In this paper, a low-complexity Programmable Cellular Automata (PCA) based versatile modular multiplier in GF(2m) is presented. The proposed versatile multiplier increases flexibility in using the same multiplier in different security environments, and it reduces the user's cost. Moreover, the multiplier can be easily extended to high order of m for more security, and low-cost serial implementation is feasible in restricted computing environments, such as smart cards and wireless devices.