# Struct elastic_elgamal::group::Curve25519Subgroup

source · `pub struct Curve25519Subgroup(/* private fields */);`

## Expand description

Prime-order subgroup of Curve25519 without any transforms performed for EC points.

Since the curve has cofactor 8, `ElementOps::deserialize_element()`

implementation
explicitly checks on deserializing each EC point that the point is torsion-free
(belongs to the prime-order subgroup), which is moderately slow (takes ~0.1ms on
a laptop).

Prefer using `Ristretto`

if compatibility with other Curve25519 applications is not a concern.
(If it *is* a concern, beware of cofactor pitfalls!)

## Trait Implementations§

source§### impl Clone for Curve25519Subgroup

### impl Clone for Curve25519Subgroup

source§#### fn clone(&self) -> Curve25519Subgroup

#### fn clone(&self) -> Curve25519Subgroup

Returns a copy of the value. Read more

1.0.0 · source§#### fn clone_from(&mut self, source: &Self)

#### fn clone_from(&mut self, source: &Self)

Performs copy-assignment from

`source`

. Read moresource§### impl Debug for Curve25519Subgroup

### impl Debug for Curve25519Subgroup

source§### impl ElementOps for Curve25519Subgroup

### impl ElementOps for Curve25519Subgroup

§#### type Element = EdwardsPoint

#### type Element = EdwardsPoint

Element of the group. Arithmetic operations requested here (addition among
elements and multiplication by a

`Scalar`

) must be constant-time.source§#### const ELEMENT_SIZE: usize = 32usize

#### const ELEMENT_SIZE: usize = 32usize

Byte size of a serialized

`Self::Element`

.source§#### fn identity() -> Self::Element

#### fn identity() -> Self::Element

Returns the identity of the group (aka point at infinity for EC groups).

source§#### fn is_identity(element: &Self::Element) -> bool

#### fn is_identity(element: &Self::Element) -> bool

Checks if the specified element is the identity.

source§#### fn serialize_element(element: &Self::Element, buffer: &mut [u8])

#### fn serialize_element(element: &Self::Element, buffer: &mut [u8])

source§#### fn deserialize_element(buffer: &[u8]) -> Option<Self::Element>

#### fn deserialize_element(buffer: &[u8]) -> Option<Self::Element>

Deserializes an element from

`buffer`

, which is guaranteed to have length
`Self::ELEMENT_SIZE`

. This method returns `None`

if the buffer
does not correspond to a representation of a valid scalar.source§### impl Group for Curve25519Subgroup

### impl Group for Curve25519Subgroup

source§#### fn mul_generator(k: &Scalar) -> Self::Element

#### fn mul_generator(k: &Scalar) -> Self::Element

Multiplies the provided scalar by

`ElementOps::generator()`

. This operation must be
constant-time. Read moresource§#### fn vartime_mul_generator(k: &Scalar) -> Self::Element

#### fn vartime_mul_generator(k: &Scalar) -> Self::Element

Multiplies the provided scalar by

`ElementOps::generator()`

.
Unlike `Self::mul_generator()`

, this operation does not need to be constant-time;
thus, it may employ additional optimizations. Read moresource§#### fn multi_mul<'a, I, J>(scalars: I, elements: J) -> Self::Element

#### fn multi_mul<'a, I, J>(scalars: I, elements: J) -> Self::Element

Multiplies provided

`scalars`

by `elements`

. This operation must be constant-time
w.r.t. the given length of elements. Read moresource§#### fn vartime_double_mul_generator(
k: &Scalar,
k_element: Self::Element,
r: &Scalar
) -> Self::Element

#### fn vartime_double_mul_generator( k: &Scalar, k_element: Self::Element, r: &Scalar ) -> Self::Element

Calculates

`k * k_element + r * G`

, where `G`

is the group generator. This operation
does not need to be constant-time. Read moresource§#### fn vartime_multi_mul<'a, I, J>(scalars: I, elements: J) -> Self::Element

