mirror of https://github.com/zcash/halo2.git
sinsemilla::note_commit: Simplify y canonicity check region layout
Instead of separately witnessing k_1 and equating it to z1_j, we can directly make use of z1_j in the gate. This allows us to fit the region into a 5 x 2 area, improving the layout. Co-authored-by: Jack Grigg <jack@electriccoin.co>
This commit is contained in:
therealyingtong
parent
b3ccd3f0dd
commit
e4a960d7f1
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@ -90,37 +90,42 @@ impl NoteCommitConfig {
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y = LSB || k_0 || k_1 || k_2 || k_3
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= (bit 0) || (bits 1..=9) || (bits 10..=249) || (bits 250..=253) || (bit 254)
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These pieces are laid out in the following configuration:
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| A_5 | A_6 | A_7 | A_8 | A_9 |
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----------------------------------------------
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| y | lsb | k_0 | k_2 | k_3 |
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| j | z1_j| z13_j | j_prime | z13_j_prime |
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where z1_j = k_1.
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*/
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meta.create_gate("y coordinate checks", |meta| {
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let q_y_canon = meta.query_selector(q_y_canon);
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let y = meta.query_advice(advices[0], Rotation::cur());
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let y = meta.query_advice(advices[5], Rotation::cur());
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// LSB has been boolean-constrained outside this gate.
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let lsb = meta.query_advice(advices[1], Rotation::cur());
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let lsb = meta.query_advice(advices[6], Rotation::cur());
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// k_0 has been constrained to 9 bits outside this gate.
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let k_0 = meta.query_advice(advices[2], Rotation::cur());
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// This gate constrains k_1 to 240 bits by equating it to z1_j.
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let k_1 = meta.query_advice(advices[3], Rotation::cur());
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let k_0 = meta.query_advice(advices[7], Rotation::cur());
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// k_1 = z1_j (witnessed in the next rotation).
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// k_2 has been constrained to 4 bits outside this gate.
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let k_2 = meta.query_advice(advices[4], Rotation::cur());
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let k_2 = meta.query_advice(advices[8], Rotation::cur());
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// This gate constrains k_3 to be boolean.
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let k_3 = meta.query_advice(advices[5], Rotation::cur());
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let k_3 = meta.query_advice(advices[9], Rotation::cur());
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// j = LSB + (2)k_0 + (2^10)k_1
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let j = meta.query_advice(advices[0], Rotation::next());
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let z1_j = meta.query_advice(advices[1], Rotation::next());
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let z13_j = meta.query_advice(advices[2], Rotation::next());
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let j = meta.query_advice(advices[5], Rotation::next());
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let z1_j = meta.query_advice(advices[6], Rotation::next());
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let z13_j = meta.query_advice(advices[7], Rotation::next());
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// j_prime = j + 2^130 - t_P
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let j_prime = meta.query_advice(advices[3], Rotation::next());
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let z13_j_prime = meta.query_advice(advices[4], Rotation::next());
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let j_prime = meta.query_advice(advices[8], Rotation::next());
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let z13_j_prime = meta.query_advice(advices[9], Rotation::next());
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// Decomposition checks
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let decomposition_checks = {
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// Check that k_1 = z1_j
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let k1_check = k_1.clone() - z1_j;
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// Check that k_3 is boolean
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let k3_check = bool_check(k_3.clone());
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// Check that j = LSB + (2)k_0 + (2^10)k_1
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let k_1 = z1_j;
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let j_check = j.clone() - (lsb + k_0 * two + k_1 * two_pow_10);
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// Check that y = j + (2^250)k_2 + (2^254)k_3
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let y_check =
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@ -129,7 +134,6 @@ impl NoteCommitConfig {
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let j_prime_check = j_prime - (j + two_pow_130.clone() - t_p.clone());
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std::iter::empty()
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.chain(Some(("k1_check", k1_check)))
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.chain(Some(("k3_check", k3_check)))
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.chain(Some(("j_check", j_check)))
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.chain(Some(("y_check", y_check)))
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@ -971,7 +975,15 @@ impl NoteCommitConfig {
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let (j_prime, z13_j_prime) =
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self.canon_bitshift_130(layouter.namespace(|| "j_prime = j + 2^130 - t_P"), j)?;
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// Assign y canonicity gate.
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/*
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Assign y canonicity gate in the following configuration:
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| A_5 | A_6 | A_7 | A_8 | A_9 |
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----------------------------------------------
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| y | lsb | k_0 | k_2 | k_3 |
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| j | z1_j| z13_j | j_prime | z13_j_prime |
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where z1_j = k_1.
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*/
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layouter.assign_region(
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|| "y canonicity",
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|mut region| {
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@ -982,32 +994,25 @@ impl NoteCommitConfig {
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let offset = 0;
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// Copy y.
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copy(&mut region, || "copy y", self.advices[0], offset, &y)?;
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copy(&mut region, || "copy y", self.advices[5], offset, &y)?;
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// Witness LSB.
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let lsb = {
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let cell = region.assign_advice(
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|| "witness LSB",
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self.advices[1],
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self.advices[6],
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offset,
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|| lsb.ok_or(Error::SynthesisError),
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)?;
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CellValue::new(cell, lsb)
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};
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// Witness k_0.
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copy(&mut region, || "copy k_0", self.advices[2], offset, &k_0)?;
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// Witness k_1.
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region.assign_advice(
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|| "witness k_1",
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self.advices[3],
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offset,
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|| k_1.ok_or(Error::SynthesisError),
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)?;
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copy(&mut region, || "copy k_0", self.advices[7], offset, &k_0)?;
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// Copy k_2.
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copy(&mut region, || "copy k_2", self.advices[4], offset, &k_2)?;
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copy(&mut region, || "copy k_2", self.advices[8], offset, &k_2)?;
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// Witness k_3.
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region.assign_advice(
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|| "witness k_3",
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self.advices[5],
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self.advices[9],
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offset,
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|| k_3.ok_or(Error::SynthesisError),
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)?;
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@ -1020,14 +1025,14 @@ impl NoteCommitConfig {
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let offset = 1;
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// Copy j.
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copy(&mut region, || "copy j", self.advices[0], offset, &j)?;
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copy(&mut region, || "copy j", self.advices[5], offset, &j)?;
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// Copy z1_j.
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copy(&mut region, || "copy z1_j", self.advices[1], offset, &z1_j)?;
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copy(&mut region, || "copy z1_j", self.advices[6], offset, &z1_j)?;
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// Copy z13_j.
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copy(
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&mut region,
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|| "copy z13_j",
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self.advices[2],
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self.advices[7],
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offset,
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&z13_j,
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)?;
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@ -1035,7 +1040,7 @@ impl NoteCommitConfig {
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copy(
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&mut region,
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|| "copy j_prime",
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self.advices[3],
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self.advices[8],
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offset,
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&j_prime,
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)?;
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@ -1043,7 +1048,7 @@ impl NoteCommitConfig {
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copy(
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&mut region,
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|| "copy z13_j_prime",
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self.advices[4],
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self.advices[9],
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offset,
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&z13_j_prime,
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)?;
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