forked from nervosnetwork/ckb
/
cuckoo.rs
384 lines (344 loc) · 12.4 KB
/
cuckoo.rs
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use super::PowEngine;
use byteorder::{ByteOrder, LittleEndian};
use ckb_core::header::BlockNumber;
use hash::blake2b_256;
use serde::{de, Deserialize as SerdeDeserialize};
use serde_derive::Deserialize;
use std::collections::HashMap;
// Cuckatoo proofs take the form of a length 42 off-by-1-cycle in a bipartite graph with
// 2^N+2^N nodes and 2^N edges, with N ranging from 10 up to 64.
#[derive(Copy, Clone, Deserialize, Eq, PartialEq, Hash, Debug)]
pub struct CuckooParams {
// the main parameter is the 2-log of the graph size,
// which is the size in bits of the node identifiers
edge_bits: u8,
// the next most important parameter is the (even) length
// of the cycle to be found. a minimum of 12 is recommended
#[serde(deserialize_with = "validate_cycle_length")]
cycle_length: u32,
}
fn validate_cycle_length<'de, D>(d: D) -> Result<u32, D::Error>
where
D: de::Deserializer<'de>,
{
let value = u32::deserialize(d)?;
if value & 1 == 1 {
Err(de::Error::invalid_value(
de::Unexpected::Unsigned(value.into()),
&"cycle_length must be even",
))
} else {
Ok(value)
}
}
pub struct CuckooEngine {
cuckoo: Cuckoo,
}
impl CuckooEngine {
pub fn new(params: CuckooParams) -> Self {
CuckooEngine {
cuckoo: Cuckoo::new(params.edge_bits, params.cycle_length as usize),
}
}
}
impl Default for CuckooParams {
fn default() -> Self {
CuckooParams {
edge_bits: 29,
cycle_length: 42,
}
}
}
impl PowEngine for CuckooEngine {
fn init(&self, _number: BlockNumber) {}
#[inline]
fn verify(&self, _number: BlockNumber, message: &[u8], proof: &[u8]) -> bool {
if proof.len() != self.cuckoo.cycle_length << 2 {
return false;
}
let mut proof_u32 = vec![0u32; self.cuckoo.cycle_length];
LittleEndian::read_u32_into(&proof, &mut proof_u32);
self.cuckoo.verify(message, &proof_u32)
}
#[inline]
fn solve(&self, _number: BlockNumber, message: &[u8]) -> Option<Vec<u8>> {
self.cuckoo.solve(message).map(|proof| {
let mut proof_u8 = vec![0u8; self.cuckoo.cycle_length << 2];
LittleEndian::write_u32_into(&proof, &mut proof_u8);
proof_u8
})
}
}
pub struct CuckooSip {
keys: [u64; 4],
}
impl CuckooSip {
pub fn new(key0: u64, key1: u64, key2: u64, key3: u64) -> Self {
Self {
keys: [key0, key1, key2, key3],
}
}
// https://github.com/tromp/cuckoo/blob/master/doc/spec#L11
fn hash(&self, val: u64) -> u64 {
let mut v0 = self.keys[0];
let mut v1 = self.keys[1];
let mut v2 = self.keys[2];
let mut v3 = self.keys[3] ^ val;
CuckooSip::sipround(&mut v0, &mut v1, &mut v2, &mut v3);
CuckooSip::sipround(&mut v0, &mut v1, &mut v2, &mut v3);
v0 ^= val;
v2 ^= 0xff;
CuckooSip::sipround(&mut v0, &mut v1, &mut v2, &mut v3);
CuckooSip::sipround(&mut v0, &mut v1, &mut v2, &mut v3);
CuckooSip::sipround(&mut v0, &mut v1, &mut v2, &mut v3);
CuckooSip::sipround(&mut v0, &mut v1, &mut v2, &mut v3);
v0 ^ v1 ^ v2 ^ v3
}
// https://github.com/tromp/cuckoo/blob/master/doc/spec#L2
fn sipround(v0: &mut u64, v1: &mut u64, v2: &mut u64, v3: &mut u64) {
*v0 = v0.wrapping_add(*v1);
*v2 = v2.wrapping_add(*v3);
*v1 = v1.rotate_left(13);
*v3 = v3.rotate_left(16);
*v1 ^= *v0;
*v3 ^= *v2;
