The team behind ZCash, a cryptocurreny that is focused on privacy, has published a paper on Zero Knowledge proofs entitled: Scalable, Transparent, and Post-Quantum Secure Computational Integrity. The paper is authored by Eli Ben-Sasson, Iddo Bentov, Yinon Horesh and Michael Riabze.
The privacy coin uses a concept called zero knowledge proofs for anonymous transactions. Zcash payments are recorded on a blockchain that is public record, but users are able to add an optional privacy feature to conceal the sender, recipient, and amount being transacted if they choose to do so. The fixed total amount of ZCash coins that will ever be produced is 21 million, which is the same as Bitcoin.
Read more about zero knowledge proofs in the published article here: https://eprint.iacr.org/2018/046.pdf