Secure Outsourcing of Multiple Modular Exponentiations

Modular exponentiation with a large modulus, which is usually accomplished by repeated modular multiplications, has been widely used in public key cryptosystems for secure data communications. Hohenberger and Lysyanskaya [14] proposed the first algorithm for secure outsourcing of modular exponentiations, and then Chen et al. [16] improved the algorithm, which can implement simultaneous modular exponentiations of u1au2b. In this paper, we present a secure algorithm for resource-constrained customers, who outsource simulataneous modular exponentiations operation, a task of intensive computation workload, to untrusted servers in the model with one malicious adversary. Based on Chen´s algorithm, our algorithm achieves n simultaneous modular exponentiations in outsourcing computation. Compared with [14] and [16], our algorithm is more efficiency.