mirror of https://github.com/zcash/orchard.git
470 lines
17 KiB
Rust
470 lines
17 KiB
Rust
use halo2::{
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circuit::{Chip, Layouter},
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plonk::{Advice, Column, ConstraintSystem, Error, Selector},
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poly::Rotation,
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};
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use pasta_curves::{arithmetic::FieldExt, pallas};
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use super::super::{
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chip::{SinsemillaChip, SinsemillaConfig},
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SinsemillaInstructions,
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};
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use super::MerkleInstructions;
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use crate::{
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circuit::gadget::utilities::{
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bitrange_subset,
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cond_swap::{CondSwapChip, CondSwapConfig, CondSwapInstructions},
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copy, CellValue, UtilitiesInstructions, Var,
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},
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constants::{L_ORCHARD_BASE, MERKLE_DEPTH_ORCHARD},
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primitives::sinsemilla,
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};
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use std::array;
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#[derive(Clone, Debug)]
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pub struct MerkleConfig {
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advices: [Column<Advice>; 5],
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q_decompose: Selector,
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pub(super) cond_swap_config: CondSwapConfig,
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pub(super) sinsemilla_config: SinsemillaConfig,
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}
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#[derive(Clone, Debug)]
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pub struct MerkleChip {
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config: MerkleConfig,
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}
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impl Chip<pallas::Base> for MerkleChip {
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type Config = MerkleConfig;
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type Loaded = ();
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fn config(&self) -> &Self::Config {
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&self.config
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}
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fn loaded(&self) -> &Self::Loaded {
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&()
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}
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}
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impl MerkleChip {
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pub fn configure(
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meta: &mut ConstraintSystem<pallas::Base>,
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sinsemilla_config: SinsemillaConfig,
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) -> MerkleConfig {
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// All five advice columns are equality-enabled by SinsemillaConfig.
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let advices = sinsemilla_config.advices();
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let cond_swap_config = CondSwapChip::configure(meta, advices);
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// This selector enables the decomposition gate.
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let q_decompose = meta.selector();
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// Check that pieces have been decomposed correctly for Sinsemilla hash.
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// <https://zips.z.cash/protocol/protocol.pdf#orchardmerklecrh>
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//
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// a = a_0||a_1 = l || (bits 0..=239 of left)
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// b = b_0||b_1||b_2
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// = (bits 240..=249 of left) || (bits 250..=254 of left) || (bits 0..=4 of right)
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// c = bits 5..=254 of right
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//
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// The message pieces `a`, `b`, `c` are constrained by Sinsemilla to be
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// 250 bits, 20 bits, and 250 bits respectively.
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//
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/*
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The pieces and subpieces are arranged in the following configuration:
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| A_0 | A_1 | A_2 | A_3 | A_4 | q_decompose |
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-------------------------------------------------------
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| a | b | c | left | right | 1 |
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| z1_a | z1_b | b_1 | b_2 | l | |
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*/
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meta.create_gate("Decomposition check", |meta| {
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let q_decompose = meta.query_selector(q_decompose);
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let l_whole = meta.query_advice(advices[4], Rotation::next());
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let two_pow_5 = pallas::Base::from_u64(1 << 5);
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let two_pow_10 = two_pow_5.square();
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// a_whole is constrained by Sinsemilla to be 250 bits.
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let a_whole = meta.query_advice(advices[0], Rotation::cur());
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// b_whole is constrained by Sinsemilla to be 20 bits.
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let b_whole = meta.query_advice(advices[1], Rotation::cur());
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// c_whole is constrained by Sinsemilla to be 250 bits.
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let c_whole = meta.query_advice(advices[2], Rotation::cur());
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let left_node = meta.query_advice(advices[3], Rotation::cur());
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let right_node = meta.query_advice(advices[4], Rotation::cur());
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// a = a_0||a_1 = l || (bits 0..=239 of left)
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// Check that a_0 = l
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//
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// z_1 of SinsemillaHash(a) = a_1
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let z1_a = meta.query_advice(advices[0], Rotation::next());
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let a_1 = z1_a;
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// a_0 = a - (a_1 * 2^10)
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let a_0 = a_whole - a_1.clone() * pallas::Base::from_u64(1 << 10);
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let l_check = a_0 - l_whole;
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// b = b_0||b_1||b_2
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// = (bits 240..=249 of left) || (bits 250..=254 of left) || (bits 0..=4 of right)
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// The Orchard specification allows this representation to be non-canonical.
