// Rust Bitcoin Library // Written in 2019 by // The rust-bitcoin developers. // To the extent possible under law, the author(s) have dedicated all // copyright and related and neighboring rights to this software to // the public domain worldwide. This software is distributed without // any warranty. // // You should have received a copy of the CC0 Public Domain Dedication // along with this software. // If not, see . // //! Bitcoin Taproot. //! //! This module provides support for taproot tagged hashes. //! use prelude::*; use io; use secp256k1::{self, Secp256k1}; use core::fmt; use core::cmp::Reverse; #[cfg(feature = "std")] use std::error; use hashes::{sha256, sha256t, Hash, HashEngine}; use schnorr::{TweakedPublicKey, UntweakedPublicKey, TapTweak}; use Script; use consensus::Encodable; /// The SHA-256 midstate value for the TapLeaf hash. const MIDSTATE_TAPLEAF: [u8; 32] = [ 156, 224, 228, 230, 124, 17, 108, 57, 56, 179, 202, 242, 195, 15, 80, 137, 211, 243, 147, 108, 71, 99, 110, 96, 125, 179, 62, 234, 221, 198, 240, 201, ]; // 9ce0e4e67c116c3938b3caf2c30f5089d3f3936c47636e607db33eeaddc6f0c9 /// The SHA-256 midstate value for the TapBranch hash. const MIDSTATE_TAPBRANCH: [u8; 32] = [ 35, 168, 101, 169, 184, 164, 13, 167, 151, 124, 30, 4, 196, 158, 36, 111, 181, 190, 19, 118, 157, 36, 201, 183, 181, 131, 181, 212, 168, 210, 38, 210, ]; // 23a865a9b8a40da7977c1e04c49e246fb5be13769d24c9b7b583b5d4a8d226d2 /// The SHA-256 midstate value for the TapTweak hash. const MIDSTATE_TAPTWEAK: [u8; 32] = [ 209, 41, 162, 243, 112, 28, 101, 93, 101, 131, 182, 195, 185, 65, 151, 39, 149, 244, 226, 50, 148, 253, 84, 244, 162, 174, 141, 133, 71, 202, 89, 11, ]; // d129a2f3701c655d6583b6c3b941972795f4e23294fd54f4a2ae8d8547ca590b /// The SHA-256 midstate value for the TapSigHash hash. const MIDSTATE_TAPSIGHASH: [u8; 32] = [ 245, 4, 164, 37, 215, 248, 120, 59, 19, 99, 134, 138, 227, 229, 86, 88, 110, 238, 148, 93, 188, 120, 136, 221, 2, 166, 226, 195, 24, 115, 254, 159, ]; // f504a425d7f8783b1363868ae3e556586eee945dbc7888dd02a6e2c31873fe9f /// Internal macro to speficy the different taproot tagged hashes. macro_rules! sha256t_hash_newtype { ($newtype:ident, $tag:ident, $midstate:ident, $midstate_len:expr, $docs:meta, $reverse: expr) => { sha256t_hash_newtype!($newtype, $tag, $midstate, $midstate_len, $docs, $reverse, stringify!($newtype)); }; ($newtype:ident, $tag:ident, $midstate:ident, $midstate_len:expr, $docs:meta, $reverse: expr, $sname:expr) => { #[doc = "The tag used for ["] #[doc = $sname] #[doc = "]"] #[derive(Copy, Clone, PartialEq, Eq, Default, PartialOrd, Ord, Hash)] pub struct $tag; impl sha256t::Tag for $tag { fn engine() -> sha256::HashEngine { let midstate = sha256::Midstate::from_inner($midstate); sha256::HashEngine::from_midstate(midstate, $midstate_len) } } hash_newtype!($newtype, sha256t::Hash<$tag>, 32, $docs, $reverse); }; } // Taproot test vectors from BIP-341 state the hashes without any reversing sha256t_hash_newtype!(TapLeafHash, TapLeafTag, MIDSTATE_TAPLEAF, 64, doc="Taproot-tagged hash for tapscript Merkle tree leafs", false ); sha256t_hash_newtype!(TapBranchHash, TapBranchTag, MIDSTATE_TAPBRANCH, 64, doc="Taproot-tagged hash for tapscript Merkle tree branches", false ); sha256t_hash_newtype!(TapTweakHash, TapTweakTag, MIDSTATE_TAPTWEAK, 64, doc="Taproot-tagged hash for public key tweaks", false ); sha256t_hash_newtype!(TapSighashHash, TapSighashTag, MIDSTATE_TAPSIGHASH, 64, doc="Taproot-tagged hash for the taproot signature hash", false ); impl TapTweakHash { /// Create a new BIP341 [`TapTweakHash`] from key and tweak /// Produces H_taptweak(P||R) where P is internal key and R is the merkle root pub fn from_key_and_tweak( internal_key: UntweakedPublicKey, merkle_root: Option, ) -> TapTweakHash { let mut eng = TapTweakHash::engine(); // always hash the key eng.input(&internal_key.serialize()); if let Some(h) = merkle_root { eng.input(&h); } else { // nothing to hash } TapTweakHash::from_engine(eng) } } impl TapLeafHash { /// function to compute leaf hash from components pub fn from_script(script: &Script, ver: LeafVersion) -> TapLeafHash { let mut eng = TapLeafHash::engine(); ver.as_u8() .consensus_encode(&mut eng) .expect("engines don't error"); script .consensus_encode(&mut eng) .expect("engines don't error"); TapLeafHash::from_engine(eng) } } /// Maximum depth of a Taproot Tree Script spend path // https://github.com/bitcoin/bitcoin/blob/e826b22da252e0599c61d21c98ff89f366b3120f/src/script/interpreter.h#L229 pub const TAPROOT_CONTROL_MAX_NODE_COUNT: usize = 128; /// Size of a taproot control node // https://github.com/bitcoin/bitcoin/blob/e826b22da252e0599c61d21c98ff89f366b3120f/src/script/interpreter.h#L228 pub const TAPROOT_CONTROL_NODE_SIZE: usize = 32; /// Tapleaf mask for getting the leaf version from first byte of control block // https://github.com/bitcoin/bitcoin/blob/e826b22da252e0599c61d21c98ff89f366b3120f/src/script/interpreter.h#L225 pub const TAPROOT_LEAF_MASK: u8 = 0xfe; /// Tapscript leaf version // https://github.com/bitcoin/bitcoin/blob/e826b22da252e0599c61d21c98ff89f366b3120f/src/script/interpreter.h#L226 pub const TAPROOT_LEAF_TAPSCRIPT: u8 = 0xc0; /// Tapscript control base size // https://github.com/bitcoin/bitcoin/blob/e826b22da252e0599c61d21c98ff89f366b3120f/src/script/interpreter.h#L227 pub const TAPROOT_CONTROL_BASE_SIZE: usize = 33; /// Tapscript control max size // https://github.com/bitcoin/bitcoin/blob/e826b22da252e0599c61d21c98ff89f366b3120f/src/script/interpreter.h#L230 pub const TAPROOT_CONTROL_MAX_SIZE: usize = TAPROOT_CONTROL_BASE_SIZE + TAPROOT_CONTROL_NODE_SIZE * TAPROOT_CONTROL_MAX_NODE_COUNT; // type alias for versioned tap script corresponding merkle proof type ScriptMerkleProofMap = BTreeMap<(Script, LeafVersion), BTreeSet>; /// Data structure for representing Taproot spending information. /// Taproot output corresponds to a combination of a /// single public key condition (known the internal key), and zero or more /// general conditions encoded in scripts organized in the form of a binary tree. /// /// Taproot can be spent be either: /// - Spending using the key path i.e., with secret key corresponding to the output_key /// - By satisfying any of the scripts in the