A blockchain bridge is a system for transferring information or representing assets across different blockchain networks. It provides a way for activity on one chain to cause a corresponding action on another. Bridges can connect separate layer 1 networks or a base chain and a rollup.1

Assets and messagesReport an error

A token representing an asset on another chain is not the original asset on its original ledger. Ethereum's bridge guide uses wrapped bitcoin to illustrate this distinction: the Ethereum token and native bitcoin belong to separate networks. The mechanism connecting them introduces its own custody and redemption assumptions.1

Not all transfers require a wrapped token or a liquidity pool. Circle's Cross-Chain Transfer Protocol burns native USDC on a source chain and mints native USDC on a destination chain. Circle documents this as an issuer-supported burn-and-mint design, distinct from moving a claim backed by tokens held in a bridge pool.2

Bridges can also carry instructions. ERC-5164 defines interfaces for dispatching a message on one chain and executing it on another. Its security requirements include identifying the source chain and sender and preventing a message from being executed more than once. A common interface does not prescribe a single verification mechanism for every implementation.3

Trust and failuresReport an error

Ethereum's bridge guide distinguishes systems relying on external operators from systems that minimise additional trust through verification. It also recognises intermediate designs. Contract errors, failures of the underlying chains, and dishonest or compromised operators can affect transfers.1

For bridges attached to rollups, upgrade permissions and exit mechanisms are material parts of the design. L2Beat's framework examines whether privileged actors can block or falsify withdrawals and whether users can leave before upgrades. A working proof mechanism alone does not describe all of those powers.4

IncidentsReport an error

Ethereum's bridge guide records the Wormhole incident in which 120,000 wrapped ETH was stolen. This is an example of bridge failure affecting assets represented across networks, rather than requiring the underlying chains themselves to stop processing blocks.1

See alsoReport an error

ReferencesReport an error

  1. ^ a b c d e ethereum.org. Introduction to blockchain bridges. https://ethereum.org/en/bridges/ 

  2. ^ a b Circle. Cross-Chain Transfer Protocol. https://developers.circle.com/cctp 

  3. ^ a b Ethereum Improvement Proposals. ERC-5164: Cross-Chain Execution. https://eips.ethereum.org/EIPS/eip-5164 

  4. ^ L2Beat. Stages framework. https://l2beat.com/stages