Signed digit representation with NAF and balanced ternary form and efficient exponentiation in GF(qn) using a Gaussian normal basis of type II

  • Authors:
  • Soonhak Kwon

  • Affiliations:
  • Inst. of Basic Science and Dept. of Mathematics, Sungkyunkwan University, Suwon, Korea

  • Venue:
  • WISA'04 Proceedings of the 5th international conference on Information Security Applications
  • Year:
  • 2004

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Abstract

We present an efficient exponentiation algorithm for a finite field GF(qn) with small characteristic determined by a Gaussian normal basis of type II using signed digit representation of the exponents. Our signed digit representation uses a nonadjacent form (NAF) for GF(2n) and the balanced ternary number system for GF(3n). It is generally believed that a signed digit representation is hard to use when a normal basis is given because the inversion of a normal element requires quite a computational delay. On the other hand, the method of a signed digit representation is easily applicable to the fields with polynomial bases. However our result shows that a special normal basis called a Gaussian normal basis of type II or an optimal normal basis (ONB) of type II has a nice property which admits an effective exponentiation using signed digit representations of the exponents.