From 2faf2afa46b6f85fd8afb22fc7e37b061ce66b6a Mon Sep 17 00:00:00 2001
From: Vladimir Komendantskiy <komendantsky@gmail.com>
Date: Sat, 9 Jun 2018 21:50:36 +0100
Subject: [PATCH] protobuf serialization

---
 mod.rs | 96 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 96 insertions(+)

diff --git a/mod.rs b/mod.rs
index 2d2e344..7b82d33 100644
--- a/mod.rs
+++ b/mod.rs
@@ -517,3 +517,99 @@ mod tests {
         assert_eq!(sig, deser_sig);
     }
 }
+
+#[cfg(feature = "serialization-serde")]
+mod serde {
+    use pairing::{CurveAffine, CurveProjective, EncodedPoint, Engine};
+
+    use super::{DecryptionShare, PublicKey, Signature};
+    use serde::de::Error as DeserializeError;
+    use serde::{Deserialize, Deserializer, Serialize, Serializer};
+
+    const ERR_LEN: &str = "wrong length of deserialized group element";
+    const ERR_CODE: &str = "deserialized bytes don't encode a group element";
+
+    impl<E: Engine> Serialize for PublicKey<E> {
+        fn serialize<S: Serializer>(&self, s: S) -> Result<S::Ok, S::Error> {
+            serialize_projective(&self.0, s)
+        }
+    }
+
+    impl<'de, E: Engine> Deserialize<'de> for PublicKey<E> {
+        fn deserialize<D: Deserializer<'de>>(d: D) -> Result<Self, D::Error> {
+            Ok(PublicKey(deserialize_projective(d)?))
+        }
+    }
+
+    impl<E: Engine> Serialize for Signature<E> {
+        fn serialize<S: Serializer>(&self, s: S) -> Result<S::Ok, S::Error> {
+            serialize_projective(&self.0, s)
+        }
+    }
+
+    impl<'de, E: Engine> Deserialize<'de> for Signature<E> {
+        fn deserialize<D: Deserializer<'de>>(d: D) -> Result<Self, D::Error> {
+            Ok(Signature(deserialize_projective(d)?))
+        }
+    }
+
+    impl<E: Engine> Serialize for DecryptionShare<E> {
+        fn serialize<S: Serializer>(&self, s: S) -> Result<S::Ok, S::Error> {
+            serialize_projective(&self.0, s)
+        }
+    }
+
+    impl<'de, E: Engine> Deserialize<'de> for DecryptionShare<E> {
+        fn deserialize<D: Deserializer<'de>>(d: D) -> Result<Self, D::Error> {
+            Ok(DecryptionShare(deserialize_projective(d)?))
+        }
+    }
+
+    /// Serializes the compressed representation of a group element.
+    fn serialize_projective<S, C>(c: &C, s: S) -> Result<S::Ok, S::Error>
+    where
+        S: Serializer,
+        C: CurveProjective,
+    {
+        c.into_affine().into_compressed().as_ref().serialize(s)
+    }
+
+    /// Deserializes the compressed representation of a group element.
+    fn deserialize_projective<'de, D, C>(d: D) -> Result<C, D::Error>
+    where
+        D: Deserializer<'de>,
+        C: CurveProjective,
+    {
+        let bytes = <Vec<u8>>::deserialize(d)?;
+        if bytes.len() != <C::Affine as CurveAffine>::Compressed::size() {
+            return Err(D::Error::custom(ERR_LEN));
+        }
+        let mut compressed = <C::Affine as CurveAffine>::Compressed::empty();
+        compressed.as_mut().copy_from_slice(&bytes);
+        let to_err = |_| D::Error::custom(ERR_CODE);
+        Ok(compressed.into_affine().map_err(to_err)?.into_projective())
+    }
+}
+
+#[cfg(feature = "serialization-protobuf")]
+pub mod proto {
+    use super::Signature;
+    use pairing::{CurveAffine, CurveProjective, EncodedPoint, Engine};
+
+    impl<E: Engine> Signature<E> {
+        pub fn to_vec(&self) -> Vec<u8> {
+            let comp = self.0.into_affine().into_compressed();
+            comp.as_ref().to_vec()
+        }
+
+        pub fn from_bytes(bytes: &[u8]) -> Option<Self> {
+            let mut comp = <E::G2Affine as CurveAffine>::Compressed::empty();
+            comp.as_mut().copy_from_slice(bytes);
+            if let Ok(affine) = comp.into_affine() {
+                Some(Signature(affine.into_projective()))
+            } else {
+                None
+            }
+        }
+    }
+}