elliptic_curve/
point.rs

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1//! Traits for elliptic curve points.
2
3#[cfg(feature = "arithmetic")]
4mod non_identity;
5
6#[cfg(feature = "arithmetic")]
7pub use {self::non_identity::NonIdentity, crate::CurveArithmetic};
8
9use crate::{Curve, FieldBytes};
10use subtle::{Choice, CtOption};
11
12/// Affine point type for a given curve with a [`CurveArithmetic`]
13/// implementation.
14#[cfg(feature = "arithmetic")]
15pub type AffinePoint<C> = <C as CurveArithmetic>::AffinePoint;
16
17/// Projective point type for a given curve with a [`CurveArithmetic`]
18/// implementation.
19#[cfg(feature = "arithmetic")]
20pub type ProjectivePoint<C> = <C as CurveArithmetic>::ProjectivePoint;
21
22/// Access to the affine coordinates of an elliptic curve point.
23// TODO: use zkcrypto/group#30 coordinate API when available
24pub trait AffineCoordinates {
25    /// Field element representation.
26    type FieldRepr: AsRef<[u8]>;
27
28    /// Get the affine x-coordinate as a serialized field element.
29    fn x(&self) -> Self::FieldRepr;
30
31    /// Is the affine y-coordinate odd?
32    fn y_is_odd(&self) -> Choice;
33}
34
35/// Normalize point(s) in projective representation by converting them to their affine ones.
36#[cfg(feature = "arithmetic")]
37pub trait BatchNormalize<Points: ?Sized>: group::Curve {
38    /// The output of the batch normalization; a container of affine points.
39    type Output: AsRef<[Self::AffineRepr]>;
40
41    /// Perform a batched conversion to affine representation on a sequence of projective points
42    /// at an amortized cost that should be practically as efficient as a single conversion.
43    /// Internally, implementors should rely upon `InvertBatch`.
44    fn batch_normalize(points: &Points) -> <Self as BatchNormalize<Points>>::Output;
45}
46
47/// Double a point (i.e. add it to itself)
48pub trait Double {
49    /// Double this point.
50    fn double(&self) -> Self;
51}
52
53/// Decompress an elliptic curve point.
54///
55/// Point decompression recovers an original curve point from its x-coordinate
56/// and a boolean flag indicating whether or not the y-coordinate is odd.
57pub trait DecompressPoint<C: Curve>: Sized {
58    /// Attempt to decompress an elliptic curve point.
59    fn decompress(x: &FieldBytes<C>, y_is_odd: Choice) -> CtOption<Self>;
60}
61
62/// Decompact an elliptic curve point from an x-coordinate.
63///
64/// Decompaction relies on properties of specially-generated keys but provides
65/// a more compact representation than standard point compression.
66pub trait DecompactPoint<C: Curve>: Sized {
67    /// Attempt to decompact an elliptic curve point
68    fn decompact(x: &FieldBytes<C>) -> CtOption<Self>;
69}
70
71/// Point compression settings.
72pub trait PointCompression {
73    /// Should point compression be applied by default?
74    const COMPRESS_POINTS: bool;
75}
76
77/// Point compaction settings.
78pub trait PointCompaction {
79    /// Should point compaction be applied by default?
80    const COMPACT_POINTS: bool;
81}
elliptic_curve/point.rs

elliptic_curve/
point.rs
