THE MODULAR EXPONENTIATION WITH PRECOMPUTATION OF REDUSED SET OF RESIDUES FOR FIXED-BASE

Abstract

Context. Modular exponentiation is an important operation in many applications that requires a large number of calculations Fast computations of the modular exponentiation are extremely necessary for efficient computations in theoretical-numerical transforms, for provide high crypto capability of information data and in many other applications. Objective – the runtime analysis of software functions for computation of modular exponentiation of the developed program that uses the precomputation of redused set of residuals for fixed-base. Method. Modular exponentiation is implemented using of the development of the right-to-left binary exponentiation method for a fixed basis with precomputation of redused set of residuals. To efficient compute the modular exponentiation over big numbers, the property of a periodicity for the sequence of residuals of a fixed base with exponents equal to an integer power of two is used. Results. Comparison of the runtimes of five variants of functions for computing the modular exponentiation is performed. In the algorithm with precomputation of redused set of residuals for fixed-base provide faster computation of modular exponentiation for values larger than 1K binary digits compared to the functions of modular exponentiation of the MPIR and Crypto++ libraries. The MPIR library with an integer data type with the number of binary digits from 256 to 2048 bits is used to develop an algorithm for computing the modular exponentiation. Conclusions. In the work has been considered and analysed the developed software implementation of the computation of modular exponentiation on universal computer systems. One of the ways to implement the speedup of computing modular exponentiation is developing algorithms that can use the precomputation of redused set of residuals for fixed-base. The software implementation of modular exponentiation with increasing from 1K the number of binary digit of exponent shows an improvement of computation time with comparison with the functions of modular exponentiation of the MPIR and Crypto++ libraries.