miden-crypto/src/merkle/path_set.rs
src/merkle/path_set.rsRaw
1use super::{BTreeMap, MerkleError, MerklePath, NodeIndex, Rpo256, ValuePath, Vec, Word, ZERO};
2
3// MERKLE PATH SET
4// ================================================================================================
5
6/// A set of Merkle paths.
7#[derive(Debug, Clone, PartialEq, Eq)]
8pub struct MerklePathSet {
9 root: Word,
10 total_depth: u8,
11 paths: BTreeMap<u64, MerklePath>,
12}
13
14impl MerklePathSet {
15 // CONSTRUCTOR
16 // --------------------------------------------------------------------------------------------
17
18 /// Returns an empty MerklePathSet.
19 pub fn new(depth: u8) -> Self {
20 let root = [ZERO; 4];
21 let paths = BTreeMap::new();
22
23 Self {
24 root,
25 total_depth: depth,
26 paths,
27 }
28 }
29
30 /// Appends the provided paths iterator into the set.
31 ///
32 /// Analogous to `[Self::add_path]`.
33 pub fn with_paths<I>(self, paths: I) -> Result<Self, MerkleError>
34 where
35 I: IntoIterator<Item = (u64, Word, MerklePath)>,
36 {
37 paths
38 .into_iter()
39 .try_fold(self, |mut set, (index, value, path)| {
40 set.add_path(index, value, path)?;
41 Ok(set)
42 })
43 }
44
45 // PUBLIC ACCESSORS
46 // --------------------------------------------------------------------------------------------
47
48 /// Returns the root to which all paths in this set resolve.
49 pub const fn root(&self) -> Word {
50 self.root
51 }
52
53 /// Returns the depth of the Merkle tree implied by the paths stored in this set.
54 ///
55 /// Merkle tree of depth 1 has two leaves, depth 2 has four leaves etc.
56 pub const fn depth(&self) -> u8 {
57 self.total_depth
58 }
59
60 /// Returns a node at the specified index.
61 ///
62 /// # Errors
63 /// Returns an error if:
64 /// * The specified index is not valid for the depth of structure.
65 /// * Requested node does not exist in the set.
66 pub fn get_node(&self, index: NodeIndex) -> Result<Word, MerkleError> {
67 if index.depth() != self.total_depth {
68 return Err(MerkleError::InvalidDepth {
69 expected: self.total_depth,
70 provided: index.depth(),
71 });
72 }
73
74 let parity = index.value() & 1;
75 let path_key = index.value() - parity;
76 self.paths
77 .get(&path_key)
78 .ok_or(MerkleError::NodeNotInSet(path_key))
79 .map(|path| path[parity as usize])
80 }
81
82 /// Returns a leaf at the specified index.
83 ///
84 /// # Errors
85 /// * The specified index is not valid for the depth of the structure.
86 /// * Leaf with the requested path does not exist in the set.
87 pub fn get_leaf(&self, index: u64) -> Result<Word, MerkleError> {
88 let index = NodeIndex::new(self.depth(), index)?;
89 self.get_node(index)
90 }
91
92 /// Returns a Merkle path to the node at the specified index. The node itself is
93 /// not included in the path.
94 ///
95 /// # Errors
96 /// Returns an error if:
97 /// * The specified index is not valid for the depth of structure.
98 /// * Node of the requested path does not exist in the set.
99 pub fn get_path(&self, index: NodeIndex) -> Result<MerklePath, MerkleError> {
100 if index.depth() != self.total_depth {
101 return Err(MerkleError::InvalidDepth {
102 expected: self.total_depth,
103 provided: index.depth(),
104 });
105 }
106
107 let parity = index.value() & 1;
108 let path_key = index.value() - parity;
109 let mut path = self
110 .paths
111 .get(&path_key)
112 .cloned()
113 .ok_or(MerkleError::NodeNotInSet(index.value()))?;
114 path.remove(parity as usize);
115 Ok(path)
116 }
117
118 /// Returns all paths in this path set together with their indexes.