script spent path. Each script can be satisfied by providing /// a witness stack consisting of the script's inputs, plus the script itself and the control block. /// /// If one or more of the spending conditions consist of just a single key (after aggregation), /// the most likely one should be made the internal key. /// See [BIP341](https://github.com/bitcoin/bips/blob/master/bip-0341.mediawiki) for more details /// on choosing internal keys for a taproot application /// /// Note: This library currently does not support [annex](https://github.com/bitcoin/bips/blob/master/bip-0341.mediawiki#cite_note-5) #[derive(Debug, Clone, PartialEq, Eq, PartialOrd, Ord, Hash)] pub struct TaprootSpendInfo { /// The BIP341 internal key. internal_key: UntweakedPublicKey, /// The Merkle root of the script tree (None if there are no scripts) merkle_root: Option, /// The sign final output pubkey as per BIP 341 output_key_parity: bool, /// The tweaked output key output_key: TweakedPublicKey, /// Map from (script, leaf_version) to (sets of) [`TaprootMerkleBranch`]. /// More than one control block for a given script is only possible if it /// appears in multiple branches of the tree. In all cases, keeping one should /// be enough for spending funds, but we keep all of the paths so that /// a full tree can be constructed again from spending data if required. script_map: ScriptMerkleProofMap, } impl TaprootSpendInfo { /// Create a new [`TaprootSpendInfo`] from a list of script(with default script version) and /// weights of satisfaction for that script. The weights represent the probability of /// each branch being taken. If probabilities/weights for each condition are known, /// constructing the tree as a Huffman tree is the optimal way to minimize average /// case satisfaction cost. This function takes input an iterator of tuple(u64, &Script) /// where usize represents the satisfaction weights of the branch. /// For example, [(3, S1), (2, S2), (5, S3)] would construct a TapTree that has optimal /// satisfaction weight when probability for S1 is 30%, S2 is 20% and S3 is 50%. /// /// # Errors: /// /// - When the optimal huffman tree has a depth more than 128 /// - If the provided list of script weights is empty /// /// # Edge Cases: /// - If the script weight calculations overflow, a sub-optimal tree may be generated. This /// should not happen unless you are dealing with billions of branches with weights close to /// 2^32. pub fn with_huffman_tree( secp: &Secp256k1, internal_key: UntweakedPublicKey, script_weights: I, ) -> Result where I: IntoIterator, C: secp256k1::Verification, { let mut node_weights = BinaryHeap::<(Reverse, NodeInfo)>::new(); for (p, leaf) in script_weights { node_weights.push((Reverse(p as u64), NodeInfo::new_leaf_with_ver(leaf, LeafVersion::default()))); } if node_weights.is_empty() { return Err(TaprootBuilderError::IncompleteTree); } while node_weights.len() > 1 { // Combine the last two elements and insert a new node let (p1, s1) = node_weights.pop().expect("len must be at least two"); let (p2, s2) = node_weights.pop().expect("len must be at least two"); // Insert the sum of first two in the tree as a new node // N.B.: p1 + p2 can not practically saturate as you would need to have 2**32 max u32s // from the input to overflow. However, saturating is a reasonable behavior here as // huffman tree construction would treat all such elements as "very likely". let p = Reverse(p1.0.saturating_add(p2.0)); node_weights.push((p, NodeInfo::combine(s1, s2)?)); } // Every iteration of the loop reduces the node_weights.len() by exactly 1 // Therefore, the loop will eventually terminate with exactly 1 element debug_assert!(node_weights.len() == 1); let node = node_weights.pop().expect("huffman tree algorithm is broken").1; return Ok(Self::from_node_info(secp, internal_key, node)); } /// Create a new key spend with internal key and proided merkle root. /// Provide [`None`] for merkle_root if there is no script path. /// /// *Note*: As per BIP341 /// /// When the merkle root is [`None`], the output key commits to an unspendable /// script path instead of having no script path. This is achieved by computing /// the output key point as Q = P + int(hashTapTweak(bytes(P)))G. /// See also [`TaprootSpendInfo::tap_tweak`]. /// Refer to BIP 341 footnote (Why should the output key always have /// a taproot commitment, even if there is no script path?) for more details /// pub fn new_key_spend( secp: &Secp256k1, internal_key: UntweakedPublicKey, merkle_root: Option, ) -> Self { let (output_key, parity) = internal_key.tap_tweak(secp, merkle_root); Self { internal_key: internal_key, merkle_root: merkle_root, output_key_parity: parity, output_key: output_key, script_map: BTreeMap::new(), } } /// Obtain the tweak and parity used to compute the output_key pub fn tap_tweak(&self) -> TapTweakHash { TapTweakHash::from_key_and_tweak(self.internal_key, self.merkle_root) } /// Obtain the internal key pub fn internal_key(&self) -> UntweakedPublicKey { self.internal_key } /// Obtain the merkle root pub fn merkle_root(&self) -> Option { self.merkle_root } /// Output key(the key used in script pubkey) from Spend data. See also /// [`TaprootSpendInfo::output_key_parity`] pub fn output_key(&self) -> TweakedPublicKey { self.output_key } /// Parity of the output key. See also [`TaprootSpendInfo::output_key`] pub fn output_key_parity(&self) -> bool { self.output_key_parity } // Internal function to compute [`TaprootSpendInfo`] from NodeInfo fn from_node_info( secp: &Secp256k1, internal_key: UntweakedPublicKey, node: NodeInfo, ) -> TaprootSpendInfo { // Create as if it is a key spend path with the given merkle root let root_hash = Some(TapBranchHash::from_inner(node.hash.into_inner())); let mut info = TaprootSpendInfo::new_key_spend(secp, internal_key, root_hash); for leaves in node.leaves { let key = (leaves.script, leaves.ver); let value = leaves.merkle_branch; match info.script_map.get_mut(&key) { Some(set) => { set.insert(value); continue; // NLL fix } None => {} } let mut set = BTreeSet::new(); set.insert(value); info.script_map.insert(key, set); } info } /// Access the internal script map pub fn as_script_map(&self) -> &ScriptMerkleProofMap { &self.script_map } /// Obtain a [`ControlBlock`] for particular script with the given version. /// Returns [`None`] if the script is not contained in the [`TaprootSpendInfo`] /// If there are multiple ControlBlocks possible, this returns the shortest one. pub fn control_block(&self, script_ver: &(Script, LeafVersion)) -> Option { let merkle_branch_set = self.script_map.get(script_ver)?; // Choose the smallest one amongst the multiple script maps let smallest = merkle_branch_set .iter() .min_by(|x, y| x.0.len().cmp(&y.0.len())) .expect("Invariant: Script map key must contain non-empty set value"); Some(ControlBlock { internal_key: self.internal_key, output_key_parity: self.output_key_parity, leaf_version: script_ver.1, merkle_branch: smallest.clone(), }) } } /// Builder for building taproot iteratively. Users can specify tap leaf or omitted/hidden /// branches in a DFS(Depth first search) walk to construct this tree. // Similar to Taproot Builder in bitcoin core #[derive(Debug, Clone, PartialEq, Eq, PartialOrd, Ord, Hash)] #[cfg_attr(feature = "serde", derive(Serialize, Deserialize))] pub struct TaprootBuilder { // The following doc-comment is from bitcoin core, but modified for rust // The comment below describes the current state of the builder for a given tree. // // For each level in the tree, one NodeInfo object may be present. branch at index 0 // is information about the root; further values are for deeper subtrees being // explored. // // During the construction of Taptree, for every right branch taken to // reach the position we're currently working in, there will be a (Some(_)) // entry in branch corresponding to the left branch at that level. // // For example, imagine this tree: - N0 - // / \ // N1 N2 // / \ / \ // A B C N3 // / \ // D E // // Initially, branch is empty. After processing leaf A, it would become // {None, None, A}. When processing leaf B, an entry at level 2 already // exists, and it would thus be combined with it to produce a level 1 one, // resulting in {None, N1}. Adding C and D takes us to {None, N1, C} // and {None, N1, C, D} respectively. When E is processed, it is combined // with D, and then C, and then N1, to produce the root, resulting in {N0}. // // This structure allows processing with just O(log n) overhead if the leaves // are computed on the fly. // // As an invariant, there can never be None entries at the end. There can // also not be more than 128 entries (as that would mean more than 128 levels // in the tree). The depth of newly added entries will always be at least // equal to the current size of branch (otherwise it does not correspond // to a depth-first traversal of a tree). branch is only empty if no entries // have ever be processed. branch having length 1 corresponds to being done. // branch: Vec>, } impl TaprootBuilder { /// Create a new instance of [`TaprootBuilder`] pub fn new() -> Self { TaprootBuilder { branch: vec![] } } /// Just like [`TaprootBuilder::add_leaf`] but allows to specify script version pub fn add_leaf_with_ver( self, depth: usize, script: Script, ver: LeafVersion, ) -> Result { let leaf = NodeInfo::new_leaf_with_ver(script, ver); self.insert(leaf, depth) } /// Add a leaf script at a depth `depth` to the builder with default script version. /// This will error if the leave are not provided in a DFS walk order. The depth of the /// root node is 0 and it's immediate child would be at depth 1. /// See [`TaprootBuilder::add_leaf_with_ver`] for adding a leaf with specific version /// See [Wikipedia](https://en.wikipedia.org/wiki/Depth-first_search) for more details pub fn add_leaf(self, depth: usize, script: Script) -> Result { self.add_leaf_with_ver(depth, script, LeafVersion::default()) } /// Add a hidden/omitted node at a depth `depth` to the builder. /// This will error if the node are not provided in a DFS walk order. The depth of the /// root node is 0 and it's immediate child would be at depth 1. pub fn add_hidden(self, depth: usize, hash: sha256::Hash) -> Result { let node = NodeInfo::new_hidden(hash); self.insert(node, depth) } /// Check if the builder is a complete tree pub fn is_complete(&self) -> bool { self.branch.len() == 1 && self.branch[0].is_some() } /// Create [`TaprootSpendInfo`] with the given internal key pub fn finalize( mut self, secp: &Secp256k1, internal_key: UntweakedPublicKey, ) -> Result { if self.branch.len() > 1 { return Err(TaprootBuilderError::IncompleteTree); } let node = self .branch .pop() .ok_or(TaprootBuilderError::EmptyTree)? .expect("Builder invariant: last element of the branch must be some"); Ok(TaprootSpendInfo::from_node_info(secp, internal_key, node)) } pub(crate) fn branch(&self) -> &[Option]{ &self.branch } // Helper function to insert a leaf at a depth fn insert(mut self, mut node: NodeInfo, mut depth: usize) -> Result { // early error on invalid depth. Though this will be checked later // while constructing TaprootMerkelBranch if depth > TAPROOT_CONTROL_MAX_NODE_COUNT { return Err(TaprootBuilderError::InvalidMerkleTreeDepth(depth)); } // We cannot insert a leaf at a lower depth while a deeper branch is unfinished. Doing // so would mean the add_leaf/add_hidden invocations do not correspond to a DFS traversal of a // binary tree. if depth + 1 < self.branch.len() { return Err(TaprootBuilderError::NodeNotInDfsOrder); } while self.branch.len() == depth + 1 { let child = match self.branch.pop() { None => unreachable!