[−][src]Struct curve25519_dalek::edwards::EdwardsPoint

pub struct EdwardsPoint {
    pub(crate) X: FieldElement51,
    pub(crate) Y: FieldElement51,
    pub(crate) Z: FieldElement51,
    pub(crate) T: FieldElement51,
}

An EdwardsPoint represents a point on the Edwards form of Curve25519.

Fields

X: FieldElement51Y: FieldElement51Z: FieldElement51T: FieldElement51

Methods

`impl EdwardsPoint`[src]

`pub(crate) fn to_projective_niels(&self) -> ProjectiveNielsPoint`[src]

Convert to a ProjectiveNielsPoint

`pub(crate) fn to_projective(&self) -> ProjectivePoint`[src]

Convert the representation of this point from extended coordinates to projective coordinates.

Free.

`pub(crate) fn to_affine_niels(&self) -> AffineNielsPoint`[src]

Dehomogenize to a AffineNielsPoint. Mainly for testing.

`pub fn to_montgomery(&self) -> MontgomeryPoint`[src]

Convert this EdwardsPoint on the Edwards model to the corresponding MontgomeryPoint on the Montgomery model.

This function has one exceptional case; the identity point of the Edwards curve is sent to the 2-torsion point \((0,0)\) on the Montgomery curve.

Note that this is a one-way conversion, since the Montgomery model does not retain sign information.

`pub fn compress(&self) -> CompressedEdwardsY`[src]

Compress this point to CompressedEdwardsY format.

`impl EdwardsPoint`[src]

`pub(crate) fn double(&self) -> EdwardsPoint`[src]

Add this point to itself.

`impl EdwardsPoint`[src]

`pub fn vartime_double_scalar_mul_basepoint( a: &Scalar, A: &EdwardsPoint, b: &Scalar ) -> EdwardsPoint`[src]

Compute \(aA + bB\) in variable time, where \(B\) is the Ed25519 basepoint.

`impl EdwardsPoint`[src]

`pub fn mul_by_cofactor(&self) -> EdwardsPoint`[src]

Multiply by the cofactor: return \([8]P\).

`pub(crate) fn mul_by_pow_2(&self, k: u32) -> EdwardsPoint`[src]

Compute \([2^k] P \) by successive doublings. Requires \( k > 0 \).

`pub fn is_small_order(&self) -> bool`[src]

Determine if this point is of small order.

Return

true if self is in the torsion subgroup \( \mathcal E[8] \);
false if self is not in the torsion subgroup \( \mathcal E[8] \).

Example

use curve25519_dalek::constants;

// Generator of the prime-order subgroup
let P = constants::ED25519_BASEPOINT_POINT;
// Generator of the torsion subgroup
let Q = constants::EIGHT_TORSION[1];

// P has large order
assert_eq!(P.is_small_order(), false);

// Q has small order
assert_eq!(Q.is_small_order(), true);

`pub fn is_torsion_free(&self) -> bool`[src]

Determine if this point is “torsion-free”, i.e., is contained in the prime-order subgroup.

Return

true if self has zero torsion component and is in the prime-order subgroup;
false if self has a nonzero torsion component and is not in the prime-order subgroup.

Example

use curve25519_dalek::constants;

// Generator of the prime-order subgroup
let P = constants::ED25519_BASEPOINT_POINT;
// Generator of the torsion subgroup
let Q = constants::EIGHT_TORSION[1];

// P is torsion-free
assert_eq!(P.is_torsion_free(), true);

// P + Q is not torsion-free
assert_eq!((P+Q).is_torsion_free(), false);