Fast Elliptic Curve Point Counting Using Gaussian Normal Basis

  • Authors:
  • Hae Young Kim;Jung Youl Park;Jung Hee Cheon;Je Hong Park;Jae Heon Kim;Sang Geun Hahn

  • Affiliations:
  • -;-;-;-;-;-

  • Venue:
  • ANTS-V Proceedings of the 5th International Symposium on Algorithmic Number Theory
  • Year:
  • 2002

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Abstract

In this paper we present an improved algorithm for counting points on elliptic curves over finite fields. It is mainly based on Satoh-Skjernaa-Taguchi algorithm [SST01], and uses a Gaussian Normal Basis (GNB) of small type t 驴 4. In practice, about 42% (36% for prime N) of fields in cryptographic context (i.e., for p = 2 and 160 N pN to ZpN in a natural way. From the specific properties of GNBs, efficient multiplication and the Frobenius substitution are available. Thus a fast norm computation algorithm is derived, which runs in O(N2碌 log N) with O(N2) space, where the time complexity of multiplying two n-bit objects is O(n碌). As a result, for all small characteristic p, we reduced the time complexity of the SST-algorithm from O(N2碌+0.5) to O(N2碌+ 1/碌+1) and the space complexity still fits in O(N2). Our approach is expected to be applicable to the AGM since the exhibited improvement is not restricted to only [SST01].