Cross-chain communication


To easily and effectively deliver multi-chain applications like atomic swaps and cross-chain bridges, Zilliqa 2.0 features a Universal Cross-Chain Broker (UCCB) built into the network.

EVM compatibility remains a key aspect of the network, enabling connection with other EVM blockchains and attracting a broad ecosystem of developers. 

Zilliqa 2.0 is designed as a fast, flexible blockchain that enables easy and efficient multi-chain applications.

The native ZIL token is wrapped in an ERC-20 interface on Zilliqa 2.0, allowing it to be uniformly handled as a fungible asset in DeFi applications.

To easily and effectively deliver multi-chain applications like atomic swaps and cross-chain bridges, Zilliqa 2.0 features a Universal Cross-Chain Broker (UCCB) built into the network.

Built-In Gateway to EVM Networks

The UCCB is an infrastructure platform built into the Zilliqa 2.0 network that acts as an integrated gateway to other EVM networks.

This allows Zilliqa 2.0 to support interactions between smart contracts deployed on different EVM chains, seamlessly integrating the blockchain with the EVM ecosystem through a network of interconnected smart contracts.

On Zilliqa 2.0, developers can use the UCCB contract to easily swap tokens, trade NFTs, and more across EVM blockchains connected to the UCCB network.

Secure Cross-Chain Transactions

The UCCB enables easy and secure transactions across EVM networks by allowing smart contracts on different networks to send asynchronous messages to each other.

By using globally unique chain ids to specify the target, smart contracts can call each other on any chain that is part of the UCCB network.

Cross-chain messages are assembled into batches and validated, after which the UCCB contract is called to send these messages to surrogate contracts on the respective EVM chain, which then interact with the target EVM smart contracts. 

The UCCB automatically handles gas costs and refunds, rewards validators, and protects against replay attacks, paving the way for building cross-chain EVM dApps on Zilliqa 2.0.

To request a cross-chain transaction, a CALLER contract passes encoded calls, the address of the SURROGATE contract on the target chain, and other transaction data to the relay function of the UCCB contract, which then emits an event with a unique nonce. Zilliqa 2.0 validators batch the UCCB events found in a finalised block and share their signatures on the batch. If the current leader has enough signatures to reach consensus, the UCCB event and the signatures are submitted in a transaction to the UCCB contract on the target chain. The UCCB contract verifies the signatures, checks and invalidates the nonce, invokes the SURROGATE contract to execute the encoded cross-chain calls, and refunds the transaction fees from the SURROGATE contract's deposit to the leader who submitted the cross-chain transaction. Finally, the UCCB contract emits an event to inform the validators that the cross-chain transaction was successfully dispatched.

Fungible Tokens and NFTs

The UCCB’s cross-chain communication protocol includes support for the cross-chain bridging of tokens and NFTs between Zilliqa 2.0 and connected EVM networks.

It is straightforward to wrap Scilla fungible tokens (ZRC-2) and NFTs (ZRC-6) in their EVM equivalent standards (ERC-20 and ERC-721), and transfer them using the UCCB to and from other chains.

Zilliqa 2.0 provides full interoperability between native Scilla and EVM contracts in addition to supporting full backwards compatibility with wallets and other tools.

The UCCB component of Zilliqa 2.0 offers multi-chain interoperability as a core aspect of its design, bringing more utility to the network through accelerating cross-chain communication.

Build Cross-Chain EVM dApps

Zilliqa 2.0’s introduction of the UCCB unlocks the ability to build cross-chain applications that leverage the customisable properties of x-shards to scale the network as necessary while remaining cost-effective.

A decentralised application running on a bespoke x-shard can be built to interface with various EVM-compatible tokens, including NFTs, with cross-chain bridging and transfers all handled by the UCCB protocol.

This makes Zilliqa 2.0 the ideal platform on which to build scalable and cost-effective Web3 apps that are easy to use and seamlessly compatible with any other EVM blockchains.