Ranged descriptors #154

uncomputable · 2023-07-11T13:27:15Z

Adds rudimentary support for ranged descriptors. ~~We could add more convenience methods, but this requires us to copy / implement a lot of traits such as ForEachKey.~~

uncomputable · 2023-07-12T15:06:00Z

~~Loosened the trait bound in Descriptor<Pk> as FromStr. Now Pk can be pretty much any MiniscriptKey.~~ We cannot deserialize Policies with xpubs. I need to fix this.

uncomputable · 2023-07-12T15:35:24Z

Fixed the issue. Now we can decode arbitrary Policys and Descriptors.

uncomputable · 2023-07-12T22:21:02Z

str::split_once() is available from 1.52.0 so I need to find a workaround.

This copies ideas from the Tr descriptor in rust-miniscript: The spend info is inside an Arc inside a Mutex. Ranged descriptors can be created but have to be converted (todo) before they can be spent. Removed the cmr() method because it is no longer used.

This might be useful when creating xpub descriptors with unspendable internal key.

This enables us to derive children descriptors from parent descriptors with ranged xpubs. Copied from rust_miniscript. Added a unit test.

This enables us to iterate over all keys of a policy or descriptor. Iterative implementation for Policy. Descriptor uses this to implement the convenience method has_wildcard().

The ToPublic bound was simply unnecessary. (Is there a tool to check this?) Now we can decode policies with xpubs, which I also added a test for. This also enables the decoding of descriptors with general keys. The next commit will drop UnspendableKey to make FromStr even more flexible.

uncomputable · 2023-07-13T13:25:35Z

Fixed and rebased on master.

apoelstra · 2023-07-14T20:12:17Z

src/policy/descriptor.rs

@@ -276,29 +277,50 @@ impl Descriptor<DescriptorPublicKey> {

 impl<Pk: MiniscriptKey> fmt::Display for Descriptor<Pk> {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        fmt::Display::fmt(&self.policy, f)
+        write!(f, "sim({},{})", self.internal_key, self.policy)


In afae99a:

This commit seems to introduce a new sim descriptor. What is the value of having such a descriptor? What is the difference between a sim and a normal tr descriptor?

sim takes a Simplicity policy as second argument while tr takes Miniscript. We can overload tr if you want, but that might be confusing.

I'm confused. The difference between Simplicity and Script happens at the tapleaf level. It wouldn't be "overloading" tr to use it for different kinds of taproot descriptors.

apoelstra · 2023-07-14T20:12:43Z

src/policy/descriptor.rs

+            .and_then(|s| {
+                let mut split = s.split(',');
+                let x = split.next()?;
+                let y = split.next()?;


In afae99a:

This code will do the wrong thing if there is more than one ,. You should use splitn rather than split.

We want to focus on the Simplicity leaves, but Simplicity descriptors are first and foremost Taproot descriptors with an internal key. We have the trait UnspendableKey to construct outputs with unspendable internal key, but for serialization we don't want to be this limited. In particular, it will be annoying to parse a descriptor with xprivs if the unspendable internal key requires special treatment because its private component is unknown.

There is no reason why PolicySatisfier is required for our satisfaction methods. We could even consider removing it entirely / moving it to the test cases.

This is a messy commit but the changes are quite limited: 1) Remove PolicySatisfier because we use generic Satisfier 2) Adapt unit tests and define HashSatisfier and SigSatisfier to that end 3) Check whether thresh satisfaction runs on the Bit Machine. This was uncovered because `env` was suddently unused.

This enables us to handle xpriv descriptors. They don't exist in data, but we can parse to a keymap and an xpub descriptor. This gives us a guarantee that the keymap corresponds to the xpub, so it's safe to use during spending. Copied from rust-bitcoin. I don't like copy-pasting so many LOC but it seems inevitable. There is a lot of boilerplate and repetions that could probably be handled by LISP-style metaprogramming that is not available to us.

This enables us to work with pubkey descriptors instead of inaccessible xpubs without wildcards. Again copied from rust-miniscript.

