Subject: [bitcoin-dev] Coinjoin with less steps using ALL|ANYONECANPAY

From: alicexbt <[email-masked]>
Date: Mon, 22 May 2023 12:51:22 +0000

Hi Bitcoin Developers,

I recently experimented with different sighash flags, PSBTs and realized ALL|ANYONECANPAY could be used to reduce some steps in coinjoin.

Steps:

- Register outputs.
- One user creates a signed PSBT with 1 input, all registered outputs and ALL|ANYONECANPAY sighash flag. Other participants keep adding their inputs to PSBT.
- Finalize and broadcast the transaction.

Proof of Concept (Aice and Bob): https://gitlab.com/-/snippets/2542297

Tx: https://mempool.space/testnet/tx/c6dd626591dca7e25bbd516f01b23171eb0f2b623471fcf8e073c87c1179c492

I plan to use this in joinstr if there are no major drawbacks and it can even be implemented by other coinjoin implementations. 

/dev/fd0
floppy disk guy

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