The problem with using ALL|ANYONECANPAY is that you cannot verify beforehand that the other inputs are the inputs you want added to the transaction.
Some examples of bad things that could happen: * Coordinator adds its own inputs, you still get your outputs but effectively paid fees for no privacy gain * The inputs added could be paying at a lower fee rate than expected, causing the tx to take longer than what you paid for * Different input types or amount are added so you no longer have the same uniformity across the inputs * (if you care) An input from a sanctioned address is added, causing you to get "tainted" coins. This is the code in ln-vortex that verifies the psbt on the client side if you are curious https://github.com/ln-vortex/ln-vortex/blob/master/client/src/main/scala/com/lnvortex/client/VortexClient.scala#L616 Best, benthecarman ________________________________ From: bitcoin-dev <bitcoin-dev-boun...@lists.linuxfoundation.org> on behalf of alicexbt via bitcoin-dev <bitcoin-dev@lists.linuxfoundation.org> Sent: Monday, May 22, 2023 7:51 AM To: Bitcoin Protocol Discussion <bitcoin-dev@lists.linuxfoundation.org> Subject: [bitcoin-dev] Coinjoin with less steps using ALL|ANYONECANPAY 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 Sent with Proton Mail secure email. _______________________________________________ bitcoin-dev mailing list bitcoin-dev@lists.linuxfoundation.org https://lists.linuxfoundation.org/mailman/listinfo/bitcoin-dev
_______________________________________________ bitcoin-dev mailing list bitcoin-dev@lists.linuxfoundation.org https://lists.linuxfoundation.org/mailman/listinfo/bitcoin-dev
