Modular exponentiation is an essential operations for various applications, such as cryptography. The performance of this operations has a tremendous im- pact on the efficiency of the whole application. There- fore, many researchers devoted special interest to pro- viding smart methods and efficient implementation for modular exponentaition. One these methods is the sliding-window method, which pre-processes the expo- nent into zero and non-zero partitions so that the num- ber of modular multiplications required to compute the modular power is reduced. In this paper, we devise a novel harwdare for computing modular exponentiation using the sliding-window method. The implementation is efficient when compared against existing hardware implementations of the modular exponentiation.