unionlabs/union

Union is a cross-chain bridging protocol that lets assets and messages move between different blockchain networks without relying on any trusted intermediary. The fundamental problem in blockchain interoperability is trust: when you want to move tokens from, say, Ethereum to the Cosmos ecosystem, you typically need to trust a bridge operator, a group of multi-signature signers, or an oracle (an external service that reports facts to the blockchain). Any of these can be compromised, and bridge hacks are among the most costly security failures in decentralized finance. Union takes a different approach using zero-knowledge proofs, a cryptographic technique that lets one party mathematically prove that something is true without revealing the underlying data or requiring trust in the prover. Instead of trusting humans or services, Union verifies the consensus of source chains directly using these proofs. This means the security guarantees come from mathematics and the blockchain's own rules rather than from any organization's integrity. The system connects multiple ecosystems: Cosmos chains (via a protocol called IBC, the Inter-Blockchain Communication protocol, a standard for Cosmos chain interoperability), and Ethereum-compatible chains such as Ethereum mainnet, Arbitrum, Base, and Berachain. It consists of several components: the Union node itself (written in Go), a zero-knowledge prover called Galois, a high-performance cross-chain message relayer called Voyager (written in Rust), smart contracts for both the Cosmos WebAssembly and Ethereum Virtual Machine environments, and a web application. You would use Union if you are building a decentralized finance application that needs to move assets or data across chains with the highest possible security guarantees. The primary language is Rust, with Go for the node and prover, and Solidity for Ethereum smart contracts.