arXiv subjects

Laurent-Stéphane Didier

Publications and source records attributed to Laurent-Stéphane Didier.

5 recordsLinked to original sources

arXiv2026

Faster PMNS Multi-precision Multiplications Using Truncated Montgomery Technique

The Polynomial Modular Number Systems (PMNS) aim to represent elements of fields or rings of large characteristics using polynomials satisfying bounds on some parameters (degree, absolute values of the coefficients). Those PMNS, while some conditions are fulfilled, using convenient parameters and implementation features, allow some speed-ups in cryptographic computations. Recent works (Meloni \emph{et al.} \cite{MeloniPV25}) propose better speed-ups by improving the parameter generation of the system, and by using multi-precision polynomial coefficients, i.e. coefficients stored using several machine words. In this work, we first present PMNS schoolbook software implementation better in some context than the Toeplitz state-of-the-art counterpart of \cite{MeloniPV25}, taking advantage of smaller memory cost by being free to choose a smaller $n$ parameter, minimizing at the same time the complexity of the multiplication. This implementation for 4096 bit modulo size shows element size smaller by 11\% and 20 \% speed-up. We thus present a new improvement on the PMNS, applying to the \textsl{internal reduction} an approach similar to the truncated Montgomery reduction technique presented by Didier \emph{et al.} in \cite{DidierEGR24}. In the context of software implementations using \texttt{AVX512} instruction set extension, and modulo size up to 8192 bits, this new approach allows speed-ups up to 15\% in modular multiplication computation, in comparison with conventional approaches.

cs.CR↗

arXiv2026

Residue Number System Comparison revisited, a software perspective

This paper presents a novel method to compare two numbers in Residue Number System (RNS) using an additional modulus, which is often already available because it is required in modular computations and digital signal processing scaling.Our method provides the comparison of two integers in the full range of the RNS base. It does not require moduli of a special form, unlike other state-of-the-art methods that are restricted to specific RNS bases or require bounds on input numbers. Our approach only requires one single conversion to a mixed radix representation with a complexity of O(n2), which can be reduced to O(log(n)) in time with parallelization. This provides a significant advantage over classical methods and more recent competitive methods which work under restrictions. This opens perspectives for advancements in challenging RNS operations such as division, scaling, and cryptographic applications.

cs.DC↗

arXiv2024

RISC-V Word-Size Modular Instructions for Residue Number Systems

Residue Number Systems (RNS) are parallel number systems that allow the computation on large numbers. They are used in high performance digital signal processing devices and cryptographic applications. However, the rigidity of instruction set architectures of the market-dominant microprocessors limits the use of such number systems in software applications. This article presents the impact of word-size modular arithmetic specific RISC-V instructions on the software implementation of Residue Number Systems. We evaluate this impact on several RNS modular multiplication sequential algorithms. We observe that the fastest implementation uses the Kawamura et. al. base extension. Simulations of architectures with GEM5 simulator show that RNS modular multiplication with Kawamura's base extension is 2.76 times faster using specific word-size modular arithmetic instructions than pseudo-Mersenne moduli for In Order processors. It is more than 3 times for Out of Order processors. Compared to x86 architectures, RISC-V simulations show that using specific instructions requires 4.5 times less cycles in In Order processors and 8 less in Out of Order ones.

cs.AR↗

arXiv2024

Truncated multiplication and batch software SIMD AVX512 implementation for faster Montgomery multiplications and modular exponentiation

This paper presents software implementations of batch computations, dealing with multi-precision integer operations. In this work, we use the Single Instruction Multiple Data (SIMD) AVX512 instruction set of the x86-64 processors, in particular the vectorized fused multiplier-adder VPMADD52. We focus on batch multiplications, squarings, modular multiplications, modular squarings and constant time modular exponentiations of 8 values using a word-slicing storage. We explore the use of Schoolbook and Karatsuba approaches with operands up to 4108 and 4154 bits respectively. We also introduce a truncated multiplication that speeds up the computation of the Montgomery modular reduction in the context of software implementation. Our Truncated Montgomery modular multiplication improvement offers speed gains of almost 20 % over the conventional non-truncated versions. Compared to the state-of-the-art GMP and OpenSSL libraries, our speedup modular operations are more than 4 times faster. Compared to OpenSSL BN_mod_exp_mont_consttimex2 using AVX512 and madd52* (madd52hi or madd52lo) in 256-bit registers, in fixed-window exponentiations of sizes 1024 and 2048 , our 512-bit implementation provides speedups of respectively 1.75 and 1.38, while the 256-bit version speedups are 1.51 and 1.05 for 1024 and 2048 -bit sizes (batch of 4 values in this case).

cs.DC↗

arXiv2019

Efficient and secure modular operations using the Adapted Modular Number System

The Adapted Modular Number System (AMNS) is a sytem of representation of integers to speed up arithmetic operations modulo a prime p. Such a system can be defined by a tuple (p, n, γ, ρ, E) where E is in Z[X]. In [13] conditions are given to build AMNS with E(X) = {X^n +1}. In this paper, we generalize their results and show how to generate multiple AMNS for a given prime p with E(X)={X^n-λ} and λ in Z. Moreover, we propose a complete set of algorithms without conditional branching to perform arithmetic and conversion operations in the AMNS, using a Montgomery-like method described in [15].

cs.CR↗