Lock-and-mint bridge

Lock-and-mint is the oldest and most common bridge design. When a user deposits, say, ETH into the bridge contract on Ethereum, the bridge's verifiers confirm the deposit and a contract on the other chain mints a wrapped version, a token that represents a claim on the locked ETH. Going back, the wrapped token is burned and the original is released from the lock.

Almost every chain bootstraps its first liquidity this way, which is why so many tokens exist in wrapped or bridged versions with suffixes like .e or names like WBTC. Rollups' official bridges also follow the lock-and-mint pattern, with the difference that their security comes from the rollup's own proofs rather than an external committee.

The locked pool becomes a honeypot: everything minted on the other side is only as good as the contract and keys guarding it. Attacks on the Ronin and Wormhole bridges in 2022 showed how a compromised verifier set or a single bug can leave wrapped tokens unbacked. Different bridges also mint incompatible wrapped versions of the same asset, fragmenting liquidity.