View source for PayJoin

PayJoin (also called ''pay-to-end-point'' or ''P2EP'') is a special type of [[CoinJoin]] between two parties where one party pays the other. This [[CoinJoin|coinjoin]] type has different (probably better) privacy properties. The [[transaction]] then doesn't have the distinctive multiple outputs with the same value, and so is not obviously visible as an equal-output [[CoinJoin]].

Consider this transaction:

 2 btc ---> 3 btc
 5 btc      4 btc

It could be interpreted as a simple [[transaction]] paying to somewhere with leftover [[change]]. Another interpretation is that the 2 BTC input is owned by a merchant and 5 BTC is owned by their customer, and that this transaction involves the customer paying 1 BTC to the merchant. There is no way to tell which of these two interpretations is correct. The result is a [[CoinJoin]] [[transaction]] which breaks the [[common-input-ownership heuristic]] and improves privacy, but is also undetectable and indistinguishable from any regular bitcoin [[transaction]].

If PayJoin [[transaction]]s became even moderately used then it would make the [[common-input-ownership heuristic]] be completely flawed in practice. As they are undetectable we wouldn't even know whether they are being used today. As [[Transaction surveillance company|Transaction surveillance companies]] mostly depend on that heuristic, as of 2019 there is great excitement about the PayJoin idea<ref>https://lists.linuxfoundation.org/pipermail/bitcoin-dev/2018-August/016340.html</ref>.


=== Probable examples ===
In general payjoins are indistinguishable from any regular bitcoin [[transaction]]s, but sometimes their creators publish them online and say they are actually payjoins.

* <code>7104bae698587b3e75563b7ea7a9aada41d9c787788bc2bf26dd201fd7eca8a2</code><ref>https://mastodon.social/@waxwing/101387762796750634</ref>.

== External links ==
* https://blockstream.com/2018/08/08/improving-privacy-using-pay-to-endpoint/
* https://medium.com/@nopara73/pay-to-endpoint-56eb05d3cac6
* https://samouraiwallet.com/stowaway - A smartphone wallet which implements payjoin.
* https://joinmarket.me/blog/blog/payjoin/
* https://gist.github.com/AdamISZ/4551b947789d3216bacfcb7af25e029e
* https://wasabiwallet.io/ - PayJoin-enabled Bitcoin Desktop Wallet
* https://www.blockstream.com/2020/04/16/en-bitcoin-privacy-improves-with-btcpay-servers-p2ep-implementation/

== See also ==

* [[CoinJoin]]
* [[PayJoin adoption]]

==References==
<references />

[[Category:Privacy]]