mirror of https://github.com/zcash/orchard.git
79 lines
2.1 KiB
Rust
79 lines
2.1 KiB
Rust
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use super::{CellValue, EccConfig, EccPoint, Var};
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use halo2::{
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arithmetic::CurveAffine,
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circuit::Region,
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plonk::{Advice, Column, ConstraintSystem, Error, Expression, 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_point: Selector,
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// x-coordinate
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pub x: Column<Advice>,
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// y-coordinate
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pub y: Column<Advice>,
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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_point: ecc_config.q_point,
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x: ecc_config.advices[0],
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y: ecc_config.advices[1],
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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<C: CurveAffine>(&self, meta: &mut ConstraintSystem<C::Base>) {
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meta.create_gate("witness point", |meta| {
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let q_point = meta.query_selector(self.q_point);
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let x = meta.query_advice(self.x, Rotation::cur());
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let y = meta.query_advice(self.y, Rotation::cur());
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// Check that y^2 = x^3 + b, where b = 5 in the Pallas equation
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vec![
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q_point
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* (y.clone() * y - (x.clone() * x.clone() * x) - Expression::Constant(C::b())),
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]
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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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value: Option<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_point` selector
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self.q_point.enable(region, offset)?;
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let value = value.map(|value| value.coordinates().unwrap());
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// Assign `x` value
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let x_val = value.map(|value| *value.x());
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let x_var = region.assign_advice(
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|| "x",
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self.x,
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offset,
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|| x_val.ok_or(Error::SynthesisError),
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)?;
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// Assign `y` value
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let y_val = value.map(|value| *value.y());
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let y_var = region.assign_advice(
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|| "y",
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self.y,
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offset,
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|| y_val.ok_or(Error::SynthesisError),
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)?;
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Ok(EccPoint {
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x: CellValue::<C::Base>::new(x_var, x_val),
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y: CellValue::<C::Base>::new(y_var, y_val),
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})
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}
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}
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