BIP draft: Raw() as subscript for descriptors

furszy commented at 9:19 pm on December 17, 2024: member

Allowing arbitrary hex data to be wrapped in sh(), wsh(), or even within the TREE argument of a tr(KEY, TREE) descriptor enables the representation of currently inexpressible information.

Specifically, the absence of this feature limits the representation of non-standard redeem and witness scripts. This occurs because they can currently only be represented as top-level raw(HEX) descriptors, which retain only the output script information and lack the ability to preserve the actual script.

This work stemmed from discussions with @sipa and @achow101 about the legacy wallet migration path, particularly while investigating migrated descriptors that lacked information about the script they were supposedly migrated from.

Additionally, issue #24114, specifically https://github.com/bitcoin/bitcoin/issues/24114#issuecomment-1127978154, provides historical context and highlights other valid use cases enabled by this behavior change.

jonatack added the label New BIP on Dec 17, 2024

jonatack renamed this:
~~Raw() as subscript for descriptors~~
BIP draft: Raw() as subscript for descriptors
on Dec 17, 2024

furszy force-pushed on Dec 18, 2024

in bip-0391.mediawiki:26 in 47fed6d9f0 outdated

21+
22+This BIP is licensed under the BSD 2-clause license.
23+
24+==Motivation==
25+
26+To ensure no information is lost during conversion to descriptors, it’s useful to wrap

sipa commented at 7:36 pm on December 18, 2024:

This seems to appear somewhat out of the blue; the reader isn’t familiar with the fact that Bitcoin Core is working on migration from pre-descriptor wallets to descriptor wallet, and I don’t think it matters if you phrase it as being able to express information that’s currently inexpressible.

furszy commented at 10:19 pm on December 18, 2024:

absolutely, thanks!

furszy force-pushed on Dec 18, 2024

furszy force-pushed on Dec 20, 2024

in bip-0391.mediawiki:44 in a67af04615 outdated

39+participating in signing a script without knowing all participants' keys, relying solely
40+on the script structure.
41+
42+==Specification==
43+
44+Allow raw(HEX) to be accepted within the context of `sh()`, `wsh()` and `tr()` descriptors.

murchandamus commented at 7:31 pm on December 20, 2024:

I think you’re mixing up MediaWiki and Markdown. If you want to use mediawiki, you would use <tt>sh()</tt>. It’s been permitted to submit BIPs in Markdown for a while though, if you prefer that.

0Allow raw(HEX) to be accepted within the context of <tt>sh()</tt>, <tt>wsh()</tt> and <tt>tr()</tt> descriptors.

furszy commented at 10:17 pm on December 23, 2024:

It’s been permitted to submit BIPs in Markdown for a while though, if you prefer that.

Ok yes, that’s better. Will inline the doc to use the `` markdown syntax.

furszy force-pushed on Dec 24, 2024

in bip-0391.mediawiki:41 in 9c5985184f outdated

36+Additionally, as noted [https://github.com/bitcoin/bitcoin/issues/24114#issuecomment-1127978154 here],
37+there are other useful scenarios for this feature. For example, it allows representing
38+in a descriptor that we lack full knowledge of all solvability paths but can still solve
39+the output, such as a taproot tree where we know only one of its paths, or even also
40+participating in signing a script without knowing all participants' keys, relying solely
41+on the script structure.

murchandamus commented at 6:29 pm on December 27, 2024:

This paragraph is hard to parse, perhaps you could split the second sentence into multiple sentences.

in bip-0391.mediawiki:50 in 9c5985184f outdated

45+### For `sh()` and `wsh()` descriptors:
46+`raw(HEX)` must represent the arbitrary script data within the provided context.
47+This for example means that a P2SH output script (OP_HASH160 <hash160(HEX_script)> OP_EQUAL)
48+must be created from the provided hex data when a `sh(raw(HEX))` descriptor is provided.
49+
50+Parallely, a P2WSH output script (OP_0 <hash160(HEX_script)>) must be created from the provided

murchandamus commented at 6:30 pm on December 27, 2024:

0Parallelly, a P2WSH output script (OP_0 <hash160(HEX_script)>) must be created from the provided

in bip-0391.mediawiki:93 in 9c5985184f outdated

88+* Non-hex in `rawnode`: `tr(a34b99f22c790c4e36b2b3c2c35a36db06226e41c692fc82b8b56ac1c540c5bd, rawnode(<complete me with a 32-bit non-hex hash>))`
89+* `raw` in the key path `tr`: `tr(raw(asdf), pk(key))`
90+
91+==Backwards Compatibility==
92+
93+`raw()` as a subscript descriptors use the format and general operation specified in [[bip-0380.mediawiki|380]].

murchandamus commented at 6:32 pm on December 27, 2024:

0`raw()` as subscript descriptors use the format and general operation specified in [[bip-0380.mediawiki|380]].

in bip-0391.mediawiki:10 in 9c5985184f outdated

 5+  Author: Pieter Wuille pieter@wuille.net
 6+          Matias Furszyfer mfurszy@protonmail.com
 7+  Comments-Summary: No comments yet.
 8+  Comments-URI: https://github.com/bitcoin/bips/wiki/Comments:BIP-???
 9+  Status: Draft
10+  Type: Informational

murchandamus commented at 6:33 pm on December 27, 2024:

0  Type: Standards Track

in bip-0391.mediawiki:11 in 9c5985184f outdated

 6+          Matias Furszyfer mfurszy@protonmail.com
 7+  Comments-Summary: No comments yet.
 8+  Comments-URI: https://github.com/bitcoin/bips/wiki/Comments:BIP-???
 9+  Status: Draft
10+  Type: Informational
11+  Created: 2024-12-16

murchandamus commented at 6:35 pm on December 27, 2024:

The Created Header stores the date a BIP was assigned a number:

0  Created: ?

in bip-0391.mediawiki:6 in 9c5985184f outdated

0@@ -0,0 +1,98 @@
1+<pre>
2+  BIP: ???
3+  Layer: Applications
4+  Title: raw() as subscript in Output Script Descriptors
5+  Author: Pieter Wuille pieter@wuille.net
6+          Matias Furszyfer mfurszy@protonmail.com

murchandamus commented at 6:36 pm on December 27, 2024:

0  Author: Pieter Wuille <pieter@wuille.net>
1          Matias Furszyfer <mfurszy@protonmail.com>

murchandamus commented at 6:37 pm on December 27, 2024: contributor

Could maybe use a bit more rationale. Has this already been submitted to the mailing list?

furszy force-pushed on Dec 27, 2024

Raw() as subscript for descriptors 3197eb9b27

furszy force-pushed on Dec 27, 2024

furszy commented at 8:51 pm on December 27, 2024: member

Has this already been submitted to the mailing list?

Not yet. Will do next year.

BIP draft: Raw() as subscript for descriptors #1721