Added serde support

In addition:
- Added `ConstantTimeEq`, `PartialEq`, and `dusk_bytes::Serializable` impls for `AffineNielsPoint` and `ExtendedNielsPoint`. Added `From<ExtendedPoint>` impl for `SubgroupPoint`
- Added serde feature tests to CI
- Added tests for `Serializable` impls of `ExtendedNielsPoint` and `AffineNielsPoint`

.github/workflows/dusk_ci.yml

@@ -26,3 +26,9 @@ jobs:
     uses: dusk-network/.github/.github/workflows/run-tests.yml@main
     with:
       test_flags: --no-default-features 
+
+  test_serde:
+    name: Serde tests
+    uses: dusk-network/.github/.github/workflows/run-tests.yml@main
+    with:
+      test_flags: --features=serde

Cargo.toml

@@ -68,6 +68,18 @@ optional = true
 default-features = false
 # End Dusk dependendencies
 
+[dependencies.serde]
+version = "1.0"
+optional = true
+
+[dependencies.serde_json]
+version = "1.0"
+optional = true
+
+[dependencies.hex]
+version = "0.4"
+optional = true
+
 [dev-dependencies]
 criterion = "0.3"
 csv = ">= 1.0, < 1.2" # csv 1.2 has MSRV 1.60
@@ -86,6 +98,7 @@ default = ["alloc", "bits"]
 alloc = ["ff/alloc", "group/alloc"]
 bits = ["ff/bits"]
 rkyv-impl = ["bytecheck", "dusk-bls12_381/rkyv-impl", "rkyv"]
+serde = ["dep:serde", "serde_json", "dusk-bls12_381/serde", "hex"]
 
 [[bench]]
 name = "fq_bench"

src/lib.rs

@@ -40,11 +40,15 @@ extern crate alloc;
 #[macro_use]
 extern crate std;
 
+#[cfg(feature = "serde")]
+mod serde_support;
+
 use bitvec::{order::Lsb0, view::AsBits};
 use core::borrow::Borrow;
 use core::fmt;
 use core::iter::Sum;
 use core::ops::{Add, AddAssign, Mul, MulAssign, Neg, Sub, SubAssign};
+use dusk_bytes::{DeserializableSlice, Serializable};
 use ff::{BatchInverter, Field};
 use group::{
     cofactor::{CofactorCurve, CofactorCurveAffine, CofactorGroup},
@@ -361,6 +365,49 @@ impl ConditionallySelectable for AffineNielsPoint {
     }
 }
 
+impl ConstantTimeEq for AffineNielsPoint {
+    fn ct_eq(&self, other: &Self) -> Choice {
+        self.t2d.ct_eq(&other.t2d)
+            & self.v_minus_u.ct_eq(&other.v_minus_u)
+            & self.v_plus_u.ct_eq(&other.v_plus_u)
+    }
+}
+
+impl PartialEq for AffineNielsPoint {
+    fn eq(&self, other: &Self) -> bool {
+        bool::from(self.ct_eq(other))
+    }
+}
+
+impl Serializable<{ Fq::SIZE * 3 }> for AffineNielsPoint {
+    type Error = dusk_bytes::Error;
+
+    fn to_bytes(&self) -> [u8; 96] {
+        let v_plus_u = self.v_plus_u.to_bytes();
+        let v_minus_u = self.v_minus_u.to_bytes();
+        let t2d = self.t2d.to_bytes();
+
+        let mut bytes = [0; Self::SIZE];
+
+        bytes[..32].copy_from_slice(&v_plus_u);
+        bytes[32..64].copy_from_slice(&v_minus_u);
+        bytes[64..].copy_from_slice(&t2d);
+
+        bytes
+    }
+
+    fn from_bytes(bytes: &[u8; 96]) -> Result<Self, Self::Error> {
+        let v_plus_u = Fq::from_slice(&bytes[..32])?;
+        let v_minus_u = Fq::from_slice(&bytes[32..64])?;
+        let t2d = Fq::from_slice(&bytes[64..])?;
+        Ok(Self {
+            v_plus_u,
+            v_minus_u,
+            t2d,
+        })
+    }
+}
+
 /// This is a pre-processed version of an extended point `(U, V, Z, T1, T2)`
 /// in the form `(V + U, V - U, Z, T1 * T2 * 2d)`.
 #[derive(Clone, Copy, Debug)]
@@ -444,6 +491,54 @@ impl<'a, 'b> Mul<&'b Fr> for &'a ExtendedNielsPoint {
     }
 }
 
