Signed Binary Representations Revisited

The most common method for computing exponentiation of random elements in Abelian groups are sliding window schemes, which enhance the efficiency of the binary method at the expense of some precomputation. In groups where inversion is easy (e.g. elliptic curves), signed representations of the exponent are meaningful because they decrease the amount of required precomputation. The asymptotic best signed method is wNAF, because it minimizes the precomputation effort whilst the non-zero density is nearly optimal. Unfortunately, wNAF can be computed only from the least significant bit, i.e. right-to-left. However, in connection with memory constraint devices left-to-right recoding schemes are by far more valuable. In this paper we define the MOF (Mutual Opposite Form), a new canonical representation of signed binary strings, which can be computed in any order. Therefore we obtain the first left-to-right signed exponentrecoding scheme for general width w by applying the width w sliding ...

• Type: Conference
• Year: 2004
• Where: CRYPTO
• Authors: Katsuyuki Okeya, Katja Schmidt-Samoa, Christian Spahn, Tsuyoshi Takagi
• Keywords: CRYPTO 2004, Left-to-right Recoding Schemes, Non-zero Density, Sliding Window