Struct curve25519_dalek::edwards::EdwardsPoint

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pub struct EdwardsPoint { /* private fields */ }
Expand description

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

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impl EdwardsPoint

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pub fn to_montgomery(&self) -> MontgomeryPoint

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.

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pub fn compress(&self) -> CompressedEdwardsY

Compress this point to CompressedEdwardsY format.

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pub fn nonspec_map_to_curve<D>(bytes: &[u8]) -> EdwardsPoint
where D: Digest<OutputSize = U64> + Default,

👎Deprecated since 4.0.0: previously named hash_from_bytes, this is not a secure hash function

Maps the digest of the input bytes to the curve. This is NOT a hash-to-curve function, as it produces points with a non-uniform distribution. Rather, it performs something that resembles (but is not) half of the hash_to_curve function from the Elligator2 spec.

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impl EdwardsPoint

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pub fn mul_base(scalar: &Scalar) -> Self

Fixed-base scalar multiplication by the Ed25519 base point.

Uses precomputed basepoint tables when the precomputed-tables feature is enabled, trading off increased code size for ~4x better performance.

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pub fn mul_clamped(self, bytes: [u8; 32]) -> Self

Multiply this point by clamp_integer(bytes). For a description of clamping, see clamp_integer.

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pub fn mul_base_clamped(bytes: [u8; 32]) -> Self

Multiply the basepoint by clamp_integer(bytes). For a description of clamping, see clamp_integer.

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impl EdwardsPoint

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pub fn vartime_double_scalar_mul_basepoint( a: &Scalar, A: &EdwardsPoint, b: &Scalar, ) -> EdwardsPoint

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

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impl EdwardsPoint

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pub fn mul_by_cofactor(&self) -> EdwardsPoint

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

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pub fn is_small_order(&self) -> bool

Determine if this point is of small order.

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  • 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);
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pub fn is_torsion_free(&self) -> bool

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

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  • 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);

Trait Implementations§

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impl<'a, 'b> Add<&'b EdwardsPoint> for &'a EdwardsPoint

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type Output = EdwardsPoint

The resulting type after applying the + operator.
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fn add(self, other: &'b EdwardsPoint) -> EdwardsPoint

Performs the + operation. Read more
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impl<'b> Add<&'b EdwardsPoint> for EdwardsPoint

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type Output = EdwardsPoint

The resulting type after applying the + operator.
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fn add(self, rhs: &'b EdwardsPoint) -> EdwardsPoint

Performs the + operation. Read more
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impl<'a> Add<EdwardsPoint> for &'a EdwardsPoint

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type Output = EdwardsPoint

The resulting type after applying the + operator.
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fn add(self, rhs: EdwardsPoint) -> EdwardsPoint

Performs the + operation. Read more
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impl Add for EdwardsPoint

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type Output = EdwardsPoint

The resulting type after applying the + operator.
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fn add(self, rhs: EdwardsPoint) -> EdwardsPoint

Performs the + operation. Read more
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impl<'b> AddAssign<&'b EdwardsPoint> for EdwardsPoint

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fn add_assign(&mut self, _rhs: &'b EdwardsPoint)

Performs the += operation. Read more
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impl AddAssign for EdwardsPoint

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fn add_assign(&mut self, rhs: EdwardsPoint)

Performs the += operation. Read more
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impl Clone for EdwardsPoint

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fn clone(&self) -> EdwardsPoint

Returns a copy of the value. Read more
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fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source. Read more
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impl ConditionallySelectable for EdwardsPoint

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fn conditional_select( a: &EdwardsPoint, b: &EdwardsPoint, choice: Choice, ) -> EdwardsPoint

Select a or b according to choice. Read more
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fn conditional_assign(&mut self, other: &Self, choice: Choice)

Conditionally assign other to self, according to choice. Read more
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fn conditional_swap(a: &mut Self, b: &mut Self, choice: Choice)

Conditionally swap self and other if choice == 1; otherwise, reassign both unto themselves. Read more
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impl ConstantTimeEq for EdwardsPoint

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fn ct_eq(&self, other: &EdwardsPoint) -> Choice

Determine if two items are equal. Read more
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fn ct_ne(&self, other: &Self) -> Choice

Determine if two items are NOT equal. Read more
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impl Debug for EdwardsPoint

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fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter. Read more
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impl Default for EdwardsPoint

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fn default() -> EdwardsPoint

Returns the “default value” for a type. Read more
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impl Identity for EdwardsPoint

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fn identity() -> EdwardsPoint

Returns the identity element of the curve. Can be used as a constructor.
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impl<'a, 'b> Mul<&'b EdwardsPoint> for &'a Scalar

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fn mul(self, point: &'b EdwardsPoint) -> EdwardsPoint

Scalar multiplication: compute scalar * self.

