The Basic Model
- Source — A smart contract on Chain A that encodes (data or value) and emits a message.
- Crosschain Message — A structured container that includes metadata about the source/destination chain and structured data for the destination contract’s business logic.
- Destination — A smart contract on Chain B that receives the message, decodes, and executes some requested business logic.
Why It Matters
Without interoperability, smart contract state, liquidity, and users remain siloed per chain, increasing fragmentation, friction, and operational overhead. Interoperability enables better UX, capital efficiency, and scalable architectures by coordinating logic and assets across chains.What Crosschain Smart Contracts Do
Interoperable smart contracts can share data, update state, trigger actions, and transfer value between different blockchain networks seamlessly, as if these contracts were deployed on a single network.1) Data Messaging
Move structured data and/or trigger logic across smart contracts on different blockchains.Push
A sends a message that B receives.Pull
A requests from B; B replies; A processes on arrival.Data Messaging is typically used for state synchronization, remote function invocation, orchestration, and governance.
2) Value Transfer
Move assets between chains while preserving global supply/ownership invariants. Value transfer in practice can take various forms, depending on the type of asset being moved (native chain currency or fungible token smart contract) and whether the bridge is the asset issuer, but the underlying pattern is the exact same: the contract debits funds on one chain, and credits an equivalent amount on another chain.Canonical Burn/Mint
Chain A burns tokens and Chain B mints the same amount, unifying supply across chains.Lock/Unlock
Chain A locks tokens on a home chain and represents elsewhere (typically Chain B mints). When B burns, A unlocks the original escrowed tokens. Forward flow (A → B):Reverse flow (B → A):
Liquidity Pools
Chain A transfers assets to pool A destination pays from pool B (fees/slippage possible).Value Transfer is typically used for crosschain payments, asset bridging, liquidity provision, and treasury management.
Value transfer is simply data messaging with token‑specific invariants/settlement logic.
How Crosschain Messages Can Be Trusted and Delivered
This concept applies to both Data Messaging and Value Transfer.A) Verification (state correctness)
Each blockchain is a network of nodes reaching consensus about the state of that specific chain. In principle, this means that nodes from one blockchain network and the consensus they reach is entirely independent of another blockchain network. Each network is effectively an isolated island without any knowledge of external state outside its own domain. The Core Challenge: How can Chain B trust a statement about Chain A when Chain B’s validators have no direct way to verify what happened on Chain A? Because of this limitation, every crosschain message requires verification. Different approaches involve different trust assumptions and trade-offs:Verifier Networks
Verifier Networks act as independent observers that watch blockchain events and provide proof to the destination chain that a state change occurred on the source network. They are opinionated about how crosschain messages are routed, what chains they support, and what trust assumptions are used to confirm the state of a message from another chain.
Note: The following is a simplified mental model. In practice, security depends on implementation details, economic incentives, validator sets, and attack vectors specific to each system.