miden_crypto/merkle/mmr/partial.rs
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use alloc::{
collections::{BTreeMap, BTreeSet},
vec::Vec,
};
use winter_utils::{Deserializable, Serializable};
use super::{MmrDelta, MmrProof, Rpo256, RpoDigest};
use crate::merkle::{
mmr::{leaf_to_corresponding_tree, nodes_in_forest},
InOrderIndex, InnerNodeInfo, MerklePath, MmrError, MmrPeaks,
};
// TYPE ALIASES
// ================================================================================================
type NodeMap = BTreeMap<InOrderIndex, RpoDigest>;
// PARTIAL MERKLE MOUNTAIN RANGE
// ================================================================================================
/// Partially materialized Merkle Mountain Range (MMR), used to efficiently store and update the
/// authentication paths for a subset of the elements in a full MMR.
///
/// This structure store only the authentication path for a value, the value itself is stored
/// separately.
#[derive(Debug, Clone, PartialEq, Eq)]
pub struct PartialMmr {
/// The version of the MMR.
///
/// This value serves the following purposes:
///
/// - The forest is a counter for the total number of elements in the MMR.
/// - Since the MMR is an append-only structure, every change to it causes a change to the
/// `forest`, so this value has a dual purpose as a version tag.
/// - The bits in the forest also corresponds to the count and size of every perfect binary
/// tree that composes the MMR structure, which server to compute indexes and perform
/// validation.
pub(crate) forest: usize,
/// The MMR peaks.
///
/// The peaks are used for two reasons:
///
/// 1. It authenticates the addition of an element to the [PartialMmr], ensuring only valid
/// elements are tracked.
/// 2. During a MMR update peaks can be merged by hashing the left and right hand sides. The
/// peaks are used as the left hand.
///
/// All the peaks of every tree in the MMR forest. The peaks are always ordered by number of
/// leaves, starting from the peak with most children, to the one with least.
pub(crate) peaks: Vec<RpoDigest>,
/// Authentication nodes used to construct merkle paths for a subset of the MMR's leaves.
///
/// This does not include the MMR's peaks nor the tracked nodes, only the elements required to
/// construct their authentication paths. This property is used to detect when elements can be
/// safely removed, because they are no longer required to authenticate any element in the
/// [PartialMmr].
///
/// The elements in the MMR are referenced using a in-order tree index. This indexing scheme
/// permits for easy computation of the relative nodes (left/right children, sibling, parent),
/// which is useful for traversal. The indexing is also stable, meaning that merges to the
/// trees in the MMR can be represented without rewrites of the indexes.
pub(crate) nodes: NodeMap,
/// Flag indicating if the odd element should be tracked.
///
/// This flag is necessary because the sibling of the odd doesn't exist yet, so it can not be
/// added into `nodes` to signal the value is being tracked.
pub(crate) track_latest: bool,
}
impl PartialMmr {
// CONSTRUCTORS
// --------------------------------------------------------------------------------------------
/// Returns a new [PartialMmr] instantiated from the specified peaks.
pub fn from_peaks(peaks: MmrPeaks) -> Self {
let forest = peaks.num_leaves();
let peaks = peaks.into();
let nodes = BTreeMap::new();
let track_latest = false;
Self { forest, peaks, nodes, track_latest }
}
/// Returns a new [PartialMmr] instantiated from the specified components.
///
/// This constructor does not check the consistency between peaks and nodes. If the specified
/// peaks are nodes are inconsistent, the returned partial MMR may exhibit undefined behavior.
pub fn from_parts(peaks: MmrPeaks, nodes: NodeMap, track_latest: bool) -> Self {
let forest = peaks.num_leaves();
let peaks = peaks.into();
Self { forest, peaks, nodes, track_latest }
}
// PUBLIC ACCESSORS
// --------------------------------------------------------------------------------------------
/// Returns the current `forest` of this [PartialMmr].
