From b69094036c7335ca651b4084c691d8871a03939c Mon Sep 17 00:00:00 2001
From: therealyingtong <yingtong@z.cash>
Date: Wed, 7 Jul 2021 15:52:31 +0800
Subject: [PATCH] chip::mul_fixed.rs: Make q_mul_fixed a selector instead of
 fixed column.

---
 src/circuit/gadget/ecc/chip.rs                | 11 ++++++----
 src/circuit/gadget/ecc/chip/mul_fixed.rs      | 20 ++++++++-----------
 .../gadget/ecc/chip/mul_fixed/full_width.rs   |  2 +-
 .../gadget/ecc/chip/mul_fixed/short.rs        |  2 +-
 4 files changed, 17 insertions(+), 18 deletions(-)

diff --git a/src/circuit/gadget/ecc/chip.rs b/src/circuit/gadget/ecc/chip.rs
index 7d9f082b..82b33f45 100644
--- a/src/circuit/gadget/ecc/chip.rs
+++ b/src/circuit/gadget/ecc/chip.rs
@@ -99,11 +99,13 @@ pub struct EccConfig {
     pub q_mul_overflow: Selector,
 
     /// Fixed-base full-width scalar multiplication
-    pub mul_fixed: Column<Fixed>,
+    pub q_mul_fixed: Selector,
     /// Fixed-base signed short scalar multiplication
     pub q_mul_fixed_short: Selector,
     /// Fixed-base multiplication using a base field element as the scalar
-    pub base_field_fixed: Column<Fixed>,
+    pub base_field_fixed_mul: Selector,
+    /// Canonicity checks on base field element used as scalar in fixed-base mul
+    pub base_field_fixed_canon: Selector,
 
     /// Witness point
     pub q_point: Selector,
@@ -184,9 +186,10 @@ impl EccChip {
             q_mul_decompose_var: meta.selector(),
             q_mul_overflow: meta.selector(),
             q_mul_lsb: meta.selector(),
-            mul_fixed: meta.fixed_column(),
+            q_mul_fixed: meta.selector(),
             q_mul_fixed_short: meta.selector(),
-            base_field_fixed: meta.fixed_column(),
+            base_field_fixed_mul: meta.selector(),
+            base_field_fixed_canon: meta.selector(),
             q_point: meta.selector(),
             q_scalar_fixed: meta.selector(),
             q_scalar_fixed_short: meta.selector(),
diff --git a/src/circuit/gadget/ecc/chip/mul_fixed.rs b/src/circuit/gadget/ecc/chip/mul_fixed.rs
index 8c812757..e31ea052 100644
--- a/src/circuit/gadget/ecc/chip/mul_fixed.rs
+++ b/src/circuit/gadget/ecc/chip/mul_fixed.rs
@@ -11,7 +11,8 @@ use group::Curve;
 use halo2::{
     circuit::Region,
     plonk::{
-        Advice, Column, ConstraintSystem, Error, Expression, Fixed, Permutation, VirtualCells,
+        Advice, Column, ConstraintSystem, Error, Expression, Fixed, Permutation, Selector,
+        VirtualCells,
     },
     poly::Rotation,
 };
@@ -62,7 +63,7 @@ impl OrchardFixedBases {
 
 #[derive(Clone, Debug)]
 pub struct Config<const NUM_WINDOWS: usize> {
-    mul_fixed: Column<Fixed>,
+    q_mul_fixed: Selector,
     // The fixed Lagrange interpolation coefficients for `x_p`.
     lagrange_coeffs: [Column<Fixed>; constants::H],
     // The fixed `z` for each window such that `y + z = u^2`.
@@ -87,7 +88,7 @@ pub struct Config<const NUM_WINDOWS: usize> {
 impl<const NUM_WINDOWS: usize> From<&EccConfig> for Config<NUM_WINDOWS> {
     fn from(ecc_config: &EccConfig) -> Self {
         let config = Self {
-            mul_fixed: ecc_config.mul_fixed,
+            q_mul_fixed: ecc_config.q_mul_fixed,
             lagrange_coeffs: ecc_config.lagrange_coeffs,
             fixed_z: ecc_config.fixed_z,
             x_p: ecc_config.advices[0],
@@ -138,7 +139,7 @@ impl<const NUM_WINDOWS: usize> Config<NUM_WINDOWS> {
         meta.create_gate(
             "x_p, y_p checks for ScalarFixed, ScalarFixedShort",
             |meta| {
-                let mul_fixed = meta.query_fixed(self.mul_fixed, Rotation::cur());
+                let mul_fixed = meta.query_selector(self.q_mul_fixed);
                 let window = meta.query_advice(self.window, Rotation::cur());
                 self.coords_check(meta, mul_fixed, window)
             },
@@ -194,7 +195,7 @@ impl<const NUM_WINDOWS: usize> Config<NUM_WINDOWS> {
         offset: usize,
         scalar: &ScalarFixed,
         base: OrchardFixedBases,
-        coords_check_toggle: Column<Fixed>,
+        coords_check_toggle: Selector,
     ) -> Result<(EccPoint, EccPoint), Error> {
         // Assign fixed columns for given fixed base
         self.assign_fixed_constants(region, offset, base, coords_check_toggle)?;
@@ -216,7 +217,7 @@ impl<const NUM_WINDOWS: usize> Config<NUM_WINDOWS> {
         region: &mut Region<'_, pallas::Base>,
         offset: usize,
         base: OrchardFixedBases,
-        fixed_column: Column<Fixed>,
+        coords_check_toggle: Selector,
     ) -> Result<(), Error> {
         let mut constants = None;
 
@@ -241,12 +242,7 @@ impl<const NUM_WINDOWS: usize> Config<NUM_WINDOWS> {
 
         // Assign fixed columns for given fixed base
         for window in 0..NUM_WINDOWS {
-            region.assign_fixed(
-                || "Enable coords check",
-                fixed_column,
-                window + offset,
-                || Ok(pallas::Base::one()),
-            )?;
+            coords_check_toggle.enable(region, window + offset)?;
 
             // Assign x-coordinate Lagrange interpolation coefficients
             for k in 0..(constants::H) {
diff --git a/src/circuit/gadget/ecc/chip/mul_fixed/full_width.rs b/src/circuit/gadget/ecc/chip/mul_fixed/full_width.rs
index ef68ae9f..b9003311 100644
--- a/src/circuit/gadget/ecc/chip/mul_fixed/full_width.rs
+++ b/src/circuit/gadget/ecc/chip/mul_fixed/full_width.rs
@@ -31,7 +31,7 @@ impl<const NUM_WINDOWS: usize> Config<NUM_WINDOWS> {
                     offset,
                     &scalar.into(),
                     base.into(),
-                    self.0.mul_fixed,
+                    self.0.q_mul_fixed,
                 )?;
 
                 // Add to the accumulator and return the final result as `[scalar]B`.
diff --git a/src/circuit/gadget/ecc/chip/mul_fixed/short.rs b/src/circuit/gadget/ecc/chip/mul_fixed/short.rs
index cc2f2d91..697d765b 100644
--- a/src/circuit/gadget/ecc/chip/mul_fixed/short.rs
+++ b/src/circuit/gadget/ecc/chip/mul_fixed/short.rs
@@ -71,7 +71,7 @@ impl<const NUM_WINDOWS: usize> Config<NUM_WINDOWS> {
                     offset,
                     &scalar.into(),
                     base.clone().into(),
-                    self.super_config.mul_fixed,
+                    self.super_config.q_mul_fixed,
                 )?;
 
                 // Add to the cumulative sum to get `[magnitude]B`.