119 pub fn to_paths(&self) -> Vec<(u64, ValuePath)> {
120 let mut result = Vec::with_capacity(self.paths.len() * 2);
121
122 for (&index, path) in self.paths.iter() {
123 // push path for the even index into the result
124 let path1 = ValuePath {
125 value: path[0],
126 path: MerklePath::new(path[1..].to_vec()),
127 };
128 result.push((index, path1));
129
130 // push path for the odd index into the result
131 let mut path2 = path.clone();
132 let leaf2 = path2.remove(1);
133 let path2 = ValuePath {
134 value: leaf2,
135 path: path2,
136 };
137 result.push((index + 1, path2));
138 }
139
140 result
141 }
142
143 // STATE MUTATORS
144 // --------------------------------------------------------------------------------------------
145
146 /// Adds the specified Merkle path to this [MerklePathSet]. The `index` and `value` parameters
147 /// specify the leaf node at which the path starts.
148 ///
149 /// # Errors
150 /// Returns an error if:
151 /// - The specified index is is not valid in the context of this Merkle path set (i.e., the
152 /// index implies a greater depth than is specified for this set).
153 /// - The specified path is not consistent with other paths in the set (i.e., resolves to a
154 /// different root).
155 pub fn add_path(
156 &mut self,
157 index_value: u64,
158 value: Word,
159 mut path: MerklePath,
160 ) -> Result<(), MerkleError> {
161 let mut index = NodeIndex::new(path.len() as u8, index_value)?;
162 if index.depth() != self.total_depth {
163 return Err(MerkleError::InvalidDepth {
164 expected: self.total_depth,
165 provided: index.depth(),
166 });
167 }
168
169 // update the current path
170 let parity = index_value & 1;
171 path.insert(parity as usize, value);
172
173 // traverse to the root, updating the nodes
174 let root: Word = Rpo256::merge(&[path[0].into(), path[1].into()]).into();
175 let root = path.iter().skip(2).copied().fold(root, |root, hash| {
176 index.move_up();
177 Rpo256::merge(&index.build_node(root.into(), hash.into())).into()
178 });
179
180 // if the path set is empty (the root is all ZEROs), set the root to the root of the added
181 // path; otherwise, the root of the added path must be identical to the current root
182 if self.root == [ZERO; 4] {
183 self.root = root;
184 } else if self.root != root {
185 return Err(MerkleError::ConflictingRoots([self.root, root].to_vec()));
186 }
187
188 // finish updating the path
189 let path_key = index_value - parity;
190 self.paths.insert(path_key, path);
191 Ok(())
192 }
193
194 /// Replaces the leaf at the specified index with the provided value.
195 ///
196 /// # Errors
197 /// Returns an error if:
198 /// * Requested node does not exist in the set.
