Elliptic Curve, Diffie Hellman, Discrete Log, Elgamal Encryption.
and Alice calculates h2^a (mod p) so that they will all wind up with g^(ab) (mod p). The problem is eavesdropper don’t have access to a or b, so they should find them from h1 and h2. However, thanks to the complexity of discrete log problem, the eavesdropper cannot figure this out. Elliptic Curve