wNAF, an efficient left-to-right signed digit recoding algorithm

  • Authors:
  • Brian King

  • Affiliations:
  • Indiana University Purdue University, Indianapolis

  • Venue:
  • ACNS'08 Proceedings of the 6th international conference on Applied cryptography and network security
  • Year:
  • 2008

Quantified Score

Hi-index 0.00

Visualization

Abstract

Efficient implementations of cryptosystems are important in order to conserve resources, memory, power, etc., which will enable resource-limited devices to compute necessary cryptographic operations. One technique that successfully reduces the number of necessary operations is the use of a signed digit representation for the key, because it reduces the nonzero density of the representation. One such signed digit representation is the non-adjacent form or NAF. Moreover, one can make more reductions in the number of nonzero symbols of the key by expressing the key with a w-ary NAF or wNAF form. A drawback is that one needs to parse the key twice, once to construct the wNAF representation and the second time to perform the necessary cryptographic operation. At Crypto 2004 [10], Okeya et. al. introduced a w-ary representation wMOF, which possess the same nonzero density as wNAF, as well as an algorithm that computes wNOF in a left-to-right manner utilizing very little memory ("memory-less"). At that time, the authors noted that a left-to-right "memory-less" algorithm that computes wNAF is an open problem. In this work, we define wNAF, a generalization of wNAF. Further, we construct a left-to-right "memory-less" algorithm that computes the w-ary wNAF representation of a key and demonstrate that wNAF is as efficient as wNAF. Our work will demonstrate that the left-to-right wNAF recoding algorithm closely resembles the right-to-left wNAF recoding algorithm.