mirror of https://github.com/zcash/orchard.git
chip::add_incomplete.rs: Implement add_incomplete() instruction
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therealyingtong
parent
7eb86eb0c2
commit
7dc11b95d2
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@ -11,7 +11,7 @@ use halo2::{
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use std::marker::PhantomData;
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// pub(super) mod add;
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// pub(super) mod add_incomplete;
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pub(super) mod add_incomplete;
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// pub(super) mod mul;
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// pub(super) mod mul_fixed;
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pub(super) mod witness_point;
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@ -151,6 +151,12 @@ where
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config.create_gate::<C>(meta);
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}
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// Create incomplete point addition gate
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{
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let config: add_incomplete::Config = (&config).into();
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config.create_gate(meta);
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}
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config
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}
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}
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@ -247,7 +253,11 @@ where
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a: &Self::Point,
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b: &Self::Point,
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) -> Result<Self::Point, Error> {
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todo!()
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let config: add_incomplete::Config = self.config().into();
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layouter.assign_region(
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|| "incomplete point addition",
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|mut region| config.assign_region(a, b, 0, &mut region),
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)
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}
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fn add(
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@ -0,0 +1,199 @@
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use std::array;
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use super::{copy, CellValue, EccConfig, EccPoint, Var};
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use ff::Field;
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use group::Curve;
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use halo2::{
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arithmetic::{CurveAffine, FieldExt},
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circuit::Region,
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plonk::{Advice, Column, ConstraintSystem, Error, Permutation, Selector},
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poly::Rotation,
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};
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#[derive(Clone, Debug)]
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pub struct Config {
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q_add_incomplete: Selector,
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// x-coordinate of P in P + Q = R
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pub x_p: Column<Advice>,
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// y-coordinate of P in P + Q = R
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pub y_p: Column<Advice>,
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// x-coordinate of Q or R in P + Q = R
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pub x_qr: Column<Advice>,
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// y-coordinate of Q or R in P + Q = R
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pub y_qr: Column<Advice>,
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// Permutation
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perm: Permutation,
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}
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impl From<&EccConfig> for Config {
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fn from(ecc_config: &EccConfig) -> Self {
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Self {
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q_add_incomplete: ecc_config.q_add_incomplete,
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x_p: ecc_config.advices[0],
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y_p: ecc_config.advices[1],
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x_qr: ecc_config.advices[2],
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y_qr: ecc_config.advices[3],
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perm: ecc_config.perm.clone(),
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}
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}
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}
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impl Config {
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pub(super) fn create_gate<F: FieldExt>(&self, meta: &mut ConstraintSystem<F>) {
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meta.create_gate("incomplete addition gates", |meta| {
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let q_add_incomplete = meta.query_selector(self.q_add_incomplete);
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let x_p = meta.query_advice(self.x_p, Rotation::cur());
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let y_p = meta.query_advice(self.y_p, Rotation::cur());
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let x_q = meta.query_advice(self.x_qr, Rotation::cur());
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let y_q = meta.query_advice(self.y_qr, Rotation::cur());
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let x_r = meta.query_advice(self.x_qr, Rotation::next());
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let y_r = meta.query_advice(self.y_qr, Rotation::next());
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// (x_r + x_q + x_p)⋅(x_p − x_q)^2 − (y_p − y_q)^2 = 0
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let poly1 = {
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(x_r.clone() + x_q.clone() + x_p.clone())
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* (x_p.clone() - x_q.clone())
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* (x_p.clone() - x_q.clone())
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- (y_p.clone() - y_q.clone()) * (y_p.clone() - y_q.clone())
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};
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// (y_r + y_q)(x_p − x_q) − (y_p − y_q)(x_q − x_r) = 0
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let poly2 = (y_r + y_q.clone()) * (x_p - x_q.clone()) - (y_p - y_q) * (x_q - x_r);
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array::IntoIter::new([poly1, poly2]).map(move |poly| q_add_incomplete.clone() * poly)
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});
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}
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pub(super) fn assign_region<C: CurveAffine>(
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&self,
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p: &EccPoint<C>,
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q: &EccPoint<C>,
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offset: usize,
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region: &mut Region<'_, C::Base>,
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) -> Result<EccPoint<C>, Error> {
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// Enable `q_add_incomplete` selector
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self.q_add_incomplete.enable(region, offset)?;
