Start building with ZetaChain
At a high level, ZetaChain is a Proof of Stake (PoS) blockchain developed using the Cosmos SDK and Tendermint Core consensus engine. As a result, ZetaChain enjoys fast block time and instant finality.
ZetaChain hosts an Ethereum Virtual Machine (EVM) compatible execution layer referred to as zEVM. In addition to supporting all EVM features and standard interactions (such as contract creation, contract interaction, and contract composition), zEVM's distinguishing characteristics include:
- The ability for contracts on zEVM to be called from external chains
- The capacity for contracts on zEVM to generate outbound transactions on external chains.
These two unique features enable zEVM to function as a general-purpose programmable platform, supporting cross-chain transactions that can atomically modify states across different chains in a single step.
When developing on ZetaChain, you create zEVM contracts. While zEVM contracts can be any standard Solidity contract, to fully utilize ZetaChain's capabilities, they must adhere to specific interfaces. These interfaces, unique to ZetaChain, enable interaction with externally connected blockchains.
ZetaChain offers two ways to develop dApps: omnichain contracts and cross-chain message passing.
Omnichain contracts
With omnichain contract you only need to deploy a single omnichain contract to ZetaChain. No contracts on connected chains are required.
For a contract to be considered omnichain, it must implement a method that is executed on a cross chain call.
On a connected chain, a user can transfer an asset to a ZetaChain address, referred to as a Threshold Signature Scheme (TSS) address.
- If the transfer only includes an asset, the asset becomes available to the omnichain contract.
- If the transfer includes an asset and a message containing the omnichain contract address and data, the asset becomes available to the omnichain contract, and the contract is called with the message data as an argument.
Assets transferred to a TSS address on ZetaChain are represented as ZRC-20 tokens. ZRC-20 is an extension of ERC-20 that supports additional functionality for deposits from and withdrawals to connected chains.
The state of your whole dApp can be stored in this omnichain contract.
Right now omnichain contracts support the following features:
- Transfer of native gas asset (ETH, BNB, MATIC, etc.) between connected chains.
- Transfer of ERC-20 tokens between connected chains.
Advantages of omnichain contracts
Developers can extend common applications like Uniswap V2/V3, Curve, Aave, and Compound by making them compatible with ZRC-20. These applications have been audited and battle-tested on Ethereum and can easily be deployed and built on ZetaChain. The changes required to add ZRC-20 support are minimal, and users may interact with these applications in single-step transactions just as they would on Ethereum.
ZRC-20 can easily support Bitcoin/Dogecoin which do not have capability or efficiency to support general purpose smart contracts for applications like swapping, lending, etc.
ZRC-20 may cost significantly less gas than message passing in many use cases because its interactions with foreign chains are confined to fungible coins (standard value transfer of ETH/BNB/MATIC costs 21k gas, moving ERC20 tokens costs around 60k gas; no logic/state on foreign chains means much less gas).
With omnichain smart contracts, you can pair and trade native asset liquidity directly against each other. This minimizes steps to trade native assets in a single step, and it doesn't involve a bridge or wrapping step or sending complex messages. For example, you could trade Ethereum ETH directly for Polygon USDC through a unified pool in a single transaction.
With ZRC-20/zEVM, exception/revert handling is much simpler as foreign interaction is confined to either a standard ERC-20/contract interaction (success) or no contract interaction (failure) immediately.
Cross-chain message passing
With cross-chain message (CCM) passing you deploy CCM-enabled contracts on connected chains that can pass arbitrary message data and value between each other.
On a connected chain a user can call a CCM-enabled contract. The contract calls the Connector API and sends a message. ZetaChain acts as relayer and transmits the message to the destination chain. On the destination chain a CCM-enabled contract uses the Connector API to receive the message and handles it.
The state is stored on a set of CCM-enabled contracts on different chains.
CCM makes sense for applications that only need unidirectional and asynchronous logic/effects and that don't need or benefit from a unified state.
Advantages of cross-chain message passing
CCM supports any type of data transfer and it's up to the contracts to decide how to handle the data.
CCM is a reliable general purpose solution for augmenting existing applications with cross-chain functionality.
With messages, you can leverage existing liquidity like Uniswap pools on existing chains, and trade via burning/minting ZETA through ZetaChain. This approach may be more complex (more transactions involved, more gas), but doesn't rely on liquidity within ZetaChain's ecosystem.
By leveraging the ZETA burn/mint functionality built into ZetaChain, one can build value-transfer applications that don't bridge/wrap assets, minimizing risk for users.