Algebraic attacks on clock-controlled cascade ciphers

  • Authors:
  • Kenneth Koon-Ho Wong;Bernard Colbert;Lynn Batten;Sultan Al-Hinai

  • Affiliations:
  • Information Security Institute (ISI), Queensland University of Technology (QUT), Brisbane, Australia;Deakin University, Melbourne, Australia;Deakin University, Melbourne, Australia;Information Security Institute (ISI), Queensland University of Technology (QUT), Brisbane, Australia

  • Venue:
  • INDOCRYPT'06 Proceedings of the 7th international conference on Cryptology in India
  • Year:
  • 2006

Quantified Score

Hi-index 0.00

Visualization

Abstract

In this paper, we mount the first algebraic attacks against clock controlled cascade stream ciphers. We first show how to obtain relations between the internal state bits and the output bits of the Gollmann clock controlled cascade stream ciphers. We demonstrate that the initial states of the last two shift registers can be determined by the initial states of the others. An alternative attack on the Gollmann cascade is also described, which requires solving quadratic equations. We then present an algebraic analysis of Pomaranch, one of the phase two proposals to eSTREAM. A system of equations of maximum degree four that describes the full cipher is derived. We also present weaknesses in the filter functions of Pomaranch by successfully computing annihilators and low degree multiples of the functions.