zec
/
incrementalmerkletree
mirror of https://github.com/zcash/incrementalmerkletree.git
1
0
Fork 0
Code Issues Projects Releases Wiki Activity

Add an as_of_root argument to Tree::authentication_path 

This requires a user of this API to specify a root of the tree
that identifies the state of the tree at which the user wishes
to construct an authentication path. This must be equal to either
the current root of the tree, or to the root of the tree at a
previous checkpoint.
This commit is contained in:
Kris Nuttycombe 2022-04-18 16:01:53 -06:00
parent fef054d43a
commit 06728b9499
5 changed files with 600 additions and 200 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

23
CHANGELOG.md
View File

@ -7,6 +7,29 @@ and this project adheres to Rust's notion of
## [Unreleased]
### Added
- `incrementalmerkletree::bridgetree`:
- `Checkpoint::witnessed` returns the set of positions that have been marked with
`BridgeTree::witness` while this checkpoint was the current checkpoint.
### Changed
- `incrementalmerkletree`:
- `Tree::authentication_path` has been changed to take an `as_of_root` parameter.
This allows computation of the authentication path as of previous tree states, in
addition to the previous behavior which only allowed computation of the path as of the
most recent tree state. The provided `as_of_root` value must be equal to either the
current root of the tree, or to the root of the tree at a previous checkpoint.
### Removed
- `incrementalmerkletree::bridgetree`:
- `Checkpoint::rewrite_indices` was an internal utility method that had inadvertently
been made a part of the public API.
## [0.3.0-beta.2] - 2022-04-06
### Added
- `incrementalmerkletree`:
- `Tree::get_witnessed_leaf`, to allow a user to query for the leaf value of

14
proptest-regressions/lib.txt
View File

@ -1,14 +0,0 @@
# Seeds for failure cases proptest has generated in the past. It is
# automatically read and these particular cases re-run before any
# novel cases are generated.
#
# It is recommended to check this file in to source control so that
# everyone who runs the test benefits from these saved cases.
cc 6a5f61f970da957baf3be8b5383d71a1510b42e9457cc00509163fde8430f198 # shrinks to ops = [Append(SipHashable(0)), Checkpoint, Witness, Rewind]
cc ed57a2e3d91f2da644f695b8698822f9eaa2b3fd1f5bd039a5753e7027623ed9 # shrinks to ops = [Append("a"), Unwitness("a"), Checkpoint, Witness, Rewind]
cc aa498d80d63c58720a913f2edcc6ba19da462f7a824f5be906e63c7ca1566076 # shrinks to ops = [Append(SipHashable(0)), Checkpoint, Checkpoint, Rewind, Append(SipHashable(0)), Rewind, Append(SipHashable(1))]
cc 7cebce1664b804d55e259c466ebcc140c4a3708f4ec49ed865d6009736b0a568 # shrinks to ops = [Append("d"), Checkpoint, Witness, Unwitness("d"), Rewind, Unwitness("d")]
cc 9078a200bceb14aa2f78743f545dab9719db29ddbbb5f1f67fae01805da90f4b # shrinks to ops = [Append("a"), Unwitness("a"), Checkpoint, Checkpoint, Rewind, Append("a"), Rewind, Append("a")]
cc 20e43678bbf38f4c40fdd9e6f5bbc2b8eebcb1756b599f443f3268d6cf8e9d22 # shrinks to ops = [Append("o"), Checkpoint, Witness, Checkpoint, Unwitness("o"), Rewind, Rewind]
cc 2b82b514115d3ddb4990853b0178e997632226be6b8f7c9cf07e94a3e9f41690 # shrinks to ops = [Checkpoint, Witness, Rewind, Unwitness(Position(0), "x"), Checkpoint, Rewind, Checkpoint, Unwitness(Position(0), "x"), Unwitness(Position(0), "x"), Witness, Unwitness(Position(0), "x"), Append("x"), Append("b"), Authpath(Position(0), "x"), Authpath(Position(0), "x"), Rewind, Rewind, Authpath(Position(0), "x"), Witness, Rewind, Witness, Rewind, Append("x"), Rewind, Authpath(Position(0), "x"), Checkpoint, Authpath(Position(0), "x"), Witness, Checkpoint, Witness, Checkpoint, Rewind, Unwitness(Position(0), "x"), Unwitness(Position(0), "x"), Rewind, Witness, Rewind, Authpath(Position(0), "x"), Unwitness(Position(0), "x"), Authpath(Position(0), "x"), Witness, Witness, Checkpoint, Rewind, Checkpoint]
cc 248258b4e2fd558b56611179f6c8493326a8a35bd3fd3ffb55634c14f6fe417a # shrinks to ops = [Append(SipHashable(0)), Checkpoint, Witness, Rewind, Rewind, Authpath(Position(0), SipHashable(0)), Authpath(Position(0), SipHashable(0)), Append(SipHashable(0)), Witness, Authpath(Position(0), SipHashable(0)), Unwitness(Position(0), SipHashable(0)), Unwitness(Position(0), SipHashable(0)), Authpath(Position(0), SipHashable(0)), Authpath(Position(0), SipHashable(0)), Unwitness(Position(0), SipHashable(0)), Witness, Rewind, Checkpoint, Authpath(Position(0), SipHashable(0)), Witness, Rewind, Authpath(Position(0), SipHashable(0)), Authpath(Position(0), SipHashable(0)), Unwitness(Position(0), SipHashable(0)), Rewind, Append(SipHashable(0)), Witness, Authpath(Position(1), SipHashable(0)), Witness, Witness, Unwitness(Position(3), SipHashable(0)), Append(SipHashable(0)), Checkpoint, Append(SipHashable(0)), Witness, Witness, Checkpoint, Unwitness(Position(5), SipHashable(0)), Unwitness(Position(1), SipHashable(0)), Append(SipHashable(0)), Checkpoint, Authpath(Position(2), SipHashable(0)), Witness, Append(SipHashable(0)), Unwitness(Position(6), SipHashable(0)), Authpath(Position(2), SipHashable(0)), Witness, Unwitness(Position(5), SipHashable(0)), Checkpoint, Rewind, Unwitness(Position(1), SipHashable(0)), Checkpoint, Rewind, Witness, Checkpoint, Unwitness(Position(5), SipHashable(0)), Authpath(Position(2), SipHashable(0)), Append(SipHashable(0)), Checkpoint, Append(SipHashable(0)), Checkpoint, Append(SipHashable(0)), Unwitness(Position(4), SipHashable(0)), Rewind, Append(SipHashable(7)), Checkpoint, Append(SipHashable(9)), Authpath(Position(5), SipHashable(0)), Checkpoint, Authpath(Position(10), SipHashable(7)), Rewind, Checkpoint, Rewind]

236
src/bridgetree.rs
View File

@ -564,6 +564,16 @@ impl<'a, H: Hashable + Ord + Clone + 'a> MerkleBridge<H> {
self.frontier.root()
}
fn root_at_altitude(&self, alt: Altitude) -> H {
// fold from the current height, combining with empty branches,
// up to the specified altitude
(self.max_altitude() + 1)
.iter_to(alt)
.fold(self.frontier.root(), |d, lvl| {
H::combine(lvl, &d, &H::empty_root(lvl))
})
}
/// Returns a single MerkleBridge that contains the aggregate information
/// of this bridge and `next`, or None if `next` is not a valid successor
/// to this bridge. The resulting Bridge will have the same state as though
@ -620,6 +630,9 @@ pub struct Checkpoint {
/// A flag indicating whether or not the current state of the tree
/// had been witnessed at the time the checkpoint was created.
is_witnessed: bool,
/// A set of the positions that have been witnessed during the period that this
/// checkpoint is the current checkpoint.
witnessed: BTreeSet<Position>,
/// When a witness is forgotten, if the index of the forgotten witness is <= bridge_idx we
/// record it in the current checkpoint so that on rollback, we restore the forgotten
/// witnesses to the BridgeTree's "saved" list. If the witness was newly created since the
@ -629,39 +642,89 @@ pub struct Checkpoint {
}
impl Checkpoint {
/// Creates a new checkpoint from its constituent parts.
pub fn from_parts(
bridges_len: usize,
is_witnessed: bool,
witnessed: BTreeSet<Position>,
forgotten: BTreeMap<Position, usize>,
) -> Self {
Self {
bridges_len,
is_witnessed,
witnessed,
forgotten,
}
}
/// Creates a new empty checkpoint for the specified [`BridgeTree`] state.
pub fn at_length(bridges_len: usize, is_witnessed: bool) -> Self {
Checkpoint {
bridges_len,
is_witnessed,
witnessed: BTreeSet::new(),
forgotten: BTreeMap::new(),
}
}
/// Returns the length of the [`prior_bridges`] vector of the [`BridgeTree`] to which
/// this checkpoint refers.
///
/// This is the number of bridges that will be retained in the event of a rewind to this
/// checkpoint.
pub fn bridges_len(&self) -> usize {
self.bridges_len
}
/// Returns whether the current state of the tree had been witnessed at the point that
/// this checkpoint was made.
///
/// In the event of a rewind, the rewind logic will ensure that witness information is
/// properly reconstituted for the checkpointed tree state.
pub fn is_witnessed(&self) -> bool {
self.is_witnessed
}
/// Returns a set of the positions that have been witnessed during the period that this
/// checkpoint is the current checkpoint.
pub fn witnessed(&self) -> &BTreeSet<Position> {
&self.witnessed
}
/// Returns the set of previously-witnessed positions that have had their witnesses removed
/// during the period that this checkpoint is the current checkpoint.
pub fn forgotten(&self) -> &BTreeMap<Position, usize> {
&self.forgotten
}
pub fn rewrite_indices<F: Fn(usize) -> usize>(&mut self, f: F) {
// A private convenience method that returns the root of the bridge corresponding to
// this checkpoint at a specified depth, given the slice of bridges from which this checkpoint
// was derived.
fn root<H: Hashable + Clone + Ord>(
&self,
bridges: &[MerkleBridge<H>],
altitude: Altitude,
) -> H {
if self.bridges_len == 0 {
H::empty_root(altitude)
} else {
bridges[self.bridges_len - 1].root_at_altitude(altitude)
}
}
// A private convenience method that returns the position of the bridge corresponding
// to this checkpoint, if the checkpoint is not for the empty bridge.
fn position<H: Ord>(&self, bridges: &[MerkleBridge<H>]) -> Option<Position> {
if self.bridges_len == 0 {
None
} else {
Some(bridges[self.bridges_len - 1].position())
}
}
// A private method that rewrites the indices of each forgotten witness record
// using the specified rewrite function. Used during garbage collection.
