Re: [PEN-TEST] Brute Forcing MS-EFS

[Dug Song <dugsong () MONKEY ORG>]

On Sun, Dec 03, 2000 at 05:53:24PM +0200, Yonatan Bokovza wrote:

> DESX is supposed to be a vesrion of DES, xorred with some values
> that are supposed to make it encrypt a wee-bit faster, without
> loosing encryption strength.
>
> A. More info about DESX. Is my overview correct?

almost. DESX uses a whitening scheme to extend its effective keylength
to 120 bits, but it's still plain old DES, apart from the whitening
and key setup (in other words, it's neither faster than DES, nor any
more secure than DES, save its longer keylength).

David Wagner and Alex Biryukov recently presented an interesting paper
on advanced slide attacks at Eurocrypt this year, outlining
known-plaintext and ciphertext-only attacks against DESX. This is the
only specific cryptanalysis of DESX I'm aware of, apart from Rogaway's
original formal verification:

        http://www.cs.berkeley.edu/~daw/papers/advslide-ec00.ps
        http://www.cs.ucdavis.edu/~rogaway/papers/desx-abstract.html

> B. Brute force cracker for EFS.

brute forcing a 120-bit key in any reasonable amount of time is
really an exercise in futility, unless a dictionary attack is
possible. if this is the case, let me know, and perhaps i can hack
something up quickly as an extension to John the Ripper... :-)

-d.

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