Subject: [bitcoindev] UTXO probing attack using payjoin

From: /dev /fd0 <[email-masked]>
Date: Tue, 25 Mar 2025 04:46:38 -0700 (PDT)

Hi everyone, 

Sometimes we are curious and want to know about UTXOs in other wallets. 
Payjoin allows you to do this and the recipient would never doubt it 
because it's a privacy tool. It's possible to find UTXO in recipient's 
wallet without sending any bitcoin. It's called UTXO probing attack and 
described in BIP 77-78.

I have shared a demo with all the details in this [post][0]. I have used 
bullbitcoin wallet for testing this because it was the only [wallet][1] 
which supports payjoin v2 (send, receive) and testnet3.

I think users should be aware of this tradeoff and the information they 
share with the sender in payjoin. Payjoin should only be used with trusted 
senders.

[0]: https://uncensoredtech.substack.com/p/utxo-probing-attack-using-payjoin
[1]: https://en.bitcoin.it/wiki/PayJoin_adoption

/dev/fd0
floppy disk guy

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