fn rewrite_indices<F: Fn(usize) -> usize>(&mut self, f: F) {
self.bridges_len = f(self.bridges_len);
for v in self.forgotten.values_mut() {
*v = f(*v)
@ -857,7 +920,7 @@ impl<H: Hashable + Ord + Clone, const DEPTH: u8> BridgeTree<H, DEPTH> {
}
}
impl<H: Hashable + Ord + Clone, const DEPTH: u8> crate::Frontier<H> for BridgeTree<H, DEPTH> {
impl<H: Hashable + Ord + Clone + Debug, const DEPTH: u8> Tree<H> for BridgeTree<H, DEPTH> {
fn append(&mut self, value: &H) -> bool {
if let Some(bridge) = self.current_bridge.as_mut() {
if bridge.frontier.position().is_complete(Altitude(DEPTH)) {
@ -872,22 +935,26 @@ impl<H: Hashable + Ord + Clone, const DEPTH: u8> crate::Frontier<H> for BridgeTr
}
}
fn root(&self) -> H {
self.current_bridge
.as_ref()
.map_or(H::empty_root(Altitude(DEPTH)), |bridge| {
// fold from the current height, combining with empty branches,
// up to the maximum height of the tree
(bridge.max_altitude() + 1)
.iter_to(Altitude(DEPTH))
.fold(bridge.root(), |d, lvl| {
H::combine(lvl, &d, &H::empty_root(lvl))
})
})
fn root(&self, checkpoint_depth: usize) -> Option<H> {
let altitude = Altitude(DEPTH);
if checkpoint_depth == 0 {
Some(
self.current_bridge
.as_ref()
.map_or(H::empty_root(altitude), |bridge| {
bridge.root_at_altitude(altitude)
}),
)
} else if self.checkpoints.len() >= checkpoint_depth {
let checkpoint_idx = self.checkpoints.len() - checkpoint_depth;
self.checkpoints
.get(checkpoint_idx)
.map(|c| c.root(&self.prior_bridges, altitude))
} else {
None
}
}
}
impl<H: Hashable + Ord + Clone + Debug, const DEPTH: u8> Tree<H> for BridgeTree<H, DEPTH> {
fn current_position(&self) -> Option<Position> {
self.current_bridge.as_ref().map(|b| b.position())
}
@ -924,6 +991,14 @@ impl<H: Hashable + Ord + Clone + Debug, const DEPTH: u8> Tree<H> for BridgeTree<
self.saved
.entry(pos)
.or_insert(self.prior_bridges.len() - 1);
// mark the position as having been witnessed in the current checkpoint
if let Some(c) = self.checkpoints.last_mut() {
if !c.is_witnessed {
c.witnessed.insert(pos);
}
}
Some(pos)
}
None => None,
@ -942,12 +1017,16 @@ impl<H: Hashable + Ord + Clone + Debug, const DEPTH: u8> Tree<H> for BridgeTree<
fn remove_witness(&mut self, position: Position) -> bool {
if let Some(idx) = self.saved.remove(&position) {
// If the index of the saved value is one that could have been known
// at the last checkpoint, then add it to the set of those forgotten
// during the current checkpoint span so that it can be restored
// on rollback.
// Stop tracking auth fragments for the removed position
if let Some(cur_b) = self.current_bridge.as_mut() {
cur_b.auth_fragments.remove(&position);
}
// If the position is one that has *not* just been witnessed since the last checkpoint,
// then add it to the set of those forgotten during the current checkpoint span so that
// it can be restored on rollback.
if let Some(c) = self.checkpoints.last_mut() {
if c.bridges_len > 0 && idx < c.bridges_len - 1 {
if !c.witnessed.contains(&position) {
c.forgotten.insert(position, idx);
}
}
@ -997,7 +1076,10 @@ impl<H: Hashable + Ord + Clone + Debug, const DEPTH: u8> Tree<H> for BridgeTree<
self.saved.append(&mut c.forgotten);
self.saved.retain(|_, i| *i + 1 < c.bridges_len);
self.prior_bridges.truncate(c.bridges_len);
self.current_bridge = self.prior_bridges.last().map(|b| b.successor(false));
self.current_bridge = self
.prior_bridges
.last()
.map(|b| b.successor(c.is_witnessed));
if c.is_witnessed {
self.witness();
}
@ -1007,24 +1089,92 @@ impl<H: Hashable + Ord + Clone + Debug, const DEPTH: u8> Tree<H> for BridgeTree<
}
}
fn authentication_path(&self, position: Position) -> Option<Vec<H>> {
self.saved.get(&position).and_then(|idx| {
fn authentication_path(&self, position: Position, as_of_root: &H) -> Option<Vec<H>> {
#[derive(Debug)]
enum AuthBase<'a> {
Current,
Checkpoint(usize, &'a Checkpoint),
NotFound,
}
let max_alt = Altitude(DEPTH);
// Find the earliest checkpoint having a matching root, or the current
// root if it matches and there is no earlier matching checkpoint.
let auth_base = self
.checkpoints
.iter()
.enumerate()
.rev()
.take_while(|(_, c)| c.position(&self.prior_bridges) >= Some(position))
.filter(|(_, c)| &c.root(&self.prior_bridges, max_alt) == as_of_root)
.last()
.map(|(i, c)| AuthBase::Checkpoint(i, c))
.unwrap_or_else(|| {
if self.root(0).as_ref() == Some(as_of_root) {
AuthBase::Current
} else {
AuthBase::NotFound
}
});
let saved_idx = self.saved.get(&position).or_else(|| {
if let AuthBase::Checkpoint(i, _) = auth_base {
// The saved position might have been forgotten since the checkpoint,
// so look for it in each of the subsequent checkpoints' forgotten
// items.
self.checkpoints[i..].iter().find_map(|c| {
// restore the forgotten position, if that position was not also witnessed
// in the same checkpoint
c.forgotten
.get(&position)
.filter(|_| !c.witnessed.contains(&position))
})
} else {
None
}
});
saved_idx.and_then(|idx| {
let frontier = &self.prior_bridges[*idx].frontier;
// Fuse the following bridges to obtain a bridge that has all
// of the data to the right of the selected value in the tree.
// The unwrap here is safe because a witnessed leaf always
// generates a subsequent bridge in the tree.
MerkleBridge::fuse_all(
self.prior_bridges[(idx + 1)..]
