Move from_key_and_merkle_root to extension trait
What the developer wrote
Authored by Mitchell Bagot
Move from_key_and_merkle_root to extension trait
The from_key_and_merkle_root method on the TapTweakHash type is the
only part of the taproot-primitives crate that causes a dependency on
the crypto crate. By moving this back to bitcoin, we can remove the
dependency on crypto, allows these types to stabilise in primitives
without waiting on crypto to stabilise.
Move from_key_and_merkle_root to new extension trait TapTweakHashExt in
bitcoin.
What changed, and why it matters
This commit is a routine code reorganization. It moves one function, `from_key_and_merkle_root`, out of a low-level crate (`taproot-primitives`) and into a higher-level crate (`bitcoin`) as an 'extension trait.' The goal is to remove an internal dependency so the low-level crate can stabilize sooner. The actual computation performed by the function is unchanged.
No security action required. Treat as normal refactoring. Reviewers may optionally verify that downstream users of `taproot-primitives` still have access to equivalent functionality through the `bitcoin` crate's extension trait.
Security signals we found
No security-relevant behavioral change: the hashing algorithm, inputs, and output type remain identical.
No new dependencies introduced; instead, one dependency edge is removed from `taproot-primitives`.
No memory-safety, cryptographic, or input-validation changes are present in the diff.
No vendor disclosure, CVE, or researcher attribution is present in the commit or supplied references.
Evidence from the diff
The patch relocates TapTweakHash::from_key_and_merkle_root from taproot-primitives/src/lib.rs to a new TapTweakHashExt extension trait in bitcoin/src/taproot/mod.rs. The implementation body is copied verbatim, including the SHA-256 engine construction, key serialization, optional Merkle-root hashing, and scalar conversion. The change removes taproot-primitives’ dependency on crypto::key::UntweakedPublicKey and hashes::HashEngine under the alloc feature. A Sealed trait impl is added for TapTweakHash. Call sites in bitcoin/src/crypto/key.rs now import TapTweakHashExt as _.
Changed components
bitcoin/src/taproot/mod.rsbitcoin/src/crypto/key.rstaproot-primitives/src/lib.rsInspect captured patch +26 / −25
diff --git a/bitcoin/src/crypto/key.rs b/bitcoin/src/crypto/key.rs
index 3bcd92ba..c1549bf7 100644
--- a/bitcoin/src/crypto/key.rs
+++ b/bitcoin/src/crypto/key.rs
@@ -12,7 +12,7 @@ use crate::internal_macros::define_extension_trait;
use crate::script::{self, PushBytes, WitnessScriptBuf};
#[cfg(feature = "secp-recovery")]
use crate::sign_message::MessageSignature;
-use crate::taproot::{TapNodeHash, TapTweakHash};
+use crate::taproot::{TapNodeHash, TapTweakHash, TapTweakHashExt as _};
#[rustfmt::skip] // Keep public re-exports separate.
pub use secp256k1::{constants, Parity, Verification};
diff --git a/bitcoin/src/taproot/mod.rs b/bitcoin/src/taproot/mod.rs
index e5037fed..12f25de8 100644
--- a/bitcoin/src/taproot/mod.rs
+++ b/bitcoin/src/taproot/mod.rs
@@ -99,10 +99,35 @@ crate::internal_macros::define_extension_trait! {
}
}
+crate::internal_macros::define_extension_trait! {
+ /// Extension functionality for the [`TapTweakHash`] type.
+ pub trait TapTweakHashExt impl for TapTweakHash {
+ /// Constructs a new BIP-0341 [`TapTweakHash`] from key and Merkle root. Produces `H_taptweak(P||R)` where
+ /// `P` is the internal key and `R` is the Merkle root.
+ fn from_key_and_merkle_root<K: Into<UntweakedPublicKey>>(
+ internal_key: K,
+ merkle_root: Option<TapNodeHash>,
+ ) -> Self {
+ let internal_key = internal_key.into();
+ let mut eng = sha256t::Hash::<TapTweakTag>::engine();
+ // always hash the key
+ eng.input(&internal_key.serialize().0);
+ if let Some(h) = merkle_root {
+ eng.input(h.as_ref());
+ } else {
+ // nothing to hash
+ }
+ let inner = sha256t::Hash::<TapTweakTag>::from_engine(eng);
+ Self::from_byte_array(inner.to_byte_array())
+ }
+ }
+}
+
mod sealed {
pub trait Sealed {}
impl Sealed for super::TapLeafHash {}
impl Sealed for super::TapNodeHash {}
+ impl Sealed for super::TapTweakHash {}
}
/// Computes branch hash given two hashes of the nodes underneath it and returns
diff --git a/taproot-primitives/src/lib.rs b/taproot-primitives/src/lib.rs
index 1dc14e17..e07992d6 100644
--- a/taproot-primitives/src/lib.rs
+++ b/taproot-primitives/src/lib.rs
@@ -36,10 +36,6 @@ use core::fmt;
#[cfg(feature = "arbitrary")]
use arbitrary::{Arbitrary, Unstructured};
-#[cfg(feature = "alloc")]
-use crypto::key::UntweakedPublicKey;
-#[cfg(feature = "alloc")]
-use hashes::HashEngine;
use hashes::{hash_newtype, sha256t, sha256t_tag};
use secp256k1::Scalar;
@@ -122,26 +118,6 @@ impl From<TapLeafHash> for TapNodeHash {
}
impl TapTweakHash {
- /// Constructs a new BIP-0341 [`TapTweakHash`] from key and Merkle root. Produces `H_taptweak(P||R)` where
- /// `P` is the internal key and `R` is the Merkle root.
- #[cfg(feature = "alloc")]
- pub fn from_key_and_merkle_root<K: Into<UntweakedPublicKey>>(
- internal_key: K,
- merkle_root: Option<TapNodeHash>,
- ) -> Self {
- let internal_key = internal_key.into();
- let mut eng = sha256t::Hash::<TapTweakTag>::engine();
- // always hash the key
- eng.input(&internal_key.serialize().0);
- if let Some(h) = merkle_root {
- eng.input(h.as_ref());
- } else {
- // nothing to hash
- }
- let inner = sha256t::Hash::<TapTweakTag>::from_engine(eng);
- Self::from_byte_array(inner.to_byte_array())
- }
-
/// Converts a `TapTweakHash` into a `Scalar` ready for use with key tweaking API.
#[allow(clippy::missing_panics_doc)]
pub fn to_scalar(self) -> Scalar {
Why this scored 18/100
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