+impl Serializable<{ Fq::SIZE * 4 }> for ExtendedNielsPoint {
+    type Error = dusk_bytes::Error;
+
+    fn to_bytes(&self) -> [u8; 128] {
+        let v_plus_u = self.v_plus_u.to_bytes();
+        let v_minus_u = self.v_minus_u.to_bytes();
+        let t2d = self.t2d.to_bytes();
+        let z = self.z.to_bytes();
+
+        let mut bytes = [0; Self::SIZE];
+
+        bytes[..32].copy_from_slice(&v_plus_u);
+        bytes[32..64].copy_from_slice(&v_minus_u);
+        bytes[64..96].copy_from_slice(&t2d);
+        bytes[96..].copy_from_slice(&z);
+
+        bytes
+    }
+
+    fn from_bytes(bytes: &[u8; 128]) -> Result<Self, Self::Error> {
+        let v_plus_u = Fq::from_slice(&bytes[..32])?;
+        let v_minus_u = Fq::from_slice(&bytes[32..64])?;
+        let t2d = Fq::from_slice(&bytes[64..96])?;
+        let z = Fq::from_slice(&bytes[96..])?;
+        Ok(Self {
+            v_plus_u,
+            v_minus_u,
+            t2d,
+            z,
+        })
+    }
+}
+
+impl ConstantTimeEq for ExtendedNielsPoint {
+    fn ct_eq(&self, other: &Self) -> Choice {
+        self.t2d.ct_eq(&other.t2d)
+            & self.v_minus_u.ct_eq(&other.v_minus_u)
+            & self.v_plus_u.ct_eq(&other.v_plus_u)
+            & self.z.ct_eq(&other.z)
+    }
+}
+
+impl PartialEq for ExtendedNielsPoint {
+    fn eq(&self, other: &Self) -> bool {
+        bool::from(self.ct_eq(other))
+    }
+}
+
 impl_binops_multiplicative_mixed!(ExtendedNielsPoint, Fr, ExtendedPoint);
 
 /// `d = -(10240/10241)`
@@ -1214,6 +1309,12 @@ impl From<SubgroupPoint> for ExtendedPoint {
     }
 }
 
+impl From<ExtendedPoint> for SubgroupPoint {
+    fn from(val: ExtendedPoint) -> Self {
+        Self(val)
+    }
+}
+
 impl<'a> From<&'a SubgroupPoint> for &'a ExtendedPoint {
     fn from(val: &'a SubgroupPoint) -> &'a ExtendedPoint {
         &val.0

