Efficient arithmetic on genus 2 hyperelliptic curves over finite fields via explicit formulae

We extend the explicit formulae for arithmetic on genus two curves of [13, 21] to fields of even characteristic and to arbitrary equation of the curve. These formulae can be evaluated faster than the more general Cantor algorithm and allow to obtain faster arithmetic on a hyperelliptic genus 2 curve than on elliptic curves. We give timings for implementations using various libraries for the field arithmetic.