Relative Strength of 40-bit Crypto Implementations

[Bill Frantz]

At 01:29 AM 1/7/97 -0500, Vin McLellan wrote:
>	A client asked me today about where he could find evidence of the
>relative strength of different encryption algorithms, when all are
>restricted to 40-bit keys.  He assumed dot-Gov was going to restrict his
>export product to the 40-bit limit, but he wanted to provide the strongest
>security he could within that limitation.

A cypher with a long key setup schedule, such as Blowfish, would be more
resistant to brute force attacks.  (Blowfish requires 500+ encryptions to
set up the key schedule.  This should be similar to adding 9 bits to the
key size.)  While I think Blowfish is good in this respect, one must be
careful to avoid systems, such as DES, which are subject to Peter Trei's
"gray code" techniques.


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