Is X25519 Associative? Sometimes!

1 · Filippo Valsorda · May 26, 2020, 10 p.m.
X25519 is a simple Elliptic Curve Diffie-Hellman (ECDH) function: it takes a scalar (a fancy name for an integer[1]) and an elliptic curve point, and it multiplies the elliptic curve point by the scalar. Point additions and multiplications work modulo the order of the point, just like hours on...