Bridge (cross-chain)

A cross-chain bridge is a system for moving value or state between two blockchains that do not natively speak to each other. The most common design is "lock and mint": the user deposits the asset (e.g. ETH) into a contract on the source chain, and the bridge mints a wrapped version (e.g. wETH) on the destination chain. To return, the user burns the wrapped token, and the bridge releases the original asset.

Bridges are historically the most-hacked category of crypto infrastructure. Because they hold large amounts of locked collateral for the wrapped tokens, they are high-value targets, and the trust model varies widely — some use a small set of multisig signers, some use a validator set, some use light clients and zero-knowledge proofs. Ronin, Wormhole, Nomad, Poly Network and others have suffered nine-figure exploits.

A non-custodial swap aggregator like SwapZilla is an alternative when the goal is "I want asset X on chain A converted to asset Y on chain B" — the swap is executed by an exchange provider that already has liquidity on both chains, without wrapping and without a persistent locked-collateral surface for hackers to attack. Bridges make sense when you specifically need the same asset (wrapped BTC on Ethereum, for example); aggregators make sense when you can accept a different asset on the destination.