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//! Traits for elliptic curve points.
#[cfg(feature = "arithmetic")]
mod non_identity;
#[cfg(feature = "arithmetic")]
pub use {self::non_identity::NonIdentity, crate::CurveArithmetic};
use crate::{Curve, FieldBytes};
use subtle::{Choice, CtOption};
/// Affine point type for a given curve with a [`CurveArithmetic`]
/// implementation.
#[cfg(feature = "arithmetic")]
pub type AffinePoint<C> = <C as CurveArithmetic>::AffinePoint;
/// Projective point type for a given curve with a [`CurveArithmetic`]
/// implementation.
#[cfg(feature = "arithmetic")]
pub type ProjectivePoint<C> = <C as CurveArithmetic>::ProjectivePoint;
/// Access to the affine coordinates of an elliptic curve point.
// TODO: use zkcrypto/group#30 coordinate API when available
pub trait AffineCoordinates {
/// Field element representation.
type FieldRepr: AsRef<[u8]>;
/// Get the affine x-coordinate as a serialized field element.
fn x(&self) -> Self::FieldRepr;
/// Is the affine y-coordinate odd?
fn y_is_odd(&self) -> Choice;
}
/// Normalize point(s) in projective representation by converting them to their affine ones.
#[cfg(feature = "arithmetic")]
pub trait BatchNormalize<Points: ?Sized>: group::Curve {
/// The output of the batch normalization; a container of affine points.
type Output: AsRef<[Self::AffineRepr]>;
/// Perform a batched conversion to affine representation on a sequence of projective points
/// at an amortized cost that should be practically as efficient as a single conversion.
/// Internally, implementors should rely upon `InvertBatch`.
fn batch_normalize(points: &Points) -> <Self as BatchNormalize<Points>>::Output;
}
/// Double a point (i.e. add it to itself)
pub trait Double {
/// Double this point.
fn double(&self) -> Self;
}
/// Decompress an elliptic curve point.
///
/// Point decompression recovers an original curve point from its x-coordinate
/// and a boolean flag indicating whether or not the y-coordinate is odd.
pub trait DecompressPoint<C: Curve>: Sized {
/// Attempt to decompress an elliptic curve point.
fn decompress(x: &FieldBytes<C>, y_is_odd: Choice) -> CtOption<Self>;
}
/// Decompact an elliptic curve point from an x-coordinate.
///
/// Decompaction relies on properties of specially-generated keys but provides
/// a more compact representation than standard point compression.
pub trait DecompactPoint<C: Curve>: Sized {
/// Attempt to decompact an elliptic curve point
fn decompact(x: &FieldBytes<C>) -> CtOption<Self>;
}
/// Point compression settings.
pub trait PointCompression {
/// Should point compression be applied by default?
const COMPRESS_POINTS: bool;
}
/// Point compaction settings.
pub trait PointCompaction {
/// Should point compaction be applied by default?
const COMPACT_POINTS: bool;
}
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