1 files changed, 100 insertions, 0 deletions
diff --git a/vendor/group/src/cofactor.rs b/vendor/group/src/cofactor.rs
new file mode 100644
index 0000000..84bfe0a
--- /dev/null
+++ b/vendor/group/src/cofactor.rs
@@ -0,0 +1,100 @@
+use core::fmt;
+use core::ops::{Mul, Neg};
+use ff::PrimeField;
+use subtle::{Choice, CtOption};
+
+use crate::{prime::PrimeGroup, Curve, Group, GroupEncoding, GroupOps, GroupOpsOwned};
+
+/// This trait represents an element of a cryptographic group with a large prime-order
+/// subgroup and a comparatively-small cofactor.
+pub trait CofactorGroup:
+    Group
+    + GroupEncoding
+    + GroupOps<<Self as CofactorGroup>::Subgroup>
+    + GroupOpsOwned<<Self as CofactorGroup>::Subgroup>
+{
+    /// The large prime-order subgroup in which cryptographic operations are performed.
+    /// If `Self` implements `PrimeGroup`, then `Self::Subgroup` may be `Self`.
+    type Subgroup: PrimeGroup<Scalar = Self::Scalar> + Into<Self>;
+
+    /// Maps `self` to the prime-order subgroup by multiplying this element by some
+    /// `k`-multiple of the cofactor.
+    ///
+    /// The value `k` does not vary between inputs for a given implementation, but may
+    /// vary between different implementations of `CofactorGroup` because some groups have
+    /// more efficient methods of clearing the cofactor when `k` is allowed to be
+    /// different than `1`.
+    ///
+    /// If `Self` implements [`PrimeGroup`], this returns `self`.
+    fn clear_cofactor(&self) -> Self::Subgroup;
+
+    /// Returns `self` if it is contained in the prime-order subgroup.
+    ///
+    /// If `Self` implements [`PrimeGroup`], this returns `Some(self)`.
+    fn into_subgroup(self) -> CtOption<Self::Subgroup>;
+
+    /// Determines if this element is of small order.
+    ///
+    /// Returns:
+    /// - `true` if `self` is in the torsion subgroup.
+    /// - `false` if `self` is not in the torsion subgroup.
+    fn is_small_order(&self) -> Choice {
+        self.clear_cofactor().is_identity()
+    }
+
+    /// Determines if this element is "torsion free", i.e., is contained in the
+    /// prime-order subgroup.
+    ///
+    /// Returns:
+    /// - `true` if `self` has trivial torsion and is in the prime-order subgroup.
+    /// - `false` if `self` has non-zero torsion component and is not in the prime-order
+    ///   subgroup.
+    fn is_torsion_free(&self) -> Choice;
+}
+
+/// Efficient representation of an elliptic curve point guaranteed to be
+/// in the correct prime order subgroup.
+pub trait CofactorCurve:
+    Curve<AffineRepr = <Self as CofactorCurve>::Affine> + CofactorGroup
+{
+    type Affine: CofactorCurveAffine<Curve = Self, Scalar = Self::Scalar>
+        + Mul<Self::Scalar, Output = Self>
+        + for<'r> Mul<&'r Self::Scalar, Output = Self>;
+}
+
+/// Affine representation of an elliptic curve point guaranteed to be
+/// in the correct prime order subgroup.
+pub trait CofactorCurveAffine:
+    GroupEncoding
+    + Copy
+    + Clone
+    + Sized
+    + Send
+    + Sync
+    + fmt::Debug
+    + PartialEq
+    + Eq
+    + 'static
+    + Neg<Output = Self>
+    + Mul<<Self as CofactorCurveAffine>::Scalar, Output = <Self as CofactorCurveAffine>::Curve>
+    + for<'r> Mul<
+        &'r <Self as CofactorCurveAffine>::Scalar,
+        Output = <Self as CofactorCurveAffine>::Curve,
+    >
+{
+    type Scalar: PrimeField;
+    type Curve: CofactorCurve<Affine = Self, Scalar = Self::Scalar>;
+
+    /// Returns the additive identity.
+    fn identity() -> Self;
+
+    /// Returns a fixed generator of unknown exponent.
+    fn generator() -> Self;
+
+    /// Determines if this point represents the point at infinity; the
+    /// additive identity.
+    fn is_identity(&self) -> Choice;
+
+    /// Converts this element to its curve representation.
+    fn to_curve(&self) -> Self::Curve;
+}