*v0 = v0.rotate_left(32);
*v2 = v2.wrapping_add(*v1);
*v0 = v0.wrapping_add(*v3);
*v1 = v1.rotate_left(17);
*v3 = v3.rotate_left(21);
*v1 ^= *v2;
*v3 ^= *v0;
*v2 = v2.rotate_left(32);
}
pub fn edge(&self, val: u32, edge_mask: u64) -> (u64, u64) {
let upper = self.hash(u64::from(val) << 1) & edge_mask;
let lower = self.hash((u64::from(val) << 1) + 1) & edge_mask;
(upper, lower)
}
}
fn message_to_keys(message: &[u8]) -> [u64; 4] {
let result = blake2b_256(message);
[
LittleEndian::read_u64(&result[0..8]).to_le(),
LittleEndian::read_u64(&result[8..16]).to_le(),
LittleEndian::read_u64(&result[16..24]).to_le(),
LittleEndian::read_u64(&result[24..32]).to_le(),
]
}
pub struct Cuckoo {
max_edge: u64,
edge_mask: u64,
cycle_length: usize,
}
impl Cuckoo {
pub fn new(edge_bits: u8, cycle_length: usize) -> Self {
Self {
max_edge: 1 << edge_bits,
edge_mask: (1 << edge_bits) - 1,
cycle_length,
}
}
// https://github.com/tromp/cuckoo/blob/master/doc/spec#L19
#[inline]
pub fn verify(&self, message: &[u8], proof: &[u32]) -> bool {
if proof.len() != self.cycle_length {
return false;
}
// Check if proof values are in valid range
if proof.iter().any(|i| *i >= self.max_edge as u32) {
return false;
}
let keys = message_to_keys(message);
let hasher = CuckooSip::new(keys[0], keys[1], keys[2], keys[3]);
let mut from_upper: HashMap<_, Vec<_>> = HashMap::with_capacity(proof.len());
let mut from_lower: HashMap<_, Vec<_>> = HashMap::with_capacity(proof.len());
for (u, v) in proof.iter().map(|i| hasher.edge(*i, self.edge_mask)) {
from_upper
.entry(u)
.and_modify(|upper| upper.push(v))
.or_insert_with(|| vec![v]);
from_lower
.entry(v)
.and_modify(|lower| lower.push(u))
.or_insert_with(|| vec![u]);
}
if from_upper.values().any(|list| list.len() != 2) {
return false;
}
if from_lower.values().any(|list| list.len() != 2) {
return false;
}
let mut cycle_length = 0;
let mut cur_edge = hasher.edge(proof[0], self.edge_mask);
let start = cur_edge.0;
loop {
let next_lower = *from_upper[&cur_edge.0]
.iter()
.find(|v| **v != cur_edge.1)
.expect("next_lower should be found");
let next_upper = *from_lower[&next_lower]
.iter()
.find(|u| **u != cur_edge.0)
.expect("next_upper should be found");
cur_edge = (next_upper, next_lower);
cycle_length += 2;
if start == cur_edge.0 {
break;
}
}
cycle_length == self.cycle_length
}
#[inline]
pub fn solve(&self, message: &[u8]) -> Option<Vec<u32>> {
let mut graph = vec![0; (self.max_edge << 1) as usize].into_boxed_slice();
let keys = message_to_keys(message);
let hasher = CuckooSip::new(keys[0], keys[1], keys[2], keys[3]);
for nonce in 0..self.max_edge {
let (u, v) = {
let edge = hasher.edge(nonce as u32, self.edge_mask);
(edge.0 << 1, (edge.1 << 1) + 1)
};
if u == 0 {
continue;
}
let path_u = Cuckoo::path(&graph, u);
let path_v = Cuckoo::path(&graph, v);
if path_u.last().is_some() && (path_u.last() == path_v.last()) {
let common = path_u
.iter()
.rev()
.zip(path_v.iter().rev())
.take_while(|(u, v)| u == v)
.count();
if (path_u.len() - common) + (path_v.len() - common) + 1 == self.cycle_length {
let mut cycle: Vec<_> = {
let list: Vec<_> = path_u
.iter()
.take(path_u.len() - common + 1)
.chain(path_v.iter().rev().skip(common))
