What is Halo for Zcash?

The Halo paper, authored in 2019 by ECC’s Sean Bowe, Jack Grigg, and Daira Hopwood, introduced a new technique for creating practical, scalable, and trustless cryptographic proving systems, ending an almost decade-long pursuit by the cryptography community. The Halo proving system eliminates protocol reliance on so-called “trusted setups” and provides a catalyst for Zcash user confidence and scalability while making the protocol more attractive, faster, and less expensive for others to build on. A technique called recursion, or nested amortization, also introduced in the Halo paper, is under development at ECC, bolstered by an agreement with Protocol Labs, the Filecoin Foundation, and the Ethereum Foundation. As Bowe put it, this cryptographic breakthrough “allows a single proof to attest to the correctness of practically unlimited other proofs, effectively allowing a large amount of computation (and information) to be compressed.” Halo lays the groundwork for cross-chain interoperability and positions Zcash as a foundational layer for a global and digital economy.