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Introduce taproot hash type extension traits 

Introduce three extension traits for the taproot hash types. All logic
for the hash types is now within the extension traits.
This commit is contained in:
Tobin C. Harding 2024-10-22 13:39:44 +11:00
parent c30ef617fb
commit 24e944ed82
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GPG Key ID: 40BF9E4C269D6607
4 changed files with 55 additions and 45 deletions
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2
bitcoin/src/blockdata/script/borrowed.rs
View File

@ -14,7 +14,7 @@ use crate::opcodes::all::*;
use crate::opcodes::{self, Opcode};
use crate::policy::DUST_RELAY_TX_FEE;
use crate::prelude::{sink, DisplayHex, String, ToString};
use crate::taproot::{LeafVersion, TapLeafHash};
use crate::taproot::{LeafVersion, TapLeafHash, TapLeafHashExt as _};
use crate::FeeRate;
#[rustfmt::skip] // Keep public re-exports separate.

2
bitcoin/src/crypto/key.rs
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@ -20,7 +20,7 @@ use crate::internal_macros::impl_asref_push_bytes;
use crate::network::NetworkKind;
use crate::prelude::{DisplayHex, String, Vec};
use crate::script::{self, ScriptBuf};
use crate::taproot::{TapNodeHash, TapTweakHash};
use crate::taproot::{TapNodeHash, TapTweakHash, TapTweakHashExt as _};
#[rustfmt::skip] // Keep public re-exports separate.
pub use secp256k1::{constants, Keypair, Parity, Secp256k1, Verification, XOnlyPublicKey};

1
bitcoin/src/crypto/sighash.rs
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@ -1509,6 +1509,7 @@ mod tests {
use crate::consensus::deserialize;
use crate::locktime::absolute;
use crate::script::ScriptBufExt as _;
use crate::taproot::TapTweakHashExt as _;
extern crate serde_json;

95
bitcoin/src/taproot/mod.rs
View File

@ -62,40 +62,46 @@ hash_newtype! {
pub struct TapTweakHash(sha256t::Hash<TapTweakTag>);
}
impl TapTweakHash {
/// Creates a new BIP341 [`TapTweakHash`] from key and tweak. Produces `H_taptweak(P||R)` where
/// `P` is the internal key and `R` is the Merkle root.
pub fn from_key_and_tweak(
internal_key: UntweakedPublicKey,
merkle_root: Option<TapNodeHash>,
) -> TapTweakHash {
let mut eng = sha256t::Hash::<TapTweakTag>::engine();
// always hash the key
eng.input(&internal_key.serialize());
if let Some(h) = merkle_root {
eng.input(h.as_ref());
} else {
// nothing to hash
crate::internal_macros::define_extension_trait! {
/// Extension functionality for the [`TapTweakHash`] type.
pub trait TapTweakHashExt impl for TapTweakHash {
/// Creates a new BIP341 [`TapTweakHash`] from key and tweak. Produces `H_taptweak(P||R)` where
/// `P` is the internal key and `R` is the Merkle root.
fn from_key_and_tweak(
internal_key: UntweakedPublicKey,
merkle_root: Option<TapNodeHash>,
) -> TapTweakHash {
let mut eng = sha256t::Hash::<TapTweakTag>::engine();
// always hash the key
eng.input(&internal_key.serialize());
if let Some(h) = merkle_root {
eng.input(h.as_ref());
} else {
// nothing to hash
}
let inner = sha256t::Hash::<TapTweakTag>::from_engine(eng);
TapTweakHash::from_byte_array(inner.to_byte_array())
}
let inner = sha256t::Hash::<TapTweakTag>::from_engine(eng);
TapTweakHash::from_byte_array(inner.to_byte_array())
}
/// Converts a `TapTweakHash` into a `Scalar` ready for use with key tweaking API.
pub fn to_scalar(self) -> Scalar {
// This is statistically extremely unlikely to panic.
Scalar::from_be_bytes(self.to_byte_array()).expect("hash value greater than curve order")
/// Converts a `TapTweakHash` into a `Scalar` ready for use with key tweaking API.
fn to_scalar(self) -> Scalar {
// This is statistically extremely unlikely to panic.
Scalar::from_be_bytes(self.to_byte_array()).expect("hash value greater than curve order")
}
}
}
impl TapLeafHash {
/// Computes the leaf hash from components.
pub fn from_script(script: &Script, ver: LeafVersion) -> TapLeafHash {
let mut eng = sha256t::Hash::<TapLeafTag>::engine();
ver.to_consensus().consensus_encode(&mut eng).expect("engines don't error");
script.consensus_encode(&mut eng).expect("engines don't error");
let inner = sha256t::Hash::<TapTweakTag>::from_engine(eng);
TapLeafHash::from_byte_array(inner.to_byte_array())
crate::internal_macros::define_extension_trait! {
/// Extension functionality for the [`TapLeafHash`] type.
pub trait TapLeafHashExt impl for TapLeafHash {
/// Computes the leaf hash from components.
fn from_script(script: &Script, ver: LeafVersion) -> TapLeafHash {
let mut eng = sha256t::Hash::<TapLeafTag>::engine();
ver.to_consensus().consensus_encode(&mut eng).expect("engines don't error");
script.consensus_encode(&mut eng).expect("engines don't error");
let inner = sha256t::Hash::<TapTweakTag>::from_engine(eng);
TapLeafHash::from_byte_array(inner.to_byte_array())
}
}
}
@ -107,22 +113,25 @@ impl From<&LeafNode> for TapNodeHash {
fn from(leaf: &LeafNode) -> TapNodeHash { leaf.node_hash() }
}
impl TapNodeHash {
/// Computes branch hash given two hashes of the nodes underneath it.
pub fn from_node_hashes(a: TapNodeHash, b: TapNodeHash) -> TapNodeHash {
combine_node_hashes(a, b).0
}
crate::internal_macros::define_extension_trait! {
/// Extension functionality for the [`TapNodeHash`] type.
pub trait TapNodeHashExt impl for TapNodeHash {
/// Computes branch hash given two hashes of the nodes underneath it.
fn from_node_hashes(a: TapNodeHash, b: TapNodeHash) -> TapNodeHash {
combine_node_hashes(a, b).0
}
/// Assumes the given 32 byte array as hidden [`TapNodeHash`].
///
/// Similar to [`TapLeafHash::from_byte_array`], but explicitly conveys that the
/// hash is constructed from a hidden node. This also has better ergonomics
/// because it does not require the caller to import the Hash trait.
pub fn assume_hidden(hash: [u8; 32]) -> TapNodeHash { TapNodeHash::from_byte_array(hash) }
/// Assumes the given 32 byte array as hidden [`TapNodeHash`].
///
/// Similar to [`TapLeafHash::from_byte_array`], but explicitly conveys that the
/// hash is constructed from a hidden node. This also has better ergonomics
/// because it does not require the caller to import the Hash trait.
fn assume_hidden(hash: [u8; 32]) -> TapNodeHash { TapNodeHash::from_byte_array(hash) }
/// Computes the [`TapNodeHash`] from a script and a leaf version.
pub fn from_script(script: &Script, ver: LeafVersion) -> TapNodeHash {
TapNodeHash::from(TapLeafHash::from_script(script, ver))
/// Computes the [`TapNodeHash`] from a script and a leaf version.
fn from_script(script: &Script, ver: LeafVersion) -> TapNodeHash {
TapNodeHash::from(TapLeafHash::from_script(script, ver))
}
}
}