From ac6565b2f15cd3ce9eee59239de65ebd7d3d54c0 Mon Sep 17 00:00:00 2001
From: winderica <winderica@gmail.com>
Date: Tue, 23 Apr 2024 20:14:26 +0800
Subject: [PATCH 1/4] Fix the subtraction between Affine and Projective points

---
 ec/src/models/short_weierstrass/affine.rs | 4 ++--
 ec/src/models/twisted_edwards/affine.rs   | 4 ++--
 2 files changed, 4 insertions(+), 4 deletions(-)

diff --git a/ec/src/models/short_weierstrass/affine.rs b/ec/src/models/short_weierstrass/affine.rs
index 2a47f5cb3..23c7cac11 100644
--- a/ec/src/models/short_weierstrass/affine.rs
+++ b/ec/src/models/short_weierstrass/affine.rs
@@ -305,14 +305,14 @@ impl<P: SWCurveConfig, T: Borrow<Self>> Sub<T> for Affine<P> {
 impl<P: SWCurveConfig> Sub<Projective<P>> for Affine<P> {
     type Output = Projective<P>;
     fn sub(self, other: Projective<P>) -> Projective<P> {
-        other - self
+        self.into_group() - other
     }
 }
 
 impl<'a, P: SWCurveConfig> Sub<&'a Projective<P>> for Affine<P> {
     type Output = Projective<P>;
     fn sub(self, other: &'a Projective<P>) -> Projective<P> {
-        *other - self
+        self.into_group() - other
     }
 }
 
diff --git a/ec/src/models/twisted_edwards/affine.rs b/ec/src/models/twisted_edwards/affine.rs
index 72a3e4f7e..91592ea58 100644
--- a/ec/src/models/twisted_edwards/affine.rs
+++ b/ec/src/models/twisted_edwards/affine.rs
@@ -255,14 +255,14 @@ impl<P: TECurveConfig, T: Borrow<Self>> Sub<T> for Affine<P> {
 impl<P: TECurveConfig> Sub<Projective<P>> for Affine<P> {
     type Output = Projective<P>;
     fn sub(self, other: Projective<P>) -> Projective<P> {
-        other - self
+        self.into_group() - other
     }
 }
 
 impl<'a, P: TECurveConfig> Sub<&'a Projective<P>> for Affine<P> {
     type Output = Projective<P>;
     fn sub(self, other: &'a Projective<P>) -> Projective<P> {
-        *other - self
+        self.into_group() - other
     }
 }
 

From 5fe0f95ce063e2594cad7f1a6cfba05df2ed6427 Mon Sep 17 00:00:00 2001
From: winderica <winderica@gmail.com>
Date: Tue, 23 Apr 2024 20:17:22 +0800
Subject: [PATCH 2/4] Add unit test for Affine - Projective

---
 test-templates/src/groups.rs | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/test-templates/src/groups.rs b/test-templates/src/groups.rs
index 5ad7e33b2..625a26d7c 100644
--- a/test-templates/src/groups.rs
+++ b/test-templates/src/groups.rs
@@ -67,6 +67,9 @@ macro_rules! __test_group {
 
                 assert_eq!(a - zero, a);
                 assert_eq!(b - zero, b);
+
+                // Affine - Projective
+                assert_eq!(a.into_affine() - b, a - b);
             }
         }
 

From eed949fd109125435fb610378609c4fda06c4c57 Mon Sep 17 00:00:00 2001
From: winderica <winderica@gmail.com>
Date: Tue, 23 Apr 2024 20:25:55 +0800
Subject: [PATCH 3/4] Update changelog

---
 CHANGELOG.md | 1 +
 1 file changed, 1 insertion(+)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index dc24c3f58..bc2472ee2 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -45,6 +45,7 @@
 - [\#747](https://github.com/arkworks-rs/algebra/pull/747) (`ark-ff-macros`) Fix fetching attributes in `MontConfig` macro.
 - [\#803](https://github.com/arkworks-rs/algebra/pull/803) (`ark-ec`, `ark-test-template`) Fix incorrect decomposition in GLV.
 - [\#806](https://github.com/arkworks-rs/algebra/pull/806) (`ark-ff`) Fix the impl for `Display`ing zero element in Fp.
+- [\#822](https://github.com/arkworks-rs/algebra/pull/822) (`ark-ec`, `ark-test-template`) Fix the incorrect `Affine - Projective` implementation
 
 ## v0.4.2
 

From 81c08a10fffb1eedb14c3df54a2622dd8f1475be Mon Sep 17 00:00:00 2001
From: Pratyush Mishra <pratyush795@gmail.com>
Date: Wed, 24 Apr 2024 11:10:58 -0700
Subject: [PATCH 4/4] Faster subtraction

---
 ec/src/models/short_weierstrass/affine.rs | 4 ++--
 ec/src/models/twisted_edwards/affine.rs   | 4 ++--
 2 files changed, 4 insertions(+), 4 deletions(-)

diff --git a/ec/src/models/short_weierstrass/affine.rs b/ec/src/models/short_weierstrass/affine.rs
index 23c7cac11..82e127928 100644
--- a/ec/src/models/short_weierstrass/affine.rs
+++ b/ec/src/models/short_weierstrass/affine.rs
@@ -305,14 +305,14 @@ impl<P: SWCurveConfig, T: Borrow<Self>> Sub<T> for Affine<P> {
 impl<P: SWCurveConfig> Sub<Projective<P>> for Affine<P> {
     type Output = Projective<P>;
     fn sub(self, other: Projective<P>) -> Projective<P> {
-        self.into_group() - other
+        self + (-other)
     }
 }
 
 impl<'a, P: SWCurveConfig> Sub<&'a Projective<P>> for Affine<P> {
     type Output = Projective<P>;
     fn sub(self, other: &'a Projective<P>) -> Projective<P> {
-        self.into_group() - other
+        self + (-*other)
     }
 }
 
diff --git a/ec/src/models/twisted_edwards/affine.rs b/ec/src/models/twisted_edwards/affine.rs
index 91592ea58..1d93882a1 100644
--- a/ec/src/models/twisted_edwards/affine.rs
+++ b/ec/src/models/twisted_edwards/affine.rs
@@ -255,14 +255,14 @@ impl<P: TECurveConfig, T: Borrow<Self>> Sub<T> for Affine<P> {
 impl<P: TECurveConfig> Sub<Projective<P>> for Affine<P> {
     type Output = Projective<P>;
     fn sub(self, other: Projective<P>) -> Projective<P> {
-        self.into_group() - other
+        self + (-other)
     }
 }
 
 impl<'a, P: TECurveConfig> Sub<&'a Projective<P>> for Affine<P> {
     type Output = Projective<P>;
     fn sub(self, other: &'a Projective<P>) -> Projective<P> {
-        self.into_group() - other
+        self + (-*other)
     }
 }