libsnark

libsnark is an open-source C++ library for constructing, proving, and verifying zero-knowledge succinct non-interactive arguments of knowledge (zk-SNARKs). It provides a practical reference implementation of zk-SNARK algorithms and serves as a platform for experimentation with cryptographic backends and curve choices.

The library uses Rank-1 Constraint Systems (R1CS) as its standard circuit representation and includes a protoboard abstraction that lets developers model arithmetic circuits, constraints, and inputs. It contains components for constraint generation, trusted setup, proving, and verification, with a modular architecture designed to accommodate different SNARK schemes and cryptographic groups.

libsnark supports multiple elliptic-curve groups and pairings commonly used in zk-SNARKs and offers a range of utilities, from high-level circuit definitions to low-level elliptic-curve operations. It has been used in research settings and in real-world projects; for example, it has influenced privacy-preserving proof systems in various cryptocurrency and academic initiatives.

The project is maintained as an open-source effort with documentation and tutorials, aiming to facilitate reproducibility of zk-SNARK research and to provide developers with a functional toolkit for building privacy-preserving applications. It has historically been used as a reference implementation and teaching resource in the broader zk-SNARK community.