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Merge rust-bitcoin/rust-bitcoin#926: Remove redundant code computing tap hashes 

f3ebfd6f8b Remove repeated tap branch hash computing logic (Dr Maxim Orlovsky)
1b28375658 Abstract tap branch hash computing into a dedicated method (Dr Maxim Orlovsky)

Pull request description:

ACKs for top commit:
  apoelstra:
    ACK f3ebfd6f8b

Tree-SHA512: d66d544df324a7d25c8cc9dc48ddedf086ac87eb2ed09a8d7a568cc1488ae44e0807d53ccb7a6e61dbeef0d3d62a1cacf0d69ba7b8de9178ac5c13bae944d08b
This commit is contained in:
sanket1729 2022-04-01 11:33:23 -07:00
parent 9316c52946 f3ebfd6f8b
commit 7fa8ce0bd0
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1 changed files with 21 additions and 18 deletions
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39
src/util/taproot.rs
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@ -131,6 +131,21 @@ impl TapLeafHash {
} }
} }
impl TapBranchHash {
/// Computes branch hash given two hashes of the nodes underneath it.
pub fn from_node_hashes(a: sha256::Hash, b: sha256::Hash) -> TapBranchHash {
let mut eng = TapBranchHash::engine();
if a < b {
eng.input(&a);
eng.input(&b);
} else {
eng.input(&b);
eng.input(&a);
};
TapBranchHash::from_engine(eng)
}
}
/// Maximum depth of a taproot tree script spend path. /// Maximum depth of a taproot tree script spend path.
// https://github.com/bitcoin/bitcoin/blob/e826b22da252e0599c61d21c98ff89f366b3120f/src/script/interpreter.h#L229 // https://github.com/bitcoin/bitcoin/blob/e826b22da252e0599c61d21c98ff89f366b3120f/src/script/interpreter.h#L229
pub const TAPROOT_CONTROL_MAX_NODE_COUNT: usize = 128; pub const TAPROOT_CONTROL_MAX_NODE_COUNT: usize = 128;
@ -565,16 +580,9 @@ impl NodeInfo {
b_leaf.merkle_branch.push(a.hash)?; // add hashing partner b_leaf.merkle_branch.push(a.hash)?; // add hashing partner
all_leaves.push(b_leaf); all_leaves.push(b_leaf);
} }
let mut eng = TapBranchHash::engine(); let hash = TapBranchHash::from_node_hashes(a.hash, b.hash);
if a.hash < b.hash {
eng.input(&a.hash);
eng.input(&b.hash);
} else {
eng.input(&b.hash);
eng.input(&a.hash);
};
Ok(Self { Ok(Self {
hash: sha256::Hash::from_engine(eng), hash: sha256::Hash::from_inner(hash.into_inner()),
leaves: all_leaves, leaves: all_leaves,
}) })
} }
@ -779,16 +787,11 @@ impl ControlBlock {
let mut curr_hash = TapBranchHash::from_inner(leaf_hash.into_inner()); let mut curr_hash = TapBranchHash::from_inner(leaf_hash.into_inner());
// Verify the proof // Verify the proof
for elem in self.merkle_branch.as_inner() { for elem in self.merkle_branch.as_inner() {
let mut eng = TapBranchHash::engine();
if curr_hash.as_inner() < elem.as_inner() {
eng.input(&curr_hash);
eng.input(elem);
} else {
eng.input(elem);
eng.input(&curr_hash);
}
// Recalculate the curr hash as parent hash // Recalculate the curr hash as parent hash
curr_hash = TapBranchHash::from_engine(eng); curr_hash = TapBranchHash::from_node_hashes(
sha256::Hash::from_inner(curr_hash.into_inner()),
*elem
);
} }
// compute the taptweak // compute the taptweak
let tweak = TapTweakHash::from_key_and_tweak(self.internal_key, Some(curr_hash)); let tweak = TapTweakHash::from_key_and_tweak(self.internal_key, Some(curr_hash));