Fast architectures for FPGA-based implementation of RSA encryption algorithm

In this paper, new structures that implement RSA cryptographic algorithm are presented. These structures are built upon a modified Montgomery modular multiplier, where the operations of multiplication and modular reductions are carried out in parallel rather than interleaved as in the traditional Montgomery multiplier. The global broadcast of data lines is avoided by interleaving two or more encryption/decryption operations onto the same structure, thus making the implementation systolic and scalable. The digit approach has been adopted in this paper. This methodology is based on varying the digit size and the level of pipelining of the structures. This parameterised approach presents the designer with an efficient way of choosing the architecture that suits better his/her requirements in terms of speed and area usage, an issue of critical importance to the resources-limited FPGA chips. The results of implementation using FPGA have shown that the proposed RSA structures outperformed those structures built around the traditional Montgomery multiplier in terms of speed, thanks to avoiding global lines broadcast.