Suppose that a blind man (let's call him the Verifier) has four coins and he wants to know how many of them are silver and how many are gold. The coins weigh and feel exactly the same, and the only difference is the color. The blind man finds a man who can see (let's call him the Prover) and decides that he will have this man help him figure out how many gold coins he has. But, he doesn't know if he can trust the prover. Describe a protocol that allows the verifier to learn whether he has an odd number of gold coins. Specifically, describe a protocol that satisfies: Perfect completeness: If there is an odd number (1 or 3) of gold coins, the verifier will accept with probability 1 Soundness: If there is an even number (0 or 2) of gold coins, then the verifier accepts with probability 1/2