199 pub fn update_leaf(&mut self, base_index_value: u64, value: Word) -> Result<(), MerkleError> {
200 let mut index = NodeIndex::new(self.depth(), base_index_value)?;
201 let parity = index.value() & 1;
202 let path_key = index.value() - parity;
203 let path = match self.paths.get_mut(&path_key) {
204 Some(path) => path,
205 None => return Err(MerkleError::NodeNotInSet(base_index_value)),
206 };
207
208 // Fill old_hashes vector -----------------------------------------------------------------
209 let mut current_index = index;
210 let mut old_hashes = Vec::with_capacity(path.len().saturating_sub(2));
211 let mut root: Word = Rpo256::merge(&[path[0].into(), path[1].into()]).into();
212 for hash in path.iter().skip(2).copied() {
213 old_hashes.push(root);
214 current_index.move_up();
215 let input = current_index.build_node(hash.into(), root.into());
216 root = Rpo256::merge(&input).into();
217 }
218
219 // Fill new_hashes vector -----------------------------------------------------------------
220 path[index.is_value_odd() as usize] = value;
221
222 let mut new_hashes = Vec::with_capacity(path.len().saturating_sub(2));
223 let mut new_root: Word = Rpo256::merge(&[path[0].into(), path[1].into()]).into();
224 for path_hash in path.iter().skip(2).copied() {
225 new_hashes.push(new_root);
226 index.move_up();
227 let input = current_index.build_node(path_hash.into(), new_root.into());
228 new_root = Rpo256::merge(&input).into();
229 }
230
231 self.root = new_root;
232
233 // update paths ---------------------------------------------------------------------------
234 for path in self.paths.values_mut() {
235 for i in (0..old_hashes.len()).rev() {
236 if path[i + 2] == old_hashes[i] {
237 path[i + 2] = new_hashes[i];
238 break;
239 }
240 }
241 }
242
243 Ok(())
244 }
245}
246
247// TESTS
248// ================================================================================================
249
250#[cfg(test)]
251mod tests {
252 use super::*;
253 use crate::merkle::int_to_node;
254
255 #[test]
256 fn get_root() {
257 let leaf0 = int_to_node(0);
258 let leaf1 = int_to_node(1);
259 let leaf2 = int_to_node(2);
260 let leaf3 = int_to_node(3);
261
262 let parent0 = calculate_parent_hash(leaf0, 0, leaf1);
263 let parent1 = calculate_parent_hash(leaf2, 2, leaf3);
264
265 let root_exp = calculate_parent_hash(parent0, 0, parent1);
266
267 let set = super::MerklePathSet::new(2)
268 .with_paths([(0, leaf0, vec![leaf1, parent1].into())])
269 .unwrap();
270
271 assert_eq!(set.root(), root_exp);
272 }
273
274 #[test]
275 fn add_and_get_path() {
276 let path_6 = vec![int_to_node(7), int_to_node(45), int_to_node(123)];
277 let hash_6 = int_to_node(6);
278 let index = 6_u64;
279 let depth = 3_u8;
280 let set = super::MerklePathSet::new(depth)
281 .with_paths([(index, hash_6, path_6.clone().into())])
282 .unwrap();
283 let stored_path_6 = set.get_path(NodeIndex::make(depth, index)).unwrap();
284
285 assert_eq!(path_6, *stored_path_6);
286 }
287
288 #[test]
289 fn get_node() {
290 let path_6 = vec![int_to_node(7), int_to_node(45), int_to_node(123)];
291 let hash_6 = int_to_node(6);
292 let index = 6_u64;
293 let depth = 3_u8;
294 let set = MerklePathSet::new(depth)
295 .with_paths([(index, hash_6, path_6.into())])
296 .unwrap();
297
298 assert_eq!(
299 int_to_node(6u64),
300 set.get_node(NodeIndex::make(depth, index)).unwrap()
301 );
302 }
303
304 #[test]
305 fn update_leaf() {
306 let hash_4 = int_to_node(4);
307 let hash_5 = int_to_node(5);
308 let hash_6 = int_to_node(6);
309 let hash_7 = int_to_node(7);
310 let hash_45 = calculate_parent_hash(hash_4, 12u64, hash_5);
311 let hash_67 = calculate_parent_hash(hash_6, 14u64, hash_7);