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// Handle exceptional cases
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let (x_p, y_p) = (p.x.value(), p.y.value());
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let (x_q, y_q) = (q.x.value(), q.y.value());
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x_p.zip(y_p)
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.zip(x_q)
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.zip(y_q)
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.map(|(((x_p, y_p), x_q), y_q)| {
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// P is point at infinity
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if (x_p == C::Base::zero() && y_p == C::Base::zero())
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// Q is point at infinity
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|| (x_q == C::Base::zero() && y_q == C::Base::zero())
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// x_p = x_q
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|| (x_p == x_q)
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{
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Err(Error::SynthesisError)
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} else {
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Ok(())
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}
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})
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.transpose()?;
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// Copy point `p` into `x_p`, `y_p` columns
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copy(region, || "x_p", self.x_p, offset, &p.x, &self.perm)?;
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copy(region, || "y_p", self.y_p, offset, &p.y, &self.perm)?;
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// Copy point `q` into `x_qr`, `y_qr` columns
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copy(region, || "x_q", self.x_qr, offset, &q.x, &self.perm)?;
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copy(region, || "y_q", self.y_qr, offset, &q.y, &self.perm)?;
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// Compute the sum `P + Q = R`
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let r = {
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let p = p.point();
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let q = q.point();
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let r = p
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.zip(q)
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.map(|(p, q)| (p + q).to_affine().coordinates().unwrap());
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let r_x = r.map(|r| *r.x());
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let r_y = r.map(|r| *r.y());
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(r_x, r_y)
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};
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// Assign the sum to `x_qr`, `y_qr` columns in the next row
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let x_r = r.0;
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let x_r_var = region.assign_advice(
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|| "x_r",
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self.x_qr,
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offset + 1,
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|| x_r.ok_or(Error::SynthesisError),
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)?;
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let y_r = r.1;
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let y_r_var = region.assign_advice(
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|| "y_r",
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self.y_qr,
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offset + 1,
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|| y_r.ok_or(Error::SynthesisError),
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)?;
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let result = EccPoint::<C> {
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x: CellValue::<C::Base>::new(x_r_var, x_r),
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y: CellValue::<C::Base>::new(y_r_var, y_r),
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};
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#[cfg(test)]
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// Check that the correct sum is obtained.
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{
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let p = p.point();
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let q = q.point();
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let real_sum = p.zip(q).map(|(p, q)| p + q);
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let result = result.point();
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if let (Some(real_sum), Some(result)) = (real_sum, result) {
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assert_eq!(real_sum.to_affine(), result);
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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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#[cfg(test)]
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pub mod tests {
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use halo2::{arithmetic::CurveAffine, circuit::Layouter, plonk::Error};
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use crate::circuit::gadget::ecc::{EccInstructions, Point};
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pub fn test_add_incomplete<
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C: CurveAffine,
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EccChip: EccInstructions<C> + Clone + Eq + std::fmt::Debug,
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>(
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mut layouter: impl Layouter<C::Base>,
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zero: &Point<C, EccChip>,
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p: &Point<C, EccChip>,
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q: &Point<C, EccChip>,
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p_neg: &Point<C, EccChip>,
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) -> Result<(), Error> {
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// P + Q
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p.add_incomplete(layouter.namespace(|| "P + Q"), &q)?;
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// P + P should return an error
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p.add_incomplete(layouter.namespace(|| "P + P"), &p)
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.expect_err("P + P should return an error");
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// P + (-P) should return an error
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p.add_incomplete(layouter.namespace(|| "P + (-P)"), &p_neg)
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.expect_err("P + (-P) should return an error");
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// P + 𝒪 should return an error
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p.add_incomplete(layouter.namespace(|| "P + 𝒪"), &zero)
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.expect_err("P + 0 should return an error");
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// 𝒪 + P should return an error
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zero.add_incomplete(layouter.namespace(|| "𝒪 + P"), &p)
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.expect_err("0 + P should return an error");
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// 𝒪 + 𝒪 should return an error
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zero.add_incomplete(layouter.namespace(|| "𝒪 + 𝒪"), &zero)
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.expect_err("𝒪 + 𝒪 should return an error");
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Ok(())
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}
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}
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