RSA public key validation

With increasing demands for internet security, the demand for distribution of public key certificates and certificate authorities spreads. This brings up the new problem of public key validation. This problem can arise in different contexts and can be adressed in some of them using novel zero knowledge protocols, while in other contexts it can be only poorly solved. The purpose of this paper is to give an overview of the topic of key validation and to discuss the possible solutions to the different instances in which it appears. We also present a new zero knowledge protocol for correctness of an RSA public exponent and a simple protocol (not zero-knowledge) for primality of a discrete logarithm. We use the latter to give a proof protocol (not zero knowledge) that an RSA key is the product of strong primes.