Common-input-ownership heuristic
(An intro to PayJoin)
Meet Alice, a new employee at a chain analysis firm
Her job?
Track and analyze transactions on the Bitcoin network
Track and analyze transactions on the Bitcoin network
Alice’s first onboarding session: "common-input heuristic"
All inputs of a given tx are assumed to be owned by the same owner
To explain it:
Let’s say Bob buys a coffee from Carol with 1 BTC
Looking at this Tx, it's clear that the outputs are:
- 1 BTC payment to Carol
- 2 BTC change back to Bob
That’s how input correlation works —
This is what surveillance companies use to violate your privacy
This is what surveillance companies use to violate your privacy
So here’s the question:
What if we could break this heuristic…
but still make the tx look totally normal?
PayJoin
PayJoin is one way to disrupt this heuristic, allowing a tx to be interpreted in various ways
So now, the same tx — but with PayJoin looks like this:
Can you tell who owns what now?
Yeah... pretty hard.
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