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// <https://zips.z.cash/protocol/protocol.pdf#merklepath>
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//
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// z_1 of SinsemillaHash(b) = b_1 + 2^5 b_2
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// => b_0 = b - (z1_b * 2^10)
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let z1_b = meta.query_advice(advices[1], Rotation::next());
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// b_1 has been constrained to be 5 bits outside this gate.
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let b_1 = meta.query_advice(advices[2], Rotation::next());
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// b_2 has been constrained to be 5 bits outside this gate.
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let b_2 = meta.query_advice(advices[3], Rotation::next());
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// Constrain b_1 + 2^5 b_2 = z1_b
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let b1_b2_check = z1_b.clone() - (b_1.clone() + b_2.clone() * two_pow_5);
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// Derive b_0 (constrained by SinsemillaHash to be 10 bits)
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let b_0 = b_whole - (z1_b * two_pow_10);
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// Check that left = a_1 (240 bits) || b_0 (10 bits) || b_1 (5 bits)
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let left_check = {
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let reconstructed = {
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let two_pow_240 = pallas::Base::from_u128(1 << 120).square();
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a_1 + (b_0 + b_1 * two_pow_10) * two_pow_240
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};
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reconstructed - left_node
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};
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// Check that right = b_2 (5 bits) || c (250 bits)
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// The Orchard specification allows this representation to be non-canonical.
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// <https://zips.z.cash/protocol/protocol.pdf#merklepath>
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let right_check = b_2 + c_whole * two_pow_5 - right_node;
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array::IntoIter::new([
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("l_check", l_check),
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("left_check", left_check),
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("right_check", right_check),
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("b1_b2_check", b1_b2_check),
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])
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.map(move |(name, poly)| (name, q_decompose.clone() * poly))
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});
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MerkleConfig {
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advices,
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q_decompose,
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cond_swap_config,
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sinsemilla_config,
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}
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}
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pub fn construct(config: MerkleConfig) -> Self {
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MerkleChip { config }
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}
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}
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impl MerkleInstructions<pallas::Affine, MERKLE_DEPTH_ORCHARD, { sinsemilla::K }, { sinsemilla::C }>
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for MerkleChip
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{
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#[allow(non_snake_case)]
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fn hash_layer(
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&self,
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mut layouter: impl Layouter<pallas::Base>,
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Q: pallas::Affine,
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// l = MERKLE_DEPTH_ORCHARD - layer - 1
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l: usize,
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left: Self::Var,
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right: Self::Var,
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) -> Result<Self::Var, Error> {
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let config = self.config().clone();
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// <https://zips.z.cash/protocol/protocol.pdf#orchardmerklecrh>
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// We need to hash `l || left || right`, where `l` is a 10-bit value.
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// We allow `left` and `right` to be non-canonical 255-bit encodings.
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//
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// a = a_0||a_1 = l || (bits 0..=239 of left)
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// b = b_0||b_1||b_2
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// = (bits 240..=249 of left) || (bits 250..=254 of left) || (bits 0..=4 of right)
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// c = bits 5..=254 of right
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// `a = a_0||a_1` = `l` || (bits 0..=239 of `left`)
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let a = {
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let a = {
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// a_0 = l
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let a_0 = bitrange_subset(pallas::Base::from_u64(l as u64), 0..10);
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// a_1 = (bits 0..=239 of `left`)
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let a_1 = left.value().map(|value| bitrange_subset(value, 0..240));
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a_1.map(|a_1| a_0 + a_1 * pallas::Base::from_u64(1 << 10))
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};
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self.witness_message_piece(layouter.namespace(|| "Witness a = a_0 || a_1"), a, 25)?
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};
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// b = b_0 || b_1 || b_2
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// = (bits 240..=249 of left) || (bits 250..=254 of left) || (bits 0..=4 of right)
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let (b_1, b_2, b) = {
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// b_0 = (bits 240..=249 of `left`)
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let b_0 = left.value().map(|value| bitrange_subset(value, 240..250));
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// b_1 = (bits 250..=254 of `left`)
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// Constrain b_1 to 5 bits.
