Union: The trust-minimized, zero-knowledge bridging protocol

Union is the hyper-efficient zero-knowledge infrastructure layer for general message passing, asset transfers, NFTs, and DeFi. It’s based on Consensus Verification and has no dependencies on trusted third parties, oracles, multi-signatures, or MPC. It implements IBC for compatibility with Cosmos chains and connects to EVM chains like Ethereum, Berachain (beacon-kit), Arbitrum, and more.

The upgradability of contracts on other chains, connections, token configurations, and evolution of the protocol will all be controlled by decentralized governance, aligning the priorities of Union with its users, validators, and operators.

Who is Union built for?

For those who care about decentralization and reliability, and believe that finance should be accessible for everyone.

Core Values

Union is developed to be a scalable powerhouse:

• Fast: bridging transactions are generated and settled quickly.
• Secure: abide by fork-choice rules.
• Future proof: core tech is built for the next decennium.
• Easy to use: high-level API usable for developers from any ecosystem.

Protocol

The Union protocol is a flavor of IBC (and fully IBC compatible), with certain extensions and innovations to make the protocol more efficient, faster, and flexible for builders, without reducing any security guarantees.

Connections and Channels

Instead of a legacy single-chain-single-connection protocol, Union uses a connection and channel standard to facilitate communication between rollups and chains. This has several advantages.

• Each connection encodes a finality mechanism and security level, such that we can support both soft and hard finalization on Arbitrum.
• Each channel encodes a messaging protocol, allowing us to support different protocols concurrently.

We currently support two categories of connections, direct and recursive. Each connection can leverage any of our light clients. Direct connections are single-hop, while recursive connections leverage statelenses to perform arbitrary amounts of hops.

The complex combinations of connection category and client type is abstracted for onchain protocols and end users, to them, connections act as simple sockets.

Versions

Union supports different protocols over each channel. Channels are connection agnostic, meaning that all channel versions support both direct and recursive connections.

Each protocol version has different functionalities and intended use cases. For most users, ucs03-zkgm-1 is the appropriate channel type.