#### fn vartime_multi_mul<'a, I, J>(scalars: I, elements: J) -> Self::Element

Multiplies provided

`scalars`

by `elements`

. Unlike `Self::multi_mul()`

,
this operation does not need to be constant-time; thus, it may employ
additional optimizations. Read moresource§### impl Hash for Curve25519Subgroup

### impl Hash for Curve25519Subgroup

source§### impl PartialEq for Curve25519Subgroup

### impl PartialEq for Curve25519Subgroup

source§#### fn eq(&self, other: &Curve25519Subgroup) -> bool

#### fn eq(&self, other: &Curve25519Subgroup) -> bool

This method tests for

`self`

and `other`

values to be equal, and is used
by `==`

.source§### impl ScalarOps for Curve25519Subgroup

### impl ScalarOps for Curve25519Subgroup

§#### type Scalar = Scalar

#### type Scalar = Scalar

Scalar type. As per

`Group`

contract, scalars must form a prime field.
Arithmetic operations on scalars requested here must be constant-time.source§#### const SCALAR_SIZE: usize = 32usize

#### const SCALAR_SIZE: usize = 32usize

Byte size of a serialized

`Self::Scalar`

.source§#### fn generate_scalar<R: CryptoRng + RngCore>(rng: &mut R) -> Self::Scalar

#### fn generate_scalar<R: CryptoRng + RngCore>(rng: &mut R) -> Self::Scalar

Generates a random scalar based on the provided CSPRNG. This operation
must be constant-time.

source§#### fn scalar_from_random_bytes(source: RandomBytesProvider<'_>) -> Self::Scalar

#### fn scalar_from_random_bytes(source: RandomBytesProvider<'_>) -> Self::Scalar

Generates a scalar from a

`source`

of random bytes. This operation must be constant-time.
The `source`

is guaranteed to return any necessary number of bytes. Read moresource§#### fn invert_scalar(scalar: Self::Scalar) -> Self::Scalar

#### fn invert_scalar(scalar: Self::Scalar) -> Self::Scalar

Inverts the

`scalar`

, which is guaranteed to be non-zero. This operation does not
need to be constant-time.source§#### fn invert_scalars(scalars: &mut [Self::Scalar])

#### fn invert_scalars(scalars: &mut [Self::Scalar])

Inverts scalars in a batch. This operation does not need to be constant-time. Read more

source§#### fn serialize_scalar(scalar: &Self::Scalar, buffer: &mut [u8])

#### fn serialize_scalar(scalar: &Self::Scalar, buffer: &mut [u8])

Serializes the scalar into the provided

`buffer`

, which is guaranteed to have length
`Self::SCALAR_SIZE`

.source§#### fn deserialize_scalar(buffer: &[u8]) -> Option<Self::Scalar>

#### fn deserialize_scalar(buffer: &[u8]) -> Option<Self::Scalar>

Deserializes the scalar from

`buffer`

, which is guaranteed to have length
`Self::SCALAR_SIZE`

. This method returns `None`

if the buffer
does not correspond to a representation of a valid scalar.### impl Copy for Curve25519Subgroup

### impl Eq for Curve25519Subgroup

### impl StructuralPartialEq for Curve25519Subgroup

## Auto Trait Implementations§

### impl Freeze for Curve25519Subgroup

### impl RefUnwindSafe for Curve25519Subgroup

### impl Send for Curve25519Subgroup

### impl Sync for Curve25519Subgroup

### impl Unpin for Curve25519Subgroup

### impl UnwindSafe for Curve25519Subgroup

## Blanket Implementations§

source§### impl<T> BorrowMut<T> for Twhere
T: ?Sized,

### impl<T> BorrowMut<T> for Twhere
T: ?Sized,

source§#### fn borrow_mut(&mut self) -> &mut T

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

Mutably borrows from an owned value. Read more