perf: optimize Record::is_owner

Signed-off-by: Maciej Zwolinski <[email protected]>
ProvableHQ · Oct 26, 2022 · 6509598 · 6509598
1 parent a05f753
commit 6509598
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Showing 4 changed files with 3 additions and 49 deletions.
diff --git a/console/program/src/data/record/is_owner.rs b/console/program/src/data/record/is_owner.rs
@@ -29,12 +29,9 @@ impl<N: Network> Record<N, Ciphertext<N>> {
                 // Compute the 0th randomizer.
                 let randomizer = N::hash_many_psd8(&[N::encryption_domain(), record_view_key], 1);
                 // Decrypt the owner.
-                let x_coordinate = ciphertext[0] - randomizer[0];
-                if let Some((point1, point2)) = N::Affine::from_x_coordinate_variants(*x_coordinate) {
-                    point1 == ***address || point2 == ***address
-                } else {
-                    false
-                }
+                let owner_x = ciphertext[0] - randomizer[0];
+                // Compare the x coordinates of computed and supplied affines.
+                owner_x == address.to_x_coordinate()
             }
         }
     }

diff --git a/curves/src/templates/short_weierstrass_jacobian/affine.rs b/curves/src/templates/short_weierstrass_jacobian/affine.rs
@@ -142,23 +142,6 @@ impl<P: Parameters> AffineCurve for Affine<P> {
         })
     }
 
-    /// Attempts to construct an affine point given an x-coordinate. The
-    /// point is not guaranteed to be in the prime order subgroup.
-    /// Returns variants with and without the lexicographically largest
-    /// y-coordinate selected.
-    fn from_x_coordinate_variants(x: Self::BaseField) -> Option<(Self, Self)> {
-        // Compute x^3 + ax + b
-        let x3b = P::add_b(&((x.square() * x) + P::mul_by_a(&x)));
-
-        x3b.sqrt().map(|y| {
-            let negy = -y;
-
-            let y1 = if (y < negy) ^ false { y } else { negy };
-            let y2 = if (y < negy) ^ true { y } else { negy };
-            (Self::new(x, y1, false), Self::new(x, y2, false))
-        })
-    }
-
     /// Attempts to construct an affine point given a y-coordinate. The
     /// point is not guaranteed to be in the prime order subgroup.
     ///

diff --git a/curves/src/templates/twisted_edwards_extended/affine.rs b/curves/src/templates/twisted_edwards_extended/affine.rs
@@ -142,26 +142,6 @@ impl<P: Parameters> AffineCurve for Affine<P> {
         })
     }
 
-    /// Attempts to construct an affine point given an x-coordinate. The
-    /// point is not guaranteed to be in the prime order subgroup.
-    /// Returns variants with and without the lexicographically largest
-    /// y-coordinate selected.
-    #[inline]
-    fn from_x_coordinate_variants(x: Self::BaseField) -> Option<(Self, Self)> {
-        // y = sqrt( (a * x^2 - 1)  / (d * x^2 - 1) )
-        let x2 = x.square();
-        let one = Self::BaseField::one();
-        let numerator = P::mul_by_a(&x2) - one;
-        let denominator = P::EDWARDS_D * x2 - one;
-        let y2 = denominator.inverse().map(|denom| denom * numerator);
-        y2.and_then(|y2| y2.sqrt()).map(|y| {
-            let negy = -y;
-            let y1 = if (y < negy) ^ false { y } else { negy };
-            let y2 = if (y < negy) ^ true { y } else { negy };
-            (Self::new(x, y1, x * y1), Self::new(x, y2, x * y2))
-        })
-    }
-
     /// Attempts to construct an affine point given a y-coordinate. The
     /// point is not guaranteed to be in the prime order subgroup.
     ///

diff --git a/curves/src/traits/group.rs b/curves/src/traits/group.rs
@@ -163,12 +163,6 @@ pub trait AffineCurve:
     /// largest y-coordinate be selected.
     fn from_x_coordinate(x: Self::BaseField, greatest: bool) -> Option<Self>;
 
-    /// Attempts to construct an affine point given an x-coordinate. The
-    /// point is not guaranteed to be in the prime order subgroup.
-    /// Returns variants with and without the lexicographically largest
-    /// y-coordinate selected.
-    fn from_x_coordinate_variants(x: Self::BaseField) -> Option<(Self, Self)>;
-
     /// Attempts to construct an affine point given a y-coordinate. The
     /// point is not guaranteed to be in the prime order subgroup.
     ///