message: Specify pre-conditions for signature validation
diff: @@ -71,6 +71,10 @@ impl<E: JubjubEngine> PublicKey<E> {
  PublicKey(res)
  }
  + // Pre-conditions:
  + // - rbar was the canonical representation of a point on the curve.
  + // - sig.s < order(G)
  + // TODO(str4d): Enforce these during deserialization of Signature
  pub fn verify(&self, msg: &[u8], sig: &Signature<E>, params: &E::Params) -> bool {
  // c = H*(Rbar || M)
  let mut rbar = [0u8; 32];
  