.iter()
.chain(self.current_bridge.iter()),
)
.map(|fused| {
// of the data to the right of the selected value in the tree,
// up to the specified checkpoint depth.
let fuse_from = idx + 1;
let fused = match auth_base {
AuthBase::Current => MerkleBridge::fuse_all(
self.prior_bridges[fuse_from..]
.iter()
.chain(&self.current_bridge),
),
AuthBase::Checkpoint(_, checkpoint) if fuse_from < checkpoint.bridges_len => {
MerkleBridge::fuse_all(
self.prior_bridges[fuse_from..checkpoint.bridges_len].iter(),
)
}
AuthBase::Checkpoint(_, checkpoint) if fuse_from == checkpoint.bridges_len => {
// The successor bridge should just be the empty successor to the
// checkpointed bridge.
if checkpoint.bridges_len > 0 {
Some(self.prior_bridges[checkpoint.bridges_len - 1].successor(false))
} else {
None
}
}
AuthBase::Checkpoint(_, _) => {
// if the saved index is after the checkpoint, we can't generate
// an auth path
None
}
AuthBase::NotFound => None,
};
fused.map(|successor| {
// construct a complete trailing edge that includes the data from
// the following frontier not yet included in the trailing edge.
let auth_fragment = fused.auth_fragments.get(&frontier.position());
let rest_frontier = fused.frontier;
let auth_fragment = successor.auth_fragments.get(&frontier.position());
let rest_frontier = successor.frontier;
let mut auth_values = auth_fragment.iter().flat_map(|auth_fragment| {
let last_altitude = auth_fragment.next_required_altitude();
@ -1147,7 +1297,7 @@ mod tests {
use super::*;
use crate::tests::{apply_operation, arb_operation};
use crate::{Frontier, Tree};
use crate::Tree;
#[test]
fn tree_depth() {
@ -1209,8 +1359,8 @@ mod tests {
for pos in tree.saved.keys() {
assert_eq!(
tree.authentication_path(*pos),
tree_mut.authentication_path(*pos)
tree.authentication_path(*pos, &tree.root(0).unwrap()),
tree_mut.authentication_path(*pos, &tree.root(0).unwrap())
);
}
}
@ -1309,7 +1459,7 @@ mod tests {
let auth_paths = has_auth_path
.iter()
.map(|pos| {
t.authentication_path(*pos)
t.authentication_path(*pos, &t.root(0).unwrap())
.expect("Must be able to get auth path")
})
.collect::<Vec<_>>();
@ -1319,7 +1469,7 @@ mod tests {
let retained_auth_paths = has_auth_path
.iter()
.map(|pos| {
t.authentication_path(*pos)
t.authentication_path(*pos, &t.root(0).unwrap())
.expect("Must be able to get auth path")
})
.collect::<Vec<_>>();
@ -1329,14 +1479,14 @@ mod tests {
#[test]
fn garbage_collect_idx() {
let mut tree: BridgeTree<String, 7> = BridgeTree::new(100);
let empty_root = tree.root();
let empty_root = tree.root(0);
tree.append(&"a".to_string());
for _ in 0..100 {
tree.checkpoint();
}
tree.garbage_collect();
assert!(tree.root() != empty_root);
assert!(tree.root(0) != empty_root);
tree.rewind();
assert!(tree.root() != empty_root);
assert!(tree.root(0) != empty_root);
}
}

452
src/lib.rs
View File

@ -232,7 +232,12 @@ pub trait Frontier<H> {
/// A Merkle tree that supports incremental appends, witnessing of
/// leaf nodes, checkpoints and rollbacks.
pub trait Tree<H>: Frontier<H> {
pub trait Tree<H> {
/// Appends a new value to the tree at the next available slot.
/// Returns true if successful and false if the tree would exceed
/// the maximum allowed depth.
fn append(&mut self, value: &H) -> bool;
/// Returns the most recently appended leaf value.
fn current_position(&self) -> Option<Position>;
@ -252,10 +257,18 @@ pub trait Tree<H>: Frontier<H> {
/// Return a set of all the positions for which we have witnessed.
fn witnessed_positions(&self) -> BTreeSet<Position>;
/// Obtains an authentication path to the value at the specified position.
/// Obtains the root of the Merkle tree at the specified checkpoint depth
/// by hashing against empty nodes up to the maximum height of the tree.
/// Returns `None` if there are not enough checkpoints available to reach the
/// requested checkpoint depth.
fn root(&self, checkpoint_depth: usize) -> Option<H>;
/// Obtains an authentication path to the value at the specified position,
/// as of the tree state corresponding to the given root.
/// Returns `None` if there is no available authentication path to that
/// value.
fn authentication_path(&self, position: Position) -> Option<Vec<H>>;
/// position or if the root does not correspond to a checkpointed
/// root of the tree.
