mirror of https://github.com/zcash/orchard.git
391 lines
14 KiB
Rust
391 lines
14 KiB
Rust
//! Types related to Orchard note commitment trees and anchors.
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use crate::{
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constants::{
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sinsemilla::{i2lebsp_k, L_ORCHARD_MERKLE, MERKLE_CRH_PERSONALIZATION},
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MERKLE_DEPTH_ORCHARD,
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},
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note::commitment::ExtractedNoteCommitment,
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};
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use incrementalmerkletree::{Altitude, Hashable};
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use pasta_curves::{arithmetic::FieldExt, pallas};
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use sinsemilla::primitive::HashDomain;
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use utilities::gen_const_array_with_default;
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use ff::{Field, PrimeField, PrimeFieldBits};
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use lazy_static::lazy_static;
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use rand::RngCore;
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use serde::de::{Deserializer, Error};
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use serde::ser::Serializer;
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use serde::{Deserialize, Serialize};
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use std::iter;
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use subtle::{Choice, ConditionallySelectable, ConstantTimeEq, CtOption};
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// The uncommitted leaf is defined as pallas::Base(2).
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// <https://zips.z.cash/protocol/protocol.pdf#thmuncommittedorchard>
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lazy_static! {
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static ref UNCOMMITTED_ORCHARD: pallas::Base = pallas::Base::from_u64(2);
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pub(crate) static ref EMPTY_ROOTS: Vec<MerkleHashOrchard> = {
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iter::empty()
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.chain(Some(MerkleHashOrchard::empty_leaf()))
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.chain(
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(0..MERKLE_DEPTH_ORCHARD).scan(MerkleHashOrchard::empty_leaf(), |state, l| {
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let l = l as u8;
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*state = MerkleHashOrchard::combine(l.into(), state, state);
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Some(*state)
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}),
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)
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.collect()
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};
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}
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/// The root of an Orchard commitment tree.
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#[derive(Eq, PartialEq, Clone, Copy, Debug)]
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pub struct Anchor(pallas::Base);
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impl From<pallas::Base> for Anchor {
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fn from(anchor_field: pallas::Base) -> Anchor {
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Anchor(anchor_field)
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}
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}
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impl From<MerkleHashOrchard> for Anchor {
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fn from(anchor: MerkleHashOrchard) -> Anchor {
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Anchor(anchor.0)
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}
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}
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impl Anchor {
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pub(crate) fn inner(&self) -> pallas::Base {
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self.0
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}
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}
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impl Anchor {
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/// Parses an Orchard anchor from a byte encoding.
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pub fn from_bytes(bytes: [u8; 32]) -> CtOption<Anchor> {
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pallas::Base::from_repr(bytes).map(Anchor)
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}
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/// Returns the byte encoding of this anchor.
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pub fn to_bytes(self) -> [u8; 32] {
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self.0.to_repr()
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}
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}
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/// The Merkle path from a leaf of the note commitment tree
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/// to its anchor.
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#[derive(Debug)]
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pub struct MerklePath {
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position: u32,
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auth_path: [MerkleHashOrchard; MERKLE_DEPTH_ORCHARD],
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}
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#[cfg(any(test, feature = "test-dependencies"))]
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impl From<(incrementalmerkletree::Position, Vec<MerkleHashOrchard>)> for MerklePath {
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fn from(path: (incrementalmerkletree::Position, Vec<MerkleHashOrchard>)) -> Self {
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use std::convert::TryInto;
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let position: u64 = path.0.into();
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Self {
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position: position as u32,
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auth_path: path.1.try_into().unwrap(),
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}
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}
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}
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impl MerklePath {
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/// Generates a dummy Merkle path for use in dummy spent notes.
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pub(crate) fn dummy(mut rng: &mut impl RngCore) -> Self {
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MerklePath {
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position: rng.next_u32(),
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auth_path: gen_const_array_with_default(MerkleHashOrchard::empty_leaf(), |_| {
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MerkleHashOrchard(pallas::Base::random(&mut rng))
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}),
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}
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}
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/// Instantiates a new Merkle path given a leaf position and authentication path.
