On Polynomial Modular Number Systems over $\mathbb{Z}/p\mathbb{Z}$

Abstract

Polynomial Modular Number System (PMNS) is a convenient number system for modular arithmetic, introduced in 2004. The main motivation was to accelerate arithmetic modulo an integer $p$. An existence theorem of PMNS with specific properties was given. The construction of such systems relies on sparse polynomials whose roots modulo $p$ can be chosen as radices of this kind of positional representation. However, the choice of those polynomials and the research of their roots are not trivial. In this paper, we introduce a general theorem on the existence of PMNS and we provide bounds on the size of the digits used to represent an integer modulo $p$. Then, we present classes of suitable polynomials to obtain systems with an efficient arithmetic. Finally, given a prime $p$, we evaluate the number of roots of polynomials modulo $p$ in order to give a number of PMNS bases we can reach. Hence, for a fixed prime $p$, it is possible to get numerous PMNS, which can be used efficiently for different applications based on large prime finite fields, such as those we find in cryptography, like RSA, Diffie-Hellmann key exchange and ECC (Elliptic Curve Cryptography)