///
/// This value corresponds to the version of the [PartialMmr] and the number of leaves in the
/// underlying MMR.
pub fn forest(&self) -> usize {
self.forest
}
/// Returns the number of leaves in the underlying MMR for this [PartialMmr].
pub fn num_leaves(&self) -> usize {
self.forest
}
/// Returns the peaks of the MMR for this [PartialMmr].
pub fn peaks(&self) -> MmrPeaks {
// expect() is OK here because the constructor ensures that MMR peaks can be constructed
// correctly
MmrPeaks::new(self.forest, self.peaks.clone()).expect("invalid MMR peaks")
}
/// Returns true if this partial MMR tracks an authentication path for the leaf at the
/// specified position.
pub fn is_tracked(&self, pos: usize) -> bool {
if pos >= self.forest {
return false;
} else if pos == self.forest - 1 && self.forest & 1 != 0 {
// if the number of leaves in the MMR is odd and the position is for the last leaf
// whether the leaf is tracked is defined by the `track_latest` flag
return self.track_latest;
}
let leaf_index = InOrderIndex::from_leaf_pos(pos);
self.is_tracked_node(&leaf_index)
}
/// Given a leaf position, returns the Merkle path to its corresponding peak, or None if this
/// partial MMR does not track an authentication paths for the specified leaf.
///
/// Note: The leaf position is the 0-indexed number corresponding to the order the leaves were
/// added, this corresponds to the MMR size _prior_ to adding the element. So the 1st element
/// has position 0, the second position 1, and so on.
///
/// # Errors
/// Returns an error if the specified position is greater-or-equal than the number of leaves
/// in the underlying MMR.
pub fn open(&self, pos: usize) -> Result<Option<MmrProof>, MmrError> {
let tree_bit =
leaf_to_corresponding_tree(pos, self.forest).ok_or(MmrError::InvalidPosition(pos))?;
let depth = tree_bit as usize;
let mut nodes = Vec::with_capacity(depth);
let mut idx = InOrderIndex::from_leaf_pos(pos);
while let Some(node) = self.nodes.get(&idx.sibling()) {
nodes.push(*node);
idx = idx.parent();
}
// If there are nodes then the path must be complete, otherwise it is a bug
debug_assert!(nodes.is_empty() || nodes.len() == depth);
if nodes.len() != depth {
// The requested `pos` is not being tracked.
Ok(None)
} else {
Ok(Some(MmrProof {
forest: self.forest,
position: pos,
merkle_path: MerklePath::new(nodes),
}))
}
}
// ITERATORS
// --------------------------------------------------------------------------------------------
/// Returns an iterator nodes of all authentication paths of this [PartialMmr].
pub fn nodes(&self) -> impl Iterator<Item = (&InOrderIndex, &RpoDigest)> {
self.nodes.iter()
}
/// Returns an iterator over inner nodes of this [PartialMmr] for the specified leaves.
///
/// The order of iteration is not defined. If a leaf is not presented in this partial MMR it
/// is silently ignored.
pub fn inner_nodes<'a, I: Iterator<Item = (usize, RpoDigest)> + 'a>(
&'a self,
mut leaves: I,
) -> impl Iterator<Item = InnerNodeInfo> + 'a {
let stack = if let Some((pos, leaf)) = leaves.next() {
let idx = InOrderIndex::from_leaf_pos(pos);
vec![(idx, leaf)]
} else {
Vec::new()
};
InnerNodeIterator {
nodes: &self.nodes,
leaves,
stack,
seen_nodes: BTreeSet::new(),
}
}
// STATE MUTATORS
// --------------------------------------------------------------------------------------------
/// Adds a new peak and optionally track it. Returns a vector of the authentication nodes
/// inserted into this [PartialMmr] as a result of this operation.
///
/// When `track` is `true` the new leaf is tracked.
pub fn add(&mut self, leaf: RpoDigest, track: bool) -> Vec<(InOrderIndex, RpoDigest)> {
self.forest += 1;
let merges = self.forest.trailing_zeros() as usize;
let mut new_nodes = Vec::with_capacity(merges);
let peak = if merges == 0 {
self.track_latest = track;
leaf
} else {
let mut track_right = track;
let mut track_left = self.track_latest;
let mut right = leaf;
let mut right_idx = forest_to_rightmost_index(self.forest);
for _ in 0..merges {
let left = self.peaks.pop().expect("Missing peak");
let left_idx = right_idx.sibling();
if track_right {
let old = self.nodes.insert(left_idx, left);
new_nodes.push((left_idx, left));
debug_assert!(
old.is_none(),
"Idx {:?} already contained an element {:?}",
left_idx,
old
);
};
if track_left {
let old = self.nodes.insert(right_idx, right);
new_nodes.push((right_idx, right));
debug_assert!(
old.is_none(),
"Idx {:?} already contained an element {:?}",
right_idx,
old
);
};
// Update state for the next iteration.
