84 sats \ 3 replies \ @kruw 16h \ on: Contemplating about payments to third parties during a coinjoin bitcoin
I have good news for you: Not only is it feasible, it's already implemented in multiple wallets! You can send payments directly in a coinjoin with BTCPay Server's coinjoin plugin or with Wasabi Wallet's RPC.
I demonstrated how you can make completely anonymous on chain Bitcoin payments by sending 100k sats to Vlad in this coinjoin transaction: https://mempool.space/tx/52a1f40b1d1dae560c02f0bb65304172d936e01d67ee633c2f846c139fef8c0b
This doesn't require the recipient to provide multiple addresses or accept specific sized amounts, you can send arbitrarily sized payments to a single address. It's extremely block space efficient because there's no premix transaction or postmix transaction required - you can consolidate UTXOs, batch payments, and anonymize any leftover change all in a single coinjoin transaction.
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The reason it isn't the default way to spend coins is because you would have to wait up to 1 hour for the other participants to join and build the transaction, which introduces the chance for prices to change in the meantime. Also, the coordinator chooses the fee rate for all participants, so if the fee for the round is higher than you are willing to pay then you would have to wait for the coordinator to create a round with a lower fee. Unfortunately, most wallets simply don't care about any privacy feature that would introduce UX tradeoffs.
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