Swaps between chains: how a trade works here

The Exchange lets you swap coins, tokens and NFTs between two different chains (Pepecoin for Dogecoin, for example) with somebody on any arcade, without trusting them, the arcade you use, or theirs. Nobody ever holds your coins: every swap is settled by lock scripts on both chains.

Swaps on a single chain (a token for PEP, an NFT priced in a token) do not need any of this. They settle instantly in one transaction on that chain's own market: the seller signs their half ahead of time and the buyer completes it.

• Either both sides get paid, or both get their own coins back. There is no outcome where one side pays and the other keeps everything.
• A swap normally takes seconds: each side acts as soon as the other's lock is in the mempool and is exactly the lock the terms say. A swap with a coin side at or above the arcade's big-swap line (1,000,000 PEP or 1,000 DOGE unless its operator sets another) waits for one confirmation on each chain instead. A token, NFT or Doginal side counts from the mempool too, once its lock transaction plainly moves exactly that asset in from its owner and nothing else in the mempool is moving it; if that cannot be told yet, it waits for the block.
• You do not have to keep the page open. Your own node finishes your side with transactions you signed in your browser in advance.
• If the other side disappears part-way, your coins come back to you automatically after at most two hours.

Say Alice lists 1,000 PEP for 300 DOGE and Bob takes it.

• 1. Bob makes a secret in his browser and keeps it. Only its fingerprint (a hash) is shared.
• 2. Bob locks his 300 DOGE on the Dogecoin chain in a lock script that says: Alice may take this if she shows the secret; otherwise Bob may take it back after two hours.
• 3. As soon as that lock is in the mempool, Alice's browser locks her 1,000 PEP on the Pepecoin chain: Bob may take this with the same secret; otherwise Alice may take it back after one hour.
• 4. As soon as that lock is in the mempool, Bob claims the PEP. To do it he has to put the secret on the Pepecoin chain, where anyone can read it.
• 5. Alice claims the DOGE with the secret she just read off the chain.

Because Bob can only take the PEP by revealing the secret, and the secret is all Alice needs to take the DOGE, the two claims stand or fall together. Alice's lock runs out before Bob's, so she always has time to claim after he does, and neither side can take the other's coins and keep their own.

When your browser locks your coins it also signs, right away, the two transactions that finish your side: the claim of the other lock and the refund of your own. It hands them to your arcade node, which sends:

• the claim as soon as the secret shows up on the chain (or, if you made the secret, as soon as the other lock is confirmed), and
• the refund once your lock's time has run out, if nobody claimed it.

Your node cannot change either one: your signature covers where the coins go, and they can only go to you. All it adds is the secret, which by then is public.

Whoever locks a side pays its fees, on top, so the other side receives exactly what was agreed:

• About 0.01 of the coin to put your side in its lock (the network fee).
• A coin lock also holds the network fee of the other side's claim (0.01; about 0.0001 on Litecoin), so the coins come out of it whole.
• A token or NFT goes into its lock with 0.02 of that chain's coin, which pays for moving it out again, whoever ends up with it.
• Your arcade's operator fee, if it charges one (Admin, Trading): a per cent of the coins you lock, at least the chain's smallest payment (0.01). It waits in the lock and is paid to the operator when the other side claims; if your lock comes back to you, so does the fee. A token or NFT lock pays only that smallest amount, unless its price is coin on the same chain.
• Trading with an arcade that has not updated yet, its claim fee still comes off what you receive from it, and its claim keeps the operator fee in your lock.
• Listing a swap writes a small record on the chain so other arcades can show it: about 0.01.

You see these amounts before you say yes. Saying yes to Take, or to List, also approves locking your side when the time comes; you are not asked again.

On the Exchange, under Swaps between arcades (or on a coin pair's market, such as PEP/DOGE), choose what you offer and what you want. Your listing shows on other arcades while an arcade page is open in your browser; close them all and it stops being shown within the hour. Withdraw it whenever you like.

When somebody takes it, your browser checks that their terms match yours exactly, locks your side once theirs is confirmed, and hands your node the claim and refund. You can close the page after that.

Press Take (or Buy / Sell on a market). Your browser makes the secret and proposes the swap to the lister. Nothing is locked until they accept. Then your side is locked, and the swap finishes by itself.

• A phone stops a browser in the background, so a swap waiting for your side to lock only moves while the arcade is on screen. Once your side is locked, your node finishes it either way.
• Your wallet has to be unlocked in some tab for anything to be signed.
• Swaps between chains move whole amounts: a listing is taken in full.