fn authentication_path(&self, position: Position, as_of_root: &H) -> Option<Vec<H>>;
/// Marks the value at the specified position as a value we're no longer
/// interested in maintaining a witness for. Returns true if successful and
@ -292,7 +305,7 @@ pub(crate) mod tests {
use super::bridgetree::BridgeTree;
use super::sample::{lazy_root, CompleteTree};
use super::{Altitude, Frontier, Hashable, Position, Tree};
use super::{Altitude, Hashable, Position, Tree};
#[test]
fn position_altitudes() {
@ -341,17 +354,17 @@ pub(crate) mod tests {
pub(crate) fn check_root_hashes<T: Tree<String>, F: Fn(usize) -> T>(new_tree: F) {
let mut tree = new_tree(100);
assert_eq!(tree.root(), "________________");
assert_eq!(tree.root(0).unwrap(), "________________");
tree.append(&"a".to_string());
assert_eq!(tree.root().len(), 16);
assert_eq!(tree.root(), "a_______________");
assert_eq!(tree.root(0).unwrap().len(), 16);
assert_eq!(tree.root(0).unwrap(), "a_______________");
tree.append(&"b".to_string());
assert_eq!(tree.root(), "ab______________");
assert_eq!(tree.root(0).unwrap(), "ab______________");
tree.append(&"c".to_string());
assert_eq!(tree.root(), "abc_____________");
assert_eq!(tree.root(0).unwrap(), "abc_____________");
let mut t = new_tree(100);
t.append(&"a".to_string());
@ -360,7 +373,7 @@ pub(crate) mod tests {
t.append(&"a".to_string());
t.append(&"a".to_string());
t.append(&"a".to_string());
assert_eq!(t.root(), "aaaa____________");
assert_eq!(t.root(0).unwrap(), "aaaa____________");
}
pub(crate) fn check_auth_paths<T: Tree<String> + std::fmt::Debug, F: Fn(usize) -> T>(
@ -370,7 +383,7 @@ pub(crate) mod tests {
tree.append(&"a".to_string());
tree.witness();
assert_eq!(
tree.authentication_path(Position::from(0)),
tree.authentication_path(Position::from(0), &tree.root(0).unwrap()),
Some(vec![
"_".to_string(),
"__".to_string(),
@ -381,7 +394,7 @@ pub(crate) mod tests {
tree.append(&"b".to_string());
assert_eq!(
tree.authentication_path(Position::zero()),
tree.authentication_path(Position::zero(), &tree.root(0).unwrap()),
Some(vec![
"b".to_string(),
"__".to_string(),
@ -393,7 +406,7 @@ pub(crate) mod tests {
tree.append(&"c".to_string());
tree.witness();
assert_eq!(
tree.authentication_path(Position::from(2)),
tree.authentication_path(Position::from(2), &tree.root(0).unwrap()),
Some(vec![
"_".to_string(),
"ab".to_string(),
@ -404,7 +417,7 @@ pub(crate) mod tests {
tree.append(&"d".to_string());
assert_eq!(
tree.authentication_path(Position::from(2)),
tree.authentication_path(Position::from(2), &tree.root(0).unwrap()),
Some(vec![
"d".to_string(),
"ab".to_string(),
@ -415,7 +428,7 @@ pub(crate) mod tests {
tree.append(&"e".to_string());
assert_eq!(
tree.authentication_path(Position::from(2)),
tree.authentication_path(Position::from(2), &tree.root(0).unwrap()),
Some(vec![
"d".to_string(),
"ab".to_string(),
@ -434,7 +447,7 @@ pub(crate) mod tests {
tree.append(&"h".to_string());
assert_eq!(
tree.authentication_path(Position::zero()),
tree.authentication_path(Position::zero(), &tree.root(0).unwrap()),
Some(vec![
"b".to_string(),
"cd".to_string(),
@ -457,7 +470,7 @@ pub(crate) mod tests {
tree.append(&"g".to_string());
assert_eq!(
tree.authentication_path(Position::from(5)),
tree.authentication_path(Position::from(5), &tree.root(0).unwrap()),
Some(vec![
"e".to_string(),
"g_".to_string(),
@ -474,7 +487,7 @@ pub(crate) mod tests {
tree.append(&'l'.to_string());
assert_eq!(
tree.authentication_path(Position::from(10)),
tree.authentication_path(Position::from(10), &tree.root(0).unwrap()),
Some(vec![
"l".to_string(),
"ij".to_string(),
@ -497,7 +510,7 @@ pub(crate) mod tests {
}
assert_eq!(
tree.authentication_path(Position::zero()),
tree.authentication_path(Position::zero(), &tree.root(0).unwrap()),
Some(vec![
"b".to_string(),
"cd".to_string(),
@ -521,7 +534,7 @@ pub(crate) mod tests {
assert!(tree.rewind());
assert_eq!(
tree.authentication_path(Position::from(2)),
tree.authentication_path(Position::from(2), &tree.root(0).unwrap()),
Some(vec![
"d".to_string(),
"ab".to_string(),
@ -534,7 +547,10 @@ pub(crate) mod tests {
tree.append(&'a'.to_string());
tree.append(&'b'.to_string());
tree.witness();
assert_eq!(tree.authentication_path(Position::from(0)), None);
assert_eq!(
tree.authentication_path(Position::from(0), &tree.root(0).unwrap()),
None
);
let mut tree = new_tree(100);
for c in 'a'..'n' {
@ -547,7 +563,7 @@ pub(crate) mod tests {
tree.append(&'p'.to_string());
assert_eq!(
tree.authentication_path(Position::from(12)),
tree.authentication_path(Position::from(12), &tree.root(0).unwrap()),
Some(vec![
"n".to_string(),
"op".to_string(),
@ -562,7 +578,7 @@ pub(crate) mod tests {
.chain(Some(Witness))
.chain(Some(Append('m'.to_string())))
.chain(Some(Append('n'.to_string())))
.chain(Some(Authpath(11usize.into())))
.chain(Some(Authpath(11usize.into(), 0)))
.collect::<Vec<_>>();
let mut tree = new_tree(100);
@ -618,7 +634,7 @@ pub(crate) mod tests {
t.append(&"b".to_string());
assert!(t.rewind());
t.append(&"b".to_string());
assert_eq!(t.root(), "ab______________");
assert_eq!(t.root(0).unwrap(), "ab______________");
}
pub(crate) fn check_rewind_remove_witness<T: Tree<String>, F: Fn(usize) -> T>(new_tree: F) {
@ -671,69 +687,46 @@ pub(crate) mod tests {
// test framework itself previously did not correctly handle
// chain state restoration.
