Summary: Windows GUI recommendation for USB disk
Robert J. Hansen
rjh at sixdemonbag.org
Fri Nov 3 17:39:54 CET 2006
David SMITH wrote:
> ...at the moment.
Welcome to the Second Law of Thermodynamics! Enjoy your stay.
By the Second Law, every time a bit of information is erased you have to
pay the entropy tax of (kT * ln 2) J. Let's assume that for each key
you try, you have to erase 1000 bits of information--this is wildly
optimistic, given how complex key schedules usually are, but it'll make
for nice numbers.
On average you'll have to brute-force 2**127 keys before you find the
proper 128-bit AES key.
1000 = 10**3
2**127 approx. eq. 10**38
10**41 * (3 * 10**-21) = 3 * 10**20 J
A one-megaton nuclear weapon liberates approximately 10**15 J of energy.
3 * 10**20 J divided by 10**15 J = 300,000 megatons
By comparison, the 1863 Krakatoa explosion liberated about 21,000 megatons.
If you're interested, we can also do a quantum-mechanical analysis of
the minimum time required to do this computation. It gets equally silly.
http://en.wikipedia.org/wiki/Rolf_Landauer
http://en.wikipedia.org/wiki/Margolus-Levitin_theorem
... It's true that quantum computers and reversible computing will both
reduce this number considerably. However, if you're going to talk about
science fiction--which is what large-scale quantum and reversible
computing is nowadays--then why not go whole-hog and posit the existence
of a psychic who's 100% effective in predicting keys?
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