Séminaire de Cryptographie

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Fangan Yssouf Dosso

PMNS for efficient arithmetic and small memory cost

The Polynomial Modular Number System (PMNS) is an integer number system which aims to speed up arithmetic operations modulo a prime p. Such a system is defined by a tuple (p, n, g, r, E), where p, n, g and r are positive integers, E is a monic polynomial with integer coefficients, having g as a root modulo p. Most of the work done on PMNS focus on polynomials E such that E(X) = X^n – l, where l is a nonzero integer, because such a polynomial provides efficiency and low memory cost, in particular for l = 2 or -2. It however appeared that these are not always the best choices. In this presentation, we first start with the necessary background on PMNS. Then, we highlight a new set of polynomials E for very efficient operations in the PMNS and low memory requirement, along with new bounds and parameters. We show that these polynomials are more interesting than (most) polynomials E(X)=X^n – l. To finish, we see how to use PMNS to randomise arithmetic operations in order to randomise high level operations like elliptic curve scalar multiplication, to protect implementations against some advanced side channel attacks like differential power analysis (DPA). Joint work with Jean-Marc Robert and Pascal Véron