p256: impl ff and group traits

Corresponding change to #164, but for the `p256` crate. - Impls `ff::{Field, PrimeField}` on `Scalar` - Impls `group::{Group, Curve}` on `ProjectivePoint`
RustCrypto · Sep 6, 2020 · 8bfa8b6 · 8bfa8b6
1 parent ebac050
commit 8bfa8b6
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Showing 8 changed files with 289 additions and 39 deletions.
diff --git a/Cargo.lock b/Cargo.lock
diff --git a/k256/src/arithmetic/projective.rs b/k256/src/arithmetic/projective.rs
@@ -7,7 +7,8 @@ use core::{
     ops::{Add, AddAssign, Neg, Sub, SubAssign},
 };
 use elliptic_curve::{
-    group::{self, Group},
+    ff::Field,
+    group::{Curve, Group},
     point::Generator,
     rand_core::RngCore,
     subtle::{Choice, ConditionallySelectable, ConstantTimeEq},
@@ -240,8 +241,8 @@ impl ProjectivePoint {
 impl Group for ProjectivePoint {
     type Scalar = Scalar;
 
-    fn random(rng: impl RngCore) -> Self {
-        Self::generator() * Scalar::generate_vartime(rng)
+    fn random(mut rng: impl RngCore) -> Self {
+        Self::generator() * Scalar::random(&mut rng)
     }
 
     fn identity() -> Self {
@@ -262,7 +263,7 @@ impl Group for ProjectivePoint {
     }
 }
 
-impl group::Curve for ProjectivePoint {
+impl Curve for ProjectivePoint {
     type AffineRepr = AffinePoint;
 
     fn to_affine(&self) -> AffinePoint {

diff --git a/k256/src/arithmetic/scalar.rs b/k256/src/arithmetic/scalar.rs
@@ -21,7 +21,7 @@ use core::{
 };
 use elliptic_curve::{
     consts::U32,
-    ff,
+    ff::{Field, PrimeField},
     ops::Invert,
     rand_core::{CryptoRng, RngCore},
     subtle::{Choice, ConditionallySelectable, ConstantTimeEq, CtOption},
@@ -238,7 +238,7 @@ impl Scalar {
     }
 }
 
-impl ff::Field for Scalar {
+impl Field for Scalar {
     fn random<R: RngCore + ?Sized>(rng: &mut R) -> Self {
         Scalar::generate_vartime(rng)
     }
@@ -275,7 +275,7 @@ impl ff::Field for Scalar {
     }
 }
 
-impl ff::PrimeField for Scalar {
+impl PrimeField for Scalar {
     type Repr = ElementBytes;
     type ReprEndianness = byteorder::BigEndian;
 

diff --git a/p256/Cargo.toml b/p256/Cargo.toml
@@ -16,6 +16,7 @@ categories = ["cryptography", "no-std"]
 keywords = ["crypto", "ecc", "nist", "prime256v1", "secp256r1"]
 
 [dependencies]
+byteorder = { version = "1", default-features = false }
 ecdsa-core = { version = "0.7", package = "ecdsa", optional = true, default-features = false }
 elliptic-curve = { version = "0.5", default-features = false }
 sha2 = { version = "0.9", optional = true, default-features = false }

diff --git a/p256/src/arithmetic/projective.rs b/p256/src/arithmetic/projective.rs
@@ -1,9 +1,16 @@
 //! Projective points
 
 use super::{AffinePoint, FieldElement, Scalar, CURVE_EQUATION_B};
-use core::ops::{Add, AddAssign, Mul, MulAssign, Neg, Sub, SubAssign};
+use core::{
+    fmt,
+    iter::Sum,
+    ops::{Add, AddAssign, Mul, MulAssign, Neg, Sub, SubAssign},
+};
 use elliptic_curve::{
+    ff::Field,
+    group::{Curve, Group},
     point::Generator,
+    rand_core::RngCore,
     subtle::{Choice, ConditionallySelectable, ConstantTimeEq},
 };
 
@@ -16,6 +23,39 @@ pub struct ProjectivePoint {
     z: FieldElement,
 }
 
+impl Group for ProjectivePoint {
+    type Scalar = Scalar;
+
+    fn random(mut rng: impl RngCore) -> Self {
+        Self::generator() * Scalar::random(&mut rng)
+    }
+
+    fn identity() -> Self {
+        ProjectivePoint::identity()
+    }
+
+    fn generator() -> Self {
+        ProjectivePoint::generator()
+    }
+
+    fn is_identity(&self) -> Choice {
+        self.ct_eq(&Self::identity())
+    }
+
+    #[must_use]
+    fn double(&self) -> Self {
+        ProjectivePoint::double(self)
+    }
+}
+
+impl Curve for ProjectivePoint {
+    type AffineRepr = AffinePoint;
+
+    fn to_affine(&self) -> AffinePoint {
+        ProjectivePoint::to_affine(self)
+    }
+}
+
 impl From<AffinePoint> for ProjectivePoint {
     fn from(p: AffinePoint) -> Self {
         let projective = ProjectivePoint {
@@ -49,6 +89,8 @@ impl PartialEq for ProjectivePoint {
     }
 }
 
