Cryptology ePrint Archive: Report 2006/438

On the pseudo-random generator ISAAC

Jean-Philippe Aumasson

Abstract: This paper presents some properties of he deterministic random bit generator ISAAC (FSE'96), contradicting several statements of its introducing article. In particular, it characterizes huge subsets of internal states which induce a strongly non-uniform distribution in the $8\,192$ first bits produced. A previous attack on ISAAC presented at Asiacrypt'06 by Paul and Preneel is demonstrated to be non relevant, since relies on an erroneous algorithm. Finally, a modification of the algorithm is proposed to fix the weaknesses discovered.

Category / Keywords: pseudo-random generator

Date: received 22 Nov 2006, last revised 3 Jan 2007

Contact author: jeanphilippe aumasson at fhnw ch

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Version: 20070103:152744 (All versions of this report)

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