Merge pull request #349 from mir-protocol/secp256k1_curve

Secp256k1 curve
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Nicholas Ward 2021-12-01 09:29:12 -08:00 committed by GitHub
commit 982f85fd1b
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22 changed files with 1977 additions and 42 deletions

156
src/curve/curve_adds.rs Normal file
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use std::ops::Add;
use crate::curve::curve_types::{AffinePoint, Curve, ProjectivePoint};
use crate::field::field_types::Field;
impl<C: Curve> Add<ProjectivePoint<C>> for ProjectivePoint<C> {
type Output = ProjectivePoint<C>;
fn add(self, rhs: ProjectivePoint<C>) -> Self::Output {
let ProjectivePoint {
x: x1,
y: y1,
z: z1,
} = self;
let ProjectivePoint {
x: x2,
y: y2,
z: z2,
} = rhs;
if z1 == C::BaseField::ZERO {
return rhs;
}
if z2 == C::BaseField::ZERO {
return self;
}
let x1z2 = x1 * z2;
let y1z2 = y1 * z2;
let x2z1 = x2 * z1;
let y2z1 = y2 * z1;
// Check if we're doubling or adding inverses.
if x1z2 == x2z1 {
if y1z2 == y2z1 {
// TODO: inline to avoid redundant muls.
return self.double();
}
if y1z2 == -y2z1 {
return ProjectivePoint::ZERO;
}
}
// From https://www.hyperelliptic.org/EFD/g1p/data/shortw/projective/addition/add-1998-cmo-2
let z1z2 = z1 * z2;
let u = y2z1 - y1z2;
let uu = u.square();
let v = x2z1 - x1z2;
let vv = v.square();
let vvv = v * vv;
let r = vv * x1z2;
let a = uu * z1z2 - vvv - r.double();
let x3 = v * a;
let y3 = u * (r - a) - vvv * y1z2;
let z3 = vvv * z1z2;
ProjectivePoint::nonzero(x3, y3, z3)
}
}
impl<C: Curve> Add<AffinePoint<C>> for ProjectivePoint<C> {
type Output = ProjectivePoint<C>;
fn add(self, rhs: AffinePoint<C>) -> Self::Output {
let ProjectivePoint {
x: x1,
y: y1,
z: z1,
} = self;
let AffinePoint {
x: x2,
y: y2,
zero: zero2,
} = rhs;
if z1 == C::BaseField::ZERO {
return rhs.to_projective();
}
if zero2 {
return self;
}
let x2z1 = x2 * z1;
let y2z1 = y2 * z1;
// Check if we're doubling or adding inverses.
if x1 == x2z1 {
if y1 == y2z1 {
// TODO: inline to avoid redundant muls.
return self.double();
}
if y1 == -y2z1 {
return ProjectivePoint::ZERO;
}
}
// From https://www.hyperelliptic.org/EFD/g1p/data/shortw/projective/addition/madd-1998-cmo
let u = y2z1 - y1;
let uu = u.square();
let v = x2z1 - x1;
let vv = v.square();
let vvv = v * vv;
let r = vv * x1;
let a = uu * z1 - vvv - r.double();
let x3 = v * a;
let y3 = u * (r - a) - vvv * y1;
let z3 = vvv * z1;
ProjectivePoint::nonzero(x3, y3, z3)
}
}
impl<C: Curve> Add<AffinePoint<C>> for AffinePoint<C> {
type Output = ProjectivePoint<C>;
fn add(self, rhs: AffinePoint<C>) -> Self::Output {
let AffinePoint {
x: x1,
y: y1,
zero: zero1,
} = self;
let AffinePoint {
x: x2,
y: y2,
zero: zero2,
} = rhs;
if zero1 {
return rhs.to_projective();
}
if zero2 {
return self.to_projective();
}
// Check if we're doubling or adding inverses.
if x1 == x2 {
if y1 == y2 {
return self.to_projective().double();
}
if y1 == -y2 {
return ProjectivePoint::ZERO;
}
}
// From https://www.hyperelliptic.org/EFD/g1p/data/shortw/projective/addition/mmadd-1998-cmo
let u = y2 - y1;
let uu = u.square();
let v = x2 - x1;
let vv = v.square();
let vvv = v * vv;
let r = vv * x1;
let a = uu - vvv - r.double();
let x3 = v * a;
let y3 = u * (r - a) - vvv * y1;
let z3 = vvv;
ProjectivePoint::nonzero(x3, y3, z3)
}
}

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src/curve/curve_msm.rs Normal file
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use itertools::Itertools;
use rayon::prelude::*;
use crate::curve::curve_summation::affine_multisummation_best;
use crate::curve::curve_types::{AffinePoint, Curve, ProjectivePoint};
use crate::field::field_types::Field;
/// In Yao's method, we compute an affine summation for each digit. In a parallel setting, it would
/// be easiest to assign individual summations to threads, but this would be sub-optimal because
/// multi-summations can be more efficient than repeating individual summations (see
/// `affine_multisummation_best`). Thus we divide digits into large chunks, and assign chunks of
/// digits to threads. Note that there is a delicate balance here, as large chunks can result in
/// uneven distributions of work among threads.
const DIGITS_PER_CHUNK: usize = 80;
#[derive(Clone, Debug)]
pub struct MsmPrecomputation<C: Curve> {
/// For each generator (in the order they were passed to `msm_precompute`), contains a vector
/// of powers, i.e. [(2^w)^i] for i < DIGITS.
// TODO: Use compressed coordinates here.
powers_per_generator: Vec<Vec<AffinePoint<C>>>,
/// The window size.
w: usize,
}
pub fn msm_precompute<C: Curve>(
generators: &[ProjectivePoint<C>],
w: usize,
) -> MsmPrecomputation<C> {
MsmPrecomputation {
powers_per_generator: generators
.into_par_iter()
.map(|&g| precompute_single_generator(g, w))
.collect(),
w,
}
}
fn precompute_single_generator<C: Curve>(g: ProjectivePoint<C>, w: usize) -> Vec<AffinePoint<C>> {
let digits = (C::ScalarField::BITS + w - 1) / w;
let mut powers: Vec<ProjectivePoint<C>> = Vec::with_capacity(digits);
powers.push(g);
for i in 1..digits {
let mut power_i_proj = powers[i - 1];
for _j in 0..w {
power_i_proj = power_i_proj.double();
}
powers.push(power_i_proj);
}
ProjectivePoint::batch_to_affine(&powers)
}
pub fn msm_parallel<C: Curve>(
scalars: &[C::ScalarField],
generators: &[ProjectivePoint<C>],
w: usize,
) -> ProjectivePoint<C> {
let precomputation = msm_precompute(generators, w);
msm_execute_parallel(&precomputation, scalars)
}
pub fn msm_execute<C: Curve>(
precomputation: &MsmPrecomputation<C>,
scalars: &[C::ScalarField],
) -> ProjectivePoint<C> {
assert_eq!(precomputation.powers_per_generator.len(), scalars.len());
let w = precomputation.w;
let digits = (C::ScalarField::BITS + w - 1) / w;
let base = 1 << w;
// This is a variant of Yao's method, adapted to the multi-scalar setting. Because we use
// extremely large windows, the repeated scans in Yao's method could be more expensive than the
// actual group operations. To avoid this, we store a multimap from each possible digit to the
// positions in which that digit occurs in the scalars. These positions have the form (i, j),
// where i is the index of the generator and j is an index into the digits of the scalar
// associated with that generator.
let mut digit_occurrences: Vec<Vec<(usize, usize)>> = Vec::with_capacity(digits);
for _i in 0..base {
digit_occurrences.push(Vec::new());
}
for (i, scalar) in scalars.iter().enumerate() {
let digits = to_digits::<C>(scalar, w);
for (j, &digit) in digits.iter().enumerate() {
digit_occurrences[digit].push((i, j));
}
}
let mut y = ProjectivePoint::ZERO;
let mut u = ProjectivePoint::ZERO;
for digit in (1..base).rev() {
for &(i, j) in &digit_occurrences[digit] {
u = u + precomputation.powers_per_generator[i][j];
}
y = y + u;
}
y
}
pub fn msm_execute_parallel<C: Curve>(
precomputation: &MsmPrecomputation<C>,
scalars: &[C::ScalarField],
) -> ProjectivePoint<C> {
assert_eq!(precomputation.powers_per_generator.len(), scalars.len());
let w = precomputation.w;
let digits = (C::ScalarField::BITS + w - 1) / w;
let base = 1 << w;
// This is a variant of Yao's method, adapted to the multi-scalar setting. Because we use
// extremely large windows, the repeated scans in Yao's method could be more expensive than the
// actual group operations. To avoid this, we store a multimap from each possible digit to the
// positions in which that digit occurs in the scalars. These positions have the form (i, j),
// where i is the index of the generator and j is an index into the digits of the scalar
// associated with that generator.
let mut digit_occurrences: Vec<Vec<(usize, usize)>> = Vec::with_capacity(digits);
for _i in 0..base {
digit_occurrences.push(Vec::new());
}
for (i, scalar) in scalars.iter().enumerate() {
let digits = to_digits::<C>(scalar, w);
for (j, &digit) in digits.iter().enumerate() {
digit_occurrences[digit].push((i, j));
}
}
// For each digit, we add up the powers associated with all occurrences that digit.
let digits: Vec<usize> = (0..base).collect();
let digit_acc: Vec<ProjectivePoint<C>> = digits
.par_chunks(DIGITS_PER_CHUNK)
.flat_map(|chunk| {
let summations: Vec<Vec<AffinePoint<C>>> = chunk
.iter()
.map(|&digit| {
digit_occurrences[digit]
.iter()
.map(|&(i, j)| precomputation.powers_per_generator[i][j])
.collect()
})
.collect();
affine_multisummation_best(summations)
})
.collect();
// println!("Computing the per-digit summations (in parallel) took {}s", start.elapsed().as_secs_f64());
let mut y = ProjectivePoint::ZERO;
let mut u = ProjectivePoint::ZERO;
for digit in (1..base).rev() {
u = u + digit_acc[digit];
y = y + u;
}
// println!("Final summation (sequential) {}s", start.elapsed().as_secs_f64());
y
}
pub(crate) fn to_digits<C: Curve>(x: &C::ScalarField, w: usize) -> Vec<usize> {
let scalar_bits = C::ScalarField::BITS;
let num_digits = (scalar_bits + w - 1) / w;
// Convert x to a bool array.
let x_canonical: Vec<_> = x
.to_biguint()
.to_u64_digits()
.iter()
.cloned()
.pad_using(scalar_bits / 64, |_| 0)
.collect();
let mut x_bits = Vec::with_capacity(scalar_bits);
for i in 0..scalar_bits {
x_bits.push((x_canonical[i / 64] >> (i as u64 % 64) & 1) != 0);
}
let mut digits = Vec::with_capacity(num_digits);
for i in 0..num_digits {
let mut digit = 0;
for j in ((i * w)..((i + 1) * w).min(scalar_bits)).rev() {
digit <<= 1;
digit |= x_bits[j] as usize;
}
digits.push(digit);
}
digits
}
#[cfg(test)]
mod tests {
use num::BigUint;
use crate::curve::curve_msm::{msm_execute, msm_precompute, to_digits};
use crate::curve::curve_types::Curve;
use crate::curve::secp256k1::Secp256K1;
use crate::field::field_types::Field;
use crate::field::secp256k1_scalar::Secp256K1Scalar;
#[test]
fn test_to_digits() {
let x_canonical = [
0b10101010101010101010101010101010,
0b10101010101010101010101010101010,
0b11001100110011001100110011001100,
0b11001100110011001100110011001100,
0b11110000111100001111000011110000,
0b11110000111100001111000011110000,
0b00001111111111111111111111111111,
0b11111111111111111111111111111111,
];
let x = Secp256K1Scalar::from_biguint(BigUint::from_slice(&x_canonical));
assert_eq!(x.to_biguint().to_u32_digits(), x_canonical);
assert_eq!(
to_digits::<Secp256K1>(&x, 17),
vec![
0b01010101010101010,
0b10101010101010101,
0b01010101010101010,
0b11001010101010101,
0b01100110011001100,
0b00110011001100110,
0b10011001100110011,
0b11110000110011001,
0b01111000011110000,
0b00111100001111000,
0b00011110000111100,
0b11111111111111110,
0b01111111111111111,
0b11111111111111000,
0b11111111111111111,
0b1,
]
);
}
#[test]
fn test_msm() {
let w = 5;
let generator_1 = Secp256K1::GENERATOR_PROJECTIVE;
let generator_2 = generator_1 + generator_1;
let generator_3 = generator_1 + generator_2;
let scalar_1 = Secp256K1Scalar::from_biguint(BigUint::from_slice(&[
11111111, 22222222, 33333333, 44444444,
]));
let scalar_2 = Secp256K1Scalar::from_biguint(BigUint::from_slice(&[
22222222, 22222222, 33333333, 44444444,
]));
let scalar_3 = Secp256K1Scalar::from_biguint(BigUint::from_slice(&[
33333333, 22222222, 33333333, 44444444,
]));
let generators = vec![generator_1, generator_2, generator_3];
let scalars = vec![scalar_1, scalar_2, scalar_3];
let precomputation = msm_precompute(&generators, w);
let result_msm = msm_execute(&precomputation, &scalars);
let result_naive = Secp256K1::convert(scalar_1) * generator_1
+ Secp256K1::convert(scalar_2) * generator_2
+ Secp256K1::convert(scalar_3) * generator_3;
assert_eq!(result_msm, result_naive);
}
}