312
313 let hash_0123 = int_to_node(123);
314
315 let path_6 = vec![hash_7, hash_45, hash_0123];
316 let path_5 = vec![hash_4, hash_67, hash_0123];
317 let path_4 = vec![hash_5, hash_67, hash_0123];
318
319 let index_6 = 6_u64;
320 let index_5 = 5_u64;
321 let index_4 = 4_u64;
322 let depth = 3_u8;
323 let mut set = MerklePathSet::new(depth)
324 .with_paths([
325 (index_6, hash_6, path_6.into()),
326 (index_5, hash_5, path_5.into()),
327 (index_4, hash_4, path_4.into()),
328 ])
329 .unwrap();
330
331 let new_hash_6 = int_to_node(100);
332 let new_hash_5 = int_to_node(55);
333
334 set.update_leaf(index_6, new_hash_6).unwrap();
335 let new_path_4 = set.get_path(NodeIndex::make(depth, index_4)).unwrap();
336 let new_hash_67 = calculate_parent_hash(new_hash_6, 14_u64, hash_7);
337 assert_eq!(new_hash_67, new_path_4[1]);
338
339 set.update_leaf(index_5, new_hash_5).unwrap();
340 let new_path_4 = set.get_path(NodeIndex::make(depth, index_4)).unwrap();
341 let new_path_6 = set.get_path(NodeIndex::make(depth, index_6)).unwrap();
342 let new_hash_45 = calculate_parent_hash(new_hash_5, 13_u64, hash_4);
343 assert_eq!(new_hash_45, new_path_6[1]);
344 assert_eq!(new_hash_5, new_path_4[0]);
345 }
346
347 #[test]
348 fn depth_3_is_correct() {
349 let a = int_to_node(1);
350 let b = int_to_node(2);
351 let c = int_to_node(3);
352 let d = int_to_node(4);
353 let e = int_to_node(5);
354 let f = int_to_node(6);
355 let g = int_to_node(7);
356 let h = int_to_node(8);
357
358 let i = Rpo256::merge(&[a.into(), b.into()]);
359 let j = Rpo256::merge(&[c.into(), d.into()]);
360 let k = Rpo256::merge(&[e.into(), f.into()]);
361 let l = Rpo256::merge(&[g.into(), h.into()]);
362
363 let m = Rpo256::merge(&[i.into(), j.into()]);
364 let n = Rpo256::merge(&[k.into(), l.into()]);
365
366 let root = Rpo256::merge(&[m.into(), n.into()]);
367
368 let mut set = MerklePathSet::new(3);
369
370 let value = b;
371 let index = 1;
372 let path = MerklePath::new([a.into(), j.into(), n.into()].to_vec());
373 set.add_path(index, value, path.clone()).unwrap();
374 assert_eq!(value, set.get_leaf(index).unwrap());
375 assert_eq!(Word::from(root), set.root());
376
377 let value = e;
378 let index = 4;
379 let path = MerklePath::new([f.into(), l.into(), m.into()].to_vec());
380 set.add_path(index, value, path.clone()).unwrap();
381 assert_eq!(value, set.get_leaf(index).unwrap());
382 assert_eq!(Word::from(root), set.root());
383
384 let value = a;
385 let index = 0;
386 let path = MerklePath::new([b.into(), j.into(), n.into()].to_vec());
387 set.add_path(index, value, path.clone()).unwrap();
388 assert_eq!(value, set.get_leaf(index).unwrap());
389 assert_eq!(Word::from(root), set.root());
390
391 let value = h;
392 let index = 7;
393 let path = MerklePath::new([g.into(), k.into(), m.into()].to_vec());
394 set.add_path(index, value, path.clone()).unwrap();
395 assert_eq!(value, set.get_leaf(index).unwrap());
396 assert_eq!(Word::from(root), set.root());
397 }
398
399 // HELPER FUNCTIONS
400 // --------------------------------------------------------------------------------------------
401
402 const fn is_even(pos: u64) -> bool {
403 pos & 1 == 0
404 }
405
406 /// Calculates the hash of the parent node by two sibling ones
407 /// - node — current node
408 /// - node_pos — position of the current node
409 /// - sibling — neighboring vertex in the tree
410 fn calculate_parent_hash(node: Word, node_pos: u64, sibling: Word) -> Word {
411 if is_even(node_pos) {
412 Rpo256::merge(&[node.into(), sibling.into()]).into()
413 } else {
414 Rpo256::merge(&[sibling.into(), node.into()]).into()
415 }
416 }
417}