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List:       linux-crypto
Subject:    Re: a question about ciphers
From:       Jerome Etienne <jme () off ! net>
Date:       2001-12-13 16:52:53
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On Thu, Dec 13, 2001 at 05:29:32PM +0100, Marc Mutz wrote:
> Cryptography isn't compatible with common sense. Read a good book about 
> it, then come back. Sorry.

you wrote in another email

> Birthday attack. Equal ciphertexts are being generated. Actually, the
> boundary is 32G, but it's best to stay away from it.

you mean books like handbook of applied cryptography[1] which 
explains that birthday attack doesnt have any boundary to
32Gbyte (square root of the space, 2^64 for blowfish).
It is probabilistic and can occur with as few as two cipher
text block (even it is less likely).
The usual example 'if you have sqrt(n) block of n bit containing
random value, the probability to have 2 blocks equal is 0.5' is an 
oversimplication to ease understanding. 

sincerely sorry to play this loosy game...

1. available for free at http://www.cacr.math.uwaterloo.ca/hac/
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Linux-crypto:  cryptography in and on the Linux system
Archive:       http://mail.nl.linux.org/linux-crypto/

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