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use std::ops::Mul;
use crate::curve::curve_types::{Curve, CurveScalar, ProjectivePoint};
use crate::field::field_types::Field;
const WINDOW_BITS: usize = 4;
const BASE: usize = 1 << WINDOW_BITS;
fn digits_per_scalar<C: Curve>() -> usize {
(C::ScalarField::BITS + WINDOW_BITS - 1) / WINDOW_BITS
}
/// Precomputed state used for scalar x ProjectivePoint multiplications,
/// specific to a particular generator.
#[derive(Clone)]
pub struct MultiplicationPrecomputation<C: Curve> {
/// [(2^w)^i] g for each i < digits_per_scalar.
powers: Vec<ProjectivePoint<C>>,
}
impl<C: Curve> ProjectivePoint<C> {
pub fn mul_precompute(&self) -> MultiplicationPrecomputation<C> {
let num_digits = digits_per_scalar::<C>();
let mut powers = Vec::with_capacity(num_digits);
powers.push(*self);
for i in 1..num_digits {
let mut power_i = powers[i - 1];
for _j in 0..WINDOW_BITS {
power_i = power_i.double();
}
powers.push(power_i);
}
MultiplicationPrecomputation { powers }
}
pub fn mul_with_precomputation(
&self,
scalar: C::ScalarField,
precomputation: MultiplicationPrecomputation<C>,
) -> Self {
// Yao's method; see https://koclab.cs.ucsb.edu/teaching/ecc/eccPapers/Doche-ch09.pdf
let precomputed_powers = precomputation.powers;
let digits = to_digits::<C>(&scalar);
let mut y = ProjectivePoint::ZERO;
let mut u = ProjectivePoint::ZERO;
let mut all_summands = Vec::new();
for j in (1..BASE).rev() {
let mut u_summands = Vec::new();
for (i, &digit) in digits.iter().enumerate() {
if digit == j as u64 {
u_summands.push(precomputed_powers[i]);
}
}
all_summands.push(u_summands);
}
let all_sums: Vec<ProjectivePoint<C>> = all_summands
.iter()
.cloned()
.map(|vec| vec.iter().fold(ProjectivePoint::ZERO, |a, &b| a + b))
.collect();
for i in 0..all_sums.len() {
u = u + all_sums[i];
y = y + u;
}
y
}
}
impl<C: Curve> Mul<ProjectivePoint<C>> for CurveScalar<C> {
type Output = ProjectivePoint<C>;
fn mul(self, rhs: ProjectivePoint<C>) -> Self::Output {
let precomputation = rhs.mul_precompute();
rhs.mul_with_precomputation(self.0, precomputation)
}
}
#[allow(clippy::assertions_on_constants)]
fn to_digits<C: Curve>(x: &C::ScalarField) -> Vec<u64> {
debug_assert!(
64 % WINDOW_BITS == 0,
"For simplicity, only power-of-two window sizes are handled for now"
);
let digits_per_u64 = 64 / WINDOW_BITS;
let mut digits = Vec::with_capacity(digits_per_scalar::<C>());
for limb in x.to_biguint().to_u64_digits() {
for j in 0..digits_per_u64 {
digits.push((limb >> (j * WINDOW_BITS) as u64) % BASE as u64);
}
}
digits
}

