Séminaire de Cryptographie

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Ben Smith

Isogenies and Discrete Logarithms in Jacobians of genus 3 curves

Until recently, the best known algorithm for solving a Discrete Logarithm Problem (DLP) in the Jacobian of a hyperelliptic genus 3 curve ran in time \softO(q^(4/3)), while the best known algorithm for non-hyperelliptic genus 3 curves ran in time \softO(q). In this talk, we describe an efficient algorithm for moving instances of the DLP from a hyperelliptic genus 3 Jacobian to a non-hyperelliptic Jacobian, by means of an explicit isogeny. This allows us to solve the DLP on a large class of hyperelliptic genus 3 Jacobians in time \softO(q).