From ae34f0a60f94dba6cd4cb580720f40a3ee2ac7c6 Mon Sep 17 00:00:00 2001
From: Luke Parker <lukeparker5132@gmail.com>
Date: Sat, 4 May 2024 07:21:54 -0400
Subject: [PATCH] Add DivisorCurve impl to Helios and Selene

---
 crypto/helioselene/Cargo.toml   |  2 ++
 crypto/helioselene/src/point.rs | 16 ++++++++++++++++
 2 files changed, 18 insertions(+)

diff --git a/crypto/helioselene/Cargo.toml b/crypto/helioselene/Cargo.toml
index dba27a29..ba569f41 100644
--- a/crypto/helioselene/Cargo.toml
+++ b/crypto/helioselene/Cargo.toml
@@ -27,6 +27,8 @@ crypto-bigint = { version = "0.5", default-features = false, features = ["zeroiz
 
 dalek-ff-group = { path = "../dalek-ff-group", version = "0.4.1", default-features = false, features = ["std"] }
 
+ec-divisors = { path = "../divisors" }
+
 [dev-dependencies]
 hex = "0.4"
 
diff --git a/crypto/helioselene/src/point.rs b/crypto/helioselene/src/point.rs
index c6c08395..e0e68682 100644
--- a/crypto/helioselene/src/point.rs
+++ b/crypto/helioselene/src/point.rs
@@ -340,6 +340,22 @@ macro_rules! curve {
     }
 
     impl PrimeGroup for $Point {}
+
+    impl ec_divisors::DivisorCurve for $Point {
+      type FieldElement = $Field;
+
+      fn a() -> Self::FieldElement {
+        -$Field::from(3u64)
+      }
+      fn b() -> Self::FieldElement {
+        B
+      }
+
+      fn to_xy(point: Self) -> (Self::FieldElement, Self::FieldElement) {
+        let z = point.z.invert().unwrap();
+        (point.x * z, point.y * z)
+      }
+    }
   };
 }