+impl Eq for ProjectivePoint {}
+
 impl ProjectivePoint {
     /// Returns the additive identity of P-256, also known as the "neutral element" or
     /// "point at infinity".
@@ -208,6 +250,14 @@ impl Default for ProjectivePoint {
     }
 }
 
+impl Add<ProjectivePoint> for ProjectivePoint {
+    type Output = ProjectivePoint;
+
+    fn add(self, other: ProjectivePoint) -> ProjectivePoint {
+        ProjectivePoint::add(&self, &other)
+    }
+}
+
 impl Add<&ProjectivePoint> for &ProjectivePoint {
     type Output = ProjectivePoint;
 
@@ -236,6 +286,14 @@ impl AddAssign<&ProjectivePoint> for ProjectivePoint {
     }
 }
 
+impl Add<AffinePoint> for ProjectivePoint {
+    type Output = ProjectivePoint;
+
+    fn add(self, other: AffinePoint) -> ProjectivePoint {
+        ProjectivePoint::add_mixed(&self, &other)
+    }
+}
+
 impl Add<&AffinePoint> for &ProjectivePoint {
     type Output = ProjectivePoint;
 
@@ -258,6 +316,32 @@ impl AddAssign<AffinePoint> for ProjectivePoint {
     }
 }
 
+impl AddAssign<&AffinePoint> for ProjectivePoint {
+    fn add_assign(&mut self, rhs: &AffinePoint) {
+        *self = ProjectivePoint::add_mixed(self, rhs);
+    }
+}
+
+impl Sum for ProjectivePoint {
+    fn sum<I: Iterator<Item = Self>>(iter: I) -> Self {
+        iter.fold(ProjectivePoint::identity(), |a, b| a + b)
+    }
+}
+
+impl<'a> Sum<&'a ProjectivePoint> for ProjectivePoint {
+    fn sum<I: Iterator<Item = &'a ProjectivePoint>>(iter: I) -> Self {
+        iter.cloned().sum()
+    }
+}
+
+impl Sub<ProjectivePoint> for ProjectivePoint {
+    type Output = ProjectivePoint;
+
+    fn sub(self, other: ProjectivePoint) -> ProjectivePoint {
+        ProjectivePoint::sub(&self, &other)
+    }
+}
+
 impl Sub<&ProjectivePoint> for &ProjectivePoint {
     type Output = ProjectivePoint;
 
@@ -286,6 +370,14 @@ impl SubAssign<&ProjectivePoint> for ProjectivePoint {
     }
 }
 
+impl Sub<AffinePoint> for ProjectivePoint {
+    type Output = ProjectivePoint;
+
+    fn sub(self, other: AffinePoint) -> ProjectivePoint {
+        ProjectivePoint::sub_mixed(&self, &other)
+    }
+}
+
 impl Sub<&AffinePoint> for &ProjectivePoint {
     type Output = ProjectivePoint;
 
@@ -308,6 +400,20 @@ impl SubAssign<AffinePoint> for ProjectivePoint {
     }
 }
 
+impl SubAssign<&AffinePoint> for ProjectivePoint {
+    fn sub_assign(&mut self, rhs: &AffinePoint) {
+        *self = ProjectivePoint::sub_mixed(self, rhs);
+    }
+}
+
+impl Mul<Scalar> for ProjectivePoint {
+    type Output = ProjectivePoint;
+
+    fn mul(self, other: Scalar) -> ProjectivePoint {
+        ProjectivePoint::mul(&self, &other)
+    }
+}
+
 impl Mul<&Scalar> for &ProjectivePoint {
     type Output = ProjectivePoint;
 
@@ -352,6 +458,12 @@ impl<'a> Neg for &'a ProjectivePoint {
     }
 }
 
+impl fmt::Display for ProjectivePoint {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        write!(f, "{:?}", self)
+    }
+}
+
 #[cfg(test)]
 mod tests {
     use super::{AffinePoint, ProjectivePoint, Scalar};
@@ -432,7 +544,7 @@ mod tests {
                 ADD_TEST_VECTORS[i]
             );
 
-            p = p + &generator;
+            p += &generator;
         }
     }