For scalar multiplication of a basepoint, EdwardsBasepointTable is approximately 4x faster.

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type Output = EdwardsPoint

The resulting type after applying the * operator.
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impl<'b> Mul<&'b EdwardsPoint> for Scalar

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type Output = EdwardsPoint

The resulting type after applying the * operator.
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fn mul(self, rhs: &'b EdwardsPoint) -> EdwardsPoint

Performs the * operation. Read more
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impl<'a, 'b> Mul<&'b Scalar> for &'a EdwardsPoint

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fn mul(self, scalar: &'b Scalar) -> EdwardsPoint

Scalar multiplication: compute scalar * self.

For scalar multiplication of a basepoint, EdwardsBasepointTable is approximately 4x faster.

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type Output = EdwardsPoint

The resulting type after applying the * operator.
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impl<'b> Mul<&'b Scalar> for EdwardsPoint

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type Output = EdwardsPoint

The resulting type after applying the * operator.
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fn mul(self, rhs: &'b Scalar) -> EdwardsPoint

Performs the * operation. Read more
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impl<'a> Mul<EdwardsPoint> for &'a Scalar

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type Output = EdwardsPoint

The resulting type after applying the * operator.
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fn mul(self, rhs: EdwardsPoint) -> EdwardsPoint

Performs the * operation. Read more
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impl Mul<EdwardsPoint> for Scalar

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type Output = EdwardsPoint

The resulting type after applying the * operator.
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fn mul(self, rhs: EdwardsPoint) -> EdwardsPoint

Performs the * operation. Read more
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impl<'a> Mul<Scalar> for &'a EdwardsPoint

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type Output = EdwardsPoint

The resulting type after applying the * operator.
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fn mul(self, rhs: Scalar) -> EdwardsPoint

Performs the * operation. Read more
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impl Mul<Scalar> for EdwardsPoint

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type Output = EdwardsPoint

The resulting type after applying the * operator.
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fn mul(self, rhs: Scalar) -> EdwardsPoint

Performs the * operation. Read more
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impl<'b> MulAssign<&'b Scalar> for EdwardsPoint

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fn mul_assign(&mut self, scalar: &'b Scalar)

Performs the *= operation. Read more
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impl MulAssign<Scalar> for EdwardsPoint

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fn mul_assign(&mut self, rhs: Scalar)

Performs the *= operation. Read more
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impl MultiscalarMul for EdwardsPoint

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type Point = EdwardsPoint

The type of point being multiplied, e.g., RistrettoPoint.
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fn multiscalar_mul<I, J>(scalars: I, points: J) -> EdwardsPoint

Given an iterator of (possibly secret) scalars and an iterator of public points, compute $$ Q = c_1 P_1 + \cdots + c_n P_n. $$ Read more
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impl<'a> Neg for &'a EdwardsPoint

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type Output = EdwardsPoint

The resulting type after applying the - operator.
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fn neg(self) -> EdwardsPoint

Performs the unary - operation. Read more
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impl Neg for EdwardsPoint

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type Output = EdwardsPoint

The resulting type after applying the - operator.
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fn neg(self) -> EdwardsPoint

Performs the unary - operation. Read more
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impl PartialEq for EdwardsPoint

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fn eq(&self, other: &EdwardsPoint) -> bool

This method tests for self and other values to be equal, and is used by ==.
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fn ne(&self, other: &Rhs) -> bool

This method tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.
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impl<'a, 'b> Sub<&'b EdwardsPoint> for &'a EdwardsPoint

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type Output = EdwardsPoint

The resulting type after applying the - operator.
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fn sub(self, other: &'b EdwardsPoint) -> EdwardsPoint

Performs the - operation. Read more
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impl<'b> Sub<&'b EdwardsPoint> for EdwardsPoint

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type Output = EdwardsPoint

The resulting type after applying the - operator.
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fn sub(self, rhs: &'b EdwardsPoint) -> EdwardsPoint

Performs the - operation. Read more
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impl<'a> Sub<EdwardsPoint> for &'a EdwardsPoint

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type Output = EdwardsPoint

The resulting type after applying the - operator.
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fn sub(self, rhs: EdwardsPoint) -> EdwardsPoint

Performs the - operation. Read more
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impl Sub for EdwardsPoint

