initial commit

src/group.rs

@@ -0,0 +1,101 @@
+use super::scalar::{Scalar, ScalarBytes, ScalarBytesFromScalar};
+use core::borrow::Borrow;
+use core::ops::{Mul, MulAssign};
+
+pub type GroupElement = curve25519_dalek::ristretto::RistrettoPoint;
+pub type CompressedGroup = curve25519_dalek::ristretto::CompressedRistretto;
+pub const GROUP_BASEPOINT_COMPRESSED: CompressedGroup =
+  curve25519_dalek::constants::RISTRETTO_BASEPOINT_COMPRESSED;
+
+impl<'b> MulAssign<&'b Scalar> for GroupElement {
+  fn mul_assign(&mut self, scalar: &'b Scalar) {
+    let result = (self as &GroupElement) * Scalar::decompress_scalar(scalar);
+    *self = result;
+  }
+}
+
+impl<'a, 'b> Mul<&'b Scalar> for &'a GroupElement {
+  type Output = GroupElement;
+  fn mul(self, scalar: &'b Scalar) -> GroupElement {
+    self * Scalar::decompress_scalar(scalar)
+  }
+}
+
+impl<'a, 'b> Mul<&'b GroupElement> for &'a Scalar {
+  type Output = GroupElement;
+
+  fn mul(self, point: &'b GroupElement) -> GroupElement {
+    Scalar::decompress_scalar(self) * point
+  }
+}
+
+macro_rules! define_mul_variants {
+  (LHS = $lhs:ty, RHS = $rhs:ty, Output = $out:ty) => {
+    impl<'b> Mul<&'b $rhs> for $lhs {
+      type Output = $out;
+      fn mul(self, rhs: &'b $rhs) -> $out {
+        &self * rhs
+      }
+    }
+
+    impl<'a> Mul<$rhs> for &'a $lhs {
+      type Output = $out;
+      fn mul(self, rhs: $rhs) -> $out {
+        self * &rhs
+      }
+    }
+
+    impl Mul<$rhs> for $lhs {
+      type Output = $out;
+      fn mul(self, rhs: $rhs) -> $out {
+        &self * &rhs
+      }
+    }
+  };
+}
+
+macro_rules! define_mul_assign_variants {
+  (LHS = $lhs:ty, RHS = $rhs:ty) => {
+    impl MulAssign<$rhs> for $lhs {
+      fn mul_assign(&mut self, rhs: $rhs) {
+        *self *= &rhs;
+      }
+    }
+  };
+}
+
+define_mul_assign_variants!(LHS = GroupElement, RHS = Scalar);
+define_mul_variants!(LHS = GroupElement, RHS = Scalar, Output = GroupElement);
+define_mul_variants!(LHS = Scalar, RHS = GroupElement, Output = GroupElement);
+
+pub trait VartimeMultiscalarMul {
+  type Scalar;
+  fn vartime_multiscalar_mul<I, J>(scalars: I, points: J) -> Self
+  where
+    I: IntoIterator,
+    I::Item: Borrow<Self::Scalar>,
+    J: IntoIterator,
+    J::Item: Borrow<Self>,
+    Self: Clone;
+}
+
+impl VartimeMultiscalarMul for GroupElement {
+  type Scalar = super::scalar::Scalar;
+  fn vartime_multiscalar_mul<I, J>(scalars: I, points: J) -> Self
+  where
+    I: IntoIterator,
+    I::Item: Borrow<Self::Scalar>,
+    J: IntoIterator,
+    J::Item: Borrow<Self>,
+    Self: Clone,
+  {
+    use curve25519_dalek::traits::VartimeMultiscalarMul;
+    <Self as VartimeMultiscalarMul>::vartime_multiscalar_mul(
+      scalars
+        .into_iter()
+        .map(|s| Scalar::decompress_scalar(s.borrow()))
+        .collect::<Vec<ScalarBytes>>(),
+      points,
+    )
+  }
+}