388: fix incorrect example #1874

1. 
   bigspider commented at 10:08 am on June 21, 2025: contributor

   As per the test vectors, musig key expressions require the aggregation step to precede the change/address_index derivations in wallet policies.
2. 388: fix incorrect example

   As per the test vectors, musig key expressions require the aggregation step
   to precede the change/address_index derivations.

   dadbbc6de4
3. jonatack added the label Proposed BIP modification on Jun 21, 2025
4. jonatack removed the label Proposed BIP modification on Jun 21, 2025
5. jonatack added the label Bug fix on Jun 21, 2025
6. in bip-0388.mediawiki:245 in dadbbc6de4

   241@@ -242,7 +242,7 @@ Common single-signature account patterns:
   242 Common multisig schemes:
   243 * <tt>wsh(multi(2,@0/**,@1/**))</tt> - SegWit 2-of-2 multisig, keys in order.
   244 * <tt>sh(sortedmulti(2,@0/**,@1/**,@2/**))</tt> - Legacy 2-of-3 multisig, sorted keys.
   245-* <tt>tr(musig(@0/**,@1/**))</tt> - MuSig2 2-of-2 in the taproot keypath
   246+* <tt>tr(musig(@0,@1)/**)</tt> - MuSig2 2-of-2 in the taproot keypath
   

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   jonatack commented at 11:22 pm on June 22, 2025:

   This does remove the contradiction between the example here being the same as the invalid policy example in line 313 below.

   Is there further explanation somewhere about the statement in line 313 "Derivation before aggregation is not allowed in wallet policies (despite being allowed in BIP-390)"?

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   bigspider commented at 2:16 pm on June 23, 2025:

   I commented here on why I believed that it was undesirable even for descriptors, and in more detail here commenting on the severe performance difference between the two - and also the additional implementation complexity it causes.

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   jonatack commented at 5:40 pm on June 25, 2025:

   Thanks! Fine for a different pull, but if there is no further explanation on this in the BIP, it may be good to add some (along with those links).
7. jonatack merged this on Jun 25, 2025
8. jonatack closed this on Jun 25, 2025

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Contributors
bigspider jonatack

Labels
Bug fix