src/serde_support.rs

@@ -0,0 +1,167 @@
+extern crate alloc;
+
+use alloc::format;
+use alloc::string::String;
+
+use dusk_bytes::Serializable;
+use serde::{de::Error, Deserialize, Deserializer, Serialize, Serializer};
+
+use crate::{
+    AffineNielsPoint, AffinePoint, ExtendedNielsPoint, ExtendedPoint, Fr,
+    SubgroupPoint,
+};
+
+impl Serialize for AffinePoint {
+    fn serialize<S: Serializer>(
+        &self,
+        serializer: S,
+    ) -> Result<S::Ok, S::Error> {
+        let s = hex::encode(self.to_bytes());
+        serializer.serialize_str(&s)
+    }
+}
+
+impl<'de> Deserialize<'de> for AffinePoint {
+    fn deserialize<D: Deserializer<'de>>(
+        deserializer: D,
+    ) -> Result<Self, D::Error> {
+        let s = String::deserialize(deserializer)?;
+        match hex::decode(s) {
+            Ok(bytes) => {
+                let bytes: [u8; 32] = bytes.try_into().map_err(|_| Error::custom(format!("Failed to deserialize AffinePoint: invalid byte length")))?;
+                AffinePoint::from_bytes(bytes).into_option().ok_or(
+                    Error::custom(format!(
+                    "Failed to deserialize AffinePoint: invalid AffinePoint"
+                )),
+                )
+            }
+            Err(e) => Err(Error::custom(format!(
+                "Failed to deserialize AffinePoint with error: {e}"
+            ))),
+        }
+    }
+}
+
+impl Serialize for ExtendedPoint {
+    fn serialize<S: Serializer>(
+        &self,
+        serializer: S,
+    ) -> Result<S::Ok, S::Error> {
+        AffinePoint::from(self).serialize(serializer)
+    }
+}
+
+impl<'de> Deserialize<'de> for ExtendedPoint {
+    fn deserialize<D: Deserializer<'de>>(
+        deserializer: D,
+    ) -> Result<Self, D::Error> {
+        AffinePoint::deserialize(deserializer).map(|point| point.into())
+    }
+}
+
+impl Serialize for Fr {
+    fn serialize<S: Serializer>(
+        &self,
+        serializer: S,
+    ) -> Result<S::Ok, S::Error> {
+        let s = hex::encode(self.to_bytes());
+        serializer.serialize_str(&s)
+    }
+}
+
+impl<'de> Deserialize<'de> for Fr {
+    fn deserialize<D: Deserializer<'de>>(
+        deserializer: D,
+    ) -> Result<Self, D::Error> {
+        let s = String::deserialize(deserializer)?;
+        match hex::decode(s) {
+            Ok(bytes) => {
+                let bytes: [u8; 32] = bytes.try_into().map_err(|_| {
+                    Error::custom(format!(
+                        "Failed to deserialize Fr: invalid byte length"
+                    ))
+                })?;
+                Fr::from_bytes(&bytes).into_option().ok_or(Error::custom(
+                    format!("Failed to deserialize Fr: invalid Fr"),
+                ))
+            }
+            Err(e) => Err(Error::custom(format!(
+                "Failed to deserialize Fr with error: {e}"
+            ))),
+        }
+    }
+}
+
+impl Serialize for AffineNielsPoint {
+    fn serialize<S: Serializer>(
+        &self,
+        serializer: S,
+    ) -> Result<S::Ok, S::Error> {
+        let s = hex::encode(self.to_bytes());
+        serializer.serialize_str(&s)
+    }
+}
+
+impl<'de> Deserialize<'de> for AffineNielsPoint {
+    fn deserialize<D: Deserializer<'de>>(
+        deserializer: D,
+    ) -> Result<Self, D::Error> {
+        let s = String::deserialize(deserializer)?;
+        match hex::decode(s) {
+            Ok(bytes) => {
+                let bytes: [u8; AffineNielsPoint::SIZE] = bytes.try_into().map_err(|_| Error::custom(format!("Failed to deserialize AffineNielsPoint: invalid byte length")))?;
+                AffineNielsPoint::from_bytes(&bytes)
+                    .map_err(|_| Error::custom(format!("Failed to deserialize AffineNielsPoint: invalid AffineNielsPoint")))
+            }
+            Err(e) => Err(Error::custom(format!(
+                "Failed to deserialize AffineNielsPoint with error: {e}"
+            ))),
+        }
+    }
+}
+
+impl Serialize for ExtendedNielsPoint {
+    fn serialize<S: Serializer>(
+        &self,
+        serializer: S,
+    ) -> Result<S::Ok, S::Error> {
+        let s = hex::encode(self.to_bytes());
+        serializer.serialize_str(&s)
+    }
+}
+
+impl<'de> Deserialize<'de> for ExtendedNielsPoint {
+    fn deserialize<D: Deserializer<'de>>(
+        deserializer: D,
+    ) -> Result<Self, D::Error> {
+        let s = String::deserialize(deserializer)?;
+        match hex::decode(s) {
+            Ok(bytes) => {
+                let bytes: [u8; 128] = bytes.try_into().map_err(|_| Error::custom(format!("Failed to deserialize ExtendedNielsPoint: invalid byte length")))?;
+                ExtendedNielsPoint::from_bytes(&bytes)
+                    .map_err(|_| Error::custom(format!("Failed to deserialize ExtendedNielsPoint: invalid ExtendedNielsPoint")))
+            }
+            Err(e) => Err(Error::custom(format!(
+                "Failed to deserialize ExtendedNielsPoint with error: {e}"
+            ))),
+        }
+    }
+}
+
+impl Serialize for SubgroupPoint {
+    fn serialize<S: Serializer>(
+        &self,
+        serializer: S,
+    ) -> Result<S::Ok, S::Error> {
+        self.0.serialize(serializer)
+    }
+}
+
+impl<'de> Deserialize<'de> for SubgroupPoint {
+    fn deserialize<D: Deserializer<'de>>(
+        deserializer: D,
+    ) -> Result<Self, D::Error> {
+        ExtendedPoint::deserialize(deserializer)
+            .map(|point| SubgroupPoint::from(point))
+    }
+}

tests/points.rs

@@ -0,0 +1,20 @@
+use dusk_bytes::Serializable;
+use dusk_jubjub::{AffineNielsPoint, ExtendedNielsPoint};
+
+#[test]
+fn affine_niels_point_encoding() {
+    let point = AffineNielsPoint::identity();
+    assert_eq!(
+        point,
+        AffineNielsPoint::from_bytes(&point.to_bytes()).unwrap()
+    );
+}
+
+#[test]
+fn extended_niels_point_encoding() {
+    let point = ExtendedNielsPoint::identity();
+    assert_eq!(
+        point,
+        ExtendedNielsPoint::from_bytes(&point.to_bytes()).unwrap()
+    );
+}