WIP: Permit Combiner to strip bip32_deriv information #30341

1. 
   willcl-ark commented at 11:01 am on June 26, 2024: member

   Closes: #30294

   Looking for approach (N)ACK.

   Previously setting the bip32derivs flag to false with the walletprocesspsbt RPC correctly does not include bip32_derivs for inputs in the PSBT, but does include bip32_derivs for outputs.

   User may want to actively strip all bip32 derivation paths from a PSBT for privacy reasons however. It may make sense to do this after signing your inputs and outputs during a manual coinjoin as demonstrated in the BIP174 example.

   To me, this makes more sense to include in the Combiner PSBT role. It’s then separated from signing done by the Signers.

   Therefore add functionality to combinepsbt permitting stripping of all bip32_derivation paths found in all provided psbts’ inputs and outputs.

   As this RPC can be called with a single PSBT, it can be used to strip derivation paths from a PSBT with any number of participants.

2. 
   DrahtBot commented at 11:01 am on June 26, 2024: contributor

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   Conflicts

   Reviewers, this pull request conflicts with the following ones:

   • #21283 (Implement BIP 370 PSBTv2 by achow101)

   If you consider this pull request important, please also help to review the conflicting pull requests. Ideally, start with the one that should be merged first.

3. willcl-ark added the label PSBT on Jun 26, 2024
4. DrahtBot added the label CI failed on Jun 26, 2024
5. willcl-ark force-pushed on Jun 26, 2024
6. DrahtBot removed the label CI failed on Jun 26, 2024
7. DrahtBot added the label Needs rebase on Jul 11, 2024
8. rpc: strip derivation paths from psbt during combine

   Previously setting bip32derivs to false with walletprocesspsbt does not
   include bip32_derivs for inputs, but does include bip32_derivs for
   outputs.
   
   User may want to strip all bip32 derivation paths for privacy reasons
   however. It may make sense to do this after signing your inputs and
   outputs during a manual coinjoin for example.
   
   Therefore add functionality to `combinepsbt` permitting stripping of
   all bip32_derivation paths found in all provided psbts.
   
   As this RPC can be called with a single psbt, it can be used to strip
   derivation paths from any psbt.

   e5aa7d96b4
9. test: exercise bip32_deriv stripping during psbt combine

   These asserts check that when calling `combinepsbt` RPC with
   `stripderivs=true`, all derivation paths are stripped from all inputs
   and outputs.

   6f5b910876
10. doc: detail psbt combiner derivation strip ability. f3e2a7f7ff
11. willcl-ark force-pushed on Oct 8, 2024
12. DrahtBot removed the label Needs rebase on Oct 8, 2024

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