The SIDH v2.0 library is a supersingular isogeny-based cryptography library that implements a new suite of algorithms for a post-quantum, ephemeral Diffie-Hellman key exchange scheme.

We present a new algorithm to compute the classical modular polynomial Phi_n in the rings Z[X,Y] and (Z/mZ)[X,Y], for a prime n and any positive integer m. Our approach uses the graph of n-isogenies ...