Atomic Swaps: Trustless XMR↔BTC

Every swap method so far trusts a service to hold your coins for a moment and play fair. An atomic swap removes even that. It's a direct, peer-to-peer trade between you and another person — most commonly XMR↔BTC — where the cryptography itself guarantees the deal: either both sides happen or neither does, and nobody can run off with your funds. No company, no custody, no account, no one to demand your ID. This is the most trust-minimized way to get (or sell) Monero. This lesson explains how it works and, in detail, how to actually do one.

What "Atomic" Means

"Atomic" means all-or-nothing. The swap is built so that the moment one party can claim their coins, the other party is mathematically able to claim theirs too. If anyone abandons the trade, built-in time-locked refunds return everyone's original coins. There is never a point where a stranger is simply holding your money and trusting you — or where you must trust them.

Why It's the Most Private / Trustless Way

• No custodian. No service ever holds your funds, so none can freeze them, demand "enhanced verification," or get hacked with your coins inside.
• No account, no logs to leak. There's no profile tying you to the trade.
• Refund by design. If your counterparty disappears, the timelock gives your coins back — you lose a little time and network fees, not your funds.

How It Works (the Idea)

You don't need the math, but the shape helps. Using clever cryptography (adaptor signatures and time-locks), the two sides each lock their coins on their own chains. Claiming a coin reveals a secret that lets the other side claim theirs. So:

1. One side locks BTC; the other locks XMR.
2. When you claim the XMR, the act of claiming reveals what the other side needs to claim the BTC.
3. If either side walks away before completing, after a timeout both parties can refund their original coins.

The result: the trade completes fully or unwinds cleanly. There's no "middle" where one person is exposed.

Makers and Takers

An atomic-swap network has two roles. Makers run software that holds liquidity and publicly advertises offers ("I'll give XMR for BTC at this rate"). Takers — that's you, normally — browse those offers and take one. You don't need to run a maker to swap; you just take an existing offer.

How to Actually Do an Atomic Swap (Taker: BTC → XMR)

Step 1 — Get the software

The XMR↔BTC atomic swap has a friendly desktop app, UnstoppableSwap (a GUI built on the open-source COMIT xmr-btc-swap project; the eigenwallet effort is folding this into an easy wallet too). There's also a command-line swap tool for advanced users. Download only from the official project source and verify it.

Step 2 — Understand what you need

• Some Bitcoin to spend (you're buying XMR with BTC).
• A Monero receive address (your own wallet) for the XMR you'll get.
• The app includes an internal Bitcoin wallet you'll fund, and it talks to an Electrum server for Bitcoin and a Monero node for XMR (your own node is best — see Running or Choosing a Node).
• It routes over Tor for privacy.

Step 3 — Pick an offer (a maker)

The app shows a public list of makers with their rates, available liquidity (max/min amounts), and uptime/reputation. Choose one with a fair rate, enough liquidity for your amount, and a good track record.

Step 4 — Fund the app's Bitcoin wallet

Send the BTC you want to swap into the app's built-in Bitcoin wallet address, and wait for it to confirm. Enter your Monero receive address for the payout.

Step 5 — Start the swap and let it run

Begin the swap with your chosen maker. Behind the scenes the protocol now:

1. Locks your BTC and the maker's XMR on their respective chains.
2. Waits for confirmations on both sides.
3. Redeems: you claim the XMR to your address, which lets the maker claim the BTC.

This takes longer than an instant swap — typically tens of minutes up to an hour or more — because it waits on Bitcoin and Monero confirmations. Keep the app running until it finishes.

Step 6 — Receive your XMR (and the safety net)

The XMR lands in your Monero wallet. If anything went wrong — the maker went offline mid-swap, say — don't panic: after the timelock, the app lets you refund, returning your BTC. Leaving a swap half-finished and closing the app is the main way to get stuck, so let it complete or follow its refund/recovery prompts.

Trade-offs — Be Realistic

• It's slower and more technical than an instant swap. You're running a little more software and waiting on two chains.
• The Bitcoin side is transparent. Your BTC input is public on Bitcoin's chain; the privacy win is that no service handles or logs the trade, and your XMR side is private.
• You need a willing maker with liquidity for your amount, at a fair rate. Big swaps may need a maker with deep liquidity.
• Mostly XMR↔BTC. It's not an any-coin instant swap — it's the trust-minimized BTC pairing.

When to Use It

Reach for an atomic swap when you want maximum sovereignty and privacy — no custodial risk, no surprise-KYC, no service that can log you — and you're willing to trade some convenience and time for it. For everyday speed, a good no-KYC instant swap is fine; for the strongest guarantees, this is the gold standard. Either way, run it over Tor and verify your software before you start.