mirror of https://github.com/zcash/halo2.git
99 lines
3.9 KiB
Rust
99 lines
3.9 KiB
Rust
use group::ff::PrimeField;
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use halo2_proofs::{
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circuit::{Layouter, Value},
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plonk::{ConstraintSystem, Error, Expression, TableColumn},
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poly::Rotation,
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};
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use super::{CommitDomains, FixedPoints, HashDomains};
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use crate::sinsemilla::primitives::{self as sinsemilla, SINSEMILLA_S};
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use pasta_curves::pallas;
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/// Table containing independent generators S[0..2^k]
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#[derive(Eq, PartialEq, Copy, Clone, Debug)]
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pub struct GeneratorTableConfig {
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pub table_idx: TableColumn,
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pub table_x: TableColumn,
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pub table_y: TableColumn,
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}
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impl GeneratorTableConfig {
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#[allow(clippy::too_many_arguments)]
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#[allow(non_snake_case)]
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/// Even though the lookup table can be used in other parts of the circuit,
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/// this specific configuration sets up Sinsemilla-specific constraints
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/// controlled by `q_sinsemilla`, and would likely not apply to other chips.
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pub fn configure<Hash, Commit, F>(
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meta: &mut ConstraintSystem<pallas::Base>,
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config: super::SinsemillaConfig<Hash, Commit, F>,
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) where
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Hash: HashDomains<pallas::Affine>,
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F: FixedPoints<pallas::Affine>,
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Commit: CommitDomains<pallas::Affine, F, Hash>,
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{
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let (table_idx, table_x, table_y) = (
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config.generator_table.table_idx,
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config.generator_table.table_x,
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config.generator_table.table_y,
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);
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// https://p.z.cash/halo2-0.1:sinsemilla-constraints?partial
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meta.lookup(|meta| {
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let q_s1 = meta.query_selector(config.q_sinsemilla1);
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let q_s2 = meta.query_fixed(config.q_sinsemilla2);
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let q_s3 = config.q_s3(meta);
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let q_run = q_s2 - q_s3;
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// m_{i+1} = z_{i} - 2^K * q_{run,i} * z_{i + 1}
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// Note that the message words m_i's are 1-indexed while the
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// running sum z_i's are 0-indexed.
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let word = {
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let z_cur = meta.query_advice(config.bits, Rotation::cur());
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let z_next = meta.query_advice(config.bits, Rotation::next());
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z_cur - (q_run * z_next * pallas::Base::from(1 << sinsemilla::K))
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};
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let x_p = meta.query_advice(config.double_and_add.x_p, Rotation::cur());
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// y_{p,i} = (Y_{A,i} / 2) - lambda1 * (x_{A,i} - x_{P,i})
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let y_p = {
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let lambda1 = meta.query_advice(config.double_and_add.lambda_1, Rotation::cur());
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let x_a = meta.query_advice(config.double_and_add.x_a, Rotation::cur());
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let Y_A = config.double_and_add.Y_A(meta, Rotation::cur());
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(Y_A * pallas::Base::TWO_INV) - (lambda1 * (x_a - x_p.clone()))
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};
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// Lookup expressions default to the first entry when `q_s1`
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// is not enabled.
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let (init_x, init_y) = SINSEMILLA_S[0];
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let not_q_s1 = Expression::Constant(pallas::Base::one()) - q_s1.clone();
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let m = q_s1.clone() * word; // The first table index is 0.
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let x_p = q_s1.clone() * x_p + not_q_s1.clone() * init_x;
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let y_p = q_s1 * y_p + not_q_s1 * init_y;
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vec![(m, table_idx), (x_p, table_x), (y_p, table_y)]
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});
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}
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pub fn load(&self, layouter: &mut impl Layouter<pallas::Base>) -> Result<(), Error> {
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layouter.assign_table(
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|| "generator_table",
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|mut table| {
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for (index, (x, y)) in SINSEMILLA_S.iter().enumerate() {
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table.assign_cell(
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|| "table_idx",
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self.table_idx,
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index,
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|| Value::known(pallas::Base::from(index as u64)),
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)?;
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table.assign_cell(|| "table_x", self.table_x, index, || Value::known(*x))?;
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table.assign_cell(|| "table_y", self.table_y, index, || Value::known(*y))?;
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}
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Ok(())
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},
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)
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}
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}
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