// --------------------------------------------------------------------------------
// This layer is merged, go up one layer.
right_idx = right_idx.parent();
// Merge the current layer. The result is either the right element of the next
// merge, or a new peak.
right = Rpo256::merge(&[left, right]);
// This iteration merged the left and right nodes, the new value is always used as
// the next iteration's right node. Therefore the tracking flags of this iteration
// have to be merged into the right side only.
track_right = track_right || track_left;
// On the next iteration, a peak will be merged. If any of its children are tracked,
// then we have to track the left side
track_left = self.is_tracked_node(&right_idx.sibling());
}
right
};
self.peaks.push(peak);
new_nodes
}
/// Adds the authentication path represented by [MerklePath] if it is valid.
///
/// The `leaf_pos` refers to the global position of the leaf in the MMR, these are 0-indexed
/// values assigned in a strictly monotonic fashion as elements are inserted into the MMR,
/// this value corresponds to the values used in the MMR structure.
///
/// The `leaf` corresponds to the value at `leaf_pos`, and `path` is the authentication path for
/// that element up to its corresponding Mmr peak. The `leaf` is only used to compute the root
/// from the authentication path to valid the data, only the authentication data is saved in
/// the structure. If the value is required it should be stored out-of-band.
pub fn track(
&mut self,
leaf_pos: usize,
leaf: RpoDigest,
path: &MerklePath,
) -> Result<(), MmrError> {
// Checks there is a tree with same depth as the authentication path, if not the path is
// invalid.
let tree = 1 << path.depth();
if tree & self.forest == 0 {
return Err(MmrError::UnknownPeak);
};
if leaf_pos + 1 == self.forest
&& path.depth() == 0
&& self.peaks.last().map_or(false, |v| *v == leaf)
{
self.track_latest = true;
return Ok(());
}
// ignore the trees smaller than the target (these elements are position after the current
// target and don't affect the target leaf_pos)
let target_forest = self.forest ^ (self.forest & (tree - 1));
let peak_pos = (target_forest.count_ones() - 1) as usize;
// translate from mmr leaf_pos to merkle path
let path_idx = leaf_pos - (target_forest ^ tree);
// Compute the root of the authentication path, and check it matches the current version of
// the PartialMmr.
let computed = path.compute_root(path_idx as u64, leaf).map_err(MmrError::MerkleError)?;
if self.peaks[peak_pos] != computed {
return Err(MmrError::InvalidPeak);
}
let mut idx = InOrderIndex::from_leaf_pos(leaf_pos);
for leaf in path.nodes() {
self.nodes.insert(idx.sibling(), *leaf);
idx = idx.parent();
}
Ok(())
}
/// Removes a leaf of the [PartialMmr] and the unused nodes from the authentication path.
///
/// Note: `leaf_pos` corresponds to the position in the MMR and not on an individual tree.
pub fn untrack(&mut self, leaf_pos: usize) {
let mut idx = InOrderIndex::from_leaf_pos(leaf_pos);
self.nodes.remove(&idx.sibling());
// `idx` represent the element that can be computed by the authentication path, because
// these elements can be computed they are not saved for the authentication of the current
// target. In other words, if the idx is present it was added for the authentication of
// another element, and no more elements should be removed otherwise it would remove that
// element's authentication data.
while !self.nodes.contains_key(&idx) {
idx = idx.parent();
self.nodes.remove(&idx.sibling());
}
}
/// Applies updates to this [PartialMmr] and returns a vector of new authentication nodes
/// inserted into the partial MMR.
