Abstract— This work describes the smallest known hardware implementation for Elliptic/Hyperelliptic Curve Cryptography (ECC/HECC). We propose two solutions for Publickey Cryptography (PKC), which are based on arithmetic on elliptic/hyperelliptic curves. One solution relies on ECC over binary fields F2n where n is a composite number of the form 2p (p is a prime) and another on HECC on curves of genus 2 over F2p . This implies the same arithmetic unit for both cases which supports arithmetic in a field F2p . Our best solution that still results in a feasible performance features less than 5 kgates with an average power consumption smaller than 10 µW.