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base_field_elem: Remove z_85_alpha = 0 check from canonicity gate. 

The decompose_running_sum gadget in strict mode already enforces
this check.

Co-authored-by: Jack Grigg <jack@electriccoin.co>
This commit is contained in:
therealyingtong 2021-07-17 19:17:49 +08:00
parent e846536b4e
commit 179cd8e940
1 changed files with 1 additions and 16 deletions
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17
src/circuit/gadget/ecc/chip/mul_fixed/base_field_elem.rs
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@ -69,14 +69,11 @@ impl Config {
.coords_check(meta, q_mul_fixed_running_sum, word)
});
// Check that we get z_85 = 0 as the final output of the three-bit decomposition running sum.
// Also check that the base field element is canonical.
// Check that the base field element is canonical.
meta.create_gate("Canonicity checks", |meta| {
let base_field_fixed_canon = meta.query_selector(self.base_field_fixed_canon);
let alpha = meta.query_advice(self.canon_advices[0], Rotation::prev());
// z_85_alpha is constrained to be zero in this gate.
let z_85_alpha = meta.query_advice(self.canon_advices[1], Rotation::prev());
// The last three bits of α.
let z_84_alpha = meta.query_advice(self.canon_advices[2], Rotation::prev());
@ -166,7 +163,6 @@ impl Config {
canon_checks
.chain(decomposition_checks)
.chain(Some(("z_85_alpha = 0", z_85_alpha)))
.chain(Some(("alpha_0_prime check", alpha_0_prime_check)))
.map(move |(name, poly)| (name, base_field_fixed_canon.clone() * poly))
});
@ -262,7 +258,6 @@ impl Config {
let z_43_alpha = running_sum[42];
let z_44_alpha = running_sum[43];
let z_84_alpha = running_sum[83];
let z_85_alpha = running_sum[84];
// α_0 = α - z_84_alpha * 2^252
let alpha_0 = alpha
@ -312,16 +307,6 @@ impl Config {
perm,
)?;
// z_85_alpha is constrained to be zero in the custom gate.
copy(
&mut region,
|| "Copy z_85_alpha",
self.canon_advices[1],
offset,
&z_85_alpha,
perm,
)?;
// z_84_alpha = the top three bits of alpha.
copy(
&mut region,