The @tokamak-network/thanos-contracts package provides the smart contracts for the Thanos network, focusing on Ethereum scalability and cross-chain communication. It includes contracts for:

• Cross-Domain Messaging: Facilitating seamless data and function calls between Ethereum (L1) and Thanos (L2).
• Token Bridging: Enabling deposits and withdrawals of ETH and ERC-20 tokens across L1 and L2.
• Protocol Infrastructure: Managing transaction batches, state commitments, and fraud-proof mechanisms for Thanos’s rollup architecture.

1. Cross-Domain Messaging

Cross-domain messaging is a core feature of Thanos, enabling communication between Ethereum(L1) and Thanos(L2). This mechanism is crucial for various use cases, such as transferring data, triggering actions across chains, and enabling interoperability between contracts on different layers.

How Cross-Domain Messaging works

Thanos employs Cross-Domain Messengers to facilitate messages passing between L1 and L2:

• L1CrossDomainMessenger: Handles sending and receiving messages from Ethereum
• L2CrossDomainMessenger: Handles sending and receiving messages from Thanos

Process flow:

1. Send messages from L1 to L2

• Message submission(L1 to L2):
  • A user or contract on L1 sends a message to the L1CrossDomainMessenger. The message is sent to the portal contract and stored on it
• Message relay(on L2):
  • The relayer processes the message on (1) and submits it to the L2CrossDomainMessenger
  • The message is executed on L2, triggering a function call or data transfer.

b. Send messages from L2 to L1

• Message submission(L2 to L1):
  • A user or contract on L2 sends a message to the L2CrossDomainMessenger. The message from L2 to L1 is initially stored in the L2 state.