Newly-released rustc 1.71 no longer compiles our rust-miniscript dependency. Patch rust-miniscript, then elements-miniscript, then this, to hack around it.

uncomputable · 2023-07-15T12:34:26Z

Same CI failure as in #158 . Cherry-picked the fix.

uncomputable · 2023-07-20T13:29:54Z

Superseded by #162. We will use ideas from this PR when we implement Simplicity descriptors over in elements-miniscript. But there is no reason to keep this PR open.

2ff1a17 Bump MSRV to 1.58.0 (Christian Lewe) 8bb85e3 examples: Adapt to Simplicity (Christian Lewe) f85036a bitcoind-tests: Adapt to Simplicity (Christian Lewe) 029848c psbt: Add support for Simplicity (Christian Lewe) 0c62c05 tr: Weight calculations for Simplicity (Christian Lewe) 2a077f5 tr: Spend Simplicity descriptors (Christian Lewe) 3a8c495 tr: Implement Simplicity spending info (Christian Lewe) 4ffcc00 tr: FromStr for Simplicity policy inside Tr (Christian Lewe) 20073b1 tr: Todo sanity check for Simplicity descriptors (Christian Lewe) edd15f3 tr: implement ForEachKey for Simplicity descriptors (Christian Lewe) 24b5296 simplicity: Parse policy (Christian Lewe) 5e06478 tr: Add Simplicity leaf to TapTree (Christian Lewe) 3e7440d fixme: Add rust-simplicity dependency (Christian Lewe) Pull request description: Takes ideas from BlockstreamResearch/rust-simplicity#154 and implements Simplicity descriptors as a special kind of script-spend inside a Taproot descriptor. Simplicity and Miniscript can be mixed in the same tree. `TapLeafScript` is an interface that unifies both worlds. All methods use this interface to work as normal. ACKs for top commit: apoelstra: ACK 2ff1a17 Tree-SHA512: cb31e8221ab976e0ab505354a1c3267d62a0c9c98c239c30ceed486f04a0fd81ce962861ef3c945438df68be5ef4d5b1e9205878de63dbeca3a5d11fbf2a1575

uncomputable force-pushed the descriptors branch 2 times, most recently from 4792869 to afc4068 Compare July 12, 2023 15:04

uncomputable force-pushed the descriptors branch from afc4068 to 8394fe7 Compare July 12, 2023 15:12

uncomputable marked this pull request as draft July 12, 2023 15:13

uncomputable marked this pull request as ready for review July 12, 2023 15:34

uncomputable force-pushed the descriptors branch from 7232899 to 5eb5195 Compare July 12, 2023 22:20

uncomputable added 5 commits July 13, 2023 14:59

descriptor: UnspendableKey for DescriptorPublicKey

ef5779c

This might be useful when creating xpub descriptors with unspendable internal key.

descriptor: at_derivation_index

e721652

This enables us to derive children descriptors from parent descriptors with ranged xpubs. Copied from rust_miniscript. Added a unit test.

descriptor: Implement ForEachKey

2ee1d2e

This enables us to iterate over all keys of a policy or descriptor. Iterative implementation for Policy. Descriptor uses this to implement the convenience method has_wildcard().

uncomputable force-pushed the descriptors branch 2 times, most recently from ea3e89a to 6eed8a0 Compare July 13, 2023 13:25

apoelstra reviewed Jul 14, 2023

View reviewed changes

uncomputable added 5 commits July 15, 2023 13:04

policy: Use generic Satisfier

6e549f7

There is no reason why PolicySatisfier is required for our satisfaction methods. We could even consider removing it entirely / moving it to the test cases.

descriptor: derived_descriptor

bcd35f8

This enables us to work with pubkey descriptors instead of inaccessible xpubs without wildcards. Again copied from rust-miniscript.

uncomputable force-pushed the descriptors branch from 6eed8a0 to bcd35f8 Compare July 15, 2023 11:05

Cargo.toml: patch for rust-lang/rust#110475

1b8a825

Newly-released rustc 1.71 no longer compiles our rust-miniscript dependency. Patch rust-miniscript, then elements-miniscript, then this, to hack around it.

uncomputable marked this pull request as draft July 15, 2023 15:24

uncomputable closed this Jul 20, 2023

uncomputable mentioned this pull request Aug 3, 2023

Simplicity descriptors ElementsProject/elements-miniscript#50

Merged

uncomputable deleted the descriptors branch October 2, 2023 14:31

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Ranged descriptors #154

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