A tiny coprocessor for elliptic curve cryptography over the 256-bit NIST prime field

Elliptic curve cryptography (ECC) over prime fields offers a wide range of portability since the underlying arithmetic operations that are performed over integers can be supported by general purpose computing devices. This portability helps in designing various ECC based public key protocols. However implementation of a fast enough ECC in tiny electronic devices such as RFID tags, sensor nodes, smart cards etc., is a very challenging design problem since such devices are very limited in terms of resources. In this paper we design the first lightweight ECC architecture over the NIST recommended 256-bit prime field, corresponding to a medium security level of 128-bits. The ECC architecture works as a coprocessor of a 16-bit microcontroller in a memory-mapped configuration. The architecture uses an area of only 5,933 GE on a 130 nm CMOS technology, and needs roughly 6 million clock cycles to calculate a scalar multiplication.