("Len of branch checked to be >= 1"), Some(Some(child)) => child, // Needs an explicit push to add the None that we just popped. // Cannot use .last() because of borrow checker issues. Some(None) => { self.branch.push(None); break; } // Cannot combine further }; if depth == 0 { // We are trying to combine two nodes at root level. // Can't propagate further up than the root return Err(TaprootBuilderError::OverCompleteTree); } node = NodeInfo::combine(node, child)?; // Propagate to combine nodes at a lower depth depth -= 1; } if self.branch.len() < depth + 1 { // add enough nodes so that we can insert node at depth `depth` let num_extra_nodes = depth + 1 - self.branch.len(); self.branch .extend((0..num_extra_nodes).into_iter().map(|_| None)); } // Push the last node to the branch self.branch[depth] = Some(node); Ok(self) } } // Internally used structure to represent the node information in taproot tree #[derive(Debug, Clone, PartialEq, Eq, PartialOrd, Ord, Hash)] #[cfg_attr(feature = "serde", derive(Serialize, Deserialize))] pub(crate) struct NodeInfo { /// Merkle Hash for this node pub(crate) hash: sha256::Hash, /// information about leaves inside this node pub(crate) leaves: Vec, } impl NodeInfo { // Create a new NodeInfo with omitted/hidden info fn new_hidden(hash: sha256::Hash) -> Self { Self { hash: hash, leaves: vec![], } } // Create a new leaf with NodeInfo fn new_leaf_with_ver(script: Script, ver: LeafVersion) -> Self { let leaf = LeafInfo::new(script, ver); Self { hash: leaf.hash(), leaves: vec![leaf], } } // Combine two NodeInfo's to create a new parent fn combine(a: Self, b: Self) -> Result { let mut all_leaves = Vec::with_capacity(a.leaves.len() + b.leaves.len()); for mut a_leaf in a.leaves { a_leaf.merkle_branch.push(b.hash)?; // add hashing partner all_leaves.push(a_leaf); } for mut b_leaf in b.leaves { b_leaf.merkle_branch.push(a.hash)?; // add hashing partner all_leaves.push(b_leaf); } let mut eng = TapBranchHash::engine(); if a.hash < b.hash { eng.input(&a.hash); eng.input(&b.hash); } else { eng.input(&b.hash); eng.input(&a.hash); }; Ok(Self { hash: sha256::Hash::from_engine(eng), leaves: all_leaves, }) } } // Internally used structure to store information about taproot leaf node #[derive(Debug, Clone, PartialEq, Eq, PartialOrd, Ord, Hash)] #[cfg_attr(feature = "serde", derive(Serialize, Deserialize))] pub(crate) struct LeafInfo { // The underlying script pub(crate) script: Script, // The leaf version pub(crate) ver: LeafVersion, // The merkle proof(hashing partners) to get this node pub(crate) merkle_branch: TaprootMerkleBranch, } impl LeafInfo { // Create an instance of Self from Script with default version and no merkle branch fn new(script: Script, ver: LeafVersion) -> Self { Self { script: script, ver: ver, merkle_branch: TaprootMerkleBranch(vec![]), } } // Compute a leaf hash for the given leaf fn hash(&self) -> sha256::Hash { let leaf_hash = TapLeafHash::from_script(&self.script, self.ver); sha256::Hash::from_inner(leaf_hash.into_inner()) } } /// The Merkle proof for inclusion of a tree in a taptree hash // The type of hash is sha256::Hash because the vector might contain // both TapBranchHash and TapLeafHash #[derive(Debug, Clone, PartialEq, Eq, PartialOrd, Ord, Hash, Default)] #[cfg_attr(feature = "serde", derive(Serialize, Deserialize))] pub struct TaprootMerkleBranch(Vec); impl TaprootMerkleBranch { /// Obtain a reference to inner pub fn as_inner(&self) -> &[sha256::Hash] { &self.0 } /// Create a merkle proof from slice pub fn from_slice(sl: &[u8]) -> Result { if sl.len() % TAPROOT_CONTROL_NODE_SIZE != 0 { Err(TaprootError::InvalidMerkleBranchSize(sl.len())) } else if sl.len() > TAPROOT_CONTROL_NODE_SIZE * TAPROOT_CONTROL_MAX_NODE_COUNT { Err(TaprootError::InvalidMerkleTreeDepth( sl.len() / TAPROOT_CONTROL_NODE_SIZE, )) } else { let inner = sl // TODO: Use chunks_exact after MSRV changes to 1.31 .chunks(TAPROOT_CONTROL_NODE_SIZE) .map(|chunk| { sha256::Hash::from_slice(chunk) .expect("chunk exact always returns the correct size") }) .collect(); Ok(TaprootMerkleBranch(inner)) } } /// Serialize to a writer. Returns the number of bytes written pub fn encode(&self, mut writer: Write) -> io::Result { let mut written = 0; for hash in self.0.iter() { written += writer.write(hash)?; } Ok(written) } /// Serialize self as bytes pub fn serialize(&self) -> Vec { self.0.iter().map(|e| e.as_inner()).flatten().map(|x| *x).collect::>() } // Internal function to append elements to proof fn push(&mut self, h: sha256::Hash) -> Result<(), TaprootBuilderError> { if self.0.len() >= TAPROOT_CONTROL_MAX_NODE_COUNT { Err(TaprootBuilderError::InvalidMerkleTreeDepth(self.0.len())) } else { self.0.push(h); Ok(()) } } /// Create a MerkleProof from Vec<[`sha256::Hash`]>. Returns an error when /// inner proof len is more than TAPROOT_CONTROL_MAX_NODE_COUNT (128) pub fn from_inner(inner: Vec) -> Result { if inner.len() > TAPROOT_CONTROL_MAX_NODE_COUNT { Err(TaprootError::InvalidMerkleTreeDepth(inner.len())) } else { Ok(TaprootMerkleBranch(inner)) } } /// Consume Self to get Vec<[`sha256::Hash`]> pub fn into_inner(self) -> Vec { self.0 } } /// Control Block data structure used in Tapscript satisfaction #[derive(Debug, Clone, PartialEq, Eq, PartialOrd, Ord, Hash)] #[cfg_attr(feature = "serde", derive(Serialize, Deserialize))] pub struct ControlBlock { /// The tapleaf version, pub leaf_version: LeafVersion, /// The parity of the output key (NOT THE INTERNAL KEY WHICH IS ALWAYS XONLY) pub output_key_parity: bool, /// The internal key pub internal_key: UntweakedPublicKey, /// The merkle proof of a script associated with this leaf pub merkle_branch: TaprootMerkleBranch, } impl ControlBlock { /// Obtain a ControlBlock from slice. This is an extra witness element /// that provides the proof that taproot script pubkey is correctly computed /// with some specified leaf hash. This is the last element in /// taproot witness when spending a output via script path. /// /// # Errors: /// - If the control block size is not of the form 33 + 32m where /// 0 <= m <= 128, InvalidControlBlock is returned pub fn from_slice(sl: &[u8]) -> Result { if sl.len() < TAPROOT_CONTROL_BASE_SIZE || (sl.len() - TAPROOT_CONTROL_BASE_SIZE) % TAPROOT_CONTROL_NODE_SIZE != 0 { return Err(TaprootError::InvalidControlBlockSize(sl.len())); } let output_key_parity = (sl[0] & 1) == 1; let leaf_version = LeafVersion::from_u8(sl[0] & TAPROOT_LEAF_MASK)?; let internal_key = UntweakedPublicKey::from_slice(&sl[1..TAPROOT_CONTROL_BASE_SIZE]) .map_err(TaprootError::InvalidInternalKey)?; let merkle_branch = TaprootMerkleBranch::from_slice(&sl[TAPROOT_CONTROL_BASE_SIZE..])