pub fn apply(&mut self, delta: MmrDelta) -> Result<Vec<(InOrderIndex, RpoDigest)>, MmrError> {
if delta.forest < self.forest {
return Err(MmrError::InvalidPeaks);
}
let mut inserted_nodes = Vec::new();
if delta.forest == self.forest {
if !delta.data.is_empty() {
return Err(MmrError::InvalidUpdate);
}
return Ok(inserted_nodes);
}
// find the tree merges
let changes = self.forest ^ delta.forest;
let largest = 1 << changes.ilog2();
let merges = self.forest & (largest - 1);
debug_assert!(
!self.track_latest || (merges & 1) == 1,
"if there is an odd element, a merge is required"
);
// count the number elements needed to produce largest from the current state
let (merge_count, new_peaks) = if merges != 0 {
let depth = largest.trailing_zeros();
let skipped = merges.trailing_zeros();
let computed = merges.count_ones() - 1;
let merge_count = depth - skipped - computed;
let new_peaks = delta.forest & (largest - 1);
(merge_count, new_peaks)
} else {
(0, changes)
};
// verify the delta size
if (delta.data.len() as u32) != merge_count + new_peaks.count_ones() {
return Err(MmrError::InvalidUpdate);
}
// keeps track of how many data elements from the update have been consumed
let mut update_count = 0;
if merges != 0 {
// starts at the smallest peak and follows the merged peaks
let mut peak_idx = forest_to_root_index(self.forest);
// match order of the update data while applying it
self.peaks.reverse();
// set to true when the data is needed for authentication paths updates
let mut track = self.track_latest;
self.track_latest = false;
let mut peak_count = 0;
let mut target = 1 << merges.trailing_zeros();
let mut new = delta.data[0];
update_count += 1;
while target < largest {
// check if either the left or right subtrees have saved for authentication paths.
// If so, turn tracking on to update those paths.
if target != 1 && !track {
track = self.is_tracked_node(&peak_idx);
}
// update data only contains the nodes from the right subtrees, left nodes are
// either previously known peaks or computed values
let (left, right) = if target & merges != 0 {
let peak = self.peaks[peak_count];
let sibling_idx = peak_idx.sibling();
// if the sibling peak is tracked, add this peaks to the set of
// authentication nodes
if self.is_tracked_node(&sibling_idx) {
self.nodes.insert(peak_idx, new);
inserted_nodes.push((peak_idx, new));
}
peak_count += 1;
(peak, new)
} else {
let update = delta.data[update_count];
update_count += 1;
(new, update)
};
if track {
let sibling_idx = peak_idx.sibling();
if peak_idx.is_left_child() {
self.nodes.insert(sibling_idx, right);
inserted_nodes.push((sibling_idx, right));
} else {
self.nodes.insert(sibling_idx, left);
inserted_nodes.push((sibling_idx, left));
}
}
peak_idx = peak_idx.parent();
new = Rpo256::merge(&[left, right]);
target <<= 1;
}
debug_assert!(peak_count == (merges.count_ones() as usize));
// restore the peaks order
self.peaks.reverse();
// remove the merged peaks
self.peaks.truncate(self.peaks.len() - peak_count);
// add the newly computed peak, the result of the merges
self.peaks.push(new);
}
// The rest of the update data is composed of peaks. None of these elements can contain
// tracked elements because the peaks were unknown, and it is not possible to add elements
// for tacking without authenticating it to a peak.
self.peaks.extend_from_slice(&delta.data[update_count..]);
self.forest = delta.forest;
debug_assert!(self.peaks.len() == (self.forest.count_ones() as usize));
Ok(inserted_nodes)
}
// HELPER METHODS
// --------------------------------------------------------------------------------------------
/// Returns true if this [PartialMmr] tracks authentication path for the node at the specified
/// index.