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let b_1 = {
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let b_1 = left
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.value()
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.map(|value| bitrange_subset(value, 250..L_ORCHARD_BASE));
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config.sinsemilla_config.lookup_config.witness_short_check(
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layouter.namespace(|| "Constrain b_1 to 5 bits"),
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b_1,
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5,
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)?
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};
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// b_2 = (bits 0..=4 of `right`)
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// Constrain b_2 to 5 bits.
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let b_2 = {
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let b_2 = right.value().map(|value| bitrange_subset(value, 0..5));
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config.sinsemilla_config.lookup_config.witness_short_check(
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layouter.namespace(|| "Constrain b_2 to 5 bits"),
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b_2,
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5,
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)?
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};
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let b = {
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let b = b_0
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.zip(b_1.value())
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.zip(b_2.value())
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.map(|((b_0, b_1), b_2)| {
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b_0 + b_1 * pallas::Base::from_u64(1 << 10)
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+ b_2 * pallas::Base::from_u64(1 << 15)
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});
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self.witness_message_piece(
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layouter.namespace(|| "Witness b = b_0 || b_1 || b_2"),
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b,
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2,
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)?
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};
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(b_1, b_2, b)
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};
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let c = {
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// `c = bits 5..=254 of `right`
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let c = right
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.value()
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.map(|value| bitrange_subset(value, 5..L_ORCHARD_BASE));
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self.witness_message_piece(layouter.namespace(|| "Witness c"), c, 25)?
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};
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let (point, zs) = self.hash_to_point(
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layouter.namespace(|| format!("hash at l = {}", l)),
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Q,
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vec![a, b, c].into(),
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)?;
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let z1_a = zs[0][1];
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let z1_b = zs[1][1];
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// Check that the pieces have been decomposed properly.
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/*
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The pieces and subpieces are arranged in the following configuration:
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| A_0 | A_1 | A_2 | A_3 | A_4 | q_decompose |
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-------------------------------------------------------
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| a | b | c | left | right | 1 |
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| z1_a | z1_b | b_1 | b_2 | l | |
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*/
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{
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layouter.assign_region(
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|| "Check piece decomposition",
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|mut region| {
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// Set the fixed column `l` to the current l.
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// Recall that l = MERKLE_DEPTH_ORCHARD - layer - 1.
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// The layer with 2^n nodes is called "layer n".
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config.q_decompose.enable(&mut region, 0)?;
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region.assign_advice_from_constant(
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|| format!("l {}", l),
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config.advices[4],
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1,
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pallas::Base::from_u64(l as u64),
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)?;
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// Offset 0
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// Copy and assign `a` at the correct position.
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copy(
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&mut region,
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|| "copy a",
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config.advices[0],
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0,
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&a.cell_value(),
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)?;
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// Copy and assign `b` at the correct position.
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copy(
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&mut region,
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|| "copy b",
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config.advices[1],
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0,
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&b.cell_value(),
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)?;
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// Copy and assign `c` at the correct position.
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copy(
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&mut region,
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|| "copy c",
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config.advices[2],
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0,
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&c.cell_value(),
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)?;
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// Copy and assign the left node at the correct position.
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copy(&mut region, || "left", config.advices[3], 0, &left)?;
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// Copy and assign the right node at the correct position.
