Zero-knowledge protocols allow identification, key exchange and other basic cryptographic operations to be implemented without leaking any secret information during the conversation and with smaller computational requirements than using comparable public key protocols. Thus Zero-knowledge protocols seem very attractive especially in smart card and embedded applications. There is quite a lot written about zero-knowledge protocols in theory, but not so much practical down-to-earth material is available even though zero-knowledge techniques have been used in many applications. Some of the practical aspects of zero-knowledge protocols and related issues are discussed, in the mind-set of minimalistic practical environments. The hardware technology used in these environments is described, and resulting real-world practical problems are related to zero-knowledge protocols. A very lightweight zero knowledge protocol is outlined and its possible uses and cryptographic strengths and weaknesses are analyzed.