3.11 PayJoin: Invisible Privacy in a Normal Payment
An ordinary-looking transaction that also breaks chain analysis.
PayJoin: Invisible Privacy in a Normal Payment
PayJoin is a clever twist on a normal payment. Instead of the sender providing all the inputs, the recipient also contributes one or more of their own coins. The recipient ends up with more bitcoin than the sender actually paid (their own coins were just shuffled), and the transaction settles normally.
PayJoin is a clever twist on a normal payment. Instead of the sender providing all the inputs, the recipient also contributes one or more of their own coins. The recipient ends up with more bitcoin than the sender actually paid (their own coins were just shuffled), and the transaction settles normally.
Because both sender AND recipient inputs appear in the same transaction, the chain analyst's biggest assumption — 'all these inputs belong to the same person' — quietly breaks down. But, crucially, the transaction looks like an ordinary payment from outside. Nobody can tell a PayJoin happened.
That makes PayJoin special: it works in the background of regular commerce. Merchants using BTCPay Server, or individuals using Sparrow, can offer or use PayJoin without any awkward signals. The more PayJoins happen, the less reliable chain analysis becomes for everyone.