Pipelined modular multiplier supporting multiple standard prime fields

Computationally-intensive cryptographic applications are critically dependent on the efficiency of modular multiplications. It is desirable for a modular multiplier to offer not only high performance, but also a certain degree of flexibility, supporting multiplications over finite fields of varying size. We propose a fast and flexible modular multiplier over five prime fields GF(p), standardized by NIST for use in elliptic curve cryptography, where the five special primes p are of size 192, 224, 256, 384, and 521 bits. A prime-specific datapath configuration of our multiplier is established automatically, based on an external control word that identifies a NIST prime in use. The pipeline latency of our multiplier (implemented on a Virtex-6 FPGA and running at 100 MHz) is 80 ns for 192-bit, 224-bit, and 256-bit NIST primes, and 200 ns for 384-bit and 521-bit NIST primes. The main limitation of this work is that our multiplier currently supports only the NIST prime fields. We believe that such a limitation is justifiable, as the NIST prime fields are widely used in practice and enable performance improvements through specialized hardware optimizations.