Fast hardware for modular exponentiation with efficient exponent pre-processing

  • Authors:
  • Nadia Nedjah;Luiza de Macedo Mourelle

  • Affiliations:
  • Department of Electronics Engineering and Telecommunication, Faculty of Engineering, State University of Rio de Janeiro, Brazil;Department of Systems Engineering and Computation, Faculty of Engineering, State University of Rio de Janeiro, Brazil

  • Venue:
  • Journal of Systems Architecture: the EUROMICRO Journal
  • Year:
  • 2007

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Abstract

Modular exponentiation is an important operation in several public-key cryptosystems. It is performed using successive modular multiplications. For the sake of efficiency, one needs to reduce the total number of required modular multiplications. In this paper, we propose two efficient hardware implementations for computing modular exponentiations, which are based on the m-ary method. The m-ary method includes a power pre-computation step. The first design ignores the exponent and pre-computes all possible powers while the second takes advantage of the formation of the exponent to compute only those powers that are really necessary for the rest of the computation. As it can be expected, the implementation of the first architecture, compared with that of the second one, requires more time to complete an exponentiation. In compensation, however, the first should require less hardware area than the second. We provide a comparison of these two implementations using the performance factor, which takes into account both space and time requirements.