[46538] in Cypherpunks
Visual Correlations of RNGs useful for cryptanalysis?
daemon@ATHENA.MIT.EDU (Deranged Mutant)
Fri Jan 5 02:37:33 1996
From: "Deranged Mutant" <WlkngOwl@UNiX.asb.com>
To: Cypherpunks@toad.com
Date: Fri, 5 Jan 1996 02:27:52 +0000
Somebody passed an interesting article to me, "Random number
generators: pretty good ones are easy to find", Clifford Pickover
(IBM Watson Research Ctr, NY), The Visual Computer (1995) 11:369-377.
The article does NOT deal with cryptographically secure RNGs, however
the author discusses some interesting methods for visualizing
correlations in RNGs that probably can be applied to crypto.
One is the "Noise Sphere", which involves plotting the last three
numbers generated by the RNG (Xn, Xn+1, Xn+2, where 0<Xn<1, and
n=0,1,2,3...N) on spherical coordinates (r, theta, phi), where
theta = 2 * pi * Xn
phi = pi * Xn+1 (note, X subscript n+1)
r = sqrt(Xn+2) ( " X subscript n+2)
The article includes some pretty interesting graphics, including a
couple that demonstrate what crappy RNGs look like. Also discusses
some other methods (terrain generation) for visualization.
Advantage is that this type of test is that it can be done on a
low-end PC, can show some complex correlations even when an RNG is
statistically good, and one doesn't have to an expert to see when
something is wrong.
Crypto output (bytes, words, dwords, etc.) can be easily(?) translated into
binary fractions for this type of test.
Take care,
--Rob
--- "Mutant" Rob <wlkngowl@unix.asb.com>
Send a blank message with the subject "send pgp-key"
(not in quotes) for a copy of my PGP key.
