Improved Modular Multiplication for Optimal Prime Fields

Optimal Prime Fields (OPFs) are considered to be one of the best choices for lightweight elliptic curve cryptography implementation on resource-constraint embedded processors. In this paper, we revisit efficient implementation of the modular arithmetic over the special prime fields, and present improved implementation of modular multiplication for OPFs, called Optimal Prime Field Coarsely Integrated Operand Caching (OPF-CIOC) method. OPF-CIOC method follows the general idea of (consecutive) operand caching technique, but has been carefully optimized and redesigned for Montgomery multiplication in an integrated fashion. We then evaluate the practical performance of proposed method on representative 8-bit AVR processor. Experimental results show that the proposed OPF-CIOC method outperforms the previous best known results in ACNS’14 by a factor of 5 %. Furthermore, our method is implemented in a regular way which helps to reduce the leakage of side-channel information.