mirror of https://github.com/zcash/orchard.git
281 lines
8.2 KiB
Rust
281 lines
8.2 KiB
Rust
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use super::EccInstructions;
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use crate::circuit::gadget::utilities::{copy, CellValue, Var};
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use crate::constants::{self, OrchardFixedBasesFull, ValueCommitV};
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use arrayvec::ArrayVec;
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use ff::{Field, PrimeFieldBits};
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use halo2::{
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arithmetic::CurveAffine,
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circuit::{Chip, Layouter},
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plonk::{Advice, Column, ConstraintSystem, Error, Fixed, Permutation, Selector},
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};
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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 mul;
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// pub(super) mod mul_fixed;
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// pub(super) mod witness_point;
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// pub(super) mod witness_scalar_fixed;
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/// A curve point represented in affine (x, y) coordinates. Each coordinate is
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/// assigned to a cell.
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#[derive(Clone, Debug)]
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pub struct EccPoint<C: CurveAffine> {
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/// x-coordinate
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pub x: CellValue<C::Base>,
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/// y-coordinate
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pub y: CellValue<C::Base>,
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}
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impl<C: CurveAffine> EccPoint<C> {
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/// Returns the value of this curve point, if known.
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pub fn point(&self) -> Option<C> {
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match (self.x.value(), self.y.value()) {
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(Some(x), Some(y)) => {
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if x == C::Base::zero() && y == C::Base::zero() {
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Some(C::identity())
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} else {
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Some(C::from_xy(x, y).unwrap())
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}
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}
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_ => None,
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}
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}
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}
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/// Configuration for the ECC chip
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#[derive(Clone, Debug, Eq, PartialEq)]
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#[allow(non_snake_case)]
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pub struct EccConfig {
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/// Advice columns needed by instructions in the ECC chip.
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pub advices: [Column<Advice>; 10],
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/// Coefficients of interpolation polynomials for x-coordinates (used in fixed-base scalar multiplication)
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pub lagrange_coeffs: [Column<Fixed>; constants::H],
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/// Fixed z such that y + z = u^2 some square, and -y + z is a non-square. (Used in fixed-base scalar multiplication)
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pub fixed_z: Column<Fixed>,
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/// Incomplete addition
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pub q_add_incomplete: Selector,
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/// Complete addition
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pub q_add: Selector,
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/// Variable-base scalar multiplication (hi half)
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pub q_mul_hi: Selector,
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/// Variable-base scalar multiplication (lo half)
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pub q_mul_lo: Selector,
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/// Selector used in scalar decomposition for variable-base scalar mul
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pub q_mul_decompose_var: Selector,
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/// Variable-base scalar multiplication (final scalar)
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pub q_mul_complete: Selector,
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/// Fixed-base full-width scalar multiplication
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pub q_mul_fixed: Selector,
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/// Fixed-base signed short scalar multiplication
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pub q_mul_fixed_short: Selector,
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/// Witness point
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pub q_point: Selector,
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/// Witness full-width scalar for fixed-base scalar mul
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pub q_scalar_fixed: Selector,
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/// Witness signed short scalar for full-width fixed-base scalar mul
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pub q_scalar_fixed_short: Selector,
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/// Permutation
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pub perm: Permutation,
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}
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/// A chip implementing EccInstructions
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#[derive(Clone, Debug, Eq, PartialEq)]
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pub struct EccChip<C: CurveAffine> {
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config: EccConfig,
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_marker: PhantomData<C>,
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}
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impl<C: CurveAffine> Chip<C::Base> for EccChip<C> {
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type Config = EccConfig;
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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<C: CurveAffine> EccChip<C>
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where
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C::Scalar: PrimeFieldBits,
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{
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pub fn construct(config: <Self as Chip<C::Base>>::Config) -> Self {
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Self {
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config,
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_marker: PhantomData,
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}
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}
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#[allow(non_snake_case)]
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pub fn configure(
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meta: &mut ConstraintSystem<C::Base>,
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advices: [Column<Advice>; 10],
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perm: Permutation,
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) -> <Self as Chip<C::Base>>::Config {
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let config = EccConfig {
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advices,
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lagrange_coeffs: [
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meta.fixed_column(),
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meta.fixed_column(),
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meta.fixed_column(),
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meta.fixed_column(),
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meta.fixed_column(),
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meta.fixed_column(),
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meta.fixed_column(),
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meta.fixed_column(),
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],
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fixed_z: meta.fixed_column(),
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q_add_incomplete: meta.selector(),
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q_add: meta.selector(),
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q_mul_hi: meta.selector(),
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q_mul_lo: meta.selector(),
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q_mul_decompose_var: meta.selector(),
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q_mul_complete: meta.selector(),
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q_mul_fixed: meta.selector(),
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q_mul_fixed_short: meta.selector(),
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q_point: meta.selector(),
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q_scalar_fixed: meta.selector(),
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q_scalar_fixed_short: meta.selector(),
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perm,
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};
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// TODO: create gates
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config
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}
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}
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/// A full-width scalar used for fixed-base scalar multiplication.
