ISO/IEC 9798-5:2009 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.