?; Ok(ControlBlock { leaf_version, output_key_parity, internal_key, merkle_branch, }) } /// Obtain the size of control block. Faster and more efficient than calling /// serialize() followed by len(). Can be handy for fee estimation pub fn size(&self) -> usize { TAPROOT_CONTROL_BASE_SIZE + TAPROOT_CONTROL_NODE_SIZE * self.merkle_branch.as_inner().len() } /// Serialize to a writer. Returns the number of bytes written pub fn encode(&self, mut writer: Write) -> io::Result { let first_byte: u8 = (if self.output_key_parity { 1 } else { 0 }) | self.leaf_version.as_u8(); let mut bytes_written = 0; bytes_written += writer.write(&[first_byte])?; bytes_written += writer.write(&self.internal_key.serialize())?; bytes_written += self.merkle_branch.encode(&mut writer)?; Ok(bytes_written) } /// Serialize the control block. This would be required when /// using ControlBlock as a witness element while spending an output via /// script path. This serialization does not include the VarInt prefix that would be /// applied when encoding this element as a witness. pub fn serialize(&self) -> Vec { let mut buf = Vec::with_capacity(self.size()); self.encode(&mut buf) .expect("writers don't error"); buf } /// Verify that a control block is correct proof for a given output key and script /// This only checks that script is contained inside the taptree described by /// output key, full verification must also execute the script with witness data pub fn verify_taproot_commitment( &self, secp: &Secp256k1, output_key: &TweakedPublicKey, script: &Script, ) -> bool { // compute the script hash // Initially the curr_hash is the leaf hash let leaf_hash = TapLeafHash::from_script(&script, self.leaf_version); let mut curr_hash = TapBranchHash::from_inner(leaf_hash.into_inner()); // Verify the proof 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 curr_hash = TapBranchHash::from_engine(eng); } // compute the taptweak let tweak = TapTweakHash::from_key_and_tweak(self.internal_key, Some(curr_hash)); self.internal_key.tweak_add_check( secp, output_key.as_inner(), self.output_key_parity, tweak.into_inner(), ) } } /// The leaf version for tapleafs #[derive(Debug, Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash)] #[cfg_attr(feature = "serde", derive(Serialize, Deserialize))] pub struct LeafVersion(u8); impl Default for LeafVersion { fn default() -> Self { LeafVersion(TAPROOT_LEAF_TAPSCRIPT) } } impl LeafVersion { /// Obtain LeafVersion from u8, will error when last bit of ver is even or /// when ver is 0x50 (ANNEX_TAG) // Text from BIP341: // In order to support some forms of static analysis that rely on // being able to identify script spends without access to the output being // spent, it is recommended to avoid using any leaf versions that would conflict // with a valid first byte of either a valid P2WPKH pubkey or a valid P2WSH script // (that is, both v and v | 1 should be an undefined, invalid or disabled opcode // or an opcode that is not valid as the first opcode). // The values that comply to this rule are the 32 even values between // 0xc0 and 0xfe and also 0x66, 0x7e, 0x80, 0x84, 0x96, 0x98, 0xba, 0xbc, 0xbe pub fn from_u8(ver: u8) -> Result { if ver & TAPROOT_LEAF_MASK == ver && ver != 0x50 { Ok(LeafVersion(ver)) } else { Err(TaprootError::InvalidTaprootLeafVersion(ver)) } } /// Get the inner version from LeafVersion pub fn as_u8(&self) -> u8 { self.0 } } impl Into for LeafVersion { fn into(self) -> u8 { self.0 } } /// Detailed error type for taproot builder #[derive(Debug, Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash)] pub enum TaprootBuilderError { /// Merkle Tree depth must not be more than 128 InvalidMerkleTreeDepth(usize), /// Nodes must be added specified in DFS order NodeNotInDfsOrder, /// Two nodes at depth 0 are not allowed OverCompleteTree, /// Invalid taproot internal key InvalidInternalKey(secp256k1::Error), /// Called finalize on an incomplete tree IncompleteTree, /// Called finalize on a empty tree EmptyTree, } impl fmt::Display for TaprootBuilderError { fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { match *self { TaprootBuilderError::NodeNotInDfsOrder => { write!(f, "add_leaf/add_hidden must be called in DFS walk order",) } TaprootBuilderError::OverCompleteTree => write!( f, "Attempted to create a tree with two nodes at depth 0. There must\ only be a exactly one node at depth 0", ), TaprootBuilderError::InvalidMerkleTreeDepth(d) => write!( f, "Merkle Tree depth({}) must be less than {}", d, TAPROOT_CONTROL_MAX_NODE_COUNT ), TaprootBuilderError::InvalidInternalKey(e) => { write!(f, "Invalid Internal XOnly key : {}", e) } TaprootBuilderError::IncompleteTree => { write!(f, "Called finalize on an incomplete tree") } TaprootBuilderError::EmptyTree => { write!(f, "Called finalize on an empty tree") } } } } #[cfg(feature = "std")] #[cfg_attr(docsrs, doc(cfg(feature = "std")))] impl error::Error for TaprootBuilderError {} /// Detailed error type for taproot utilities #[derive(Debug, Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash)] pub enum TaprootError { /// Proof size must be a multiple of 32 InvalidMerkleBranchSize(usize), /// Merkle Tree depth must not be more than 128 InvalidMerkleTreeDepth(usize), /// The last bit of tapleaf version must be zero InvalidTaprootLeafVersion(u8), /// Invalid Control Block Size InvalidControlBlockSize(usize), /// Invalid taproot internal key InvalidInternalKey(secp256k1::Error), /// Empty TapTree EmptyTree, } impl fmt::Display for TaprootError { fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { match *self { TaprootError::InvalidMerkleBranchSize(sz) => write!( f, "Merkle branch size({}) must be a multiple of {}", sz, TAPROOT_CONTROL_NODE_SIZE ), TaprootError::InvalidMerkleTreeDepth(d) => write!( f, "Merkle Tree depth({}) must be less than {}", d, TAPROOT_CONTROL_MAX_NODE_COUNT ), TaprootError::InvalidTaprootLeafVersion(v) => write!( f, "Leaf version({}) must have the least significant bit 0", v ), TaprootError::InvalidControlBlockSize(sz) => write!( f, "Control Block size({}) must be of the form 33 + 32*m where 0 <= m <= {} ", sz, TAPROOT_CONTROL_MAX_NODE_COUNT ), // TODO: add source when in MSRV TaprootError::InvalidInternalKey(e) => write!(f, "Invalid Internal XOnly key : {}", e), TaprootError::EmptyTree => write!