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use std::iter::Sum;
use crate::curve::curve_types::{AffinePoint, Curve, ProjectivePoint};
use crate::field::field_types::Field;
impl<C: Curve> Sum<AffinePoint<C>> for ProjectivePoint<C> {
fn sum<I: Iterator<Item = AffinePoint<C>>>(iter: I) -> ProjectivePoint<C> {
let points: Vec<_> = iter.collect();
affine_summation_best(points)
}
}
impl<C: Curve> Sum for ProjectivePoint<C> {
fn sum<I: Iterator<Item = ProjectivePoint<C>>>(iter: I) -> ProjectivePoint<C> {
iter.fold(ProjectivePoint::ZERO, |acc, x| acc + x)
}
}
pub fn affine_summation_best<C: Curve>(summation: Vec<AffinePoint<C>>) -> ProjectivePoint<C> {
let result = affine_multisummation_best(vec![summation]);
debug_assert_eq!(result.len(), 1);
result[0]
}
pub fn affine_multisummation_best<C: Curve>(
summations: Vec<Vec<AffinePoint<C>>>,
) -> Vec<ProjectivePoint<C>> {
let pairwise_sums: usize = summations.iter().map(|summation| summation.len() / 2).sum();
// This threshold is chosen based on data from the summation benchmarks.
if pairwise_sums < 70 {
affine_multisummation_pairwise(summations)
} else {
affine_multisummation_batch_inversion(summations)
}
}
/// Adds each pair of points using an affine + affine = projective formula, then adds up the
/// intermediate sums using a projective formula.
pub fn affine_multisummation_pairwise<C: Curve>(
summations: Vec<Vec<AffinePoint<C>>>,
) -> Vec<ProjectivePoint<C>> {
summations
.into_iter()
.map(affine_summation_pairwise)
.collect()
}
/// Adds each pair of points using an affine + affine = projective formula, then adds up the
/// intermediate sums using a projective formula.
pub fn affine_summation_pairwise<C: Curve>(points: Vec<AffinePoint<C>>) -> ProjectivePoint<C> {
let mut reduced_points: Vec<ProjectivePoint<C>> = Vec::new();
for chunk in points.chunks(2) {
match chunk.len() {
1 => reduced_points.push(chunk[0].to_projective()),
2 => reduced_points.push(chunk[0] + chunk[1]),
_ => panic!(),
}
}
// TODO: Avoid copying (deref)
reduced_points
.iter()
.fold(ProjectivePoint::ZERO, |sum, x| sum + *x)
}
/// Computes several summations of affine points by applying an affine group law, except that the
/// divisions are batched via Montgomery's trick.
pub fn affine_summation_batch_inversion<C: Curve>(
summation: Vec<AffinePoint<C>>,
) -> ProjectivePoint<C> {
let result = affine_multisummation_batch_inversion(vec![summation]);
debug_assert_eq!(result.len(), 1);
result[0]
}
/// Computes several summations of affine points by applying an affine group law, except that the
/// divisions are batched via Montgomery's trick.
pub fn affine_multisummation_batch_inversion<C: Curve>(
summations: Vec<Vec<AffinePoint<C>>>,
) -> Vec<ProjectivePoint<C>> {
let mut elements_to_invert = Vec::new();
// For each pair of points, (x1, y1) and (x2, y2), that we're going to add later, we want to
// invert either y (if the points are equal) or x1 - x2 (otherwise). We will use these later.
for summation in &summations {
let n = summation.len();
// The special case for n=0 is to avoid underflow.
let range_end = if n == 0 { 0 } else { n - 1 };
for i in (0..range_end).step_by(2) {
let p1 = summation[i];
let p2 = summation[i + 1];
let AffinePoint {
x: x1,
y: y1,
zero: zero1,
} = p1;
let AffinePoint {
x: x2,
y: _y2,
zero: zero2,
} = p2;
if zero1 || zero2 || p1 == -p2 {
// These are trivial cases where we won't need any inverse.
} else if p1 == p2 {
elements_to_invert.push(y1.double());
} else {
elements_to_invert.push(x1 - x2);
}
}
}
let inverses: Vec<C::BaseField> =
C::BaseField::batch_multiplicative_inverse(&elements_to_invert);
let mut all_reduced_points = Vec::with_capacity(summations.len());
let mut inverse_index = 0;
for summation in summations {
let n = summation.len();
let mut reduced_points = Vec::with_capacity((n + 1) / 2);
// The special case for n=0 is to avoid underflow.
let range_end = if n == 0 { 0 } else { n - 1 };
for i in (0..range_end).step_by(2) {
let p1 = summation[i];
let p2 = summation[i + 1];
let AffinePoint {
x: x1,
y: y1,
zero: zero1,
} = p1;
let AffinePoint {
x: x2,
y: y2,
zero: zero2,
} = p2;
let sum = if zero1 {
p2
} else if zero2 {
p1
} else if p1 == -p2 {
AffinePoint::ZERO
} else {
// It's a non-trivial case where we need one of the inverses we computed earlier.
let inverse = inverses[inverse_index];
inverse_index += 1;
if p1 == p2 {
// This is the doubling case.
let mut numerator = x1.square().triple();
if C::A.is_nonzero() {
numerator += C::A;
}
let quotient = numerator * inverse;
let x3 = quotient.square() - x1.double();
let y3 = quotient * (x1 - x3) - y1;
AffinePoint::nonzero(x3, y3)
} else {
// This is the general case. We use the incomplete addition formulas 4.3 and 4.4.
let quotient = (y1 - y2) * inverse;
let x3 = quotient.square() - x1 - x2;
let y3 = quotient * (x1 - x3) - y1;
AffinePoint::nonzero(x3, y3)
}
};
reduced_points.push(sum);
}
// If n is odd, the last point was not part of a pair.
if n % 2 == 1 {
reduced_points.push(summation[n - 1]);
}
all_reduced_points.push(reduced_points);
}
// We should have consumed all of the inverses from the batch computation.
debug_assert_eq!(inverse_index, inverses.len());
// Recurse with our smaller set of points.
affine_multisummation_best(all_reduced_points)
}
#[cfg(test)]
mod tests {
use crate::curve::curve_summation::{
affine_summation_batch_inversion, affine_summation_pairwise,
};
use crate::curve::curve_types::{Curve, ProjectivePoint};
use crate::curve::secp256k1::Secp256K1;
#[test]
fn test_pairwise_affine_summation() {
let g_affine = Secp256K1::GENERATOR_AFFINE;
let g2_affine = (g_affine + g_affine).to_affine();
let g3_affine = (g_affine + g_affine + g_affine).to_affine();
let g2_proj = g2_affine.to_projective();
let g3_proj = g3_affine.to_projective();
assert_eq!(
affine_summation_pairwise::<Secp256K1>(vec![g_affine, g_affine]),
g2_proj
);
assert_eq!(
affine_summation_pairwise::<Secp256K1>(vec![g_affine, g2_affine]),
g3_proj
);
assert_eq!(
affine_summation_pairwise::<Secp256K1>(vec![g_affine, g_affine, g_affine]),
g3_proj
);
assert_eq!(
affine_summation_pairwise::<Secp256K1>(vec![]),
ProjectivePoint::ZERO
);
}
#[test]
fn test_pairwise_affine_summation_batch_inversion() {
let g = Secp256K1::GENERATOR_AFFINE;
let g_proj = g.to_projective();
assert_eq!(
affine_summation_batch_inversion::<Secp256K1>(vec![g, g]),
g_proj + g_proj
);
assert_eq!(
affine_summation_batch_inversion::<Secp256K1>(vec![g, g, g]),
g_proj + g_proj + g_proj
);
assert_eq!(
affine_summation_batch_inversion::<Secp256K1>(vec![]),
ProjectivePoint::ZERO
);
}
}

