Re: Time-Memory-Key tradeoff attacks?
My paper ``Understanding brute force'' explains an attack with a much better price-performance ratio than the attack described by Biryukov: http://cr.yp.to/talks.html#2005.05.27 http://cr.yp.to/papers.html#bruteforce Biryukov's central point regarding key amortization was made earlier (and, I think, more clearly) in my paper. My paper also analyzes the merits of various defenses against the attack. ---D. J. Bernstein, Associate Professor, Department of Mathematics, Statistics, and Computer Science, University of Illinois at Chicago - The Cryptography Mailing List Unsubscribe by sending "unsubscribe cryptography" to [EMAIL PROTECTED]
Time-Memory-Key tradeoff attacks?
The following has appeared in the IACR preprint archive. I would
appreciate comments. The author certainly has reasonable credentials,
but the document is low on detail:
http://eprint.iacr.org/2005/207
Some Thoughts on Time-Memory-Data Tradeoffs
Author: Alex Biryukov
Abstract: In this paper we show that Time-Memory tradeoff by Hellman
may be extended to Time-Memory-Key tradeoff thus allowing attacks much
faster than exhaustive search for ciphers for which typically it is
stated that no such attack exists. For example, as a result AES with
128-bit key has only 85-bit security if $2^{43}$ encryptions of an
arbitrary fixed text under different keys are available to the
attacker. Such attacks are generic and are more practical than some
recent high complexity chosen related-key attacks on round-reduced
versions of AES. They constitute a practical threat for any cipher
with 80-bit or shorter keys and are marginally practical for 128-bit
key ciphers. We also show that UNIX password scheme even with
carefully generated passwords is vulnerable to practical tradeoff
attacks. Finally we also demonstrate a combination of rainbow tables
with the time-memory-data tradeoff which results in a new tradeoff
curve.
By the way, much thanks to Eric Rescorla for pointing this out to me.
Perry
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Perry E. Metzger[EMAIL PROTECTED]
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