(f, "Taproot Tree must contain at least one script"), } } } #[cfg(feature = "std")] #[cfg_attr(docsrs, doc(cfg(feature = "std")))] impl error::Error for TaprootError {} #[cfg(test)] mod test { use {Address, Network}; use schnorr::TapTweak; use super::*; use hashes::hex::{FromHex, ToHex}; use hashes::sha256t::Tag; use hashes::{sha256, Hash, HashEngine}; use secp256k1::VerifyOnly; use core::str::FromStr; use schnorr; extern crate serde_json; fn tag_engine(tag_name: &str) -> sha256::HashEngine { let mut engine = sha256::Hash::engine(); let tag_hash = sha256::Hash::hash(tag_name.as_bytes()); engine.input(&tag_hash[..]); engine.input(&tag_hash[..]); engine } #[test] fn test_midstates() { // check midstate against hard-coded values assert_eq!(MIDSTATE_TAPLEAF, tag_engine("TapLeaf").midstate().into_inner()); assert_eq!(MIDSTATE_TAPBRANCH, tag_engine("TapBranch").midstate().into_inner()); assert_eq!(MIDSTATE_TAPTWEAK, tag_engine("TapTweak").midstate().into_inner()); assert_eq!(MIDSTATE_TAPSIGHASH, tag_engine("TapSighash").midstate().into_inner()); // test that engine creation roundtrips assert_eq!(tag_engine("TapLeaf").midstate(), TapLeafTag::engine().midstate()); assert_eq!(tag_engine("TapBranch").midstate(), TapBranchTag::engine().midstate()); assert_eq!(tag_engine("TapTweak").midstate(), TapTweakTag::engine().midstate()); assert_eq!(tag_engine("TapSighash").midstate(), TapSighashTag::engine().midstate()); // check that hash creation is the same as building into the same engine fn empty_hash(tag_name: &str) -> [u8; 32] { let mut e = tag_engine(tag_name); e.input(&[]); sha256::Hash::from_engine(e).into_inner() } assert_eq!(empty_hash("TapLeaf"), TapLeafHash::hash(&[]).into_inner()); assert_eq!(empty_hash("TapBranch"), TapBranchHash::hash(&[]).into_inner()); assert_eq!(empty_hash("TapTweak"), TapTweakHash::hash(&[]).into_inner()); assert_eq!(empty_hash("TapSighash"), TapSighashHash::hash(&[]).into_inner()); } #[test] fn test_vectors_core() { //! Test vectors taken from Core // uninitialized writers // CHashWriter writer = HasherTapLeaf; // writer.GetSHA256().GetHex() assert_eq!( TapLeafHash::from_engine(TapLeafTag::engine()).to_hex(), "5212c288a377d1f8164962a5a13429f9ba6a7b84e59776a52c6637df2106facb" ); assert_eq!( TapBranchHash::from_engine(TapBranchTag::engine()).to_hex(), "53c373ec4d6f3c53c1f5fb2ff506dcefe1a0ed74874f93fa93c8214cbe9ffddf" ); assert_eq!( TapTweakHash::from_engine(TapTweakTag::engine()).to_hex(), "8aa4229474ab0100b2d6f0687f031d1fc9d8eef92a042ad97d279bff456b15e4" ); assert_eq!( TapSighashHash::from_engine(TapSighashTag::engine()).to_hex(), "dabc11914abcd8072900042a2681e52f8dba99ce82e224f97b5fdb7cd4b9c803" ); // 0-byte // CHashWriter writer = HasherTapLeaf; // writer << std::vector{}; // writer.GetSHA256().GetHex() // Note that Core writes the 0 length prefix when an empty vector is written. assert_eq!( TapLeafHash::hash(&[0]).to_hex(), "ed1382037800c9dd938dd8854f1a8863bcdeb6705069b4b56a66ec22519d5829" ); assert_eq!( TapBranchHash::hash(&[0]).to_hex(), "92534b1960c7e6245af7d5fda2588db04aa6d646abc2b588dab2b69e5645eb1d" ); assert_eq!( TapTweakHash::hash(&[0]).to_hex(), "cd8737b5e6047fc3f16f03e8b9959e3440e1bdf6dd02f7bb899c352ad490ea1e" ); assert_eq!( TapSighashHash::hash(&[0]).to_hex(), "c2fd0de003889a09c4afcf676656a0d8a1fb706313ff7d509afb00c323c010cd" ); } fn _verify_tap_commitments(secp: &Secp256k1, out_spk_hex: &str, script_hex : &str, control_block_hex: &str) { let out_pk = schnorr::PublicKey::from_str(&out_spk_hex[4..]).unwrap(); let out_pk = TweakedPublicKey::dangerous_assume_tweaked(out_pk); let script = Script::from_hex(script_hex).unwrap(); let control_block = ControlBlock::from_slice(&Vec::::from_hex(control_block_hex).unwrap()).unwrap(); assert_eq!(control_block_hex, control_block.serialize().to_hex()); assert!(control_block.verify_taproot_commitment(secp, &out_pk, &script)); } #[test] fn control_block_verify() { let secp = Secp256k1::verification_only(); // test vectors obtained from printing values in feature_taproot.py from bitcoin core _verify_tap_commitments(&secp, "51205dc8e62b15e0ebdf44751676be35ba32eed2e84608b290d4061bbff136cd7ba9", "6a", "c1a9d6f66cd4b25004f526bfa873e56942f98e8e492bd79ed6532b966104817c2bda584e7d32612381cf88edc1c02e28a296e807c16ad22f591ee113946e48a71e0641e660d1e5392fb79d64838c2b84faf04b7f5f283c9d8bf83e39e177b64372a0cd22eeab7e093873e851e247714eff762d8a30be699ba4456cfe6491b282e193a071350ae099005a5950d74f73ba13077a57bc478007fb0e4d1099ce9cf3d4"); _verify_tap_commitments(&secp, "5120e208c869c40d8827101c5ad3238018de0f3f5183d77a0c53d18ac28ddcbcd8ad", "f4", "c0a0eb12e60a52614986c623cbb6621dcdba3a47e3be6b37e032b7a11c7b98f40090ab1f4890d51115998242ebce636efb9ede1b516d9eb8952dc1068e0335306199aaf103cceb41d9bc37ec231aca89b984b5fd3c65977ce764d51033ac65adb4da14e029b1e154a85bfd9139e7aa2720b6070a4ceba8264ca61d5d3ac27aceb9ef4b54cd43c2d1fd5e11b5c2e93cf29b91ea3dc5b832201f02f7473a28c63246"); _verify_tap_commitments(&secp, "5120567666e7df90e0450bb608e17c01ed3fbcfa5355a5f8273e34e583bfaa70ce09", "203455139bf238a3067bd72ed77e0ab8db590330f55ed58dba7366b53bf4734279ac", "c1a0eb12e60a52614986c623cbb6621dcdba3a47e3be6b37e032b7a11c7b98f400"); _verify_tap_commitments(&secp, "5120580a19e47269414a55eb86d5d0c6c9b371455d9fd2154412a57dec840df99fe1", "6a", "bca0eb12e60a52614986c623cbb6621dcdba3a47e3be6b37e032b7a11c7b98f40042ba1bd1c63c03ccff60d4c4d53a653f87909eb3358e7fa45c9d805231fb08c933e1f4e0f9d17f591df1419df7d5b7eb5f744f404c5ef9ecdb1b89b18cafa3a816d8b5dba3205f9a9c05f866d91f40d2793a7586d502cb42f46c7a11f66ad4aa"); _verify_tap_commitments(&secp, "5120228b94a4806254a38d6efa8a134c28ebc89546209559dfe40b2b0493bafacc5b", "6a50", "c0a0eb12e60a52614986c623cbb6621dcdba3a47e3be6b37e032b7a11c7b98f4009c9aed3dfd11ab0e78bf87ef3bf296269dc4b0f7712140386d6980992bab4b45"); _verify_tap_commitments(&secp, "5120567666e7df90e0450bb608e17c01ed3fbcfa5355a5f8273e34e583bfaa70ce09", "203455139bf238a3067bd72ed77e0ab8db590330f55ed58dba7366b53bf4734279ac", "c1a0eb12e60a52614986c623cbb6621dcdba3a47e3be6b37e032b7a11c7b98f400"); _verify_tap_commitments(&secp, "5120b0a79103c31fe51eea61d2873bad8a25a310da319d7e7a85f825fa7a00ea3f85", "203455139bf238a3067bd72ed77e0ab8db590330f55ed58dba7366b53bf4734279ad51", "c1a0eb12e60a52614986c623cbb6621dcdba3a47e3be6b37e032b7a11c7b98f400"); _verify_tap_commitments(&secp, "5120f2f62e854a0012aeba78cd4ba4a0832447a5262d4c6eb4f1c95c7914b536fc6c", "6a86", "c1a0eb12e60a52614986c623cbb6621dcdba3a47e3be6b37e032b7a11c7b98f4009ad3d30479f0689dbdf59a6b840d60ad485b2effbed1825a75ce19a44e460e09056f60ea686d79cfa4fb79f197b2e905ac857a983be4a5a41a4873e865aa950780c0237de279dc063e67deec46ef8e1bc351