260
src/curve/curve_types.rs Normal file
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@ -0,0 +1,260 @@
use std::fmt::Debug;
use std::ops::Neg;
use crate::field::field_types::Field;
// To avoid implementation conflicts from associated types,
// see https://github.com/rust-lang/rust/issues/20400
pub struct CurveScalar<C: Curve>(pub <C as Curve>::ScalarField);
/// A short Weierstrass curve.
pub trait Curve: 'static + Sync + Sized + Copy + Debug {
type BaseField: Field;
type ScalarField: Field;
const A: Self::BaseField;
const B: Self::BaseField;
const GENERATOR_AFFINE: AffinePoint<Self>;
const GENERATOR_PROJECTIVE: ProjectivePoint<Self> = ProjectivePoint {
x: Self::GENERATOR_AFFINE.x,
y: Self::GENERATOR_AFFINE.y,
z: Self::BaseField::ONE,
};
fn convert(x: Self::ScalarField) -> CurveScalar<Self> {
CurveScalar(x)
}
fn is_safe_curve() -> bool {
// Added additional check to prevent using vulnerabilties in case a discriminant is equal to 0.
(Self::A.cube().double().double() + Self::B.square().triple().triple().triple())
.is_nonzero()
}
}
/// A point on a short Weierstrass curve, represented in affine coordinates.
#[derive(Copy, Clone, Debug)]
pub struct AffinePoint<C: Curve> {
pub x: C::BaseField,
pub y: C::BaseField,
pub zero: bool,
}
impl<C: Curve> AffinePoint<C> {
pub const ZERO: Self = Self {
x: C::BaseField::ZERO,
y: C::BaseField::ZERO,
zero: true,
};
pub fn nonzero(x: C::BaseField, y: C::BaseField) -> Self {
let point = Self { x, y, zero: false };
debug_assert!(point.is_valid());
point
}
pub fn is_valid(&self) -> bool {
let Self { x, y, zero } = *self;
zero || y.square() == x.cube() + C::A * x + C::B
}
pub fn to_projective(&self) -> ProjectivePoint<C> {
let Self { x, y, zero } = *self;
let z = if zero {
C::BaseField::ZERO
} else {
C::BaseField::ONE
};
ProjectivePoint { x, y, z }
}
pub fn batch_to_projective(affine_points: &[Self]) -> Vec<ProjectivePoint<C>> {
affine_points.iter().map(Self::to_projective).collect()
}
pub fn double(&self) -> Self {
let AffinePoint { x: x1, y: y1, zero } = *self;
if zero {
return AffinePoint::ZERO;
}
let double_y = y1.double();
let inv_double_y = double_y.inverse(); // (2y)^(-1)
let triple_xx = x1.square().triple(); // 3x^2
let lambda = (triple_xx + C::A) * inv_double_y;
let x3 = lambda.square() - self.x.double();
let y3 = lambda * (x1 - x3) - y1;
Self {
x: x3,
y: y3,
zero: false,
}
}
}
impl<C: Curve> PartialEq for AffinePoint<C> {
fn eq(&self, other: &Self) -> bool {
let AffinePoint {
x: x1,
y: y1,
zero: zero1,
} = *self;
let AffinePoint {
x: x2,
y: y2,
zero: zero2,
} = *other;
if zero1 || zero2 {
return zero1 == zero2;
}
x1 == x2 && y1 == y2
}
}
impl<C: Curve> Eq for AffinePoint<C> {}
/// A point on a short Weierstrass curve, represented in projective coordinates.
#[derive(Copy, Clone, Debug)]
pub struct ProjectivePoint<C: Curve> {
pub x: C::BaseField,
pub y: C::BaseField,
pub z: C::BaseField,
}
impl<C: Curve> ProjectivePoint<C> {
pub const ZERO: Self = Self {
x: C::BaseField::ZERO,
y: C::BaseField::ONE,
z: C::BaseField::ZERO,
};
pub fn nonzero(x: C::BaseField, y: C::BaseField, z: C::BaseField) -> Self {
let point = Self { x, y, z };
debug_assert!(point.is_valid());
point
}
pub fn is_valid(&self) -> bool {
let Self { x, y, z } = *self;
z.is_zero() || y.square() * z == x.cube() + C::A * x * z.square() + C::B * z.cube()
}
pub fn to_affine(&self) -> AffinePoint<C> {
let Self { x, y, z } = *self;
if z == C::BaseField::ZERO {
AffinePoint::ZERO
} else {
let z_inv = z.inverse();
AffinePoint::nonzero(x * z_inv, y * z_inv)
}
}
pub fn batch_to_affine(proj_points: &[Self]) -> Vec<AffinePoint<C>> {
let n = proj_points.len();
let zs: Vec<C::BaseField> = proj_points.iter().map(|pp| pp.z).collect();
let z_invs = C::BaseField::batch_multiplicative_inverse(&zs);
let mut result = Vec::with_capacity(n);
for i in 0..n {
let Self { x, y, z } = proj_points[i];
result.push(if z == C::BaseField::ZERO {
AffinePoint::ZERO
} else {
let z_inv = z_invs[i];
AffinePoint::nonzero(x * z_inv, y * z_inv)
});
}
result
}
// From https://www.hyperelliptic.org/EFD/g1p/data/shortw/projective/doubling/dbl-2007-bl
pub fn double(&self) -> Self {
let Self { x, y, z } = *self;
if z == C::BaseField::ZERO {
return ProjectivePoint::ZERO;
}
let xx = x.square();
let zz = z.square();
let mut w = xx.triple();
if C::A.is_nonzero() {
w += C::A * zz;
}
let s = y.double() * z;
let r = y * s;
let rr = r.square();
let b = (x + r).square() - (xx + rr);
let h = w.square() - b.double();
let x3 = h * s;
let y3 = w * (b - h) - rr.double();
let z3 = s.cube();
Self {
x: x3,
y: y3,
z: z3,
}
}
pub fn add_slices(a: &[Self], b: &[Self]) -> Vec<Self> {
assert_eq!(a.len(), b.len());
a.iter()
.zip(b.iter())
.map(|(&a_i, &b_i)| a_i + b_i)
.collect()
}
pub fn neg(&self) -> Self {
Self {
x: self.x,
y: -self.y,
z: self.z,
}
}
}
impl<C: Curve> PartialEq for ProjectivePoint<C> {
fn eq(&self, other: &Self) -> bool {
let ProjectivePoint {
x: x1,
y: y1,
z: z1,
} = *self;
let ProjectivePoint {
x: x2,
y: y2,
z: z2,
} = *other;
if z1 == C::BaseField::ZERO || z2 == C::BaseField::ZERO {
return z1 == z2;
}
// We want to compare (x1/z1, y1/z1) == (x2/z2, y2/z2).
// But to avoid field division, it is better to compare (x1*z2, y1*z2) == (x2*z1, y2*z1).
x1 * z2 == x2 * z1 && y1 * z2 == y2 * z1
}
}
impl<C: Curve> Eq for ProjectivePoint<C> {}
impl<C: Curve> Neg for AffinePoint<C> {
type Output = AffinePoint<C>;
fn neg(self) -> Self::Output {
let AffinePoint { x, y, zero } = self;
AffinePoint { x, y: -y, zero }
}
}
impl<C: Curve> Neg for ProjectivePoint<C> {
type Output = ProjectivePoint<C>;
fn neg(self) -> Self::Output {
let ProjectivePoint { x, y, z } = self;
ProjectivePoint { x, y: -y, z }
}
}

6
src/curve/mod.rs Normal file
View File

@ -0,0 +1,6 @@
pub mod curve_adds;
pub mod curve_msm;
pub mod curve_multiplication;
pub mod curve_summation;
pub mod curve_types;
pub mod secp256k1;

98
src/curve/secp256k1.rs Normal file
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@ -0,0 +1,98 @@
use crate::curve::curve_types::{AffinePoint, Curve};
use crate::field::field_types::Field;
use crate::field::secp256k1_base::Secp256K1Base;
use crate::field::secp256k1_scalar::Secp256K1Scalar;
#[derive(Debug, Copy, Clone)]
pub struct Secp256K1;
impl Curve for Secp256K1 {
type BaseField = Secp256K1Base;
type ScalarField = Secp256K1Scalar;
const A: Secp256K1Base = Secp256K1Base::ZERO;
const B: Secp256K1Base = Secp256K1Base([7, 0, 0, 0]);
const GENERATOR_AFFINE: AffinePoint<Self> = AffinePoint {
x: SECP256K1_GENERATOR_X,
y: SECP256K1_GENERATOR_Y,
zero: false,
};
}
// 55066263022277343669578718895168534326250603453777594175500187360389116729240
const SECP256K1_GENERATOR_X: Secp256K1Base = Secp256K1Base([
0x59F2815B16F81798,
0x029BFCDB2DCE28D9,
0x55A06295CE870B07,
0x79BE667EF9DCBBAC,
]);
/// 32670510020758816978083085130507043184471273380659243275938904335757337482424
const SECP256K1_GENERATOR_Y: Secp256K1Base = Secp256K1Base([
0x9C47D08FFB10D4B8,
0xFD17B448A6855419,
0x5DA4FBFC0E1108A8,
0x483ADA7726A3C465,
]);
#[cfg(test)]
mod tests {
use num::BigUint;
use crate::curve::curve_types::{AffinePoint, Curve, ProjectivePoint};
use crate::curve::secp256k1::Secp256K1;
use crate::field::field_types::Field;
use crate::field::secp256k1_scalar::Secp256K1Scalar;
#[test]
fn test_generator() {
let g = Secp256K1::GENERATOR_AFFINE;
assert!(g.is_valid());
let neg_g = AffinePoint::<Secp256K1> {
x: g.x,
y: -g.y,
zero: g.zero,
};
assert!(neg_g.is_valid());
}
#[test]
fn test_naive_multiplication() {
let g = Secp256K1::GENERATOR_PROJECTIVE;
let ten = Secp256K1Scalar::from_canonical_u64(10);
let product = mul_naive(ten, g);
let sum = g + g + g + g + g + g + g + g + g + g;
assert_eq!(product, sum);
}
#[test]
fn test_g1_multiplication() {
let lhs = Secp256K1Scalar::from_biguint(BigUint::from_slice(&[
1111, 2222, 3333, 4444, 5555, 6666, 7777, 8888,
]));
assert_eq!(
Secp256K1::convert(lhs) * Secp256K1::GENERATOR_PROJECTIVE,
mul_naive(lhs, Secp256K1::GENERATOR_PROJECTIVE)
);
}
/// A simple, somewhat inefficient implementation of multiplication which is used as a reference
/// for correctness.
fn mul_naive(
lhs: Secp256K1Scalar,
rhs: ProjectivePoint<Secp256K1>,
) -> ProjectivePoint<Secp256K1> {
let mut g = rhs;
let mut sum = ProjectivePoint::ZERO;
for limb in lhs.to_biguint().to_u64_digits().iter() {
for j in 0..64 {
if (limb >> j & 1u64) != 0u64 {
sum = sum + g;
}
g = g.double();
}
}
sum
}
}

View File

@ -67,6 +67,8 @@ impl<F: Extendable<2>> Field for QuadraticExtension<F> {
const MULTIPLICATIVE_GROUP_GENERATOR: Self = Self(F::EXT_MULTIPLICATIVE_GROUP_GENERATOR);
const POWER_OF_TWO_GENERATOR: Self = Self(F::EXT_POWER_OF_TWO_GENERATOR);
const BITS: usize = F::BITS * 2;
fn order() -> BigUint {
F::order() * F::order()
}

View File

@ -69,6 +69,8 @@ impl<F: Extendable<4>> Field for QuarticExtension<F> {
const MULTIPLICATIVE_GROUP_GENERATOR: Self = Self(F::EXT_MULTIPLICATIVE_GROUP_GENERATOR);
const POWER_OF_TWO_GENERATOR: Self = Self(F::EXT_POWER_OF_TWO_GENERATOR);
const BITS: usize = F::BITS * 4;
fn order() -> BigUint {
F::order().pow(4u32)
}

View File

@ -84,6 +84,19 @@ macro_rules! test_field_arithmetic {
assert_eq!(base.exp_biguint(&pow), base.exp_biguint(&big_pow));
assert_ne!(base.exp_biguint(&pow), base.exp_biguint(&big_pow_wrong));
}
#[test]
fn inverses() {
type F = $field;
let x = F::rand();
let x1 = x.inverse();
let x2 = x1.inverse();
let x3 = x2.inverse();
assert_eq!(x, x2);
assert_eq!(x1, x3);
}
}
};
}

