What is an atomic swap and why is it safe
Note: MoneroP2P charges a fee on every completed swap (see FAQ ). The service is in testing and only runs on testnet.
Short answer: an atomic swap is a trade between two cryptocurrencies on different chains where neither party can keep the other’s funds. It is called “atomic” because it is indivisible: either both transfers complete, or both are undone. Its safety does not depend on trusting anyone, but on cryptography and a contract with deadlines.
The idea in one sentence
Each party locks their funds so that the only way to get paid is to reveal the key the other party needs to take theirs.
How it works between USDT and Monero
Monero has no smart contracts, so the protocol uses two pieces:
- A shared Monero address, whose private key is split in two halves: the XMR buyer holds one and the seller holds the other. Nobody can spend from it with only one half.
- A contract on the USDT network that holds the USDT and only pays the seller if they reveal their key half.
When the seller claims the USDT, their half is published on-chain; the buyer uses it to complete the key and take the XMR. If the seller never locks the XMR, the buyer recovers the USDT.
Why it is safe
| Risk in a trade | How the atomic swap handles it |
|---|---|
| The other party does not send | You can refund within the deadline |
| The other party gets paid without delivering | To get paid, they must reveal the key that gives you the XMR |
| A custodian disappears | There is no custodian: a contract and split keys |
| The other party uses a different key on each chain | A cryptographic proof (DLEQ) shows it is the same |
What you must take care of
- Deadlines. Atomic swaps are safe if each party acts in time. On MoneroP2P, if the XMR is not verified before deadline t0, you must refund.
- Your recovery file. If you close the browser, you need it to finish or refund.
- The software. Safety depends on the code being correct; MoneroP2P is not audited yet.
A bit of history
Atomic swaps have been discussed for Bitcoin since the early 2010s. For Monero, which has no scripts, split-key protocols were developed: COMIT’s (now eigenwallet) for Bitcoin, and AthanorLabs’ for Ethereum, which MoneroP2P builds on.