Struct curve25519_dalek::scalar::Scalar [−][src]
The Scalar
struct holds an integer \(s < 2^{255} \) which
represents an element of \(\mathbb Z / \ell\).
Implementations
impl Scalar
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pub fn from_bytes_mod_order(bytes: [u8; 32]) -> Scalar
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Construct a Scalar
by reducing a 256-bit little-endian integer
modulo the group order \( \ell \).
pub fn from_bytes_mod_order_wide(input: &[u8; 64]) -> Scalar
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Construct a Scalar
by reducing a 512-bit little-endian integer
modulo the group order \( \ell \).
pub fn from_canonical_bytes(bytes: [u8; 32]) -> Option<Scalar>
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Attempt to construct a Scalar
from a canonical byte representation.
Return
Some(s)
, wheres
is theScalar
corresponding tobytes
, ifbytes
is a canonical byte representation;None
ifbytes
is not a canonical byte representation.
pub const fn from_bits(bytes: [u8; 32]) -> Scalar
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Construct a Scalar
from the low 255 bits of a 256-bit integer.
This function is intended for applications like X25519 which require specific bit-patterns when performing scalar multiplication.
impl Scalar
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pub fn random<R: RngCore + CryptoRng>(rng: &mut R) -> Self
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Return a Scalar
chosen uniformly at random using a user-provided RNG.
Inputs
rng
: any RNG which implements theRngCore + CryptoRng
interface.
Returns
A random scalar within ℤ/lℤ.
Example
extern crate rand_core; use curve25519_dalek::scalar::Scalar; use rand_core::OsRng; let mut csprng = OsRng; let a: Scalar = Scalar::random(&mut csprng);
pub fn hash_from_bytes<D>(input: &[u8]) -> Scalar where
D: Digest<OutputSize = U64> + Default,
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D: Digest<OutputSize = U64> + Default,
Hash a slice of bytes into a scalar.
Takes a type parameter D
, which is any Digest
producing 64
bytes (512 bits) of output.
Convenience wrapper around from_hash
.
Example
extern crate sha2; use sha2::Sha512; let msg = "To really appreciate architecture, you may even need to commit a murder"; let s = Scalar::hash_from_bytes::<Sha512>(msg.as_bytes());
pub fn from_hash<D>(hash: D) -> Scalar where
D: Digest<OutputSize = U64>,
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D: Digest<OutputSize = U64>,
Construct a scalar from an existing Digest
instance.
Use this instead of hash_from_bytes
if it is more convenient
to stream data into the Digest
than to pass a single byte
slice.
Example
extern crate sha2; use sha2::Digest; use sha2::Sha512; let mut h = Sha512::new() .chain("To really appreciate architecture, you may even need to commit a murder.") .chain("While the programs used for The Manhattan Transcripts are of the most extreme") .chain("nature, they also parallel the most common formula plot: the archetype of") .chain("murder. Other phantasms were occasionally used to underline the fact that") .chain("perhaps all architecture, rather than being about functional standards, is") .chain("about love and death."); let s = Scalar::from_hash(h); println!("{:?}", s.to_bytes()); assert!(s == Scalar::from_bits([ 21, 88, 208, 252, 63, 122, 210, 152, 154, 38, 15, 23, 16, 167, 80, 150, 192, 221, 77, 226, 62, 25, 224, 148, 239, 48, 176, 10, 185, 69, 168, 11, ]));
pub fn to_bytes(&self) -> [u8; 32]
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Convert this Scalar
to its underlying sequence of bytes.
Example
use curve25519_dalek::scalar::Scalar; let s: Scalar = Scalar::zero(); assert!(s.to_bytes() == [0u8; 32]);
pub fn as_bytes(&self) -> &[u8; 32]
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View the little-endian byte encoding of the integer representing this Scalar.
Example
use curve25519_dalek::scalar::Scalar; let s: Scalar = Scalar::zero(); assert!(s.as_bytes() == &[0u8; 32]);
pub fn zero() -> Self
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Construct the scalar \( 0 \).
pub fn one() -> Self
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Construct the scalar \( 1 \).
pub fn invert(&self) -> Scalar
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Given a nonzero Scalar
, compute its multiplicative inverse.
Warning
self
MUST be nonzero. If you cannot
prove that this is the case, you SHOULD NOT USE THIS
FUNCTION.
Returns
The multiplicative inverse of the this Scalar
.
