Abstract. We propose a superscalar coprocessor for high-speed curvebased cryptography. It accelerates scalar multiplication by exploiting instruction-level parallelism (ILP) dynamically and processing multiple instructions in parallel. The system-level architecture is designed so that the coprocessor can fully utilize the superscalar feature. The implementation results show that scalar multiplication of Elliptic Curve Cryptography (ECC) over GF(2163 ), Hyperelliptic Curve Cryptography (HECC) of genus 2 over GF(283 ) and ECC over a composite field, GF((283 )2 ) can