Construction of Secure CabCurves Using Modular Curves

This paper proposes a heuristic algorithm which, given a basis of a subspace of the space of cuspforms of weight 2 for Γ0(N) which is invariant for the action of the Hecke operators, tests whether the subspace corresponds to a quotient A of the jacobian of the modular curve X0(N) such that A is the jacobian of a curve C. Moreover, equations for such a curve C are computed which make the quotient suitable for applications in cryptography. One advantage of using such quotients of modular jacobians is that fast methods are known for finding their number of points over finite fields. key words: discrete logarithm, modular curve, hyperelliptic curve, Cab curve