Firo (FIRO), originally known as Zcoin, is a cryptocurrency that aims to provide a private digital payment alternative. It developed the Lelantus privacy system, which allows users to burn their coins and then exchange them for fresh ones with no transaction history.Firo's Lelantus and Sigma privacy protocols use a specific zero-knowledge proof termed one-out-of-many proofs, which, unlike other zk constructions, does not require a trusted setup or complex cryptographic assumptions while maintaining strong anonymity settings.Firo has devoted itself to becoming a privacy-preserving cryptocurrency, designing and building trustless privacy protocols like Lelantus that have influenced the design of other privacy protocols.