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copy(&mut region, || "right", config.advices[4], 0, &right)?;
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// Offset 1
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// Copy and assign z_1 of SinsemillaHash(a) = a_1
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copy(&mut region, || "z1_a", config.advices[0], 1, &z1_a)?;
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// Copy and assign z_1 of SinsemillaHash(b) = b_1
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copy(&mut region, || "z1_b", config.advices[1], 1, &z1_b)?;
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// Copy `b_1`, which has been constrained to be a 5-bit value
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copy(&mut region, || "b_1", config.advices[2], 1, &b_1)?;
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// Copy `b_2`, which has been constrained to be a 5-bit value
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copy(&mut region, || "b_2", config.advices[3], 1, &b_2)?;
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Ok(())
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},
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)?;
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}
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let result = Self::extract(&point);
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// Check layer hash output against Sinsemilla primitives hash
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#[cfg(test)]
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{
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use crate::{
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constants::MERKLE_CRH_PERSONALIZATION, primitives::sinsemilla::HashDomain,
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spec::i2lebsp,
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};
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use ff::PrimeFieldBits;
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if let (Some(left), Some(right)) = (left.value(), right.value()) {
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let l = i2lebsp::<10>(l as u64);
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let left: Vec<_> = left
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.to_le_bits()
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.iter()
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.by_val()
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.take(L_ORCHARD_BASE)
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.collect();
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let right: Vec<_> = right
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.to_le_bits()
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.iter()
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.by_val()
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.take(L_ORCHARD_BASE)
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.collect();
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let merkle_crh = HashDomain::new(MERKLE_CRH_PERSONALIZATION);
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let mut message = l.to_vec();
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message.extend_from_slice(&left);
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message.extend_from_slice(&right);
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let expected = merkle_crh.hash(message.into_iter()).unwrap();
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assert_eq!(expected.to_bytes(), result.value().unwrap().to_bytes());
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}
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}
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Ok(result)
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}
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}
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impl UtilitiesInstructions<pallas::Base> for MerkleChip {
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type Var = CellValue<pallas::Base>;
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}
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impl CondSwapInstructions<pallas::Base> for MerkleChip {
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#[allow(clippy::type_complexity)]
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fn swap(
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&self,
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layouter: impl Layouter<pallas::Base>,
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pair: (Self::Var, Option<pallas::Base>),
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swap: Option<bool>,
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) -> Result<(Self::Var, Self::Var), Error> {
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let config = self.config().cond_swap_config.clone();
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let chip = CondSwapChip::<pallas::Base>::construct(config);
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chip.swap(layouter, pair, swap)
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}
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}
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impl SinsemillaInstructions<pallas::Affine, { sinsemilla::K }, { sinsemilla::C }> for MerkleChip {
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type CellValue = <SinsemillaChip as SinsemillaInstructions<
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pallas::Affine,
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{ sinsemilla::K },
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{ sinsemilla::C },
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>>::CellValue;
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type Message = <SinsemillaChip as SinsemillaInstructions<
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pallas::Affine,
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{ sinsemilla::K },
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{ sinsemilla::C },
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>>::Message;
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type MessagePiece = <SinsemillaChip as SinsemillaInstructions<
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pallas::Affine,
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{ sinsemilla::K },
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{ sinsemilla::C },
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>>::MessagePiece;
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type RunningSum = <SinsemillaChip as SinsemillaInstructions<
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pallas::Affine,
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{ sinsemilla::K },
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{ sinsemilla::C },
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>>::RunningSum;
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type X = <SinsemillaChip as SinsemillaInstructions<
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pallas::Affine,
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{ sinsemilla::K },
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{ sinsemilla::C },
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>>::X;
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type NonIdentityPoint = <SinsemillaChip as SinsemillaInstructions<
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pallas::Affine,
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{ sinsemilla::K },
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{ sinsemilla::C },
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>>::NonIdentityPoint;
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type FixedPoints = <SinsemillaChip as SinsemillaInstructions<
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pallas::Affine,
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{ sinsemilla::K },
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{ sinsemilla::C },
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>>::FixedPoints;
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type HashDomains = <SinsemillaChip as SinsemillaInstructions<
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pallas::Affine,
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{ sinsemilla::K },
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{ sinsemilla::C },
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>>::HashDomains;
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type CommitDomains = <SinsemillaChip as SinsemillaInstructions<
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pallas::Affine,
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{ sinsemilla::K },
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{ sinsemilla::C },
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>>::CommitDomains;
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fn witness_message_piece(
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&self,
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layouter: impl Layouter<pallas::Base>,
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value: Option<pallas::Base>,
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num_words: usize,
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) -> Result<Self::MessagePiece, Error> {
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let config = self.config().sinsemilla_config.clone();
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let chip = SinsemillaChip::construct(config);
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chip.witness_message_piece(layouter, value, num_words)
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}
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#[allow(non_snake_case)]
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#[allow(clippy::type_complexity)]
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fn hash_to_point(
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&self,
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layouter: impl Layouter<pallas::Base>,
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Q: pallas::Affine,
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message: Self::Message,
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) -> Result<(Self::NonIdentityPoint, Vec<Vec<Self::CellValue>>), Error> {
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let config = self.config().sinsemilla_config.clone();
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let chip = SinsemillaChip::construct(config);
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chip.hash_to_point(layouter, Q, message)
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}
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fn extract(point: &Self::NonIdentityPoint) -> Self::X {
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SinsemillaChip::extract(point)
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}
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}
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