📅 Original date posted:2023-05-23
🗒️ Summary of this message: A proposal to use ALL|ANYONECANPAY sighash flag to reduce steps in coinjoin, but concerns about DoS attacks and input verification remain.
📝 Original message:Hi all,
In some coinjoin implementations inputs are registered first because in
that way, if the user fails or refuses to sign the transaction the input is
banned and denial of service is made a bit more expensive, in the sense
that an attacker needs more and more utxos to keep the attack going.
Your proposal can work if you find an alternative mechanism for mitigating
the DoS attacks or when DoS attacks are not a problem (I can imagine there
are scenarios where it is not really important).
Best
- Lucas
On Mon, May 22, 2023 at 7:53 PM Ben Carman via bitcoin-dev <
bitcoin-dev at lists.linuxfoundation.org> wrote:
> 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-bounces at lists.linuxfoundation.org> on
> behalf of alicexbt via bitcoin-dev <bitcoin-dev at lists.linuxfoundation.org>
> *Sent:* Monday, May 22, 2023 7:51 AM
> *To:* Bitcoin Protocol Discussion <bitcoin-dev at 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 at lists.linuxfoundation.org
> https://lists.linuxfoundation.org/mailman/listinfo/bitcoin-dev
> _______________________________________________
> bitcoin-dev mailing list
> bitcoin-dev at lists.linuxfoundation.org
> https://lists.linuxfoundation.org/mailman/listinfo/bitcoin-dev
>
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Lucas Ontivero [ARCHIVE] /
npub16q…gqufk
2023-06-07 23:21:58
in reply to nevent1q…tv3z
Author Public Key
npub16q9ngejhxtupvrmnmcrhdqag5dcgfyxvc5mhequv4w7637xvp3ss7gqufkPublished at
2023-06-07 23:21:58Event JSON
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"content": "📅 Original date posted:2023-05-23\n🗒️ Summary of this message: A proposal to use ALL|ANYONECANPAY sighash flag to reduce steps in coinjoin, but concerns about DoS attacks and input verification remain.\n📝 Original message:Hi all,\n\nIn some coinjoin implementations inputs are registered first because in\nthat way, if the user fails or refuses to sign the transaction the input is\nbanned and denial of service is made a bit more expensive, in the sense\nthat an attacker needs more and more utxos to keep the attack going.\n\nYour proposal can work if you find an alternative mechanism for mitigating\nthe DoS attacks or when DoS attacks are not a problem (I can imagine there\nare scenarios where it is not really important).\n\nBest\n\n- Lucas\n\n\nOn Mon, May 22, 2023 at 7:53 PM Ben Carman via bitcoin-dev \u003c\nbitcoin-dev at lists.linuxfoundation.org\u003e wrote:\n\n\u003e The problem with using ALL|ANYONECANPAY is that you cannot verify\n\u003e beforehand that the other inputs are the inputs you want added to the\n\u003e transaction.\n\u003e\n\u003e Some examples of bad things that could happen:\n\u003e\n\u003e\n\u003e - Coordinator adds its own inputs, you still get your outputs but\n\u003e effectively paid fees for no privacy gain\n\u003e - The inputs added could be paying at a lower fee rate than expected,\n\u003e causing the tx to take longer than what you paid for\n\u003e - Different input types or amount are added so you no longer have the\n\u003e same uniformity across the inputs\n\u003e - (if you care) An input from a sanctioned address is added, causing\n\u003e you to get \"tainted\" coins.\n\u003e\n\u003e This is the code in ln-vortex that verifies the psbt on the client side if\n\u003e you are curious\n\u003e\n\u003e\n\u003e https://github.com/ln-vortex/ln-vortex/blob/master/client/src/main/scala/com/lnvortex/client/VortexClient.scala#L616\n\u003e\n\u003e\n\u003e Best,\n\u003e\n\u003e benthecarman\n\u003e\n\u003e ------------------------------\n\u003e *From:* bitcoin-dev \u003cbitcoin-dev-bounces at lists.linuxfoundation.org\u003e on\n\u003e behalf of alicexbt via bitcoin-dev \u003cbitcoin-dev at lists.linuxfoundation.org\u003e\n\u003e *Sent:* Monday, May 22, 2023 7:51 AM\n\u003e *To:* Bitcoin Protocol Discussion \u003cbitcoin-dev at lists.linuxfoundation.org\u003e\n\u003e *Subject:* [bitcoin-dev] Coinjoin with less steps using ALL|ANYONECANPAY\n\u003e\n\u003e Hi Bitcoin Developers,\n\u003e\n\u003e I recently experimented with different sighash flags, PSBTs and realized\n\u003e ALL|ANYONECANPAY could be used to reduce some steps in coinjoin.\n\u003e\n\u003e Steps:\n\u003e\n\u003e - Register outputs.\n\u003e - One user creates a signed PSBT with 1 input, all registered outputs and\n\u003e ALL|ANYONECANPAY sighash flag. Other participants keep adding their inputs\n\u003e to PSBT.\n\u003e - Finalize and broadcast the transaction.\n\u003e\n\u003e Proof of Concept (Aice and Bob): https://gitlab.com/-/snippets/2542297\n\u003e\n\u003e Tx:\n\u003e https://mempool.space/testnet/tx/c6dd626591dca7e25bbd516f01b23171eb0f2b623471fcf8e073c87c1179c492\n\u003e\n\u003e I plan to use this in joinstr if there are no major drawbacks and it can\n\u003e even be implemented by other coinjoin implementations.\n\u003e\n\u003e /dev/fd0\n\u003e floppy disk guy\n\u003e\n\u003e Sent with Proton Mail secure email.\n\u003e _______________________________________________\n\u003e bitcoin-dev mailing list\n\u003e bitcoin-dev at lists.linuxfoundation.org\n\u003e https://lists.linuxfoundation.org/mailman/listinfo/bitcoin-dev\n\u003e _______________________________________________\n\u003e bitcoin-dev mailing list\n\u003e bitcoin-dev at lists.linuxfoundation.org\n\u003e https://lists.linuxfoundation.org/mailman/listinfo/bitcoin-dev\n\u003e\n-------------- next part --------------\nAn HTML attachment was scrubbed...\nURL: \u003chttp://lists.linuxfoundation.org/pipermail/bitcoin-dev/attachments/20230523/4bc0294c/attachment-0001.html\u003e",
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