fn is_tracked_node(&self, node_index: &InOrderIndex) -> bool {
if node_index.is_leaf() {
self.nodes.contains_key(&node_index.sibling())
} else {
let left_child = node_index.left_child();
let right_child = node_index.right_child();
self.nodes.contains_key(&left_child) | self.nodes.contains_key(&right_child)
}
}
}
// CONVERSIONS
// ================================================================================================
impl From<MmrPeaks> for PartialMmr {
fn from(peaks: MmrPeaks) -> Self {
Self::from_peaks(peaks)
}
}
impl From<PartialMmr> for MmrPeaks {
fn from(partial_mmr: PartialMmr) -> Self {
// Safety: the [PartialMmr] maintains the constraints the number of true bits in the forest
// matches the number of peaks, as required by the [MmrPeaks]
MmrPeaks::new(partial_mmr.forest, partial_mmr.peaks).unwrap()
}
}
impl From<&MmrPeaks> for PartialMmr {
fn from(peaks: &MmrPeaks) -> Self {
Self::from_peaks(peaks.clone())
}
}
impl From<&PartialMmr> for MmrPeaks {
fn from(partial_mmr: &PartialMmr) -> Self {
// Safety: the [PartialMmr] maintains the constraints the number of true bits in the forest
// matches the number of peaks, as required by the [MmrPeaks]
MmrPeaks::new(partial_mmr.forest, partial_mmr.peaks.clone()).unwrap()
}
}
// ITERATORS
// ================================================================================================
/// An iterator over every inner node of the [PartialMmr].
pub struct InnerNodeIterator<'a, I: Iterator<Item = (usize, RpoDigest)>> {
nodes: &'a NodeMap,
leaves: I,
stack: Vec<(InOrderIndex, RpoDigest)>,
seen_nodes: BTreeSet<InOrderIndex>,
}
impl<I: Iterator<Item = (usize, RpoDigest)>> Iterator for InnerNodeIterator<'_, I> {
type Item = InnerNodeInfo;
fn next(&mut self) -> Option<Self::Item> {
while let Some((idx, node)) = self.stack.pop() {
let parent_idx = idx.parent();
let new_node = self.seen_nodes.insert(parent_idx);
// if we haven't seen this node's parent before, and the node has a sibling, return
// the inner node defined by the parent of this node, and move up the branch
if new_node {
if let Some(sibling) = self.nodes.get(&idx.sibling()) {
let (left, right) = if parent_idx.left_child() == idx {
(node, *sibling)
} else {
(*sibling, node)
};
let parent = Rpo256::merge(&[left, right]);
let inner_node = InnerNodeInfo { value: parent, left, right };
self.stack.push((parent_idx, parent));
return Some(inner_node);
}
}
// the previous leaf has been processed, try to process the next leaf
if let Some((pos, leaf)) = self.leaves.next() {
let idx = InOrderIndex::from_leaf_pos(pos);
self.stack.push((idx, leaf));
}
}
None
}
}
impl Serializable for PartialMmr {
fn write_into<W: winter_utils::ByteWriter>(&self, target: &mut W) {
self.forest.write_into(target);
self.peaks.write_into(target);
self.nodes.write_into(target);
target.write_bool(self.track_latest);
}
}
impl Deserializable for PartialMmr {
fn read_from<R: winter_utils::ByteReader>(
source: &mut R,
) -> Result<Self, winter_utils::DeserializationError> {
let forest = usize::read_from(source)?;
let peaks = Vec::<RpoDigest>::read_from(source)?;
let nodes = NodeMap::read_from(source)?;
let track_latest = source.read_bool()?;
Ok(Self { forest, peaks, nodes, track_latest })
}
}
// UTILS
// ================================================================================================
/// Given the description of a `forest`, returns the index of the root element of the smallest tree
/// in it.
fn forest_to_root_index(forest: usize) -> InOrderIndex {
// Count total size of all trees in the forest.
let nodes = nodes_in_forest(forest);
// Add the count for the parent nodes that separate each tree. These are allocated but
// currently empty, and correspond to the nodes that will be used once the trees are merged.
let open_trees = (forest.count_ones() - 1) as usize;
// Remove the count of the right subtree of the target tree, target tree root index comes
// before the subtree for the in-order tree walk.
let right_subtree_count = ((1u32 << forest.trailing_zeros()) - 1) as usize;
let idx = nodes + open_trees - right_subtree_count;
InOrderIndex::new(idx.try_into().unwrap())
}
/// Given the description of a `forest`, returns the index of the right most element.
fn forest_to_rightmost_index(forest: usize) -> InOrderIndex {
// Count total size of all trees in the forest.
