CoinJoin
A Bitcoin privacy technique that combines multiple users' transactions into one, making it harder to trace which input funded which output.
CoinJoin is a Bitcoin privacy technique in which multiple participants combine their individual transactions into a single, larger joint transaction, with multiple inputs and multiple outputs, making it meaningfully harder for an outside observer to determine which specific input actually funded which specific output.
Unlike Monero, where privacy techniques are built into the protocol and applied by default (see Kaavon's "Privacy Coins Explained" guide), CoinJoin is an optional, opt-in technique applied on top of Bitcoin's otherwise fully transparent, pseudonymous base layer — participants have to actively choose to use it, and only transactions that do benefit from the added ambiguity.
Examples
- A CoinJoin transaction with many participants and uniform output amounts makes it harder to link any single input to any single output by simply inspecting the transaction.
- CoinJoin is an optional technique a Bitcoin user has to actively choose to use — unlike Monero's privacy features, which apply to every transaction automatically.