Hybrid method for modular exponentiation with precomputation

The authors present a new hybrid method for performing modular exponentiation using a hybrid ternary-quinary number system. A recent result concerning performing modular exponentiation with precomputation was presented by Dimitrov and Cooklev (see IEICE Trans. Fundam., vol. E78-A, no. 1, p. 82-7, 1995): their average number of modular multiplications is 0.3381n, where n is the length of the modulus, while the authors´ proposed method only needs 0.3246n modular multiplications. Furthermore, compared to Dimitrov and Cooklev´s approach, the authors´ method reduces the amount of storage by 56.8% if the modulus is a 512 bit number