View File

@ -59,6 +59,8 @@ pub trait Field:
/// Generator of a multiplicative subgroup of order `2^TWO_ADICITY`.
const POWER_OF_TWO_GENERATOR: Self;
const BITS: usize;
fn order() -> BigUint;
#[inline]
@ -91,6 +93,10 @@ pub trait Field:
self.square() * *self
}
fn triple(&self) -> Self {
*self * (Self::ONE + Self::TWO)
}
/// Compute the multiplicative inverse of this field element.
fn try_inverse(&self) -> Option<Self>;

View File

@ -82,6 +82,8 @@ impl Field for GoldilocksField {
// ```
const POWER_OF_TWO_GENERATOR: Self = Self(1753635133440165772);
const BITS: usize = 64;
fn order() -> BigUint {
Self::ORDER.into()
}

View File

@ -7,7 +7,8 @@ pub(crate) mod interpolation;
mod inversion;
pub(crate) mod packable;
pub(crate) mod packed_field;
pub mod secp256k1;
pub mod secp256k1_base;
pub mod secp256k1_scalar;
#[cfg(target_feature = "avx2")]
pub(crate) mod packed_avx2;

View File

@ -91,6 +91,8 @@ impl Field for Secp256K1Base {
// Sage: `g_2 = g^((p - 1) / 2)`
const POWER_OF_TWO_GENERATOR: Self = Self::NEG_ONE;
const BITS: usize = 256;
fn order() -> BigUint {
BigUint::from_slice(&[
0xFFFFFC2F, 0xFFFFFFFE, 0xFFFFFFFF, 0xFFFFFFFF, 0xFFFFFFFF, 0xFFFFFFFF, 0xFFFFFFFF,
@ -239,3 +241,10 @@ impl DivAssign for Secp256K1Base {
*self = *self / rhs;
}
}
#[cfg(test)]
mod tests {
use crate::test_field_arithmetic;
test_field_arithmetic!(crate::field::secp256k1_base::Secp256K1Base);
}

View File

@ -0,0 +1,260 @@
use std::convert::TryInto;
use std::fmt;
use std::fmt::{Debug, Display, Formatter};
use std::hash::{Hash, Hasher};
use std::iter::{Product, Sum};
use std::ops::{Add, AddAssign, Div, DivAssign, Mul, MulAssign, Neg, Sub, SubAssign};
use itertools::Itertools;
use num::bigint::{BigUint, RandBigInt};
use num::{Integer, One};
use rand::Rng;
use serde::{Deserialize, Serialize};
use crate::field::field_types::Field;
use crate::field::goldilocks_field::GoldilocksField;
/// The base field of the secp256k1 elliptic curve.
///
/// Its order is
/// ```ignore
/// P = 0xFFFFFFFF FFFFFFFF FFFFFFFF FFFFFFFE BAAEDCE6 AF48A03B BFD25E8C D0364141
/// = 115792089237316195423570985008687907852837564279074904382605163141518161494337
/// = 2**256 - 432420386565659656852420866394968145599
/// ```
#[derive(Copy, Clone, Serialize, Deserialize)]
pub struct Secp256K1Scalar(pub [u64; 4]);
fn biguint_from_array(arr: [u64; 4]) -> BigUint {
BigUint::from_slice(&[
arr[0] as u32,
(arr[0] >> 32) as u32,
arr[1] as u32,
(arr[1] >> 32) as u32,
arr[2] as u32,
(arr[2] >> 32) as u32,
arr[3] as u32,
(arr[3] >> 32) as u32,
])
}
impl Default for Secp256K1Scalar {
fn default() -> Self {
Self::ZERO
}
}
impl PartialEq for Secp256K1Scalar {
fn eq(&self, other: &Self) -> bool {
self.to_biguint() == other.to_biguint()
}
}
impl Eq for Secp256K1Scalar {}
impl Hash for Secp256K1Scalar {
fn hash<H: Hasher>(&self, state: &mut H) {
self.to_biguint().hash(state)
}
}
impl Display for Secp256K1Scalar {
fn fmt(&self, f: &mut Formatter<'_>) -> fmt::Result {
Display::fmt(&self.to_biguint(), f)
}
}
impl Debug for Secp256K1Scalar {
fn fmt(&self, f: &mut Formatter<'_>) -> fmt::Result {
Debug::fmt(&self.to_biguint(), f)
}
}
impl Field for Secp256K1Scalar {
// TODO: fix
type PrimeField = GoldilocksField;
const ZERO: Self = Self([0; 4]);
const ONE: Self = Self([1, 0, 0, 0]);
const TWO: Self = Self([2, 0, 0, 0]);
const NEG_ONE: Self = Self([
0xBFD25E8CD0364140,
0xBAAEDCE6AF48A03B,
0xFFFFFFFFFFFFFFFE,
0xFFFFFFFFFFFFFFFF,
]);
// TODO: fix
const CHARACTERISTIC: u64 = 0;
const TWO_ADICITY: usize = 6;
// Sage: `g = GF(p).multiplicative_generator()`
const MULTIPLICATIVE_GROUP_GENERATOR: Self = Self([7, 0, 0, 0]);
// Sage: `g_2 = power_mod(g, (p - 1) // 2^6), p)`
// 5480320495727936603795231718619559942670027629901634955707709633242980176626
const POWER_OF_TWO_GENERATOR: Self = Self([
0x992f4b5402b052f2,
0x98BDEAB680756045,
0xDF9879A3FBC483A8,
0xC1DC060E7A91986,
]);
const BITS: usize = 256;
fn order() -> BigUint {
BigUint::from_slice(&[
0xD0364141, 0xBFD25E8C, 0xAF48A03B, 0xBAAEDCE6, 0xFFFFFFFE, 0xFFFFFFFF, 0xFFFFFFFF,
0xFFFFFFFF,
])
}
fn try_inverse(&self) -> Option<Self> {
if self.is_zero() {
return None;
}
// Fermat's Little Theorem
Some(self.exp_biguint(&(Self::order() - BigUint::one() - BigUint::one())))
}
fn to_biguint(&self) -> BigUint {
let mut result = biguint_from_array(self.0);
if result >= Self::order() {
result -= Self::order();
}
result
}
fn from_biguint(val: BigUint) -> Self {
Self(
val.to_u64_digits()
.into_iter()
.pad_using(4, |_| 0)
.collect::<Vec<_>>()[..]
.try_into()
.expect("error converting to u64 array"),
)
}
#[inline]
fn from_canonical_u64(n: u64) -> Self {
Self([n, 0, 0, 0])
}
#[inline]
fn from_noncanonical_u128(n: u128) -> Self {
Self([n as u64, (n >> 64) as u64, 0, 0])
}
#[inline]
fn from_noncanonical_u96(n: (u64, u32)) -> Self {
Self([n.0, n.1 as u64, 0, 0])
}
fn rand_from_rng<R: Rng>(rng: &mut R) -> Self {
Self::from_biguint(rng.gen_biguint_below(&Self::order()))
}
}
impl Neg for Secp256K1Scalar {
type Output = Self;
#[inline]
fn neg(self) -> Self {
if self.is_zero() {
Self::ZERO
} else {
Self::from_biguint(Self::order() - self.to_biguint())
}
}
}
impl Add for Secp256K1Scalar {
type Output = Self;
#[inline]
fn add(self, rhs: Self) -> Self {
let mut result = self.to_biguint() + rhs.to_biguint();
if result >= Self::order() {
result -= Self::order();
}
Self::from_biguint(result)
}
}
impl AddAssign for Secp256K1Scalar {
#[inline]
fn add_assign(&mut self, rhs: Self) {
*self = *self + rhs;
}
}
impl Sum for Secp256K1Scalar {
fn sum<I: Iterator<Item = Self>>(iter: I) -> Self {
iter.fold(Self::ZERO, |acc, x| acc + x)
}
}
impl Sub for Secp256K1Scalar {
type Output = Self;
#[inline]
#[allow(clippy::suspicious_arithmetic_impl)]
fn sub(self, rhs: Self) -> Self {
self + -rhs
}
}
impl SubAssign for Secp256K1Scalar {
#[inline]
fn sub_assign(&mut self, rhs: Self) {
*self = *self - rhs;
}
}
impl Mul for Secp256K1Scalar {
type Output = Self;
#[inline]
fn mul(self, rhs: Self) -> Self {
Self::from_biguint((self.to_biguint() * rhs.to_biguint()).mod_floor(&Self::order()))
}
}
impl MulAssign for Secp256K1Scalar {
#[inline]
fn mul_assign(&mut self, rhs: Self) {
*self = *self * rhs;
}
}
impl Product for Secp256K1Scalar {
#[inline]
fn product<I: Iterator<Item = Self>>(iter: I) -> Self {
iter.reduce(|acc, x| acc * x).unwrap_or(Self::ONE)
}
}
impl Div for Secp256K1Scalar {
type Output = Self;
#[allow(clippy::suspicious_arithmetic_impl)]
fn div(self, rhs: Self) -> Self::Output {
self * rhs.inverse()
}
}
impl DivAssign for Secp256K1Scalar {
fn div_assign(&mut self, rhs: Self) {
*self = *self / rhs;
}
}
#[cfg(test)]
mod tests {
use crate::test_field_arithmetic;
test_field_arithmetic!(crate::field::secp256k1_scalar::Secp256K1Scalar);
}

