Paper 2001/049

A known plaintext attack on the ISAAC keystream generator

Marina Pudovkina

Abstract

Stream ciphers are often used in applications where high speed and low delay are a requirement. The ISAAC keystream generator is a fast software-oriented encryption algorithm. In this papers the security of the ISAAC keystream generator is investigated. Cryptanalytic algorithm is developed for a known plaintext attack where only a small segment of plaintext is assumed to be known. Keywords. ISAAC. Keystream generator. Cryptanalysis.