fn append(x: &str) -> Operation<String> {
Append(x.to_string())
let samples = vec![
vec![append("x"), Checkpoint, Witness, Rewind, unwitness(0)],
vec![
append("d"),
Checkpoint,
Witness,
unwitness(0),
Rewind,
unwitness(0),
],
vec![
append("o"),
Checkpoint,
Witness,
Checkpoint,
unwitness(0),
Rewind,
Rewind,
],
vec![
append("s"),
Witness,
append("m"),
Checkpoint,
unwitness(0),
Rewind,
unwitness(0),
unwitness(0),
],
];
for (i, sample) in samples.iter().enumerate() {
let result = check_operations(sample);
assert!(
matches!(result, Ok(())),
"Reference/Test mismatch at index {}: {:?}",
i,
result
);
}
fn unwitness(pos: usize) -> Operation<String> {
Unwitness(Position::from(pos))
}
let ops = vec![append("x"), Checkpoint, Witness, Rewind, unwitness(0)];
let result = check_operations(ops);
assert!(
matches!(result, Ok(())),
"Reference/Test mismatch: {:?}",
result
);
let ops = vec![
append("d"),
Checkpoint,
Witness,
unwitness(0),
Rewind,
unwitness(0),
];
let result = check_operations(ops);
assert!(
matches!(result, Ok(())),
"Reference/Test mismatch: {:?}",
result
);
let ops = vec![
append("o"),
Checkpoint,
Witness,
Checkpoint,
unwitness(0),
Rewind,
Rewind,
];
let result = check_operations(ops);
assert!(
matches!(result, Ok(())),
"Reference/Test mismatch: {:?}",
result
);
let ops = vec![
append("s"),
Witness,
append("m"),
Checkpoint,
unwitness(0),
Rewind,
unwitness(0),
unwitness(0),
];
let result = check_operations(ops);
assert!(
matches!(result, Ok(())),
"Reference/Test mismatch: {:?}",
result
);
}
//
@ -755,7 +748,7 @@ pub(crate) mod tests {
}
}
impl<H: Hashable + Ord + Clone + Debug, const DEPTH: u8> Frontier<H> for CombinedTree<H, DEPTH> {
impl<H: Hashable + Ord + Clone + Debug, const DEPTH: u8> Tree<H> for CombinedTree<H, DEPTH> {
fn append(&mut self, value: &H) -> bool {
let a = self.inefficient.append(value);
let b = self.efficient.append(value);
@ -763,16 +756,13 @@ pub(crate) mod tests {
a
}
/// Obtains the current root of this Merkle tree.
fn root(&self) -> H {
let a = self.inefficient.root();
let b = self.efficient.root();
fn root(&self, checkpoint_depth: usize) -> Option<H> {
let a = self.inefficient.root(checkpoint_depth);
let b = self.efficient.root(checkpoint_depth);
assert_eq!(a, b);
a
}
}
impl<H: Hashable + Ord + Clone + Debug, const DEPTH: u8> Tree<H> for CombinedTree<H, DEPTH> {
fn current_position(&self) -> Option<Position> {
let a = self.inefficient.current_position();
let b = self.efficient.current_position();
@ -811,9 +801,9 @@ pub(crate) mod tests {
a
}
fn authentication_path(&self, position: Position) -> Option<Vec<H>> {
let a = self.inefficient.authentication_path(position);
let b = self.efficient.authentication_path(position);
fn authentication_path(&self, position: Position, as_of_root: &H) -> Option<Vec<H>> {
let a = self.inefficient.authentication_path(position, as_of_root);
let b = self.efficient.authentication_path(position, as_of_root);
assert_eq!(a, b);
a
}
@ -843,6 +833,10 @@ pub(crate) mod tests {
}
}
//
// Operations
//
#[derive(Clone, Debug)]
pub enum Operation<A> {
Append(A),
@ -854,12 +848,24 @@ pub(crate) mod tests {
Unwitness(Position),
Checkpoint,
Rewind,
Authpath(Position),
Authpath(Position, usize),
GarbageCollect,
}
use Operation::*;
fn append(x: &str) -> Operation<String> {
Operation::Append(x.to_string())
}
fn unwitness(pos: usize) -> Operation<String> {
Operation::Unwitness(Position::from(pos))
}
fn authpath(pos: usize, depth: usize) -> Operation<String> {
Operation::Authpath(Position::from(pos), depth)
}
impl<H: Hashable> Operation<H> {
pub fn apply<T: Tree<H>>(&self, tree: &mut T) -> Option<(Position, Vec<H>)> {
match self {
@ -887,7 +893,10 @@ pub(crate) mod tests {
assert!(tree.rewind(), "rewind failed");
None
}
Authpath(p) => tree.authentication_path(*p).map(|xs| (*p, xs)),
Authpath(p, d) => tree
.root(*d)
.and_then(|root| tree.authentication_path(*p, &root))
.map(|xs| (*p, xs)),
GarbageCollect => None,
}
}
@ -977,6 +986,192 @@ pub(crate) mod tests {
);
}
#[test]
fn test_auth_path_consistency() {
let samples = vec![
// Reduced examples
vec![
append("a"),
append("b"),
Checkpoint,
Witness,
authpath(0, 1),
],
vec![
append("c"),
append("d"),
Witness,
Checkpoint,
authpath(1, 1),
],
vec![
append("e"),
Checkpoint,
Witness,
append("f"),
authpath(0, 1),
],
vec![
append("g"),
Witness,
Checkpoint,
unwitness(0),
append("h"),
authpath(0, 0),
],
vec![
append("i"),
Checkpoint,
Witness,
unwitness(0),
append("j"),
authpath(0, 0),
],
vec![
append("i"),
Witness,
append("j"),
Checkpoint,
append("k"),
authpath(0, 1),
],
vec![
append("l"),
Checkpoint,
Witness,
Checkpoint,
append("m"),
Checkpoint,
authpath(0, 2),
],
vec![Checkpoint, append("n"), Witness, authpath(0, 1)],
vec![
append("a"),
Witness,
Checkpoint,
unwitness(0),
Checkpoint,
append("b"),
authpath(0, 1),
],
vec![
append("a"),
Witness,
append("b"),
unwitness(0),
Checkpoint,
authpath(0, 0),
],
vec![
append("a"),
Witness,
Checkpoint,
unwitness(0),
Checkpoint,
Rewind,
append("b"),
authpath(0, 0),
],
vec![
append("a"),
Witness,
Checkpoint,
Checkpoint,
Rewind,
append("a"),
unwitness(0),
authpath(0, 1),
],
// Unreduced examples
vec![
append("o"),
append("p"),
Witness,
append("q"),
Checkpoint,
unwitness(1),
authpath(1, 1),
],
vec![
append("r"),
append("s"),
append("t"),
Witness,
Checkpoint,
unwitness(2),
Checkpoint,
authpath(2, 2),
],
vec![
append("u"),
Witness,
append("v"),
append("w"),
Checkpoint,
unwitness(0),
append("x"),
Checkpoint,
Checkpoint,
authpath(0, 3),
],
];
for (i, sample) in samples.iter().enumerate() {
let result = check_operations(sample);
assert!(
matches!(result, Ok(())),
"Reference/Test mismatch at index {}: {:?}",
i,
result
);
}
}
// These check_operations tests cover errors where the test framework itself previously did not
// correctly handle chain state restoration.
