looking for a key.
>
> 2^40 = 1.10 trillion. If one can look at a key every microsecond, that
> only takes about a week and a half. That's about what it took a French
> compute farm, if memory serves.
>
> 2^56 = 7.21 * 10^16. At the same key rate, that'll only take about 2.3
> millennia. Fortunately, distributed.net has a faster key rate, since
> the problem is inherently parallel.
>
> 2^1024 = 1.80 * 10^100, or 1.80 googols. Search company, meet
> military-grade encryption-cipher. Dare I mention that the Universe is
> at the very very most 80 billion years old or so?
More reason to use AES-256 if you're performance can handle. Should
survive brute force until the data is in our sun's black-hole.
However, if the key is left on a post-it on the keyboard, or in a dump
or a stack trace....
> >
> > When it is doable in a relatively short time, it's broken. Not
> > circumvented or broken "into", no magic bullet, but might as well be -
> > even if you can't derive the key, if you can run through all
> > possibilities, then what's the difference? You can get the key, and
> > systems built on this are houses-of-cards. Hence, AES, 3DES, etc.
> >
> > So, our boy got a PowerDVD software key to then expose the DVD title &
> > volume keys and such. And this is impossible for other players, how?
> > Yawn.
>
> How big is the key?
He doesn't get into this, but seems to hint that memory helps. Doesn't
really matter how big it is if you find it.
I understand the time required to DIY and the way distributed.net got
DES done. But a 2^25 step brute-force as stated by Tim seemed to be a
cakewalk. If 40 bits goes in 10 days, 25 should fall in under a minute.
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