Zeta Function and Cryptographic Exponent of Supersingular Curves of Genus 2

We compute in a direct (not algorithmic) way the zeta function of all supersingular curves of genus 2 over a finite field k, with many geometric automorphisms. We display these computations in an appendix where we select a family of representatives of all these curves up to k-isomorphism and we exhibit equations and the zeta function of all their k/k-twists. As an application we obtain a direct computation of the cryptographic exponent of the Jacobians of these curves.