ilan@Gang-of-Four.Stanford.EDU (Ilan Vardi) (11/18/89)
This problem is already intractable for k=1. Let G be the multiplicative group of integers (mod p), p prime. Then G is known to be a cyclic group. If g is a generator of G (primitive root), then for a given a in G, finding x such that g^x = a (mod p) is called the discrete logarithm problem. Finding x is hard, so that g^x is considered a trap door function and is used for cryptography (Diffie--Hellman).