let nodes = nodes_in_forest(forest);
// Add the count for the parent nodes that separate each tree. These are allocated but
// currently empty, and correspond to the nodes that will be used once the trees are merged.
let open_trees = (forest.count_ones() - 1) as usize;
let idx = nodes + open_trees;
InOrderIndex::new(idx.try_into().unwrap())
}
// TESTS
// ================================================================================================
#[cfg(test)]
mod tests {
use alloc::{collections::BTreeSet, vec::Vec};
use winter_utils::{Deserializable, Serializable};
use super::{
forest_to_rightmost_index, forest_to_root_index, InOrderIndex, MmrPeaks, PartialMmr,
RpoDigest,
};
use crate::merkle::{int_to_node, MerkleStore, Mmr, NodeIndex};
const LEAVES: [RpoDigest; 7] = [
int_to_node(0),
int_to_node(1),
int_to_node(2),
int_to_node(3),
int_to_node(4),
int_to_node(5),
int_to_node(6),
];
#[test]
fn test_forest_to_root_index() {
fn idx(pos: usize) -> InOrderIndex {
InOrderIndex::new(pos.try_into().unwrap())
}
// When there is a single tree in the forest, the index is equivalent to the number of
// leaves in that tree, which is `2^n`.
assert_eq!(forest_to_root_index(0b0001), idx(1));
assert_eq!(forest_to_root_index(0b0010), idx(2));
assert_eq!(forest_to_root_index(0b0100), idx(4));
assert_eq!(forest_to_root_index(0b1000), idx(8));
assert_eq!(forest_to_root_index(0b0011), idx(5));
assert_eq!(forest_to_root_index(0b0101), idx(9));
assert_eq!(forest_to_root_index(0b1001), idx(17));
assert_eq!(forest_to_root_index(0b0111), idx(13));
assert_eq!(forest_to_root_index(0b1011), idx(21));
assert_eq!(forest_to_root_index(0b1111), idx(29));
assert_eq!(forest_to_root_index(0b0110), idx(10));
assert_eq!(forest_to_root_index(0b1010), idx(18));
assert_eq!(forest_to_root_index(0b1100), idx(20));
assert_eq!(forest_to_root_index(0b1110), idx(26));
}
#[test]
fn test_forest_to_rightmost_index() {
fn idx(pos: usize) -> InOrderIndex {
InOrderIndex::new(pos.try_into().unwrap())
}
for forest in 1..256 {
assert!(forest_to_rightmost_index(forest).inner() % 2 == 1, "Leaves are always odd");
}
assert_eq!(forest_to_rightmost_index(0b0001), idx(1));
assert_eq!(forest_to_rightmost_index(0b0010), idx(3));
assert_eq!(forest_to_rightmost_index(0b0011), idx(5));
assert_eq!(forest_to_rightmost_index(0b0100), idx(7));
assert_eq!(forest_to_rightmost_index(0b0101), idx(9));
assert_eq!(forest_to_rightmost_index(0b0110), idx(11));
assert_eq!(forest_to_rightmost_index(0b0111), idx(13));
assert_eq!(forest_to_rightmost_index(0b1000), idx(15));
assert_eq!(forest_to_rightmost_index(0b1001), idx(17));
assert_eq!(forest_to_rightmost_index(0b1010), idx(19));
assert_eq!(forest_to_rightmost_index(0b1011), idx(21));
assert_eq!(forest_to_rightmost_index(0b1100), idx(23));
assert_eq!(forest_to_rightmost_index(0b1101), idx(25));
assert_eq!(forest_to_rightmost_index(0b1110), idx(27));
assert_eq!(forest_to_rightmost_index(0b1111), idx(29));
}
#[test]
fn test_partial_mmr_apply_delta() {
// build an MMR with 10 nodes (2 peaks) and a partial MMR based on it
let mut mmr = Mmr::default();
(0..10).for_each(|i| mmr.add(int_to_node(i)));
let mut partial_mmr: PartialMmr = mmr.peaks().into();
// add authentication path for position 1 and 8
{
let node = mmr.get(1).unwrap();
let proof = mmr.open(1).unwrap();
partial_mmr.track(1, node, &proof.merkle_path).unwrap();
}
{
