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Overview

The Chromia token bridge enables you to seamlessly transfer EVM-compatible tokens and NFTs between EVM-compatible chains and Chromia. This is made possible by leveraging the EIF module, which stands for Ethereum Interoperation Framework. The EIF module facilitates decentralized communication between EVM-compatible chains and Chromia. This allows you to build interoperable Chromia dapps with Ethereum and other platforms. Also, the Originals NFT Protocol allows projects from various blockchains to migrate their metadata, images, and other information to our network.

The pegged bridge of the Chromia token bridge is specifically designed for existing tokens on EVM-compatible chains. It creates a “copy” of the original token that is pegged to the original token. An admin account on the Chromia blockchain manages the pegged tokens on the Chromia side. Subsequently, you can seamlessly utilize Chromia cross-chain transfer to move pegged tokens between Chromia blockchains.

How does the bridge work?

Chromia uses the following bridge mechanisms:

  • Lock and mint – Lock assets on the source chain and mint assets on the destination chain.

  • Burn and release – Burn assets on the Chromia chain and release assets on the destination chain.

Lock and mint

  1. Deposit: Users deposit tokens (ERC20, ERC721) on an EVM-compatible chain, which are locked in a smart contract on that chain.
  2. Monitor: Chromia validator nodes monitor the deposit event on the EVM-compatible chain.
  3. Detect: Upon detecting the deposit event, Chromia validator nodes create, validate, and execute a special transaction using a specific Rell operation called __evm_block.
  4. Mint: This transaction mints equivalent pegged tokens for the user on the Chromia chain.

When the user wishes to withdraw the pegged tokens from Chromia back to the original token on the EVM-compatible chain, the bridge follows the Burn and release mechanism.

Burn and release

  1. Burn: The pegged token is burned on the Chromia chain.
  2. Withdrawal event: A withdrawal event is emitted on the Chromia chain.
  3. Query proof: Users can query the token withdraw event Merkle proof on the Chromia node.
  4. Release: They can then use the proof data to call the smart contract for releasing the original token on the EVM-compatible chain.