implement decoding from raw representation

src/bls12_381/ec.rs

@@ -760,6 +760,45 @@ pub mod g1 {
 
             res
         }
+
+        fn from_raw_uncompressed_le_unchecked(
+            encoded: &Self::Uncompressed, 
+            _infinity: bool
+        ) -> Result<Self, GroupDecodingError> {
+            let copy = encoded.0;
+            if copy.iter().all(|b| *b == 0) {
+                return Ok(Self::zero());
+            }
+
+            let mut x = FqRepr([0; 6]);
+            let mut y = FqRepr([0; 6]);
+
+            {
+                let mut reader = &copy[..];
+                x.read_be(&mut reader).unwrap();
+                y.read_be(&mut reader).unwrap();
+            }
+
+            Ok(G1Affine {
+                x: Fq::from_raw_repr(x).map_err(|e| {
+                    GroupDecodingError::CoordinateDecodingError("x coordinate", e)
+                })?,
+                y: Fq::from_raw_repr(y).map_err(|e| {
+                    GroupDecodingError::CoordinateDecodingError("y coordinate", e)
+                })?,
+                infinity: false,
+            })
+        }
+
+        fn from_raw_uncompressed_le(encoded: &Self::Uncompressed, _infinity: bool) -> Result<Self, GroupDecodingError> {
+            let affine = Self::from_raw_uncompressed_le_unchecked(&encoded, _infinity)?;
+
+            if !affine.is_on_curve() {
+                Err(GroupDecodingError::NotOnCurve)
+            } else {
+                Ok(affine)
+            }
+        }
     }
 
     #[derive(Copy, Clone)]

src/bn256/ec.rs

@@ -652,6 +652,47 @@ pub mod g1 {
 
             res
         }
+
+        /// Creates a point from raw encoded coordinates without checking on curve
+        fn from_raw_uncompressed_le_unchecked(
+            encoded: &Self::Uncompressed, 
+            _infinity: bool
+        ) -> Result<Self, GroupDecodingError> {
+            let copy = encoded.0;
+
+            if copy.iter().all(|b| *b == 0) {
+                return Ok(Self::zero());
+            }
+
+            let mut x = FqRepr([0; 4]);
+            let mut y = FqRepr([0; 4]);
+
+            {
+                let mut reader = &copy[..];
+                x.read_be(&mut reader).unwrap();
+                y.read_be(&mut reader).unwrap();
+            }
+
+            Ok(G1Affine {
+                x: Fq::from_raw_repr(x).map_err(|e| {
+                    GroupDecodingError::CoordinateDecodingError("x coordinate", e)
+                })?,
+                y: Fq::from_raw_repr(y).map_err(|e| {
+                    GroupDecodingError::CoordinateDecodingError("y coordinate", e)
+                })?,
+                infinity: false,
+            })
+        }
+
+        fn from_raw_uncompressed_le(encoded: &Self::Uncompressed, _infinity: bool) -> Result<Self, GroupDecodingError> {
+            let affine = Self::from_raw_uncompressed_le_unchecked(&encoded, _infinity)?;
+
+            if !affine.is_on_curve() {
+                Err(GroupDecodingError::NotOnCurve)
+            } else {
+                Ok(affine)
+            }
+        }
     }
 
     #[derive(Copy, Clone)]

src/lib.rs

@@ -246,6 +246,12 @@ pub trait RawEncodable: CurveAffine {
     /// Converts this element into its uncompressed encoding, so long as it's not
     /// the point at infinity. Leaves coordinates in Montgommery form
     fn into_raw_uncompressed_le(&self) -> Self::Uncompressed;
+
+    /// Creates a point from raw encoded coordinates without checking on curve
+    fn from_raw_uncompressed_le_unchecked(encoded: &Self::Uncompressed, infinity: bool) -> Result<Self, GroupDecodingError>;
+
+    /// Creates a point from raw encoded coordinates
+    fn from_raw_uncompressed_le(encoded: &Self::Uncompressed, infinity: bool) -> Result<Self, GroupDecodingError>;
 }
 
 /// An encoded elliptic curve point, which should essentially wrap a `[u8; N]`.