Augmented PDM

• Authentication of Alice - Only a person who knows the correct W can calculate 2^bWmodp
• Authentication of Bob - Bob must know 2W mod p and b in order to compute 2bW mod p
• Security against Dictionary Attacks - Since the hash cannot be reversed, attacker cannot determine W
• Security against Server Compromise - Even if the attacker knew 2^Wmodp, need to solve DLP