Atomic Swap

An atomic swap is a technology that allows two people to exchange different cryptocurrencies directly with each other — peer to peer — without using a centralized exchange or requiring either party to trust the other. The word “atomic” refers to the all-or-nothing nature of the exchange: either the entire trade happens simultaneously for both parties, or it does not happen at all. There is no scenario where one person sends their coins and the other person does not send theirs back.

This is achieved through a cryptographic mechanism called a Hash Time-Locked Contract (HTLC). Alice wants to trade her Bitcoin for Bob’s Litecoin. She generates a secret number, creates a cryptographic hash of it, and locks her Bitcoin in a contract: “anyone who can reveal the secret behind this hash can claim these Bitcoin, but only within 24 hours.” Bob uses the same hash to lock his Litecoin in a matching contract. When Alice reveals the secret to claim Bob’s Litecoin, that same secret automatically becomes visible to Bob, allowing him to claim Alice’s Bitcoin. If either party fails to act within the time limit, both contracts expire and everyone gets their money back. Atomic swaps eliminate counterparty risk but remain technically complex for everyday use.

Example: Think of an atomic swap like two people exchanging sealed envelopes simultaneously in person. Neither person opens their envelope until both are handed over at the exact same moment. The rules are enforced by the physical constraint of the handoff — both envelopes change hands at once, or neither does. No trust required, no escrow service needed — the mechanism itself guarantees fairness.