#[test]
fn test_rewind_remove_witness_consistency() {
let samples = vec![
vec![append("x"), Checkpoint, Witness, Rewind, unwitness(0)],
vec![
append("d"),
Checkpoint,
Witness,
unwitness(0),
Rewind,
unwitness(0),
],
vec![
append("o"),
Checkpoint,
Witness,
Checkpoint,
unwitness(0),
Rewind,
Rewind,
],
vec![
append("s"),
Witness,
append("m"),
Checkpoint,
unwitness(0),
Rewind,
unwitness(0),
unwitness(0),
],
];
for (i, sample) in samples.iter().enumerate() {
let result = check_operations(sample);
assert!(
matches!(result, Ok(())),
"Reference/Test mismatch at index {}: {:?}",
i,
result
);
}
}
use proptest::prelude::*;
pub fn arb_operation<G: Strategy + Clone>(
@ -1003,7 +1198,8 @@ pub(crate) mod tests {
.prop_map(|i| Operation::Unwitness(Position::from(i))),
Just(Operation::Checkpoint),
Just(Operation::Rewind),
pos_gen.prop_map(|i| Operation::Authpath(Position::from(i))),
pos_gen.prop_flat_map(|i| (0usize..10)
.prop_map(move |depth| Operation::Authpath(Position::from(i), depth))),
]
}
@ -1026,7 +1222,7 @@ pub(crate) mod tests {
}
CurrentPosition => {}
CurrentLeaf => {}
Authpath(_) => {}
Authpath(_, _) => {}
WitnessedLeaf(_) => {}
WitnessedPositions => {}
GarbageCollect => {}
@ -1034,7 +1230,7 @@ pub(crate) mod tests {
}
fn check_operations<H: Hashable + Ord + Clone + Debug>(
ops: Vec<Operation<H>>,
ops: &[Operation<H>],
) -> Result<(), TestCaseError> {
const DEPTH: u8 = 4;
let mut tree = CombinedTree::<H, DEPTH>::new();
@ -1048,7 +1244,7 @@ pub(crate) mod tests {
prop_assert_eq!(tree_size, tree_values.len());
match op {
Append(value) => {
if tree.append(&value) {
if tree.append(value) {
prop_assert!(tree_size < (1 << DEPTH));
tree_size += 1;
tree_values.push(value.clone());
@ -1073,12 +1269,12 @@ pub(crate) mod tests {
}
}
WitnessedLeaf(position) => {
if tree.get_witnessed_leaf(position).is_some() {
prop_assert!(<usize>::from(position) < tree_size);
if tree.get_witnessed_leaf(*position).is_some() {
prop_assert!(<usize>::from(*position) < tree_size);
}
}
Unwitness(position) => {
tree.remove_witness(position);
tree.remove_witness(*position);
}
WitnessedPositions => {}
Checkpoint => {
@ -1093,20 +1289,36 @@ pub(crate) mod tests {
tree_size = checkpointed_tree_size;
}
}
Authpath(position) => {
if let Some(path) = tree.authentication_path(position) {
let value: H = tree_values.get(<usize>::from(position)).unwrap().clone();
let mut extended_tree_values = tree_values.clone();
extended_tree_values.resize(1 << DEPTH, H::empty_leaf());
let expected_root = lazy_root::<H>(extended_tree_values);
Authpath(position, depth) => {
if let Some(path) = tree
.root(*depth)
.and_then(|r| tree.authentication_path(*position, &r))
{
let value: H = tree_values[<usize>::from(*position)].clone();
let tree_root = tree.root(*depth);
let tree_root = tree.root();
prop_assert_eq!(&tree_root, &expected_root);
if tree_checkpoints.len() >= *depth {
let mut extended_tree_values = tree_values.clone();
if *depth > 0 {
// prune the tree back to the checkpointed size.