Example
use curve25519_dalek::scalar::Scalar; // x = 2238329342913194256032495932344128051776374960164957527413114840482143558222 let X: Scalar = Scalar::from_bytes_mod_order([ 0x4e, 0x5a, 0xb4, 0x34, 0x5d, 0x47, 0x08, 0x84, 0x59, 0x13, 0xb4, 0x64, 0x1b, 0xc2, 0x7d, 0x52, 0x52, 0xa5, 0x85, 0x10, 0x1b, 0xcc, 0x42, 0x44, 0xd4, 0x49, 0xf4, 0xa8, 0x79, 0xd9, 0xf2, 0x04, ]); // 1/x = 6859937278830797291664592131120606308688036382723378951768035303146619657244 let XINV: Scalar = Scalar::from_bytes_mod_order([ 0x1c, 0xdc, 0x17, 0xfc, 0xe0, 0xe9, 0xa5, 0xbb, 0xd9, 0x24, 0x7e, 0x56, 0xbb, 0x01, 0x63, 0x47, 0xbb, 0xba, 0x31, 0xed, 0xd5, 0xa9, 0xbb, 0x96, 0xd5, 0x0b, 0xcd, 0x7a, 0x3f, 0x96, 0x2a, 0x0f, ]); let inv_X: Scalar = X.invert(); assert!(XINV == inv_X); let should_be_one: Scalar = &inv_X * &X; assert!(should_be_one == Scalar::one());
pub fn batch_invert(inputs: &mut [Scalar]) -> Scalar
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Given a slice of nonzero (possibly secret) Scalar
s,
compute their inverses in a batch.
Return
Each element of inputs
is replaced by its inverse.
The product of all inverses is returned.
Warning
All input Scalars
MUST be nonzero. If you cannot
prove that this is the case, you SHOULD NOT USE THIS
FUNCTION.
Example
let mut scalars = [ Scalar::from(3u64), Scalar::from(5u64), Scalar::from(7u64), Scalar::from(11u64), ]; let allinv = Scalar::batch_invert(&mut scalars); assert_eq!(allinv, Scalar::from(3*5*7*11u64).invert()); assert_eq!(scalars[0], Scalar::from(3u64).invert()); assert_eq!(scalars[1], Scalar::from(5u64).invert()); assert_eq!(scalars[2], Scalar::from(7u64).invert()); assert_eq!(scalars[3], Scalar::from(11u64).invert());
pub fn reduce(&self) -> Scalar
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Reduce this Scalar
modulo \(\ell\).
pub fn is_canonical(&self) -> bool
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Check whether this Scalar
is the canonical representative mod \(\ell\).
This is intended for uses like input validation, where variable-time code is acceptable.
// 2^255 - 1, since `from_bits` clears the high bit let _2_255_minus_1 = Scalar::from_bits([0xff;32]); assert!(!_2_255_minus_1.is_canonical()); let reduced = _2_255_minus_1.reduce(); assert!(reduced.is_canonical());
Trait Implementations
impl<'a, 'b> Add<&'b Scalar> for &'a Scalar
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impl<'b> Add<&'b Scalar> for Scalar
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impl<'a> Add<Scalar> for &'a Scalar
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impl Add<Scalar> for Scalar
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impl<'b> AddAssign<&'b Scalar> for Scalar
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impl AddAssign<Scalar> for Scalar
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impl Clone for Scalar
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impl ConditionallySelectable for Scalar
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impl ConstantTimeEq for Scalar
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impl Copy for Scalar
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impl Debug for Scalar
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impl Default for Scalar
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impl Eq for Scalar
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impl From<u128> for Scalar
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impl From<u16> for Scalar
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impl From<u32> for Scalar
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impl From<u64> for Scalar
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impl From<u8> for Scalar
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impl Hash for Scalar
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impl Index<usize> for Scalar
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impl<'a, 'b> Mul<&'a EdwardsBasepointTable> for &'b Scalar
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impl<'a, 'b> Mul<&'a RistrettoBasepointTable> for &'b Scalar
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impl<'b> Mul<&'b EdwardsPoint> for Scalar
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impl<'a, 'b> Mul<&'b EdwardsPoint> for &'a Scalar
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impl<'b> Mul<&'b MontgomeryPoint> for Scalar
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impl<'a, 'b> Mul<&'b MontgomeryPoint> for &'a Scalar
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impl<'a, 'b> Mul<&'b RistrettoPoint> for &'a Scalar
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impl<'b> Mul<&'b RistrettoPoint> for Scalar
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impl<'a, 'b> Mul<&'b Scalar> for &'a Scalar
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impl<'b> Mul<&'b Scalar> for Scalar
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impl<'b> Mul<&'b Scalar> for MontgomeryPoint
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impl<'a, 'b> Mul<&'b Scalar> for &'a MontgomeryPoint
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type Output = MontgomeryPoint
fn mul(self, scalar: &'b Scalar) -> MontgomeryPoint
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impl<'b> Mul<&'b Scalar> for EdwardsPoint
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impl<'a, 'b> Mul<&'b Scalar> for &'a EdwardsPoint
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impl<'a, 'b> Mul<&'b Scalar> for &'a EdwardsBasepointTable
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impl<'a, 'b> Mul<&'b Scalar> for &'a RistrettoPoint
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impl<'b> Mul<&'b Scalar> for RistrettoPoint
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impl<'a, 'b> