common coin implementation

mod.rs

@@ -1,4 +1,4 @@
-mod error;
+pub mod error;
 pub mod keygen;
 #[cfg(feature = "serialization-serde")]
 mod serde_impl;
@@ -59,7 +59,7 @@ impl<E: Engine> PublicKey<E> {
 }
 
 /// A signature, or a signature share.
-#[derive(Debug)]
+#[derive(Clone, Debug, PartialOrd)]
 pub struct Signature<E: Engine>(E::G2);
 
 impl<E: Engine> PartialEq for Signature<E> {
@@ -68,6 +68,18 @@ impl<E: Engine> PartialEq for Signature<E> {
     }
 }
 
+impl<E: Engine> Signature<E> {
+    pub fn parity(&self) -> bool {
+        2 % self
+            .0
+            .into_affine()
+            .into_uncompressed()
+            .as_ref()
+            .last()
+            .expect("non-empty signature") == 0
+    }
+}
+
 /// A secret key, or a secret key share.
 #[derive(Debug)]
 pub struct SecretKey<E: Engine>(E::Fr);