mirror of https://github.com/zcash/orchard.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.
This commit is contained in:
parent
ebb7dae063
commit
74e617b46d
|
@ -23,9 +23,9 @@ use pasta_curves::pallas;
|
|||
|
||||
use std::convert::TryInto;
|
||||
|
||||
// mod generator_table;
|
||||
// pub use generator_table::get_s_by_idx;
|
||||
// use generator_table::GeneratorTableConfig;
|
||||
mod generator_table;
|
||||
pub use generator_table::get_s_by_idx;
|
||||
use generator_table::GeneratorTableConfig;
|
||||
|
||||
// mod hash_to_point;
|
||||
|
||||
|
@ -54,6 +54,9 @@ pub struct SinsemillaConfig {
|
|||
// Advice column used to store the lambda_2 intermediate value at each
|
||||
// iteration.
|
||||
lambda_2: Column<Advice>,
|
||||
// The lookup table where (idx, x_p, y_p) are loaded for the 2^K generators
|
||||
// of the Sinsemilla hash.
|
||||
generator_table: GeneratorTableConfig,
|
||||
// Fixed column shared by the whole circuit. This is used to load the
|
||||
// x-coordinate of the domain Q, which is then constrained to equal the
|
||||
// initial x_a.
|
||||
|
@ -89,7 +92,8 @@ impl SinsemillaChip {
|
|||
config: SinsemillaConfig,
|
||||
layouter: &mut impl Layouter<pallas::Base>,
|
||||
) -> Result<<Self as Chip<pallas::Base>>::Loaded, Error> {
|
||||
todo!()
|
||||
// Load the lookup table.
|
||||
config.generator_table.load(layouter)
|
||||
}
|
||||
|
||||
#[allow(clippy::too_many_arguments)]
|
||||
|
|
|
@ -0,0 +1,127 @@
|
|||
use crate::primitives::sinsemilla::{self, sinsemilla_s_generators, S_PERSONALIZATION};
|
||||
use halo2::{
|
||||
circuit::Layouter,
|
||||
plonk::{Column, ConstraintSystem, Error, Expression, Fixed},
|
||||
poly::Rotation,
|
||||
};
|
||||
|
||||
use pasta_curves::{
|
||||
arithmetic::{CurveAffine, CurveExt, FieldExt},
|
||||
pallas,
|
||||
};
|
||||
|
||||
use group::Curve;
|
||||
|
||||
/// Table containing independent generators S[0..2^k]
|
||||
#[derive(Eq, PartialEq, Copy, Clone, Debug)]
|
||||
pub struct GeneratorTableConfig {
|
||||
table_idx: Column<Fixed>,
|
||||
table_x: Column<Fixed>,
|
||||
table_y: Column<Fixed>,
|
||||
}
|
||||
|
||||
impl GeneratorTableConfig {
|
||||
#[allow(clippy::too_many_arguments)]
|
||||
#[allow(non_snake_case)]
|
||||
// Even though the lookup table can be used in other parts of the circuit,
|
||||
// this specific configuration sets up Sinsemilla-specific constraints
|
||||
// controlled by `q_sinsemilla`, and would likely not apply to other chips.
|
||||
pub fn configure(meta: &mut ConstraintSystem<pallas::Base>, config: super::SinsemillaConfig) {
|
||||
let (table_idx, table_x, table_y) = (
|
||||
config.generator_table.table_idx,
|
||||
config.generator_table.table_x,
|
||||
config.generator_table.table_y,
|
||||
);
|
||||
|
||||
meta.lookup(|meta| {
|
||||
let q_s1 = meta.query_selector(config.q_sinsemilla1);
|
||||
let q_s2 = meta.query_fixed(config.q_sinsemilla2, Rotation::cur());
|
||||
|
||||
let table_idx_cur = meta.query_fixed(table_idx, Rotation::cur());
|
||||
let table_x_cur = meta.query_fixed(table_x, Rotation::cur());
|
||||
let table_y_cur = meta.query_fixed(table_y, Rotation::cur());
|
||||
|
||||
// m_{i+1} = z_{i} - 2^K * q_s2 * z_{i + 1}
|
||||
// Note that the message words m_i's are 1-indexed while the
|
||||
// running sum z_i's are 0-indexed.
|
||||
let word = {
|
||||
let z_cur = meta.query_advice(config.bits, Rotation::cur());
|
||||
let z_next = meta.query_advice(config.bits, Rotation::next());
|
||||
z_cur - (q_s2 * z_next * pallas::Base::from_u64(1 << sinsemilla::K))
|
||||
};
|
||||
|
||||
let x_p = meta.query_advice(config.x_p, Rotation::cur());
|
||||
|
||||
// y_{p,i} = (Y_{A,i} / 2) - lambda1 * (x_{A,i} - x_{R,i}),
|
||||
// where Y_{A,i} = (lambda1_i + lambda2_i) * (x_{A,i} - x_{R,i}),
|
||||
// x_{R,i} = lambda1^2 - x_{A,i} - x_{P,i}
|
||||
//
|
||||
let y_p = {
|
||||
let lambda1 = meta.query_advice(config.lambda_1, Rotation::cur());
|
||||
let lambda2 = meta.query_advice(config.lambda_2, Rotation::cur());
|
||||
let x_a = meta.query_advice(config.x_a, Rotation::cur());
|
||||
|
||||
let x_r = lambda1.clone().square() - x_a.clone() - x_p.clone();
|
||||
let Y_A = (lambda1.clone() + lambda2) * (x_a.clone() - x_r.clone());
|
||||
|
||||
(Y_A * pallas::Base::TWO_INV) * (lambda1 * (x_a - x_r))
|
||||
};
|
||||
|
||||
// Lookup expressions default to the first entry when `q_s1`
|
||||
// is not enabled.
