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7 sats \ 4 replies \ @kruw 20 Jan \ on: Question on Wasabi Coinjoin bitcoin
If you are sending your BTC back to the same exchange you originally got it from, then there's no reason to coinjoin it at all. They already know you have X amount of BTC since they sold it to you in the first place.
The proper procedure is to first make sure the xpub address of your cold storage wallet is never leaked to third party servers. This means running your own node EVERY TIME when using your hardware wallet with software like Trezor Suite, Electrum, or Sparrow. It isn't required to run a node for privacy when using your HWW with Wasabi since it uses BIP157/BIP158 filters for synchronization.
Second, when sending your funds from cold storage to Wasabi for coinjoin, you should use coin control to make sure your transaction does not create a change output. By creating a 1 output sweep transaction, it terminates the trail entirely once that output goes into the coinjoin tx.
Very clear answer, thank you I appreciate that. Very helpful.
What about the UTXO's that you are given after the coinjoin? Isn't this an issue?
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Combining your coinjoined outputs is slightly less private than spending them individually, but you generally shouldn't worry about this unless you are a huge whale. If there's still any doubt, you can remix an extra time before spending.
For the absolute maximum privacy, you can make small or medium sized payments directly inside a coinjoin. This feature is currently only available in Wasabi's RPC, the UX for the GUI is still being worked on. https://docs.wasabiwallet.io/using-wasabi/RPC.html#payincoinjoin
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Combining your coinjoined outputs is slightly less private than spending them individually, but you generally shouldn't worry about this unless you are a huge whale. If there's still any doubt, you can remix an extra time before spending.
Let's assume I sent an UTXO with random amount like 0.12345 BTC to Wasabi and do a single coinjoin with settings set to "fast". Then I transfer everything back to my cold storage, by merging all the coinjoined UTXOs resulting in singe UTXO of amount (0.12345 minus fees). Isn't it quite obvious that it is still my UTXO?
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Yes. Although the link would not be deterministic, it would be a practical guess.
To solve this problem, I researched the worst case scenarios for consolidation of coinjoin outputs and proposed "Safety Coinjoins". This hidden feature automatically remixes coins that are vulnerable to weak spending patterns: https://github.com/WalletWasabi/WalletWasabi/issues/10567
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