bf12c4d67a6d568001faf097e797e6ee620f53cfe0f8acaddf2063c39c3577853bb46d61ffcba5a024c3e1216837"); _verify_tap_commitments(&secp, "51202a4772070b49bae68b44315032cdbf9c40c7c2f896781b32b931b73dbfb26d7e", "6af8", "c0a0eb12e60a52614986c623cbb6621dcdba3a47e3be6b37e032b7a11c7b98f4006f183944a14618fc7fe9ceade0f58e43a19d3c3b179ea6c43c29616413b6971c99aaf103cceb41d9bc37ec231aca89b984b5fd3c65977ce764d51033ac65adb4c3462adec78cd04f3cc156bdadec50def99feae0dc6a23664e8a2b0d42d6ca9eb968dfdf46c23af642b2688351904e0a0630e71ffac5bcaba33b9b2c8a7495ec"); _verify_tap_commitments(&secp, "5120a32b0b8cfafe0f0f8d5870030ba4d19a8725ad345cb3c8420f86ac4e0dff6207", "4c", "e8a0eb12e60a52614986c623cbb6621dcdba3a47e3be6b37e032b7a11c7b98f400615da7ac8d078e5fc7f4690fc2127ba40f0f97cc070ade5b3a7919783d91ef3f13734aab908ae998e57848a01268fe8217d70bc3ee8ea8ceae158ae964a4b5f3af20b50d7019bf47fde210eee5c52f1cfe71cfca78f2d3e7c1fd828c80351525"); _verify_tap_commitments(&secp, "5120b0a79103c31fe51eea61d2873bad8a25a310da319d7e7a85f825fa7a00ea3f85", "203455139bf238a3067bd72ed77e0ab8db590330f55ed58dba7366b53bf4734279ad51", "c1a0eb12e60a52614986c623cbb6621dcdba3a47e3be6b37e032b7a11c7b98f400"); _verify_tap_commitments(&secp, "51208678459f1fa0f80e9b89b8ffdcaf46a022bdf60aa45f1fed9a96145edf4ec400", "6a50", "c0a0eb12e60a52614986c623cbb6621dcdba3a47e3be6b37e032b7a11c7b98f4001eff29e1a89e650076b8d3c56302881d09c9df215774ed99993aaed14acd6615"); _verify_tap_commitments(&secp, "5120017316303aed02bcdec424c851c9eacbe192b013139bd9634c4e19b3475b06e1", "61", "02a0eb12e60a52614986c623cbb6621dcdba3a47e3be6b37e032b7a11c7b98f40050462265ca552b23cbb4fe021b474313c8cb87d4a18b3f7bdbeb2b418279ba31fc6509d829cd42336f563363cb3538d78758e0876c71e13012eb2b656eb0edb051a2420a840d5c8c6c762abc7410af2c311f606b20ca2ace56a8139f84b1379a"); _verify_tap_commitments(&secp, "5120896d4d5d2236e86c6e9320e86d1a7822e652907cbd508360e8c71aefc127c77d", "61", "14a0eb12e60a52614986c623cbb6621dcdba3a47e3be6b37e032b7a11c7b98f4001ab0e9d9a4858a0e69605fe9c5a42d739fbe26fa79650e7074f462b02645f7ea1c91802b298cd91e6b5af57c6a013d93397cd2ecbd5569382cc27becf44ff4fff8960b20f846160c159c58350f6b6072cf1b3daa5185b7a42524fb72cbc252576ae46732b8e31ac24bfa7d72f4c3713e8696f99d8ac6c07e4c820a03f249f144"); _verify_tap_commitments(&secp, "512093c7378d96518a75448821c4f7c8f4bae7ce60f804d03d1f0628dd5dd0f5de51", "04ffffffff203455139bf238a3067bd72ed77e0ab8db590330f55ed58dba7366b53bf4734279ba04feffffff87ab", "c1a0eb12e60a52614986c623cbb6621dcdba3a47e3be6b37e032b7a11c7b98f400c9a5cd1f6c8a81f5648e39f9810591df1c9a8f1fe97c92e03ecd7c0c016c951983e05473c6e8238cb4c780ea2ce62552b2a3eee068ceffc00517cd7b97e10dad"); _verify_tap_commitments(&secp, "5120b28d75a7179de6feb66b8bb0bfa2b2c739d1a41cf7366a1b393804a844db8a28", "61", "c4a0eb12e60a52614986c623cbb6621dcdba3a47e3be6b37e032b7a11c7b98f400eebc95ded88fb8050094e8dfa958c3be0894eaff0fafae678206b26918d8d7ac47039d40fe34d04b4155df7f1be7f2a49253c7e87812ea9e569e683ac27459e652d6503aa32d64734d00adfee8798b2eed28858abf3bd038e8fa58eb7df4a2d9"); _verify_tap_commitments(&secp, "512043e4aa733fc6f43c78a31c2b3c192623acf5cc8c01199ebcc4de88067baca83e", "bd4c", "c1a0eb12e60a52614986c623cbb6621dcdba3a47e3be6b37e032b7a11c7b98f4003f7be6f8848b5bddf332c4d7bd83077f73701e2479f70e02b5730e841234d082b8b41ebea96ffd937715d9faeaa6895e6ef3b22919c554b75df12b3371d328023e443d1df50634ecc1cd169803a1e546f0d44304d8fc5056c408e597fed469b8437d6660eaad3cf72e35ba6e5ff7ddd5e293c1e7e813c871df4f46508e9946ec"); _verify_tap_commitments(&secp, "5120ee9aecb28f5f35ce1f8b5ec80275ac0f81bca4a21b29b4632fb4bcbef8823e6a", "2021a5981b13be29c9d4ea179ea44a8b773ea8c02d68f6f6eefd98de20d4bd055fac", "c13359c284c196b6e80f0cf1d93b6a397cf7ee722f0427b705bd954b88ada8838bd2622fd0e104fc50aa763b43c6a792d7d117029983abd687223b4344a9402c618bba7f5fc3fa8a57491f6842acde88c1e675ca35caea3b1a69ee2c2d9b10f615"); _verify_tap_commitments(&secp, "5120885274df2252b44764dcef53c21f21154e8488b7e79fafbc96b9ebb22ad0200d", "6a50", "c1a0eb12e60a52614986c623cbb6621dcdba3a47e3be6b37e032b7a11c7b98f4000793597254158918e3369507f2d6fdbef17d18b1028bbb0719450ded0f42c58f"); _verify_tap_commitments(&secp, "512066f6f6f91d47674d198a28388e1eb05ec24e6ddbba10f16396b1a80c08675121", "6a50", "c1a0eb12e60a52614986c623cbb6621dcdba3a47e3be6b37e032b7a11c7b98f400fe92aff70a2e8e2a4f34a913b99612468a41e0f8ecaff9a729a173d11013c27e"); _verify_tap_commitments(&secp, "5120868ed9307bd4637491ff03e3aa2c216a08fe213cac8b6cedbb9ab31dbfa6512c", "61", "a2a0eb12e60a52614986c623cbb6621dcdba3a47e3be6b37e032b7a11c7b98f400da584e7d32612381cf88edc1c02e28a296e807c16ad22f591ee113946e48a71e46c7eccffefd2d573ec014130e508f0c9963ccebd7830409f7b1b1301725e9fa759d4ef857ec8e0bb42d6d31609d3c7e77de3bfa28c38f93393a6ddbabe819ec560ed4f061fbe742a5fd2a648d5209469420434c8753da3fa7067cc2bb4c172a"); _verify_tap_commitments(&secp, "5120c1a00a9baa82888fd7d30291135a7eaa9e9966a5f16db2b10460572f8b108d8d", "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000", "5ba0eb12e60a52614986c623cbb6621dcdba3a47e3be6b37e032b7a11c7b98f4007960d7b37dd1361aee34510e77acb4d27ddca17648a17e28475032538c1eb500f5a747f2c0893f79fe153ae918ac3d696de9322aa679aae62051ff5ed83aa502b338bd907346abd4cd9cf06117cb35d55a5a8dd950843522f8de7b5c7fba1804c38b0778d3d76b383f6db6fdf9d6e770da8fffbfa5152c0b8b38129885bcdee6"); _verify_tap_commitments(&secp, "5120bb9abeff7286b76dfc61800c548fe2621ff47506e47201a85c543b4a9a96fead", "75203455139bf238a3067bd72ed77e0ab8db590330f55ed58dba7366b53bf47342796ead6ead6ead6ead6ead6ead6ead6ead6ead6ead6ead6ead6eadac", "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"); _verify_tap_commitments(&secp, "5120afddc189ea51094b4cbf463806792e9c8b35dfdc5e01228c78376380d0046b00", "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", "c0a0eb12e60a52614986c623cbb6621dcdba3a47e3be6b37e032b7a11c7b98f400ff698adfda0327f188e2ee35f7aecc0f90c9138a350d450648d968c2b5dd7ef94ddd3ec418dc0d03ee4956feb708d838ed2b20e5a193465a6a1467fd3054e1ea141ea4c4c503a6271e19a090e2a69a24282e3be04c4f98720f7a0eb274d9693d13a8e3c139aa625fa2aefd09854570527f9ac545bda1b689719f5cb715612c07"); _verify_tap_commitments(&secp, "5120afddc189ea51094b4cbf463806792e9c8b35dfdc5e01228c78376380d0046b00", "83", "c0a0eb12e60a52614986c623cbb6621dcdba3a47e3be6b37e032b7a11c7b98f4007388cda01113397d4cd00bcfbd08fd68c3cfe3a42cbfe3a7651c1d5e6dacf1ad99aaf103cceb41d9bc37ec231aca89b984b5fd3c65977ce764d51033ac65adb4b59764bec92507e4a4c3f01a06f05980163ca10f1c549bfe01f85fa4f109a1295e607f5ed9f1008048474de336f11f67a1fbf2012f58944dede0ab19a3ca81f5"); _verify_tap_commitments(&secp, "512093c7378d96518a75448821c4f7c8f4bae7ce60f804d03d1f0628dd5dd0f5de51", "04ffffffff203455139bf238a3067bd72ed77e0ab8db590330f55ed58dba7366b53bf4734279ba04feffffff87ab", "c1a0eb12e60a52614986c623cbb6621dcdba3a47e3be6b37e032b7a11c7b98f400c9a5cd1f6c8a81f5648e39f9810591df1c9a8f1fe97c92e03ecd7c0c016c951983e05473c6e8238cb4c780ea2ce62552b2a3eee068ceffc00517cd7b97e10dad"); } #[test] fn