|
||||
let (init_x, init_y) = {
|
||||
let init_p = get_s_by_idx(0).to_affine().coordinates().unwrap();
|
||||
(*init_p.x(), *init_p.y())
|
||||
};
|
||||
let not_q_s1 = Expression::Constant(pallas::Base::one()) - q_s1.clone();
|
||||
|
||||
let m = q_s1.clone() * word; // The first table index is 0.
|
||||
let x_p = q_s1.clone() * x_p + not_q_s1.clone() * init_x;
|
||||
let y_p = q_s1 * y_p + not_q_s1 * init_y;
|
||||
|
||||
vec![(m, table_idx_cur), (x_p, table_x_cur), (y_p, table_y_cur)]
|
||||
});
|
||||
}
|
||||
|
||||
pub fn load(&self, layouter: &mut impl Layouter<pallas::Base>) -> Result<(), Error> {
|
||||
layouter.assign_region(
|
||||
|| "generator_table",
|
||||
|mut gate| {
|
||||
// We generate the row values lazily (we only need them during keygen).
|
||||
let mut rows = sinsemilla_s_generators();
|
||||
|
||||
for index in 0..(1 << sinsemilla::K) {
|
||||
let mut row = None;
|
||||
gate.assign_fixed(
|
||||
|| "table_idx",
|
||||
self.table_idx,
|
||||
index,
|
||||
|| {
|
||||
row = rows.next();
|
||||
Ok(pallas::Base::from_u64(index as u64))
|
||||
},
|
||||
)?;
|
||||
gate.assign_fixed(
|
||||
|| "table_x",
|
||||
self.table_x,
|
||||
index,
|
||||
|| row.map(|(x, _)| x).ok_or(Error::SynthesisError),
|
||||
)?;
|
||||
gate.assign_fixed(
|
||||
|| "table_y",
|
||||
self.table_y,
|
||||
index,
|
||||
|| row.map(|(_, y)| y).ok_or(Error::SynthesisError),
|
||||
)?;
|
||||
}
|
||||
Ok(())
|
||||
},
|
||||
)
|
||||
}
|
||||
}
|
||||
|
||||
/// Get generator S by index
|
||||
pub fn get_s_by_idx(idx: u32) -> pallas::Point {
|
||||
let hash = pallas::Point::hash_to_curve(S_PERSONALIZATION);
|
||||
hash(&idx.to_le_bytes())
|
||||
}
|
|
@ -1,6 +1,7 @@
|
|||
//! Sinsemilla generators
|
||||
use group::Curve;
|
||||
use halo2::arithmetic::{CurveAffine, CurveExt};
|
||||
use pasta_curves::pallas;
|
||||
|
||||
/// Number of bits of each message piece in $\mathsf{SinsemillaHashToPoint}$
|
||||
pub const K: usize = 10;
|
||||
|
@ -62,8 +63,8 @@ pub const Q_MERKLE_CRH: ([u8; 32], [u8; 32]) = (
|
|||
pub const S_PERSONALIZATION: &str = "z.cash:SinsemillaS";
|
||||
|
||||
/// Creates the Sinsemilla S generators used in each round of the Sinsemilla hash
|
||||
pub fn sinsemilla_s_generators<C: CurveAffine>() -> impl Iterator<Item = (C::Base, C::Base)> {
|
||||
let hasher = C::CurveExt::hash_to_curve(S_PERSONALIZATION);
|
||||
pub fn sinsemilla_s_generators() -> impl Iterator<Item = (pallas::Base, pallas::Base)> {
|
||||
let hasher = pallas::Point::hash_to_curve(S_PERSONALIZATION);
|
||||
(0..(1u32 << K)).map(move |j| {
|
||||
let point = hasher(&j.to_le_bytes()).to_affine().coordinates().unwrap();
|
||||
(*point.x(), *point.y())
|
||||
|
@ -84,7 +85,7 @@ mod tests {
|
|||
#[test]
|
||||
fn sinsemilla_s() {
|
||||
use super::super::sinsemilla_s::SINSEMILLA_S;
|
||||
let sinsemilla_s: Vec<_> = sinsemilla_s_generators::<pallas::Affine>().collect();
|
||||
let sinsemilla_s: Vec<_> = sinsemilla_s_generators().collect();
|
||||
assert_eq!(sinsemilla_s.len(), SINSEMILLA_S.len());
|
||||
for (expected, actual) in sinsemilla_s.iter().zip(&SINSEMILLA_S[..]) {
|
||||
assert_eq!(expected, actual);
|
||||
|
|
Loading…
Reference in New Issue