let node = mmr.get(8).unwrap();
let proof = mmr.open(8).unwrap();
partial_mmr.track(8, node, &proof.merkle_path).unwrap();
}
// add 2 more nodes into the MMR and validate apply_delta()
(10..12).for_each(|i| mmr.add(int_to_node(i)));
validate_apply_delta(&mmr, &mut partial_mmr);
// add 1 more node to the MMR, validate apply_delta() and start tracking the node
mmr.add(int_to_node(12));
validate_apply_delta(&mmr, &mut partial_mmr);
{
let node = mmr.get(12).unwrap();
let proof = mmr.open(12).unwrap();
partial_mmr.track(12, node, &proof.merkle_path).unwrap();
assert!(partial_mmr.track_latest);
}
// by this point we are tracking authentication paths for positions: 1, 8, and 12
// add 3 more nodes to the MMR (collapses to 1 peak) and validate apply_delta()
(13..16).for_each(|i| mmr.add(int_to_node(i)));
validate_apply_delta(&mmr, &mut partial_mmr);
}
fn validate_apply_delta(mmr: &Mmr, partial: &mut PartialMmr) {
let tracked_leaves = partial
.nodes
.iter()
.filter_map(|(index, _)| if index.is_leaf() { Some(index.sibling()) } else { None })
.collect::<Vec<_>>();
let nodes_before = partial.nodes.clone();
// compute and apply delta
let delta = mmr.get_delta(partial.forest(), mmr.forest()).unwrap();
let nodes_delta = partial.apply(delta).unwrap();
// new peaks were computed correctly
assert_eq!(mmr.peaks(), partial.peaks());
let mut expected_nodes = nodes_before;
for (key, value) in nodes_delta {
// nodes should not be duplicated
assert!(expected_nodes.insert(key, value).is_none());
}
// new nodes should be a combination of original nodes and delta
assert_eq!(expected_nodes, partial.nodes);
// make sure tracked leaves open to the same proofs as in the underlying MMR
for index in tracked_leaves {
let index_value: u64 = index.into();
let pos = index_value / 2;
let proof1 = partial.open(pos as usize).unwrap().unwrap();
let proof2 = mmr.open(pos as usize).unwrap();
assert_eq!(proof1, proof2);
}
}
#[test]
fn test_partial_mmr_inner_nodes_iterator() {
// build the MMR
let mmr: Mmr = LEAVES.into();
let first_peak = mmr.peaks().peaks()[0];
// -- test single tree ----------------------------
// get path and node for position 1
let node1 = mmr.get(1).unwrap();
let proof1 = mmr.open(1).unwrap();
// create partial MMR and add authentication path to node at position 1
let mut partial_mmr: PartialMmr = mmr.peaks().into();
partial_mmr.track(1, node1, &proof1.merkle_path).unwrap();
// empty iterator should have no nodes
assert_eq!(partial_mmr.inner_nodes([].iter().cloned()).next(), None);
// build Merkle store from authentication paths in partial MMR
let mut store: MerkleStore = MerkleStore::new();
store.extend(partial_mmr.inner_nodes([(1, node1)].iter().cloned()));
let index1 = NodeIndex::new(2, 1).unwrap();
let path1 = store.get_path(first_peak, index1).unwrap().path;
assert_eq!(path1, proof1.merkle_path);
// -- test no duplicates --------------------------
// build the partial MMR
let mut partial_mmr: PartialMmr = mmr.peaks().into();
let node0 = mmr.get(0).unwrap();
let proof0 = mmr.open(0).unwrap();
let node2 = mmr.get(2).unwrap();
let proof2 = mmr.open(2).unwrap();
partial_mmr.track(0, node0, &proof0.merkle_path).unwrap();
partial_mmr.track(1, node1, &proof1.merkle_path).unwrap();
partial_mmr.track(2, node2, &proof2.merkle_path).unwrap();
// make sure there are no duplicates
let leaves = [(0, node0), (1, node1), (2, node2)];
