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What is cross-chain messaging?
Cross-chain messaging is a way for a smart contract on one blockchain to send instructions or data to a contract on another. It sits underneath many bridges: instead of only moving tokens, it can carry messages such as 'mint this', 'unlock that' or 'record this vote' between chains.
What it means for you
A message from another chain is only as reliable as whoever verifies it. If a small group of signers attests messages, that group colluding or being hacked can tell a contract to release funds that were never deposited. Before using a cross-chain app, check what verifies its messages: the chains' own validators, a light client, or an external committee.
How it works
Arbitrary messaging bridges transfer assets along with messages and arbitrary data. How a message is verified is the central design choice. Some rely on an external set of verifiers, such as a multisig federation, a multi-party computation system or an oracle network, which is fast and widely connected but adds a party users must count on not to collude. Others rely on the connected chains and their own validators, for example through light clients, adding no new trust assumption but often giving up speed or connectivity. Optimistic designs accept messages unless someone challenges them with a fraud proof.
Source: ethereum.org: Bridges · checked 4 October 2026
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