How Cross-Chain Bridges Actually Move Value

Moving assets between blockchains is not a transfer in the way people usually picture it. Nothing crosses. A bridge locks or burns the asset on the source chain and releases an equivalent amount on the destination, and the whole question of safety comes down to who is allowed to authorise that release.

Lock-and-mint versus burn-and-mint

Lock-and-mint keeps the original token in a vault on the source chain and issues a wrapped version on the far side. The wrapped token is only worth what the vault is worth, so custody of that vault is the real risk.

Burn-and-mint destroys the token on the source chain and recreates it on the destination. Total supply stays constant and there is no vault to drain, but the minting authority becomes the thing you have to trust.

What decides whether a bridge is safe

• Who confirms the transfer — a multisig, a validator set, or a light client verifying consensus directly
• Whether the wrapped asset is redeemable one-to-one, and what happens if it is not
• Settlement time and fees, which vary far more than the interfaces suggest

A light client that verifies the source chain's consensus is a different security model from a five-of-nine multisig, even when the user experience looks identical. The Ethereum documentation on bridges is a reasonable place to start if you want the underlying mechanics rather than marketing copy.

The practical takeaway

Read the settlement model before you read the fee table. Once you know who is authorised to release funds on the destination chain, you know exactly where your trust is sitting — and that is the only part of a bridge that really matters.