This part of ISO/IEC 9798 specifies entity authentication mechanisms using zero-knowledge techniques: - mechanisms based on identities and providing unilateral authentication; - mechanisms based on integer factorization and providing unilateral authentication; - mechanisms based on discrete logarithms with respect to numbers that are either prime or composite@ and providing unilateral authentication; - mechanisms based on asymmetric encryption systems and providing either unilateral authentication@ or mutual authentication; - mechanisms based on discrete logarithms on elliptic curves and providing unilateral authentication. These mechanisms are constructed using the principles of zero-knowledge techniques@ but they are not necessarily zero-knowledge according to the strict definition for every choice of parameters.