View File

@ -110,8 +110,8 @@ impl<F: RichField + Extendable<D>, const D: usize> CircuitBuilder<F, D> {
// Subtract two `BigUintTarget`s. We assume that the first is larger than the second.
pub fn sub_biguint(&mut self, a: &BigUintTarget, b: &BigUintTarget) -> BigUintTarget {
let num_limbs = a.limbs.len();
let (a, b) = self.pad_biguints(a, b);
let num_limbs = a.limbs.len();
let mut result_limbs = vec![];
@ -155,14 +155,31 @@ impl<F: RichField + Extendable<D>, const D: usize> CircuitBuilder<F, D> {
}
}
// Returns x * y + z. This is no more efficient than mul-then-add; it's purely for convenience (only need to call one CircuitBuilder function).
pub fn mul_add_biguint(
&mut self,
x: &BigUintTarget,
y: &BigUintTarget,
z: &BigUintTarget,
) -> BigUintTarget {
let prod = self.mul_biguint(x, y);
self.add_biguint(&prod, z)
}
pub fn div_rem_biguint(
&mut self,
a: &BigUintTarget,
b: &BigUintTarget,
) -> (BigUintTarget, BigUintTarget) {
let num_limbs = a.limbs.len();
let div = self.add_virtual_biguint_target(num_limbs);
let rem = self.add_virtual_biguint_target(num_limbs);
let a_len = a.limbs.len();
let b_len = b.limbs.len();
let div_num_limbs = if b_len > a_len + 1 {
0
} else {
a_len - b_len + 1
};
let div = self.add_virtual_biguint_target(div_num_limbs);
let rem = self.add_virtual_biguint_target(b_len);
self.add_simple_generator(BigUintDivRemGenerator::<F, D> {
a: a.clone(),

368
src/gadgets/curve.rs Normal file
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@ -0,0 +1,368 @@
use crate::curve::curve_types::{AffinePoint, Curve, CurveScalar};
use crate::field::extension_field::Extendable;
use crate::field::field_types::{Field, RichField};
use crate::gadgets::nonnative::NonNativeTarget;
use crate::plonk::circuit_builder::CircuitBuilder;
/// A Target representing an affine point on the curve `C`. We use incomplete arithmetic for efficiency,
/// so we assume these points are not zero.
#[derive(Clone, Debug)]
pub struct AffinePointTarget<C: Curve> {
pub x: NonNativeTarget<C::BaseField>,
pub y: NonNativeTarget<C::BaseField>,
}
impl<C: Curve> AffinePointTarget<C> {
pub fn to_vec(&self) -> Vec<NonNativeTarget<C::BaseField>> {
vec![self.x.clone(), self.y.clone()]
}
}
impl<F: RichField + Extendable<D>, const D: usize> CircuitBuilder<F, D> {
pub fn constant_affine_point<C: Curve>(
&mut self,
point: AffinePoint<C>,
) -> AffinePointTarget<C> {
debug_assert!(!point.zero);
AffinePointTarget {
x: self.constant_nonnative(point.x),
y: self.constant_nonnative(point.y),
}
}
pub fn connect_affine_point<C: Curve>(
&mut self,
lhs: &AffinePointTarget<C>,
rhs: &AffinePointTarget<C>,
) {
self.connect_nonnative(&lhs.x, &rhs.x);
self.connect_nonnative(&lhs.y, &rhs.y);
}
pub fn add_virtual_affine_point_target<C: Curve>(&mut self) -> AffinePointTarget<C> {
let x = self.add_virtual_nonnative_target();
let y = self.add_virtual_nonnative_target();
AffinePointTarget { x, y }
}
pub fn curve_assert_valid<C: Curve>(&mut self, p: &AffinePointTarget<C>) {
let a = self.constant_nonnative(C::A);
let b = self.constant_nonnative(C::B);
let y_squared = self.mul_nonnative(&p.y, &p.y);
let x_squared = self.mul_nonnative(&p.x, &p.x);
let x_cubed = self.mul_nonnative(&x_squared, &p.x);
let a_x = self.mul_nonnative(&a, &p.x);
let a_x_plus_b = self.add_nonnative(&a_x, &b);
let rhs = self.add_nonnative(&x_cubed, &a_x_plus_b);
self.connect_nonnative(&y_squared, &rhs);
}
pub fn curve_neg<C: Curve>(&mut self, p: &AffinePointTarget<C>) -> AffinePointTarget<C> {
let neg_y = self.neg_nonnative(&p.y);
AffinePointTarget {
x: p.x.clone(),
y: neg_y,
}
}
pub fn curve_double<C: Curve>(&mut self, p: &AffinePointTarget<C>) -> AffinePointTarget<C> {
let AffinePointTarget { x, y } = p;
let double_y = self.add_nonnative(y, y);
let inv_double_y = self.inv_nonnative(&double_y);
let x_squared = self.mul_nonnative(x, x);
let double_x_squared = self.add_nonnative(&x_squared, &x_squared);
let triple_x_squared = self.add_nonnative(&double_x_squared, &x_squared);
let a = self.constant_nonnative(C::A);
let triple_xx_a = self.add_nonnative(&triple_x_squared, &a);
let lambda = self.mul_nonnative(&triple_xx_a, &inv_double_y);
let lambda_squared = self.mul_nonnative(&lambda, &lambda);
let x_double = self.add_nonnative(x, x);
let x3 = self.sub_nonnative(&lambda_squared, &x_double);
let x_diff = self.sub_nonnative(x, &x3);
let lambda_x_diff = self.mul_nonnative(&lambda, &x_diff);
let y3 = self.sub_nonnative(&lambda_x_diff, y);
AffinePointTarget { x: x3, y: y3 }
}
// Add two points, which are assumed to be non-equal.
pub fn curve_add<C: Curve>(
&mut self,
p1: &AffinePointTarget<C>,
p2: &AffinePointTarget<C>,
) -> AffinePointTarget<C> {
let AffinePointTarget { x: x1, y: y1 } = p1;
let AffinePointTarget { x: x2, y: y2 } = p2;
let u = self.sub_nonnative(y2, y1);
let uu = self.mul_nonnative(&u, &u);
let v = self.sub_nonnative(x2, x1);
let vv = self.mul_nonnative(&v, &v);
let vvv = self.mul_nonnative(&v, &vv);
let r = self.mul_nonnative(&vv, x1);
let diff = self.sub_nonnative(&uu, &vvv);
let r2 = self.add_nonnative(&r, &r);
let a = self.sub_nonnative(&diff, &r2);
let x3 = self.mul_nonnative(&v, &a);
let r_a = self.sub_nonnative(&r, &a);
let y3_first = self.mul_nonnative(&u, &r_a);
let y3_second = self.mul_nonnative(&vvv, y1);
let y3 = self.sub_nonnative(&y3_first, &y3_second);
let z3_inv = self.inv_nonnative(&vvv);
let x3_norm = self.mul_nonnative(&x3, &z3_inv);
let y3_norm = self.mul_nonnative(&y3, &z3_inv);
AffinePointTarget {
x: x3_norm,
y: y3_norm,
}
}
pub fn curve_scalar_mul<C: Curve>(
&mut self,
p: &AffinePointTarget<C>,
n: &NonNativeTarget<C::ScalarField>,
) -> AffinePointTarget<C> {
let one = self.constant_nonnative(C::BaseField::ONE);
let bits = self.split_nonnative_to_bits(n);
let bits_as_base: Vec<NonNativeTarget<C::BaseField>> =
bits.iter().map(|b| self.bool_to_nonnative(b)).collect();
let rando = (CurveScalar(C::ScalarField::rand()) * C::GENERATOR_PROJECTIVE).to_affine();
let randot = self.constant_affine_point(rando);
// Result starts at `rando`, which is later subtracted, because we don't support arithmetic with the zero point.
let mut result = self.add_virtual_affine_point_target();
self.connect_affine_point(&randot, &result);
let mut two_i_times_p = self.add_virtual_affine_point_target();
self.connect_affine_point(p, &two_i_times_p);
