Zero-knowledge Proofs and Blockchain

It's not terribly uncommon for a big money Bitcoin transaction to make the news. These events are very plain demonstrations that some aspects of Bitcoin's blockchain (and others that followed) are actually very public, and, in particular, Bitcoin solves the double spending problem in part by making transaction amounts publicly visible.

This is not quite necessary, as a payee really only needs to verify that a payer has been keeping their books correctly and has enough money to do the deal. This can be accomplished with a cryptographic technique called a zero-knowledge proof – the payee provides proof they have the money, but provides zero specific knowledge of their finances.

The cryptocurrency Zcash was an influential early adopter of this technology. In particular, they applied a relatively new form of zero-knowledge proof called a zk-snark that embodies the big ideas of some of the more exciting cryptographic research of recent years.

In this talk, Alexander Mueller will explain zero-knowledge proofs, what is special about zk-snarks, how they are applied in Zcash, and situate all these ideas in the context of recent academic research.