build_huffman_tree() { let secp = Secp256k1::verification_only(); let internal_key = UntweakedPublicKey::from_str("93c7378d96518a75448821c4f7c8f4bae7ce60f804d03d1f0628dd5dd0f5de51").unwrap(); let script_weights = vec![ (10, Script::from_hex("51").unwrap()), // semantics of script don't matter for this test (20, Script::from_hex("52").unwrap()), (20, Script::from_hex("53").unwrap()), (30, Script::from_hex("54").unwrap()), (19, Script::from_hex("55").unwrap()), ]; let tree_info = TaprootSpendInfo::with_huffman_tree(&secp, internal_key, script_weights.clone()).unwrap(); /* The resulting tree should put the scripts into a tree similar * to the following: * * 1 __/\__ * / \ * /\ / \ * 2 54 52 53 /\ * 3 55 51 */ for (script, length) in vec![("51", 3), ("52", 2), ("53", 2), ("54", 2), ("55", 3)] { assert_eq!( length, tree_info .script_map .get(&(Script::from_hex(script).unwrap(), LeafVersion::default())) .expect("Present Key") .iter() .next() .expect("Present Path") .0 .len() ); } // Obtain the output key let output_key = tree_info.output_key(); // Try to create and verify a control block from each path for (_weights, script) in script_weights { let ver_script = (script, LeafVersion::default()); let ctrl_block = tree_info.control_block(&ver_script).unwrap(); assert!(ctrl_block.verify_taproot_commitment(&secp, &output_key, &ver_script.0)) } } #[test] fn taptree_builder() { let secp = Secp256k1::verification_only(); let internal_key = UntweakedPublicKey::from_str("93c7378d96518a75448821c4f7c8f4bae7ce60f804d03d1f0628dd5dd0f5de51").unwrap(); let builder = TaprootBuilder::new(); // Create a tree as shown below // For example, imagine this tree: // A, B , C are at depth 2 and D,E are at 3 // .... // / \ // /\ /\ // / \ / \ // A B C / \ // D E let a = Script::from_hex("51").unwrap(); let b = Script::from_hex("52").unwrap(); let c = Script::from_hex("53").unwrap(); let d = Script::from_hex("54").unwrap(); let e = Script::from_hex("55").unwrap(); let builder = builder.add_leaf(2, a.clone()).unwrap(); let builder = builder.add_leaf(2, b.clone()).unwrap(); let builder = builder.add_leaf(2, c.clone()).unwrap(); let builder = builder.add_leaf(3, d.clone()).unwrap(); let builder = builder.add_leaf(3, e.clone()).unwrap(); let tree_info = builder.finalize(&secp, internal_key).unwrap(); let output_key = tree_info.output_key(); for script in vec![a, b, c, d, e] { let ver_script = (script, LeafVersion::default()); let ctrl_block = tree_info.control_block(&ver_script).unwrap(); assert!(ctrl_block.verify_taproot_commitment(&secp, &output_key, &ver_script.0)) } } #[test] fn bip_341_tests() { fn process_script_trees( v: &serde_json::Value, mut builder: TaprootBuilder, leaves: &mut Vec<(Script, LeafVersion)>, depth: usize, ) -> TaprootBuilder { if v.is_null() { // nothing to push } else if v.is_array() { for leaf in v.as_array().unwrap() { builder = process_script_trees(leaf, builder, leaves, depth + 1); } } else { let script = Script::from_str(v["script"].as_str().unwrap()).unwrap(); let ver = LeafVersion::from_u8(v["leafVersion"].as_u64().unwrap() as u8).unwrap(); leaves.push((script.clone(), ver)); builder = builder.add_leaf_with_ver(depth, script, ver).unwrap(); } builder } let data = bip_341_read_json(); // Check the version of data assert!(data["version"] == 1); let secp = &secp256k1::Secp256k1::verification_only(); for arr in data["scriptPubKey"].as_array().unwrap() { let internal_key = schnorr::PublicKey::from_str(arr["given"]["internalPubkey"].as_str().unwrap()).unwrap(); // process the tree let script_tree = &arr["given"]["scriptTree"]; let mut merkle_root = None; if script_tree.is_null() { assert!(arr["intermediary"]["merkleRoot"].is_null()); } else { merkle_root = Some(TapBranchHash::from_str(&arr["intermediary"]["merkleRoot"].as_str().unwrap()).unwrap()); let leaf_hashes = arr["intermediary"]["leafHashes"].as_array().unwrap(); let ctrl_blks = arr["expected"]["scriptPathControlBlocks"].as_array().unwrap(); let mut builder = TaprootBuilder::new(); let mut leaves = vec![]; builder = process_script_trees(&script_tree, builder, &mut leaves, 0); let spend_info = builder.finalize(secp, internal_key).unwrap(); for (i, script_ver) in leaves.iter().enumerate() { let expected_leaf_hash = leaf_hashes[i].as_str().unwrap(); let expected_ctrl_blk = ControlBlock::from_slice(&Vec::::from_hex(ctrl_blks[i].as_str().unwrap()).unwrap()).unwrap(); let leaf_hash = TapLeafHash::from_script(&script_ver.0, script_ver.1); let ctrl_blk = spend_info.control_block(script_ver).unwrap(); assert_eq!(leaf_hash.to_hex(), expected_leaf_hash); assert_eq!(ctrl_blk, expected_ctrl_blk); } } let expected_output_key = schnorr::PublicKey::from_str(arr["intermediary"]["tweakedPubkey"].as_str().unwrap()).unwrap(); let expected_tweak = TapTweakHash::from_str(arr["intermediary"]["tweak"].as_str().unwrap()).unwrap(); let expected_spk = Script::from_str(arr["expected"]["scriptPubKey"].as_str().unwrap()).unwrap(); let expected_addr = Address::from_str(arr["expected"]["bip350Address"].as_str().unwrap()).unwrap(); let tweak = TapTweakHash::from_key_and_tweak(internal_key, merkle_root); let (output_key, _parity) = internal_key.tap_tweak(&secp, merkle_root); let addr = Address::p2tr(&secp, internal_key, merkle_root, Network::Bitcoin); let spk = addr.script_pubkey(); assert_eq!(expected_output_key, output_key.into_inner()); assert_eq!(expected_tweak, tweak); assert_eq!(expected_addr, addr); assert_eq!(expected_spk, spk); } } fn bip_341_read_json() -> serde_json::Value { let json_str = include_str!("../../test_data/bip341_tests.json"); serde_json::from_str(json_str).expect("JSON was not well-formatted") } }