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type Output = EdwardsPoint

The resulting type after applying the - operator.
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fn sub(self, rhs: EdwardsPoint) -> EdwardsPoint

Performs the - operation. Read more
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impl<'b> SubAssign<&'b EdwardsPoint> for EdwardsPoint

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fn sub_assign(&mut self, _rhs: &'b EdwardsPoint)

Performs the -= operation. Read more
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impl SubAssign for EdwardsPoint

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fn sub_assign(&mut self, rhs: EdwardsPoint)

Performs the -= operation. Read more
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impl<T> Sum<T> for EdwardsPoint
where T: Borrow<EdwardsPoint>,

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fn sum<I>(iter: I) -> Self
where I: Iterator<Item = T>,

Method which takes an iterator and generates Self from the elements by “summing up” the items.
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impl VartimeMultiscalarMul for EdwardsPoint

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type Point = EdwardsPoint

The type of point being multiplied, e.g., RistrettoPoint.
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fn optional_multiscalar_mul<I, J>(scalars: I, points: J) -> Option<EdwardsPoint>

Given an iterator of public scalars and an iterator of Options of points, compute either Some(Q), where $$ Q = c_1 P_1 + \cdots + c_n P_n, $$ if all points were Some(P_i), or else return None. Read more
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fn vartime_multiscalar_mul<I, J>(scalars: I, points: J) -> Self::Point
where I: IntoIterator, I::Item: Borrow<Scalar>, J: IntoIterator, J::Item: Borrow<Self::Point>, Self::Point: Clone,

Given an iterator of public scalars and an iterator of public points, compute $$ Q = c_1 P_1 + \cdots + c_n P_n, $$ using variable-time operations. Read more
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impl Zeroize for EdwardsPoint

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fn zeroize(&mut self)

Reset this CompressedEdwardsPoint to the identity element.

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impl Copy for EdwardsPoint

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impl Eq for EdwardsPoint

Auto Trait Implementations§

Blanket Implementations§

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impl<T> Any for T
where T: 'static + ?Sized,

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fn type_id(&self) -> TypeId

Gets the TypeId of self. Read more
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impl<T> Borrow<T> for T
where T: ?Sized,

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fn borrow(&self) -> &T

Immutably borrows from an owned value. Read more
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impl<T> BorrowMut<T> for T
where T: ?Sized,

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fn borrow_mut(&mut self) -> &mut T

Mutably borrows from an owned value. Read more
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impl<T> CloneToUninit for T
where T: Copy,

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unsafe fn clone_to_uninit(&self, dst: *mut T)

🔬This is a nightly-only experimental API. (clone_to_uninit)
Performs copy-assignment from self to dst. Read more
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impl<T> CloneToUninit for T
where T: Clone,

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default unsafe fn clone_to_uninit(&self, dst: *mut T)

🔬This is a nightly-only experimental API. (clone_to_uninit)
Performs copy-assignment from self to dst. Read more
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impl<T> ConditionallyNegatable for T
where T: ConditionallySelectable, &'a T: for<'a> Neg<Output = T>,

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fn conditional_negate(&mut self, choice: Choice)

Negate self if choice == Choice(1); otherwise, leave it unchanged. Read more
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impl<T> From<T> for T

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fn from(t: T) -> T

Returns the argument unchanged.

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impl<T, U> Into<U> for T
where U: From<T>,

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fn into(self) -> U

Calls U::from(self).

That is, this conversion is whatever the implementation of From<T> for U chooses to do.

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impl<T> IsIdentity for T

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fn is_identity(&self) -> bool

Return true if this element is the identity element of the curve.
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impl<T> Same for T

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type Output = T

Should always be Self
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impl<T> ToOwned for T
where T: Clone,

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type Owned = T

The resulting type after obtaining ownership.
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fn to_owned(&self) -> T

Creates owned data from borrowed data, usually by cloning. Read more
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fn clone_into(&self, target: &mut T)

Uses borrowed data to replace owned data, usually by cloning. Read more
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impl<T, U> TryFrom<U> for T
where U: Into<T>,

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type Error = Infallible

The type returned in the event of a conversion error.
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fn try_from(value: U) -> Result<T, <T as TryFrom<U>>::Error>

Performs the conversion.
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impl<T, U> TryInto<U> for T
where U: TryFrom<T>,

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type Error = <U as TryFrom<T>>::Error

The type returned in the event of a conversion error.
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fn try_into(self) -> Result<U, <U as TryFrom<T>>::Error>

Performs the conversion.