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Re: Wired query on Windows 2000 and DES/3DES
On Mon, 15 May 2000, Declan McCullagh wrote:
> * 3DES is up to 10^17 (2^(112-56)) times as resistant as DES to an
> exhaustive search.
It's 2^112 (about 10^34) better against a simple exhaustive search, thanks
to having 112 more key bits. It's only 2^56 (about 10^17) better against
a meet-in-the-middle exhaustive search, with a *very* large memory in the
middle -- the memory is big enough to be expensive and problematic but not
utterly infeasible.
> I assume that differential cryptanalysis cuts this
> substantially, but I haven't been able to find any figures.
Last I heard -- caution, this is not an area I keep up on -- it didn't
help things very much. Differential cryptanalysis, at least in its pure
form, is a largely theoretical approach: it requires preconditions which
are very difficult to arrange in practice, partly because DES was
specifically designed to resist it.
Henry Spencer
henry@spsystems.net
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