for bit in bits_as_base.iter() {
let not_bit = self.sub_nonnative(&one, bit);
let result_plus_2_i_p = self.curve_add(&result, &two_i_times_p);
let new_x_if_bit = self.mul_nonnative(bit, &result_plus_2_i_p.x);
let new_x_if_not_bit = self.mul_nonnative(&not_bit, &result.x);
let new_y_if_bit = self.mul_nonnative(bit, &result_plus_2_i_p.y);
let new_y_if_not_bit = self.mul_nonnative(&not_bit, &result.y);
let new_x = self.add_nonnative(&new_x_if_bit, &new_x_if_not_bit);
let new_y = self.add_nonnative(&new_y_if_bit, &new_y_if_not_bit);
result = AffinePointTarget { x: new_x, y: new_y };
two_i_times_p = self.curve_double(&two_i_times_p);
}
// Subtract off result's intial value of `rando`.
let neg_r = self.curve_neg(&randot);
result = self.curve_add(&result, &neg_r);
result
}
}
#[cfg(test)]
mod tests {
use anyhow::Result;
use crate::curve::curve_types::{AffinePoint, Curve, CurveScalar};
use crate::curve::secp256k1::Secp256K1;
use crate::field::field_types::Field;
use crate::field::goldilocks_field::GoldilocksField;
use crate::field::secp256k1_base::Secp256K1Base;
use crate::field::secp256k1_scalar::Secp256K1Scalar;
use crate::iop::witness::PartialWitness;
use crate::plonk::circuit_builder::CircuitBuilder;
use crate::plonk::circuit_data::CircuitConfig;
use crate::plonk::verifier::verify;
#[test]
fn test_curve_point_is_valid() -> Result<()> {
type F = GoldilocksField;
const D: usize = 4;
let config = CircuitConfig::standard_recursion_config();
let pw = PartialWitness::new();
let mut builder = CircuitBuilder::<F, D>::new(config);
let g = Secp256K1::GENERATOR_AFFINE;
let g_target = builder.constant_affine_point(g);
let neg_g_target = builder.curve_neg(&g_target);
builder.curve_assert_valid(&g_target);
builder.curve_assert_valid(&neg_g_target);
let data = builder.build();
let proof = data.prove(pw).unwrap();
verify(proof, &data.verifier_only, &data.common)
}
#[test]
#[should_panic]
fn test_curve_point_is_not_valid() {
type F = GoldilocksField;
const D: usize = 4;
let config = CircuitConfig::standard_recursion_config();
let pw = PartialWitness::new();
let mut builder = CircuitBuilder::<F, D>::new(config);
let g = Secp256K1::GENERATOR_AFFINE;
let not_g = AffinePoint::<Secp256K1> {
x: g.x,
y: g.y + Secp256K1Base::ONE,
zero: g.zero,
};
let not_g_target = builder.constant_affine_point(not_g);
builder.curve_assert_valid(&not_g_target);
let data = builder.build();
let proof = data.prove(pw).unwrap();
verify(proof, &data.verifier_only, &data.common).unwrap();
}
#[test]
fn test_curve_double() -> Result<()> {
type F = GoldilocksField;
const D: usize = 4;
let config = CircuitConfig::standard_recursion_config();
let pw = PartialWitness::new();
let mut builder = CircuitBuilder::<F, D>::new(config);
let g = Secp256K1::GENERATOR_AFFINE;
let g_target = builder.constant_affine_point(g);
let neg_g_target = builder.curve_neg(&g_target);
let double_g = g.double();
let double_g_expected = builder.constant_affine_point(double_g);
builder.curve_assert_valid(&double_g_expected);
let double_neg_g = (-g).double();
let double_neg_g_expected = builder.constant_affine_point(double_neg_g);
builder.curve_assert_valid(&double_neg_g_expected);
let double_g_actual = builder.curve_double(&g_target);
let double_neg_g_actual = builder.curve_double(&neg_g_target);
builder.curve_assert_valid(&double_g_actual);
builder.curve_assert_valid(&double_neg_g_actual);
builder.connect_affine_point(&double_g_expected, &double_g_actual);
builder.connect_affine_point(&double_neg_g_expected, &double_neg_g_actual);
let data = builder.build();
let proof = data.prove(pw).unwrap();
verify(proof, &data.verifier_only, &data.common)
}
#[test]
fn test_curve_add() -> Result<()> {
type F = GoldilocksField;
const D: usize = 4;
let config = CircuitConfig::standard_recursion_config();
let pw = PartialWitness::new();
let mut builder = CircuitBuilder::<F, D>::new(config);
let g = Secp256K1::GENERATOR_AFFINE;
let double_g = g.double();
let g_plus_2g = (g + double_g).to_affine();
let g_plus_2g_expected = builder.constant_affine_point(g_plus_2g);
builder.curve_assert_valid(&g_plus_2g_expected);
let g_target = builder.constant_affine_point(g);
let double_g_target = builder.curve_double(&g_target);
let g_plus_2g_actual = builder.curve_add(&g_target, &double_g_target);
builder.curve_assert_valid(&g_plus_2g_actual);
builder.connect_affine_point(&g_plus_2g_expected, &g_plus_2g_actual);
let data = builder.build();
let proof = data.prove(pw).unwrap();
verify(proof, &data.verifier_only, &data.common)
}
#[test]
#[ignore]
fn test_curve_mul() -> Result<()> {
type F = GoldilocksField;
const D: usize = 4;
let config = CircuitConfig {
num_routed_wires: 33,
..CircuitConfig::standard_recursion_config()
};
let pw = PartialWitness::new();
let mut builder = CircuitBuilder::<F, D>::new(config);
let g = Secp256K1::GENERATOR_AFFINE;
let five = Secp256K1Scalar::from_canonical_usize(5);
let five_scalar = CurveScalar::<Secp256K1>(five);
let five_g = (five_scalar * g.to_projective()).to_affine();
let five_g_expected = builder.constant_affine_point(five_g);
builder.curve_assert_valid(&five_g_expected);
let g_target = builder.constant_affine_point(g);
let five_target = builder.constant_nonnative(five);
let five_g_actual = builder.curve_scalar_mul(&g_target, &five_target);
builder.curve_assert_valid(&five_g_actual);
builder.connect_affine_point(&five_g_expected, &five_g_actual);
let data = builder.build();
let proof = data.prove(pw).unwrap();
verify(proof, &data.verifier_only, &data.common)
}
#[test]
#[ignore]
fn test_curve_random() -> Result<()> {
type F = GoldilocksField;
const D: usize = 4;
let config = CircuitConfig {
num_routed_wires: 33,
..CircuitConfig::standard_recursion_config()
};
let pw = PartialWitness::new();
let mut builder = CircuitBuilder::<F, D>::new(config);
let rando =
(CurveScalar(Secp256K1Scalar::rand()) * Secp256K1::GENERATOR_PROJECTIVE).to_affine();
let randot = builder.constant_affine_point(rando);
let two_target = builder.constant_nonnative(Secp256K1Scalar::TWO);
let randot_doubled = builder.curve_double(&randot);
let randot_times_two = builder.curve_scalar_mul(&randot, &two_target);
builder.connect_affine_point(&randot_doubled, &randot_times_two);
let data = builder.build();
let proof = data.prove(pw).unwrap();
verify(proof, &data.verifier_only, &data.common)
}
}