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/// This is decomposed in chunks of `window_width` bits in little-endian order.
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/// For example, if `window_width` = 3, we will have [k_0, k_1, ..., k_n]
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/// where `scalar = k_0 + k_1 * (2^3) + ... + k_n * (2^3)^n` and each `k_i` is
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/// in the range [0..2^3).
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#[derive(Clone, Debug)]
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pub struct EccScalarFixed<C: CurveAffine> {
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value: Option<C::Scalar>,
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windows: ArrayVec<CellValue<C::Base>, { constants::NUM_WINDOWS }>,
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}
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/// A signed short scalar used for fixed-base scalar multiplication.
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/// This is decomposed in chunks of `window_width` bits in little-endian order.
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/// For example, if `window_width` = 3, we will have [k_0, k_1, ..., k_n]
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/// where `scalar = k_0 + k_1 * (2^3) + ... + k_n * (2^3)^n` and each `k_i` is
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/// in the range [0..2^3).
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#[derive(Clone, Debug)]
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pub struct EccScalarFixedShort<C: CurveAffine> {
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magnitude: Option<C::Scalar>,
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sign: CellValue<C::Base>,
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windows: ArrayVec<CellValue<C::Base>, { constants::NUM_WINDOWS_SHORT }>,
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}
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impl<C: CurveAffine> EccInstructions<C> for EccChip<C>
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where
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C::Scalar: PrimeFieldBits,
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{
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type ScalarFixed = EccScalarFixed<C>;
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type ScalarFixedShort = EccScalarFixedShort<C>;
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type ScalarVar = CellValue<C::Base>;
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type Point = EccPoint<C>;
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type X = CellValue<C::Base>;
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type FixedPoints = OrchardFixedBasesFull<C>;
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type FixedPointsShort = ValueCommitV<C>;
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fn witness_scalar_var(
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&self,
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layouter: &mut impl Layouter<C::Base>,
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value: Option<C::Base>,
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) -> Result<Self::ScalarVar, Error> {
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layouter.assign_region(
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|| "Witness scalar for variable-base mul",
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|mut region| {
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let cell = region.assign_advice(
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|| "Scalar var",
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self.config().advices[0],
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0,
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|| value.ok_or(Error::SynthesisError),
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)?;
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Ok(CellValue::new(cell, value))
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},
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)
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}
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fn witness_scalar_fixed(
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&self,
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layouter: &mut impl Layouter<C::Base>,
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value: Option<C::Scalar>,
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) -> Result<Self::ScalarFixed, Error> {
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todo!()
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}
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fn witness_scalar_fixed_short(
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&self,
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layouter: &mut impl Layouter<C::Base>,
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value: Option<C::Scalar>,
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) -> Result<Self::ScalarFixedShort, Error> {
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todo!()
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}
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fn witness_point(
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&self,
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layouter: &mut impl Layouter<C::Base>,
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value: Option<C>,
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) -> Result<Self::Point, Error> {
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todo!()
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}
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fn extract_p(point: &Self::Point) -> &Self::X {
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&point.x
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}
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fn add_incomplete(
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&self,
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layouter: &mut impl Layouter<C::Base>,
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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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}
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fn add(
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&self,
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layouter: &mut impl Layouter<C::Base>,
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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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}
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fn mul(
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&self,
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layouter: &mut impl Layouter<C::Base>,
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scalar: &Self::ScalarVar,
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base: &Self::Point,
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) -> Result<Self::Point, Error> {
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todo!()
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}
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fn mul_fixed(
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&self,
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layouter: &mut impl Layouter<C::Base>,
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scalar: &Self::ScalarFixed,
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base: &Self::FixedPoints,
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) -> Result<Self::Point, Error> {
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todo!()
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}
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fn mul_fixed_short(
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&self,
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layouter: &mut impl Layouter<C::Base>,
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scalar: &Self::ScalarFixedShort,
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base: &Self::FixedPointsShort,
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) -> Result<Self::Point, Error> {
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todo!()
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}
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}
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