Bivium as a Mixed-Integer Linear Programming Problem

  • Authors:
  • Julia Borghoff;Lars R. Knudsen;Mathias Stolpe

  • Affiliations:
  • DTU Mathematics, Technical University of Denmark,;DTU Mathematics, Technical University of Denmark,;DTU Mathematics, Technical University of Denmark,

  • Venue:
  • Cryptography and Coding '09 Proceedings of the 12th IMA International Conference on Cryptography and Coding
  • Year:
  • 2009

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Abstract

Trivium is a stream cipher proposed for the eSTREAM project. Raddum introduced some reduced versions of Trivium, named Bivium A and Bivium B. In this article we present a numerical attack on the Biviums. The main idea is to transform the problem of solving a sparse system of quadratic equations over GF (2) into a combinatorial optimization problem. We convert the Boolean equation system into an equation system over *** and formulate the problem of finding a 0-1-valued solution for the system as a mixed-integer programming problem. This enables us to make use of several algorithms in the field of combinatorial optimization in order to find a solution for the problem and recover the initial state of Bivium. In particular this gives us an attack on Bivium B in estimated time complexity of 263.7 seconds. But this kind of attack is also applicable to other cryptographic algorithms.