if let Some(checkpointed_tree_size) =
tree_checkpoints.get(tree_checkpoints.len() - depth)
{
extended_tree_values.truncate(*checkpointed_tree_size);
}
}
// extend the tree with empty leaves until it is full
extended_tree_values.resize(1 << DEPTH, H::empty_leaf());
prop_assert_eq!(
&compute_root_from_auth_path(value, position, &path),
&expected_root
);
// compute the root
let expected_root = lazy_root::<H>(extended_tree_values);
prop_assert_eq!(&tree_root.unwrap(), &expected_root);
prop_assert_eq!(
&compute_root_from_auth_path(value, *position, &path),
&expected_root
);
}
}
}
GarbageCollect => {}
@ -1126,7 +1338,7 @@ pub(crate) mod tests {
1..100
)
) {
check_operations(ops)?;
check_operations(&ops)?;
}
#[test]
@ -1136,7 +1348,7 @@ pub(crate) mod tests {
1..100
)
) {
check_operations::<String>(ops)?;
check_operations::<String>(&ops)?;
}
}
}

75
src/sample.rs
View File

@ -69,9 +69,7 @@ impl<H: Hashable + PartialEq + Clone> TreeState<H> {
/// witnessing. Returns the current position if the tree is non-empty.
fn witness(&mut self) -> Option<Position> {
self.current_position().map(|pos| {
if !self.witnesses.contains(&pos) {
self.witnesses.insert(pos);
}
self.witnesses.insert(pos);
pos
})
}
@ -80,7 +78,7 @@ impl<H: Hashable + PartialEq + Clone> TreeState<H> {
/// Returns `None` if there is no available authentication path to that
/// value.
fn authentication_path(&self, position: Position) -> Option<Vec<H>> {
if self.witnesses.contains(&position) {
if Some(position) <= self.current_position() {
let mut path = vec![];
let mut leaf_idx: usize = position.into();
@ -117,7 +115,7 @@ impl<H: Hashable + Clone> CompleteTree<H> {
/// Creates a new, empty binary tree of specified depth.
#[cfg(test)]
pub fn new(depth: usize, max_checkpoints: usize) -> Self {
CompleteTree {
Self {
tree_state: TreeState::new(depth),
checkpoints: vec![],
max_checkpoints,
@ -125,16 +123,6 @@ impl<H: Hashable + Clone> CompleteTree<H> {
}
}
impl<H: Hashable + Clone> Frontier<H> for CompleteTree<H> {
fn append(&mut self, value: &H) -> bool {
self.tree_state.append(value)
}
fn root(&self) -> H {
self.tree_state.root()
}
}
impl<H: Hashable + PartialEq + Clone> CompleteTree<H> {
/// Removes the oldest checkpoint. Returns true if successful and false if
/// there are no checkpoints.
@ -146,9 +134,30 @@ impl<H: Hashable + PartialEq + Clone> CompleteTree<H> {
true
}
}
/// Retrieve the tree state at the specified checkpoint depth. This
/// is the current tree state if the depth is 0, and this will return
/// None if not enough checkpoints exist to obtain the requested depth.
fn tree_state_at_checkpoint_depth(&self, checkpoint_depth: usize) -> Option<&TreeState<H>> {
if self.checkpoints.len() < checkpoint_depth {
None
} else if checkpoint_depth == 0 {
Some(&self.tree_state)
} else {
self.checkpoints
.get(self.checkpoints.len() - checkpoint_depth)
}
}
}
impl<H: Hashable + PartialEq + Clone> Tree<H> for CompleteTree<H> {
impl<H: Hashable + PartialEq + Clone + std::fmt::Debug> Tree<H> for CompleteTree<H> {
/// Appends a new value to the tree at the next available slot. Returns true
/// if successful and false if the tree is full.
fn append(&mut self, value: &H) -> bool {
self.tree_state.append(value)
}
/// Returns the most recently appended leaf value.
fn current_position(&self) -> Option<Position> {
self.tree_state.current_position()
}
@ -169,8 +178,26 @@ impl<H: Hashable + PartialEq + Clone> Tree<H> for CompleteTree<H> {
self.tree_state.witnesses.clone()
}
fn authentication_path(&self, position: Position) -> Option<Vec<H>> {
self.tree_state.authentication_path(position)
fn root(&self, checkpoint_depth: usize) -> Option<H> {
self.tree_state_at_checkpoint_depth(checkpoint_depth)
.map(|s| s.root())
}
fn authentication_path(&self, position: Position, root: &H) -> Option<Vec<H>> {
// Search for the checkpointed state corresponding to the provided root, and if one is
// found, compute the authentication path as of that root.
self.checkpoints
.iter()
.chain(Some(&self.tree_state))
.rev()
.skip_while(|c| !c.witnesses.contains(&position))
.find_map(|c| {
if &c.root() == root {
c.authentication_path(position)
} else {
None
}
})
}
fn remove_witness(&mut self, position: Position) -> bool {
@ -225,7 +252,7 @@ pub(crate) fn lazy_root<H: Hashable + Clone>(mut leaves: Vec<H>) -> H {
#[cfg(test)]
mod tests {
use crate::tests::{compute_root_from_auth_path, SipHashable};
use crate::{Altitude, Frontier, Hashable, Position, Tree};
use crate::{Altitude, Hashable, Position, Tree};
use std::convert::TryFrom;
use super::CompleteTree;
@ -239,7 +266,7 @@ mod tests {
}
let tree = CompleteTree::<SipHashable>::new(DEPTH as usize, 100);
assert_eq!(tree.root(), expected);
assert_eq!(tree.root(0).unwrap(), expected);
}
#[test]
@ -267,7 +294,7 @@ mod tests {
),
);
assert_eq!(tree.root(), expected);
assert_eq!(tree.root(0).unwrap(), expected);
}
#[test]
@ -306,11 +333,13 @@ mod tests {
),
);
assert_eq!(tree.root(), expected);
assert_eq!(tree.root(0).unwrap(), expected);
for i in 0u64..(1 << DEPTH) {
let position = Position::try_from(i).unwrap();
let path = tree.authentication_path(position).unwrap();
let path = tree
.authentication_path(position, &tree.root(0).unwrap())
.unwrap();
assert_eq!(
compute_root_from_auth_path(SipHashable(i), position, &path),
expected