## Cryptology ePrint Archive: Report 2021/013

An atlas of the Richelot isogeny graph

Enric Florit and Benjamin Smith

Abstract: We describe and illustrate the local neighbourhoods of vertices and edges in the (2, 2)-isogeny graph of principally polarized abelian surfaces, considering the action of automorphisms. Our diagrams are intended to build intuition for number theorists and cryptographers investigating isogeny graphs in dimension/genus 2, and the superspecial isogeny graph in particular.

Category / Keywords: Isogenies; post-quantum cryptography; abelian varieties; hyperelliptic-curve cryptography