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pub(crate) fn new(position: u32, auth_path: [pallas::Base; MERKLE_DEPTH_ORCHARD]) -> Self {
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Self {
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position,
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auth_path: gen_const_array_with_default(MerkleHashOrchard::empty_leaf(), |i| {
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MerkleHashOrchard(auth_path[i])
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}),
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}
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}
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/// <https://zips.z.cash/protocol/protocol.pdf#orchardmerklecrh>
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/// The layer with 2^n nodes is called "layer n":
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/// - leaves are at layer MERKLE_DEPTH_ORCHARD = 32;
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/// - the root is at layer 0.
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/// `l` is MERKLE_DEPTH_ORCHARD - layer - 1.
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/// - when hashing two leaves, we produce a node on the layer above the leaves, i.e.
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/// layer = 31, l = 0
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/// - when hashing to the final root, we produce the anchor with layer = 0, l = 31.
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pub fn root(&self, cmx: ExtractedNoteCommitment) -> Anchor {
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self.auth_path
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.iter()
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.enumerate()
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.fold(MerkleHashOrchard::from_cmx(&cmx), |node, (l, sibling)| {
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let l = l as u8;
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if self.position & (1 << l) == 0 {
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MerkleHashOrchard::combine(l.into(), &node, sibling)
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} else {
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MerkleHashOrchard::combine(l.into(), sibling, &node)
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}
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})
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.into()
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}
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/// Returns the position of the leaf using this Merkle path.
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pub(crate) fn position(&self) -> u32 {
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self.position
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}
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/// Returns the authentication path.
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pub(crate) fn auth_path(&self) -> [MerkleHashOrchard; MERKLE_DEPTH_ORCHARD] {
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self.auth_path
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}
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}
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/// A newtype wrapper for leaves and internal nodes in the Orchard
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/// incremental note commitment tree.
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///
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/// This wraps a CtOption<pallas::Base> because Sinsemilla hashes
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/// can produce a bottom value which needs to be accounted for in
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/// the production of a Merkle root. Leaf nodes are always wrapped
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/// with the `Some` constructor.
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#[derive(Copy, Clone, Debug)]
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pub struct MerkleHashOrchard(pallas::Base);
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impl MerkleHashOrchard {
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/// Creates an incremental tree leaf digest from the specified
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/// Orchard extracted note commitment.
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pub fn from_cmx(value: &ExtractedNoteCommitment) -> Self {
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MerkleHashOrchard(value.inner())
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}
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/// Only used in the circuit.
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pub(crate) fn inner(&self) -> pallas::Base {
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self.0
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}
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/// Convert this digest to its canonical byte representation.
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pub fn to_bytes(&self) -> [u8; 32] {
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self.0.to_bytes()
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}
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/// Parses a incremental tree leaf digest from the bytes of
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/// a note commitment.
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///
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/// Returns the empty `CtOption` if the provided bytes represent
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/// a non-canonical encoding.
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pub fn from_bytes(bytes: &[u8; 32]) -> CtOption<Self> {
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pallas::Base::from_bytes(bytes).map(MerkleHashOrchard)
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}
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}
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/// This instance should only be used for hash table key comparisons.
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impl std::cmp::PartialEq for MerkleHashOrchard {
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fn eq(&self, other: &Self) -> bool {
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self.0.ct_eq(&other.0).into()
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}
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}
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/// This instance should only be used for hash table key comparisons.
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impl std::cmp::Eq for MerkleHashOrchard {}
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/// This instance should only be used for hash table key hashing.
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impl std::hash::Hash for MerkleHashOrchard {
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fn hash<H: std::hash::Hasher>(&self, state: &mut H) {
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<Option<pallas::Base>>::from(self.0)
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.map(|b| b.to_bytes())
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.hash(state)
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}
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}
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impl ConditionallySelectable for MerkleHashOrchard {
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fn conditional_select(a: &Self, b: &Self, choice: Choice) -> Self {
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MerkleHashOrchard(pallas::Base::conditional_select(&a.0, &b.0, choice))
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}
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}
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impl Hashable for MerkleHashOrchard {
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fn empty_leaf() -> Self {
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MerkleHashOrchard(*UNCOMMITTED_ORCHARD)
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}
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/// Implements `MerkleCRH^Orchard` as defined in
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/// <https://zips.z.cash/protocol/protocol.pdf#orchardmerklecrh>
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///
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/// The layer with 2^n nodes is called "layer n":
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/// - leaves are at layer MERKLE_DEPTH_ORCHARD = 32;
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/// - the root is at layer 0.
