Zerocash is an academic paper and early implementation from a group of researchers -- a proof of concept of using zero-knowledge proofs to add privacy to a publ

Zerocash is an academic paper and early implementation from a group of researchers -- a proof of concept of using zero-knowledge proofs to add privacy to a public blockchain ledger. Zcash is the ongoing project based on Zerocash, started in large part by those same researchers, but with funded teams of engineers continuously iterating on the protocol and implementations.