Cryptanalysis of ``2 R'' Schemes

  • Authors:
  • Ding-Feng Ye;Kwok-Yan Lam;Zong-Duo Dai

  • Affiliations:
  • -;-;-

  • Venue:
  • CRYPTO '99 Proceedings of the 19th Annual International Cryptology Conference on Advances in Cryptology
  • Year:
  • 1999

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Abstract

The function decomposition problem can be stated as: Given the algebraic expression of the composition of two mappings, how can we identify the two factors? This problem is believed to be in general intractable [1]. Based on this belief, J. Patarin and L. Goubin designed a new family of candidates for public key cryptography, the so called "2R-schemes" [10, 11]. The public key of a "2R"-scheme is a composition of two quadratic mappings, which is given by n polynomials in n variables over a finite field K with q elements. In this paper, we contend that a composition of two quadratic mappings can be decomposed in most cases as long as q 4. Our method is based on heuristic arguments rather than rigorous proofs. However, through computer experiments, we have observed its effectiveness when applied to the example scheme "D**"given in [10].