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merkle: Replace l_plus_1 with l 

Since l_plus_1 is no longer used as a selector, we can directly
use the value l in the gate.
This commit is contained in:
therealyingtong 2021-07-24 00:36:50 +08:00
parent 29f185014f
commit 283b45169a
1 changed files with 18 additions and 20 deletions
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38
src/circuit/gadget/sinsemilla/merkle/chip.rs
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@ -1,6 +1,6 @@
use halo2::{
circuit::{Chip, Layouter},
plonk::{Advice, Column, ConstraintSystem, Error, Expression, Selector},
plonk::{Advice, Column, ConstraintSystem, Error, Selector},
poly::Rotation,
};
use pasta_curves::{arithmetic::FieldExt, pallas};
@ -63,7 +63,7 @@ impl MerkleChip {
// Check that pieces have been decomposed correctly for Sinsemilla hash.
// <https://zips.z.cash/protocol/protocol.pdf#orchardmerklecrh>
//
// a = a_0||a_1 = l_star || (bits 0..=239 of left)
// a = a_0||a_1 = l || (bits 0..=239 of left)
// b = b_0||b_1||b_2
// = (bits 240..=249 of left) || (bits 250..=254 of left) || (bits 0..=4 of right)
// c = bits 5..=254 of right
@ -76,11 +76,11 @@ impl MerkleChip {
| A_0 | A_1 | A_2 | A_3 | A_4 | q_decompose |
-------------------------------------------------------
| a | b | c | left | right | 1 |
| z1_a | z1_b | b_1 | b_2 | l + 1 | |
| z1_a | z1_b | b_1 | b_2 | l | |
*/
meta.create_gate("Decomposition check", |meta| {
let q_decompose = meta.query_selector(q_decompose);
let l_plus_1_whole = meta.query_advice(advices[4], Rotation::next());
let l_whole = meta.query_advice(advices[4], Rotation::next());
let two_pow_5 = pallas::Base::from_u64(1 << 5);
let two_pow_10 = two_pow_5.square();
@ -94,16 +94,15 @@ impl MerkleChip {
let left_node = meta.query_advice(advices[3], Rotation::cur());
let right_node = meta.query_advice(advices[4], Rotation::cur());
// a = a_0||a_1 = l_star || (bits 0..=239 of left)
// Check that a_0 = l_star
// a = a_0||a_1 = l || (bits 0..=239 of left)
// Check that a_0 = l
//
// z_1 of SinsemillaHash(a) = a_1
let z1_a = meta.query_advice(advices[0], Rotation::next());
let a_1 = z1_a;
// a_0 = a - (a_1 * 2^10)
let a_0 = a_whole - a_1.clone() * pallas::Base::from_u64(1 << 10);
let l_star_check =
a_0 - (l_plus_1_whole.clone() - Expression::Constant(pallas::Base::one()));
let l_check = a_0 - l_whole;
// b = b_0||b_1||b_2
// = (bits 240..=249 of left) || (bits 250..=254 of left) || (bits 0..=4 of right)
@ -137,7 +136,7 @@ impl MerkleChip {
let right_check = b_2 + c_whole * two_pow_5 - right_node;
array::IntoIter::new([
("l_star_check", l_star_check),
("l_check", l_check),
("left_check", left_check),
("right_check", right_check),
("b1_b2_check", b1_b2_check),
@ -174,18 +173,18 @@ impl MerkleInstructions<pallas::Affine, MERKLE_DEPTH_ORCHARD, { sinsemilla::K },
let config = self.config().clone();
// <https://zips.z.cash/protocol/protocol.pdf#orchardmerklecrh>
// We need to hash `l_star || left || right`, where `l_star` is a 10-bit value.
// We need to hash `l || left || right`, where `l` is a 10-bit value.
// We allow `left` and `right` to be non-canonical 255-bit encodings.
//
// a = a_0||a_1 = l_star || (bits 0..=239 of left)
// a = a_0||a_1 = l || (bits 0..=239 of left)
// b = b_0||b_1||b_2
// = (bits 240..=249 of left) || (bits 250..=254 of left) || (bits 0..=4 of right)
// c = bits 5..=254 of right
// `a = a_0||a_1` = `l_star` || (bits 0..=239 of `left`)
// `a = a_0||a_1` = `l` || (bits 0..=239 of `left`)
let a = {
let a = {
// a_0 = l_star
// a_0 = l
let a_0 = bitrange_subset(pallas::Base::from_u64(l as u64), 0..10);
// a_1 = (bits 0..=239 of `left`)
@ -269,22 +268,21 @@ impl MerkleInstructions<pallas::Affine, MERKLE_DEPTH_ORCHARD, { sinsemilla::K },
| A_0 | A_1 | A_2 | A_3 | A_4 | q_decompose |
-------------------------------------------------------
| a | b | c | left | right | 1 |
| z1_a | z1_b | b_1 | b_2 | l + 1 | |
| z1_a | z1_b | b_1 | b_2 | l | |
*/
{
layouter.assign_region(
|| "Check piece decomposition",
|mut region| {
// Set the fixed column `l_plus_1` to the current l + 1.
// Set the fixed column `l` to the current l.
// Recall that l = MERKLE_DEPTH_ORCHARD - layer - 1.
// The layer with 2^n nodes is called "layer n".
let l_plus_1 = (l as u64) + 1;
config.q_decompose.enable(&mut region, 0)?;
region.assign_advice_from_constant(
|| format!("l_plus_1 {}", l_plus_1),
|| format!("l {}", l),
config.advices[4],
1,
pallas::Base::from_u64(l_plus_1),
pallas::Base::from_u64(l as u64),
)?;
// Offset 0
@ -344,7 +342,7 @@ impl MerkleInstructions<pallas::Affine, MERKLE_DEPTH_ORCHARD, { sinsemilla::K },
use ff::PrimeFieldBits;
if let (Some(left), Some(right)) = (left.value(), right.value()) {
let l_star = i2lebsp::<10>(l as u64);
let l = i2lebsp::<10>(l as u64);
let left: Vec<_> = left
.to_le_bits()
.iter()
@ -359,7 +357,7 @@ impl MerkleInstructions<pallas::Affine, MERKLE_DEPTH_ORCHARD, { sinsemilla::K },
.collect();
let merkle_crh = HashDomain::new(MERKLE_CRH_PERSONALIZATION);
let mut message = l_star.to_vec();
let mut message = l.to_vec();
message.extend_from_slice(&left);
message.extend_from_slice(&right);