View File

@ -2,6 +2,7 @@ pub mod arithmetic;
pub mod arithmetic_extension;
pub mod arithmetic_u32;
pub mod biguint;
pub mod curve;
pub mod hash;
pub mod insert;
pub mod interpolation;

View File

@ -1,60 +1,81 @@
use std::marker::PhantomData;
use num::{BigUint, One};
use num::{BigUint, Zero};
use crate::field::field_types::RichField;
use crate::field::{extension_field::Extendable, field_types::Field};
use crate::gadgets::arithmetic_u32::U32Target;
use crate::gadgets::biguint::BigUintTarget;
use crate::iop::generator::{GeneratedValues, SimpleGenerator};
use crate::iop::target::{BoolTarget, Target};
use crate::iop::witness::{PartitionWitness, Witness};
use crate::plonk::circuit_builder::CircuitBuilder;
use crate::util::ceil_div_usize;
pub struct ForeignFieldTarget<FF: Field> {
value: BigUintTarget,
#[derive(Clone, Debug)]
pub struct NonNativeTarget<FF: Field> {
pub(crate) value: BigUintTarget,
_phantom: PhantomData<FF>,
}
impl<F: RichField + Extendable<D>, const D: usize> CircuitBuilder<F, D> {
pub fn biguint_to_nonnative<FF: Field>(&mut self, x: &BigUintTarget) -> ForeignFieldTarget<FF> {
ForeignFieldTarget {
fn num_nonnative_limbs<FF: Field>() -> usize {
ceil_div_usize(FF::BITS, 32)
}
pub fn biguint_to_nonnative<FF: Field>(&mut self, x: &BigUintTarget) -> NonNativeTarget<FF> {
NonNativeTarget {
value: x.clone(),
_phantom: PhantomData,
}
}
pub fn nonnative_to_biguint<FF: Field>(&mut self, x: &ForeignFieldTarget<FF>) -> BigUintTarget {
pub fn nonnative_to_biguint<FF: Field>(&mut self, x: &NonNativeTarget<FF>) -> BigUintTarget {
x.value.clone()
}
pub fn constant_nonnative<FF: Field>(&mut self, x: FF) -> ForeignFieldTarget<FF> {
pub fn constant_nonnative<FF: Field>(&mut self, x: FF) -> NonNativeTarget<FF> {
let x_biguint = self.constant_biguint(&x.to_biguint());
self.biguint_to_nonnative(&x_biguint)
}
// Assert that two ForeignFieldTarget's, both assumed to be in reduced form, are equal.
// Assert that two NonNativeTarget's, both assumed to be in reduced form, are equal.
pub fn connect_nonnative<FF: Field>(
&mut self,
lhs: &ForeignFieldTarget<FF>,
rhs: &ForeignFieldTarget<FF>,
lhs: &NonNativeTarget<FF>,
rhs: &NonNativeTarget<FF>,
) {
self.connect_biguint(&lhs.value, &rhs.value);
}
// Add two `ForeignFieldTarget`s.
pub fn add_virtual_nonnative_target<FF: Field>(&mut self) -> NonNativeTarget<FF> {
let num_limbs = Self::num_nonnative_limbs::<FF>();
let value = self.add_virtual_biguint_target(num_limbs);
NonNativeTarget {
value,
_phantom: PhantomData,
}
}
// Add two `NonNativeTarget`s.
pub fn add_nonnative<FF: Field>(
&mut self,
a: &ForeignFieldTarget<FF>,
b: &ForeignFieldTarget<FF>,
) -> ForeignFieldTarget<FF> {
a: &NonNativeTarget<FF>,
b: &NonNativeTarget<FF>,
) -> NonNativeTarget<FF> {
let result = self.add_biguint(&a.value, &b.value);
// TODO: reduce add result with only one conditional subtraction
self.reduce(&result)
}
// Subtract two `ForeignFieldTarget`s.
// Subtract two `NonNativeTarget`s.
pub fn sub_nonnative<FF: Field>(
&mut self,
a: &ForeignFieldTarget<FF>,
b: &ForeignFieldTarget<FF>,
) -> ForeignFieldTarget<FF> {
a: &NonNativeTarget<FF>,
b: &NonNativeTarget<FF>,
) -> NonNativeTarget<FF> {
let order = self.constant_biguint(&FF::order());
let a_plus_order = self.add_biguint(&order, &a.value);
let result = self.sub_biguint(&a_plus_order, &b.value);
@ -65,45 +86,127 @@ impl<F: RichField + Extendable<D>, const D: usize> CircuitBuilder<F, D> {
pub fn mul_nonnative<FF: Field>(
&mut self,
a: &ForeignFieldTarget<FF>,
b: &ForeignFieldTarget<FF>,
) -> ForeignFieldTarget<FF> {
a: &NonNativeTarget<FF>,
b: &NonNativeTarget<FF>,
) -> NonNativeTarget<FF> {
let result = self.mul_biguint(&a.value, &b.value);
self.reduce(&result)
}
pub fn neg_nonnative<FF: Field>(
&mut self,
x: &ForeignFieldTarget<FF>,
) -> ForeignFieldTarget<FF> {
let neg_one = FF::order() - BigUint::one();
let neg_one_target = self.constant_biguint(&neg_one);
let neg_one_ff = self.biguint_to_nonnative(&neg_one_target);
pub fn neg_nonnative<FF: Field>(&mut self, x: &NonNativeTarget<FF>) -> NonNativeTarget<FF> {
let zero_target = self.constant_biguint(&BigUint::zero());
let zero_ff = self.biguint_to_nonnative(&zero_target);
self.mul_nonnative(&neg_one_ff, x)
self.sub_nonnative(&zero_ff, x)
}
/// Returns `x % |FF|` as a `ForeignFieldTarget`.
fn reduce<FF: Field>(&mut self, x: &BigUintTarget) -> ForeignFieldTarget<FF> {
pub fn inv_nonnative<FF: Field>(&mut self, x: &NonNativeTarget<FF>) -> NonNativeTarget<FF> {
let num_limbs = x.value.num_limbs();
let inv_biguint = self.add_virtual_biguint_target(num_limbs);
let inv = NonNativeTarget::<FF> {
value: inv_biguint,
_phantom: PhantomData,
};
self.add_simple_generator(NonNativeInverseGenerator::<F, D, FF> {
x: x.clone(),
inv: inv.clone(),
_phantom: PhantomData,
});
let product = self.mul_nonnative(x, &inv);
let one = self.constant_nonnative(FF::ONE);
self.connect_nonnative(&product, &one);
inv
}
pub fn div_rem_nonnative<FF: Field>(
&mut self,
x: &NonNativeTarget<FF>,
y: &NonNativeTarget<FF>,
) -> (NonNativeTarget<FF>, NonNativeTarget<FF>) {
let x_biguint = self.nonnative_to_biguint(x);
let y_biguint = self.nonnative_to_biguint(y);
let (div_biguint, rem_biguint) = self.div_rem_biguint(&x_biguint, &y_biguint);
let div = self.biguint_to_nonnative(&div_biguint);
let rem = self.biguint_to_nonnative(&rem_biguint);
(div, rem)
}
/// Returns `x % |FF|` as a `NonNativeTarget`.
fn reduce<FF: Field>(&mut self, x: &BigUintTarget) -> NonNativeTarget<FF> {
let modulus = FF::order();
let order_target = self.constant_biguint(&modulus);
let value = self.rem_biguint(x, &order_target);
ForeignFieldTarget {
NonNativeTarget {
value,
_phantom: PhantomData,
}
}
#[allow(dead_code)]
fn reduce_nonnative<FF: Field>(
&mut self,
x: &ForeignFieldTarget<FF>,
) -> ForeignFieldTarget<FF> {
fn reduce_nonnative<FF: Field>(&mut self, x: &NonNativeTarget<FF>) -> NonNativeTarget<FF> {
let x_biguint = self.nonnative_to_biguint(x);
self.reduce(&x_biguint)
}
pub fn bool_to_nonnative<FF: Field>(&mut self, b: &BoolTarget) -> NonNativeTarget<FF> {
let limbs = vec![U32Target(b.target)];
let value = BigUintTarget { limbs };
NonNativeTarget {
value,
_phantom: PhantomData,
}
}
// Split a nonnative field element to bits.
pub fn split_nonnative_to_bits<FF: Field>(
&mut self,
x: &NonNativeTarget<FF>,
) -> Vec<BoolTarget> {
let num_limbs = x.value.num_limbs();
let mut result = Vec::with_capacity(num_limbs * 32);
for i in 0..num_limbs {
let limb = x.value.get_limb(i);
let bit_targets = self.split_le_base::<2>(limb.0, 32);
let mut bits: Vec<_> = bit_targets
.iter()
.map(|&t| BoolTarget::new_unsafe(t))
.collect();
result.append(&mut bits);
}
result
}
}
#[derive(Debug)]
struct NonNativeInverseGenerator<F: RichField + Extendable<D>, const D: usize, FF: Field> {
x: NonNativeTarget<FF>,
inv: NonNativeTarget<FF>,
_phantom: PhantomData<F>,
}
impl<F: RichField + Extendable<D>, const D: usize, FF: Field> SimpleGenerator<F>
for NonNativeInverseGenerator<F, D, FF>
{
fn dependencies(&self) -> Vec<Target> {
self.x.value.limbs.iter().map(|&l| l.0).collect()
}
fn run_once(&self, witness: &PartitionWitness<F>, out_buffer: &mut GeneratedValues<F>) {
let x = witness.get_nonnative_target(self.x.clone());
let inv = x.inverse();
out_buffer.set_nonnative_target(self.inv.clone(), inv);
}
}
#[cfg(test)]
@ -112,7 +215,7 @@ mod tests {
use crate::field::field_types::Field;
use crate::field::goldilocks_field::GoldilocksField;
use crate::field::secp256k1::Secp256K1Base;
use crate::field::secp256k1_base::Secp256K1Base;
use crate::iop::witness::PartialWitness;
use crate::plonk::circuit_builder::CircuitBuilder;
use crate::plonk::circuit_data::CircuitConfig;
@ -214,4 +317,26 @@ mod tests {
let proof = data.prove(pw).unwrap();
verify(proof, &data.verifier_only, &data.common)
}
#[test]
fn test_nonnative_inv() -> Result<()> {
type FF = Secp256K1Base;
let x_ff = FF::rand();
let inv_x_ff = x_ff.inverse();
type F = GoldilocksField;
let config = CircuitConfig::standard_recursion_config();
let pw = PartialWitness::new();
let mut builder = CircuitBuilder::<F, 4>::new(config);
let x = builder.constant_nonnative(x_ff);
let inv_x = builder.inv_nonnative(&x);
let inv_x_expected = builder.constant_nonnative(inv_x_ff);
builder.connect_nonnative(&inv_x, &inv_x_expected);
let data = builder.build();
let proof = data.prove(pw).unwrap();
verify(proof, &data.verifier_only, &data.common)
}
}

View File

@ -8,6 +8,7 @@ use crate::field::extension_field::{Extendable, FieldExtension};
use crate::field::field_types::{Field, RichField};
use crate::gadgets::arithmetic_u32::U32Target;
use crate::gadgets::biguint::BigUintTarget;
use crate::gadgets::nonnative::NonNativeTarget;
use crate::hash::hash_types::{HashOut, HashOutTarget};
use crate::iop::target::Target;
use crate::iop::wire::Wire;
@ -168,6 +169,10 @@ impl<F: Field> GeneratedValues<F> {
}
}
pub fn set_nonnative_target<FF: Field>(&mut self, target: NonNativeTarget<FF>, value: FF) {
self.set_biguint_target(target.value, value.to_biguint())
}
pub fn set_hash_target(&mut self, ht: HashOutTarget, value: HashOut<F>) {
ht.elements
.iter()

View File

@ -6,6 +6,7 @@ use crate::field::extension_field::target::ExtensionTarget;
use crate::field::extension_field::{Extendable, FieldExtension};
use crate::field::field_types::Field;
use crate::gadgets::biguint::BigUintTarget;
use crate::gadgets::nonnative::NonNativeTarget;
use crate::hash::hash_types::HashOutTarget;
use crate::hash::hash_types::{HashOut, MerkleCapTarget};
use crate::hash::merkle_tree::MerkleCap;
@ -68,6 +69,11 @@ pub trait Witness<F: Field> {
result
}
fn get_nonnative_target<FF: Field>(&self, target: NonNativeTarget<FF>) -> FF {
let val = self.get_biguint_target(target.value);
FF::from_biguint(val)
}
fn get_hash_target(&self, ht: HashOutTarget) -> HashOut<F> {
HashOut {
elements: self.get_targets(&ht.elements).try_into().unwrap(),

View File

@ -11,6 +11,7 @@
#![feature(specialization)]
#![feature(stdsimd)]
pub mod curve;
pub mod field;
pub mod fri;
pub mod gadgets;