mirror of https://github.com/zcash/halo2.git
chip::generator_table.rs: Load Sinsemilla generator lookup table.
The 2^K table of generators used in the Sinsemilla hash. These are loaded into a lookup table.
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ebb7dae063
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@ -23,9 +23,9 @@ use pasta_curves::pallas;
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use std::convert::TryInto;
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use std::convert::TryInto;
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// mod generator_table;
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mod generator_table;
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// pub use generator_table::get_s_by_idx;
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pub use generator_table::get_s_by_idx;
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// use generator_table::GeneratorTableConfig;
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use generator_table::GeneratorTableConfig;
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// mod hash_to_point;
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// mod hash_to_point;
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@ -54,6 +54,9 @@ pub struct SinsemillaConfig {
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// Advice column used to store the lambda_2 intermediate value at each
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// Advice column used to store the lambda_2 intermediate value at each
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// iteration.
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// iteration.
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lambda_2: Column<Advice>,
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lambda_2: Column<Advice>,
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// The lookup table where (idx, x_p, y_p) are loaded for the 2^K generators
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// of the Sinsemilla hash.
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generator_table: GeneratorTableConfig,
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// Fixed column shared by the whole circuit. This is used to load the
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// Fixed column shared by the whole circuit. This is used to load the
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// x-coordinate of the domain Q, which is then constrained to equal the
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// x-coordinate of the domain Q, which is then constrained to equal the
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// initial x_a.
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// initial x_a.
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@ -89,7 +92,8 @@ impl SinsemillaChip {
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config: SinsemillaConfig,
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config: SinsemillaConfig,
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layouter: &mut impl Layouter<pallas::Base>,
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layouter: &mut impl Layouter<pallas::Base>,
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) -> Result<<Self as Chip<pallas::Base>>::Loaded, Error> {
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) -> Result<<Self as Chip<pallas::Base>>::Loaded, Error> {
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todo!()
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// Load the lookup table.
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config.generator_table.load(layouter)
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}
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}
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#[allow(clippy::too_many_arguments)]
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#[allow(clippy::too_many_arguments)]
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@ -0,0 +1,127 @@
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use crate::primitives::sinsemilla::{self, sinsemilla_s_generators, S_PERSONALIZATION};
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use halo2::{
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circuit::Layouter,
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plonk::{Column, ConstraintSystem, Error, Expression, Fixed},
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poly::Rotation,
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};
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use pasta_curves::{
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arithmetic::{CurveAffine, CurveExt, FieldExt},
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pallas,
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};
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use group::Curve;
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/// Table containing independent generators S[0..2^k]
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#[derive(Eq, PartialEq, Copy, Clone, Debug)]
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pub struct GeneratorTableConfig {
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table_idx: Column<Fixed>,
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table_x: Column<Fixed>,
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table_y: Column<Fixed>,
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}
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impl GeneratorTableConfig {
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#[allow(clippy::too_many_arguments)]
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#[allow(non_snake_case)]
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// Even though the lookup table can be used in other parts of the circuit,
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// this specific configuration sets up Sinsemilla-specific constraints
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// controlled by `q_sinsemilla`, and would likely not apply to other chips.
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pub fn configure(meta: &mut ConstraintSystem<pallas::Base>, config: super::SinsemillaConfig) {
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let (table_idx, table_x, table_y) = (
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config.generator_table.table_idx,
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config.generator_table.table_x,
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config.generator_table.table_y,
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);
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meta.lookup(|meta| {
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let q_s1 = meta.query_selector(config.q_sinsemilla1);
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let q_s2 = meta.query_fixed(config.q_sinsemilla2, Rotation::cur());
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let table_idx_cur = meta.query_fixed(table_idx, Rotation::cur());
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let table_x_cur = meta.query_fixed(table_x, Rotation::cur());
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let table_y_cur = meta.query_fixed(table_y, Rotation::cur());
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// m_{i+1} = z_{i} - 2^K * q_s2 * z_{i + 1}
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// Note that the message words m_i's are 1-indexed while the
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// running sum z_i's are 0-indexed.
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let word = {
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let z_cur = meta.query_advice(config.bits, Rotation::cur());
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let z_next = meta.query_advice(config.bits, Rotation::next());
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z_cur - (q_s2 * z_next * pallas::Base::from_u64(1 << sinsemilla::K))
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};
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let x_p = meta.query_advice(config.x_p, Rotation::cur());
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// y_{p,i} = (Y_{A,i} / 2) - lambda1 * (x_{A,i} - x_{R,i}),
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// where Y_{A,i} = (lambda1_i + lambda2_i) * (x_{A,i} - x_{R,i}),
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// x_{R,i} = lambda1^2 - x_{A,i} - x_{P,i}
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//
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let y_p = {
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let lambda1 = meta.query_advice(config.lambda_1, Rotation::cur());
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let lambda2 = meta.query_advice(config.lambda_2, Rotation::cur());
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let x_a = meta.query_advice(config.x_a, Rotation::cur());
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let x_r = lambda1.clone().square() - x_a.clone() - x_p.clone();
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let Y_A = (lambda1.clone() + lambda2) * (x_a.clone() - x_r.clone());
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(Y_A * pallas::Base::TWO_INV) * (lambda1 * (x_a - x_r))
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};
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// Lookup expressions default to the first entry when `q_s1`
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// is not enabled.