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/// `l` is MERKLE_DEPTH_ORCHARD - layer - 1.
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/// - when hashing two leaves, we produce a node on the layer above the leaves, i.e.
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/// layer = 31, l = 0
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/// - when hashing to the final root, we produce the anchor with layer = 0, l = 31.
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fn combine(altitude: Altitude, left: &Self, right: &Self) -> Self {
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// MerkleCRH Sinsemilla hash domain.
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let domain = HashDomain::new(MERKLE_CRH_PERSONALIZATION);
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MerkleHashOrchard(
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domain
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.hash(
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iter::empty()
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.chain(i2lebsp_k(altitude.into()).iter().copied())
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.chain(left.0.to_le_bits().iter().by_val().take(L_ORCHARD_MERKLE))
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.chain(right.0.to_le_bits().iter().by_val().take(L_ORCHARD_MERKLE)),
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)
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.unwrap_or(pallas::Base::zero()),
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)
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}
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fn empty_root(altitude: Altitude) -> Self {
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EMPTY_ROOTS[<usize>::from(altitude)]
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}
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}
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impl Serialize for MerkleHashOrchard {
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fn serialize<S: Serializer>(&self, serializer: S) -> Result<S::Ok, S::Error> {
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self.to_bytes().serialize(serializer)
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}
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}
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impl<'de> Deserialize<'de> for MerkleHashOrchard {
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fn deserialize<D: Deserializer<'de>>(deserializer: D) -> Result<Self, D::Error> {
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let parsed = <[u8; 32]>::deserialize(deserializer)?;
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<Option<_>>::from(Self::from_bytes(&parsed)).ok_or_else(|| {
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Error::custom(
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"Attempted to deserialize a non-canonical representation of a Pallas base field element.",
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)
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})
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}
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}
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/// Generators for property testing.
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#[cfg(any(test, feature = "test-dependencies"))]
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pub mod testing {
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#[cfg(test)]
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use incrementalmerkletree::{
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bridgetree::{BridgeTree, Frontier as BridgeFrontier},
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Altitude, Frontier, Tree,
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};
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#[cfg(test)]
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use crate::tree::{MerkleHashOrchard, EMPTY_ROOTS};
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#[cfg(test)]
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use pasta_curves::{arithmetic::FieldExt, pallas};
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#[cfg(test)]
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use std::convert::TryInto;
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#[test]
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fn test_vectors() {
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let tv_empty_roots = crate::test_vectors::commitment_tree::test_vectors().empty_roots;
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for (height, root) in EMPTY_ROOTS.iter().enumerate() {
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assert_eq!(tv_empty_roots[height], root.to_bytes());
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}
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let mut tree = BridgeTree::<MerkleHashOrchard, 4>::new(100);
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for (i, tv) in crate::test_vectors::merkle_path::test_vectors()
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.into_iter()
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.enumerate()
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{
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let cmx = MerkleHashOrchard::from_bytes(&tv.leaves[i]).unwrap();
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tree.append(&cmx);
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tree.witness();
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assert_eq!(tree.root().0, pallas::Base::from_bytes(&tv.root).unwrap());
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// Check paths for all leaves up to this point. The test vectors include paths
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// for not-yet-appended leaves (using UNCOMMITTED_ORCHARD as the leaf value),
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// but BridgeTree doesn't encode these.
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for j in 0..=i {
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let leaf = MerkleHashOrchard::from_bytes(&tv.leaves[j]).unwrap();
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assert_eq!(
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tree.authentication_path(&leaf),
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Some((
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j.try_into().unwrap(),
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tv.paths[j]
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.iter()
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.map(|v| MerkleHashOrchard::from_bytes(v).unwrap())
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.collect()
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))
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);
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}
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}
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}
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#[test]
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fn empty_roots_incremental() {
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use incrementalmerkletree::Hashable;
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let tv_empty_roots = crate::test_vectors::commitment_tree::test_vectors().empty_roots;
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for (altitude, tv_root) in tv_empty_roots.iter().enumerate() {
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assert_eq!(
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MerkleHashOrchard::empty_root(Altitude::from(altitude as u8))
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.0
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.to_bytes(),
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*tv_root,
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"Empty root mismatch at altitude {}",
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altitude
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);
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}
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}
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#[test]
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fn anchor_incremental() {
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// These commitment values are derived from the bundle data that was generated for
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// testing commitment tree construction inside of zcashd here.
