Atomic Swap

An atomic swap is a direct exchange of coins between two people on different blockchains that either completes fully for both sides or does not happen at all. The classic implementation uses hashed timelock contracts: one party locks funds behind the hash of a secret, the other mirrors the lock on their chain, and revealing the secret to claim one side automatically exposes it to claim the other. If either party walks away, the timelocks expire and each refund returns to its owner, so neither side ever holds the other's money. Atomic swaps remove custodial and bridge risk, but they need both chains to support compatible scripting, both parties online, and they offer none of the depth or price discovery of an order book.