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Re: Brute Force DES
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On Tue, 23 Jul 1996, Kevin L Prigge wrote:
> Date: Tue, 23 Jul 1996 11:02:06 -0500 (CDT)
> From: Kevin L Prigge <[email protected]>
> To: [email protected]
> Cc: [email protected], [email protected]
> Subject: Re: Brute Force DES
>
> Perry E. Metzger said:
> >
> > "Peter Trei" writes:
> > > The fastest general purpose, freely available des implementation I'm
> > > aware of is libdes. by Eric Young. With this, I can do a set_key in
> > > 15.8 us, and an ecb_encrypt in 95 us/block. That adds up to
> > > about 9,000 keytests/sec (this is on a 90 MHz P5, running NT).
> >
> > I'll point out that like most DES implementations, Eric's tries to
> > spend a lot of time in key setup to save time later on in
> > encryption/decryption. This tradeoff would probably be very different
> > if you didn't plan on trying more than one or two blocks of decryption
> > after getting a key.
> >
>
> For instance if you had a DES encrypted gzipped file. The first 2 bytes
> plaintext will be Ox1f8b. You'd only have to try to fully decrypt
> 1 out of 65535 keys.
>
Buy the point is to prove that DES shouldn't be used, not that it CAN
be brute forced. A known-plaintext attack doesn't show that. We hafta
attack something we've never seen. (i.e. talk Netscape, or some other
company, into generating a DES'd message, and keeping the keys safe)
--Deviant
Whatever occurs from love is always beyond good and evil.
-- Friedrich Nietzsche
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