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// https://github.com/zcash/zcash/blob/ecec1f9769a5e37eb3f7fd89a4fcfb35bc28eed7/src/test/data/merkle_roots_orchard.h
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let commitments = [
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[
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0x68, 0x13, 0x5c, 0xf4, 0x99, 0x33, 0x22, 0x90, 0x99, 0xa4, 0x4e, 0xc9, 0x9a, 0x75,
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0xe1, 0xe1, 0xcb, 0x46, 0x40, 0xf9, 0xb5, 0xbd, 0xec, 0x6b, 0x32, 0x23, 0x85, 0x6f,
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0xea, 0x16, 0x39, 0x0a,
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],
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[
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0x78, 0x31, 0x50, 0x08, 0xfb, 0x29, 0x98, 0xb4, 0x30, 0xa5, 0x73, 0x1d, 0x67, 0x26,
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0x20, 0x7d, 0xc0, 0xf0, 0xec, 0x81, 0xea, 0x64, 0xaf, 0x5c, 0xf6, 0x12, 0x95, 0x69,
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0x01, 0xe7, 0x2f, 0x0e,
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],
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[
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0xee, 0x94, 0x88, 0x05, 0x3a, 0x30, 0xc5, 0x96, 0xb4, 0x30, 0x14, 0x10, 0x5d, 0x34,
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0x77, 0xe6, 0xf5, 0x78, 0xc8, 0x92, 0x40, 0xd1, 0xd1, 0xee, 0x17, 0x43, 0xb7, 0x7b,
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0xb6, 0xad, 0xc4, 0x0a,
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],
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[
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0x9d, 0xdc, 0xe7, 0xf0, 0x65, 0x01, 0xf3, 0x63, 0x76, 0x8c, 0x5b, 0xca, 0x3f, 0x26,
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0x46, 0x60, 0x83, 0x4d, 0x4d, 0xf4, 0x46, 0xd1, 0x3e, 0xfc, 0xd7, 0xc6, 0xf1, 0x7b,
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0x16, 0x7a, 0xac, 0x1a,
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],
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[
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0xbd, 0x86, 0x16, 0x81, 0x1c, 0x6f, 0x5f, 0x76, 0x9e, 0xa4, 0x53, 0x9b, 0xba, 0xff,
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0x0f, 0x19, 0x8a, 0x6c, 0xdf, 0x3b, 0x28, 0x0d, 0xd4, 0x99, 0x26, 0x16, 0x3b, 0xd5,
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0x3f, 0x53, 0xa1, 0x21,
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],
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];
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// This value was produced by the Python test vector generation code implemented here:
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// https://github.com/zcash-hackworks/zcash-test-vectors/blob/f4d756410c8f2456f5d84cedf6dac6eb8c068eed/orchard_merkle_tree.py
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let anchor = [
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0xc8, 0x75, 0xbe, 0x2d, 0x60, 0x87, 0x3f, 0x8b, 0xcd, 0xeb, 0x91, 0x28, 0x2e, 0x64,
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0x2e, 0x0c, 0xc6, 0x5f, 0xf7, 0xd0, 0x64, 0x2d, 0x13, 0x7b, 0x28, 0xcf, 0x28, 0xcc,
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0x9c, 0x52, 0x7f, 0x0e,
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];
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let mut frontier = BridgeFrontier::<MerkleHashOrchard, 32>::empty();
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for commitment in commitments.iter() {
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let cmx = MerkleHashOrchard(pallas::Base::from_bytes(commitment).unwrap());
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frontier.append(&cmx);
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}
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assert_eq!(
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frontier.root().0,
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pallas::Base::from_bytes(&anchor).unwrap()
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);
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}
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}
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