Two Trivial Attacks on Trivium

Trivium is a stream cipher designed in 2005 by C. De Canni`ere and B. Preneel for the European project eSTREAM. It has successfully passed the first phase of the project and has been selected for a special focus in the second phase for the hardware portfolio of the project. Trivium has an internal state of size 288 bits and the key of length 80 bits. Although the design has a simple and elegant structure, no attack on it has been found yet. In this paper we study a class of Trivium-like designs. We propose a set of techniques that one can apply in cryptanalysis of such constructions. The first group of methods is for recovering the internal state and the secret key of the cipher, given a piece of a known keystream. Our attack is more than 230 faster than the best known attack. Another group of techniques allows to gather statistics on the keystream, and to build a distinguisher. We study two designs: the original design of Trivium and a truncated version Bivium, which follows the sa...

• Type: Conference
• Year: 2007
• Where: SACRYPT
• Authors: Alexander Maximov, Alex Biryukov
• Keywords: Internal State, Length 80 Bits, SACRYPT 2007, Size 288 Bits