Add DecafAffinePoint::GENERATOR

Author: daxpedda

ed448-goldilocks/src/curve/twedwards/affine.rs

@@ -1,4 +1,5 @@
 #![allow(dead_code)]
+use crate::TWISTED_EDWARDS_BASE_POINT;
 use crate::curve::twedwards::{extended::ExtendedPoint, extensible::ExtensiblePoint};
 use crate::field::FieldElement;
 use subtle::{Choice, ConditionallySelectable, ConstantTimeEq};
@@ -30,6 +31,12 @@ impl AffinePoint {
         y: FieldElement::ONE,
     };
 
+    /// Identity element
+    pub(crate) const GENERATOR: AffinePoint = AffinePoint {
+        x: TWISTED_EDWARDS_BASE_POINT.X,
+        y: TWISTED_EDWARDS_BASE_POINT.Y,
+    };
+
     /// Checks if the AffinePoint is on the TwistedEdwards curve
     pub(crate) fn is_on_curve(&self) -> Choice {
         let xx = self.x.square();
@@ -140,7 +147,6 @@ mod tests {
 
     #[test]
     fn test_negation() {
-        use crate::TWISTED_EDWARDS_BASE_POINT;
         let a = TWISTED_EDWARDS_BASE_POINT.to_extensible().to_affine();
         assert_eq!(a.is_on_curve().unwrap_u8(), 1);
 

ed448-goldilocks/src/decaf/affine.rs

@@ -73,6 +73,8 @@ impl DefaultIsZeroes for AffinePoint {}
 impl AffinePoint {
     /// The identity point
     pub const IDENTITY: Self = Self(InnerAffinePoint::IDENTITY);
+    /// The generator point
+    pub const GENERATOR: Self = Self(InnerAffinePoint::GENERATOR);
 
     /// Convert to DecafPoint
     pub fn to_decaf(&self) -> DecafPoint {
@@ -115,3 +117,15 @@ impl Mul<&DecafScalar> for &AffinePoint {
 }
 
 define_mul_variants!(LHS = AffinePoint, RHS = DecafScalar, Output = DecafPoint);
+
+#[cfg(test)]
+mod test {
+    use super::*;
+    use elliptic_curve::CurveGroup;
+
+    #[test]
+    fn generator() {
+        assert_eq!(AffinePoint::GENERATOR.to_decaf(), DecafPoint::GENERATOR);
+        assert_eq!(DecafPoint::GENERATOR.to_affine(), AffinePoint::GENERATOR);
+    }
+}