let mut nodes = BTreeSet::new();
for node in partial_mmr.inner_nodes(leaves.iter().cloned()) {
assert!(nodes.insert(node.value));
}
// and also that the store is still be built correctly
store.extend(partial_mmr.inner_nodes(leaves.iter().cloned()));
let index0 = NodeIndex::new(2, 0).unwrap();
let index1 = NodeIndex::new(2, 1).unwrap();
let index2 = NodeIndex::new(2, 2).unwrap();
let path0 = store.get_path(first_peak, index0).unwrap().path;
let path1 = store.get_path(first_peak, index1).unwrap().path;
let path2 = store.get_path(first_peak, index2).unwrap().path;
assert_eq!(path0, proof0.merkle_path);
assert_eq!(path1, proof1.merkle_path);
assert_eq!(path2, proof2.merkle_path);
// -- test multiple trees -------------------------
// build the partial MMR
let mut partial_mmr: PartialMmr = mmr.peaks().into();
let node5 = mmr.get(5).unwrap();
let proof5 = mmr.open(5).unwrap();
partial_mmr.track(1, node1, &proof1.merkle_path).unwrap();
partial_mmr.track(5, node5, &proof5.merkle_path).unwrap();
// build Merkle store from authentication paths in partial MMR
let mut store: MerkleStore = MerkleStore::new();
store.extend(partial_mmr.inner_nodes([(1, node1), (5, node5)].iter().cloned()));
let index1 = NodeIndex::new(2, 1).unwrap();
let index5 = NodeIndex::new(1, 1).unwrap();
let second_peak = mmr.peaks().peaks()[1];
let path1 = store.get_path(first_peak, index1).unwrap().path;
let path5 = store.get_path(second_peak, index5).unwrap().path;
assert_eq!(path1, proof1.merkle_path);
assert_eq!(path5, proof5.merkle_path);
}
#[test]
fn test_partial_mmr_add_without_track() {
let mut mmr = Mmr::default();
let empty_peaks = MmrPeaks::new(0, vec![]).unwrap();
let mut partial_mmr = PartialMmr::from_peaks(empty_peaks);
for el in (0..256).map(int_to_node) {
mmr.add(el);
partial_mmr.add(el, false);
assert_eq!(mmr.peaks(), partial_mmr.peaks());
assert_eq!(mmr.forest(), partial_mmr.forest());
}
}
#[test]
fn test_partial_mmr_add_with_track() {
let mut mmr = Mmr::default();
let empty_peaks = MmrPeaks::new(0, vec![]).unwrap();
let mut partial_mmr = PartialMmr::from_peaks(empty_peaks);
for i in 0..256 {
let el = int_to_node(i);
mmr.add(el);
partial_mmr.add(el, true);
assert_eq!(mmr.peaks(), partial_mmr.peaks());
assert_eq!(mmr.forest(), partial_mmr.forest());
for pos in 0..i {
let mmr_proof = mmr.open(pos as usize).unwrap();
let partialmmr_proof = partial_mmr.open(pos as usize).unwrap().unwrap();
assert_eq!(mmr_proof, partialmmr_proof);
}
}
}
#[test]
fn test_partial_mmr_add_existing_track() {
let mut mmr = Mmr::from((0..7).map(int_to_node));
// derive a partial Mmr from it which tracks authentication path to leaf 5
let mut partial_mmr = PartialMmr::from_peaks(mmr.peaks());
let path_to_5 = mmr.open(5).unwrap().merkle_path;
let leaf_at_5 = mmr.get(5).unwrap();
partial_mmr.track(5, leaf_at_5, &path_to_5).unwrap();
// add a new leaf to both Mmr and partial Mmr
let leaf_at_7 = int_to_node(7);
mmr.add(leaf_at_7);
partial_mmr.add(leaf_at_7, false);
// the openings should be the same
assert_eq!(mmr.open(5).unwrap(), partial_mmr.open(5).unwrap().unwrap());
}
#[test]
fn test_partial_mmr_serialization() {
let mmr = Mmr::from((0..7).map(int_to_node));
let partial_mmr = PartialMmr::from_peaks(mmr.peaks());
let bytes = partial_mmr.to_bytes();
let decoded = PartialMmr::read_from_bytes(&bytes).unwrap();
assert_eq!(partial_mmr, decoded);
}
}