Zero knowledge proofs in practice What are the practical problems of using zero knowledge proofs, for instance in the field of authentication?
Currently, there are very few practical barriers to deploying zero-knowledge proofs. They've been deployed in everything from anonymous credentials to cryptocurrencies to privacy-preserving survey systems. Very fast academic systems have been developed which use zero-knowledge proofs for privacy-preserving distributed machine learning. This last example hasn't been deployed yet, but clearly is fast and scalable enough to be used in practice.