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let (init_x, init_y) = {
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let init_p = get_s_by_idx(0).to_affine().coordinates().unwrap();
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(*init_p.x(), *init_p.y())
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};
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let not_q_s1 = Expression::Constant(pallas::Base::one()) - q_s1.clone();
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let m = q_s1.clone() * word; // The first table index is 0.
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let x_p = q_s1.clone() * x_p + not_q_s1.clone() * init_x;
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let y_p = q_s1 * y_p + not_q_s1 * init_y;
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vec![(m, table_idx_cur), (x_p, table_x_cur), (y_p, table_y_cur)]
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});
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}
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pub fn load(&self, layouter: &mut impl Layouter<pallas::Base>) -> Result<(), Error> {
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layouter.assign_region(
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|| "generator_table",
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|mut gate| {
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// We generate the row values lazily (we only need them during keygen).
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let mut rows = sinsemilla_s_generators();
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for index in 0..(1 << sinsemilla::K) {
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let mut row = None;
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gate.assign_fixed(
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|| "table_idx",
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self.table_idx,
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index,
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|| {
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row = rows.next();
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Ok(pallas::Base::from_u64(index as u64))
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},
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)?;
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gate.assign_fixed(
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|| "table_x",
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self.table_x,
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index,
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|| row.map(|(x, _)| x).ok_or(Error::SynthesisError),
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)?;
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gate.assign_fixed(
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|| "table_y",
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self.table_y,
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index,
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|| row.map(|(_, y)| y).ok_or(Error::SynthesisError),
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)?;
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}
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Ok(())
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},
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)
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}
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}
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/// Get generator S by index
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pub fn get_s_by_idx(idx: u32) -> pallas::Point {
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let hash = pallas::Point::hash_to_curve(S_PERSONALIZATION);
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hash(&idx.to_le_bytes())
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}
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@ -1,6 +1,7 @@
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//! Sinsemilla generators
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//! Sinsemilla generators
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use group::Curve;
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use group::Curve;
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use halo2::arithmetic::{CurveAffine, CurveExt};
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use halo2::arithmetic::{CurveAffine, CurveExt};
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use pasta_curves::pallas;
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/// Number of bits of each message piece in $\mathsf{SinsemillaHashToPoint}$
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/// Number of bits of each message piece in $\mathsf{SinsemillaHashToPoint}$
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pub const K: usize = 10;
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pub const K: usize = 10;
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@ -62,8 +63,8 @@ pub const Q_MERKLE_CRH: ([u8; 32], [u8; 32]) = (
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pub const S_PERSONALIZATION: &str = "z.cash:SinsemillaS";
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pub const S_PERSONALIZATION: &str = "z.cash:SinsemillaS";
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/// Creates the Sinsemilla S generators used in each round of the Sinsemilla hash
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/// Creates the Sinsemilla S generators used in each round of the Sinsemilla hash
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pub fn sinsemilla_s_generators<C: CurveAffine>() -> impl Iterator<Item = (C::Base, C::Base)> {
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pub fn sinsemilla_s_generators() -> impl Iterator<Item = (pallas::Base, pallas::Base)> {
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let hasher = C::CurveExt::hash_to_curve(S_PERSONALIZATION);
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let hasher = pallas::Point::hash_to_curve(S_PERSONALIZATION);
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(0..(1u32 << K)).map(move |j| {
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(0..(1u32 << K)).map(move |j| {
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let point = hasher(&j.to_le_bytes()).to_affine().coordinates().unwrap();
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let point = hasher(&j.to_le_bytes()).to_affine().coordinates().unwrap();
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(*point.x(), *point.y())
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(*point.x(), *point.y())
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@ -84,7 +85,7 @@ mod tests {
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#[test]
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#[test]
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fn sinsemilla_s() {
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fn sinsemilla_s() {
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use super::super::sinsemilla_s::SINSEMILLA_S;
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use super::super::sinsemilla_s::SINSEMILLA_S;
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let sinsemilla_s: Vec<_> = sinsemilla_s_generators::<pallas::Affine>().collect();
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let sinsemilla_s: Vec<_> = sinsemilla_s_generators().collect();
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assert_eq!(sinsemilla_s.len(), SINSEMILLA_S.len());
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assert_eq!(sinsemilla_s.len(), SINSEMILLA_S.len());
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for (expected, actual) in sinsemilla_s.iter().zip(&SINSEMILLA_S[..]) {
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for (expected, actual) in sinsemilla_s.iter().zip(&SINSEMILLA_S[..]) {
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assert_eq!(expected, actual);
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assert_eq!(expected, actual);
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