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// Copyright 2017-2019 int08h LLC
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
//!
//! Merkle Tree implementation using SHA-512 and the Roughtime leaf and node tweak values.
//!
use ring::digest;
use super::{HASH_LENGTH, TREE_LEAF_TWEAK, TREE_NODE_TWEAK};
type Data = Vec<u8>;
type Hash = Data;
///
/// Merkle Tree implementation using SHA-512 and the Roughtime leaf and node tweak values.
///
pub struct MerkleTree {
levels: Vec<Vec<Data>>,
}
impl MerkleTree {
///
/// Create a new empty Merkle Tree
///
pub fn new() -> MerkleTree {
MerkleTree {
levels: vec![vec![]],
}
}
pub fn push_leaf(&mut self, data: &[u8]) {
let hash = self.hash_leaf(data);
self.levels[0].push(hash);
}
pub fn get_paths(&self, mut index: usize) -> Vec<u8> {
let mut paths = Vec::with_capacity(self.levels.len() * 64);
let mut level = 0;
while !self.levels[level].is_empty() {
let sibling = if index % 2 == 0 { index + 1 } else { index - 1 };
paths.extend(self.levels[level][sibling].clone());
level += 1;
index /= 2;
}
paths
}
pub fn compute_root(&mut self) -> Hash {
assert!(
!self.levels[0].is_empty(),
"Must have at least one leaf to hash!"
);
let mut level = 0;
let mut node_count = self.levels[0].len();
while node_count > 1 {
level += 1;
if self.levels.len() < level + 1 {
self.levels.push(vec![]);
}
if node_count % 2 != 0 {
self.levels[level - 1].push(vec![0; HASH_LENGTH as usize]);
node_count += 1;
}
node_count /= 2;
for i in 0..node_count {
let hash = self.hash_nodes(
&self.levels[level - 1][i * 2],
&self.levels[level - 1][(i * 2) + 1],
);
self.levels[level].push(hash);
}
}
assert_eq!(self.levels[level].len(), 1);
self.levels[level].pop().unwrap()
}
pub fn reset(&mut self) {
for level in &mut self.levels {
level.clear();
}
}
fn hash_leaf(&self, leaf: &[u8]) -> Data {
self.hash(&[TREE_LEAF_TWEAK, leaf])
}
fn hash_nodes(&self, first: &[u8], second: &[u8]) -> Data {
self.hash(&[TREE_NODE_TWEAK, first, second])
}
fn hash(&self, to_hash: &[&[u8]]) -> Data {
let mut ctx = digest::Context::new(&digest::SHA512);
for data in to_hash {
ctx.update(data);
}
Data::from(ctx.finish().as_ref())
}
}
pub fn root_from_paths(mut index: usize, data: &[u8], paths: &[u8]) -> Hash {
let mut hash = {
let mut ctx = digest::Context::new(&digest::SHA512);
ctx.update(TREE_LEAF_TWEAK);
ctx.update(data);
Hash::from(ctx.finish().as_ref())
};
assert_eq!(paths.len() % 64, 0);
for path in paths.chunks(64) {
let mut ctx = digest::Context::new(&digest::SHA512);
ctx.update(TREE_NODE_TWEAK);
if index & 1 == 0 {
// Left
ctx.update(&hash);
ctx.update(path);
} else {
// Right
ctx.update(path);
ctx.update(&hash);
}
hash = Hash::from(ctx.finish().as_ref());
index >>= 1;
}
hash
}
#[cfg(test)]
mod test {
use crate::merkle::*;
fn test_paths_with_num(num: usize) {
let mut merkle = MerkleTree::new();
for i in 0..num {
merkle.push_leaf(&[i as u8]);
}
let root = merkle.compute_root();
for i in 0..num {
println!("Testing {:?} {:?}", num, i);
let paths: Vec<u8> = merkle.get_paths(i);
let computed_root = root_from_paths(i, &[i as u8], &paths);
assert_eq!(root, computed_root);
}
}
#[test]
fn power_of_two() {
test_paths_with_num(2);
test_paths_with_num(4);
test_paths_with_num(8);
test_paths_with_num(16);
}
#[test]
fn not_power_of_two() {
test_paths_with_num(1);
test_paths_with_num(20);
}
}
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