Expand tests for ethereum-schnorr-contract

networks/ethereum/schnorr/src/tests/public_key.rs

@@ -0,0 +1,69 @@
+use rand_core::OsRng;
+
+use subtle::Choice;
+use group::ff::{Field, PrimeField};
+use k256::{
+  elliptic_curve::{
+    FieldBytesEncoding,
+    ops::Reduce,
+    point::{AffineCoordinates, DecompressPoint},
+  },
+  AffinePoint, ProjectivePoint, Scalar, U256 as KU256,
+};
+
+use crate::PublicKey;
+
+// Generates a key usable within tests
+pub(crate) fn test_key() -> (Scalar, PublicKey) {
+  loop {
+    let key = Scalar::random(&mut OsRng);
+    let point = ProjectivePoint::GENERATOR * key;
+    if let Some(public_key) = PublicKey::new(point) {
+      // While here, test `PublicKey::point` and its serialization functions
+      assert_eq!(point, public_key.point());
+      assert_eq!(PublicKey::from_eth_repr(public_key.eth_repr()).unwrap(), public_key);
+      return (key, public_key);
+    }
+  }
+}
+
+#[test]
+fn test_odd_key() {
+  // We generate a valid key to ensure there's not some distinct reason this key is invalid
+  let (_, key) = test_key();
+  // We then take its point and negate it so its y-coordinate is odd
+  let odd = -key.point();
+  assert!(PublicKey::new(odd).is_none());
+}
+
+#[test]
+fn test_non_mutual_key() {
+  let mut x_coordinate = KU256::from(-(Scalar::ONE)).saturating_add(&KU256::ONE);
+
+  let y_is_odd = Choice::from(0);
+  let non_mutual = loop {
+    if let Some(point) = Option::<AffinePoint>::from(AffinePoint::decompress(
+      &FieldBytesEncoding::encode_field_bytes(&x_coordinate),
+      y_is_odd,
+    )) {
+      break point;
+    }
+    x_coordinate = x_coordinate.saturating_add(&KU256::ONE);
+  };
+  let x_coordinate = non_mutual.x();
+  assert!(<Scalar as Reduce<KU256>>::reduce_bytes(&x_coordinate).to_repr() != x_coordinate);
+
+  // Even point whose x-coordinate isn't mutual to both fields (making it non-zero)
+  assert!(PublicKey::new(non_mutual.into()).is_none());
+}
+
+#[test]
+fn test_zero_key() {
+  let y_is_odd = Choice::from(0);
+  if let Some(A_affine) =
+    Option::<AffinePoint>::from(AffinePoint::decompress(&[0; 32].into(), y_is_odd))
+  {
+    let A = ProjectivePoint::from(A_affine);
+    assert!(PublicKey::new(A).is_none());
+  }
+}