.chain(::std::iter::once(&u))
.cloned()
.collect();
list.windows(2).map(|edge| (edge[0], edge[1])).collect()
};
let mut result = Vec::with_capacity(self.cycle_length);
for n in 0..self.max_edge {
let cur_edge = {
let edge = hasher.edge(n as u32, self.edge_mask);
(edge.0 << 1, (edge.1 << 1) + 1)
};
for i in 0..cycle.len() {
let cycle_edge = cycle[i];
if cycle_edge == cur_edge || (cycle_edge.1, cycle_edge.0) == cur_edge {
result.push(n as u32);
cycle.remove(i);
break;
}
}
}
return Some(result);
}
} else if path_u.len() < path_v.len() {
for edge in path_u.windows(2) {
graph[edge[1] as usize] = edge[0];
}
graph[u as usize] = v;
} else {
for edge in path_v.windows(2) {
graph[edge[1] as usize] = edge[0];
}
graph[v as usize] = u;
}
}
None
}
fn path(graph: &[u64], start: u64) -> Vec<u64> {
let mut node = start;
let mut path = vec![start];
loop {
node = graph[node as usize];
if node != 0 {
path.push(node);
} else {
break;
}
}
path
}
}
#[cfg(test)]
mod test {
use super::*;
use proptest::{collection::size_range, prelude::*};
fn _cuckoo_solve(message: &[u8]) -> Result<(), TestCaseError> {
let engine = CuckooEngine::new(CuckooParams {
edge_bits: 6,
cycle_length: 8,
});
if let Some(proof) = engine.solve(0, message) {
prop_assert!(engine.verify(0, message, &proof));
}
Ok(())
}
proptest! {
#[test]
fn cuckoo_solve(ref message in any_with::<Vec<u8>>(size_range(80).lift())) {
_cuckoo_solve(message)?;
}
}
const TESTSET: [([u8; 80], [u32; 8]); 3] = [
(
[
238, 237, 143, 251, 211, 26, 16, 237, 158, 89, 77, 62, 49, 241, 85, 233, 49, 77,
230, 148, 177, 49, 129, 38, 152, 148, 40, 170, 1, 115, 145, 191, 44, 10, 206, 23,
226, 132, 186, 196, 204, 205, 133, 173, 209, 20, 116, 16, 159, 161, 117, 167, 151,
171, 246, 181, 209, 140, 189, 163, 206, 155, 209, 157, 110, 2, 79, 249, 34, 228,
252, 245, 141, 27, 9, 156, 85, 58, 121, 46,
],
[1, 12, 23, 27, 31, 48, 50, 60],
),
(
[
146, 101, 131, 178, 127, 39, 4, 255, 226, 74, 32, 146, 158, 0, 206, 120, 198, 96,
227, 140, 133, 121, 248, 27, 69, 136, 108, 226, 11, 47, 250, 27, 3, 94, 249, 46,
158, 71, 83, 205, 196, 206, 65, 31, 158, 62, 7, 45, 235, 234, 165, 137, 253, 210,
15, 224, 232, 233, 116, 214, 231, 234, 47, 3, 64, 250, 246, 80, 161, 51, 61, 153,
217, 101, 82, 189, 62, 247, 194, 3,
],
[16, 26, 29, 33, 39, 43, 44, 54],
),
(
[
24, 75, 179, 121, 98, 241, 250, 124, 100, 197, 125, 237, 29, 128, 222, 12, 134, 5,
241, 148, 87, 86, 159, 53, 217, 6, 202, 87, 71, 169, 8, 6, 202, 47, 50, 214, 18,
68, 84, 248, 105, 201, 162, 182, 95, 189, 145, 108, 234, 173, 81, 191, 109, 56,
192, 59, 176, 113, 85, 75, 254, 237, 161, 177, 189, 22, 219, 131, 24, 67, 96, 12,
22, 192, 108, 1, 189, 243, 22, 31,
],
[1, 15, 20, 22, 39, 41, 52, 56],
),
];
#[test]
fn solve_cuckoo() {
let cuckoo = Cuckoo::new(6, 8);
for (message, proof) in TESTSET.iter() {
assert_eq!(cuckoo.solve(message).unwrap(), proof);
}
}
#[test]
fn verify_cuckoo() {
let cuckoo = Cuckoo::new(6, 8);
for (message, proof) in TESTSET.iter() {
assert!(cuckoo.verify(message, proof));
}
}
#[test]
fn verify_invalid_length_should_not_panic() {
let engine = CuckooEngine::new(CuckooParams {
edge_bits: 6,
cycle_length: 8,
});
assert!(!engine.verify(0, &[0, 1], &[0, 1]));
}
}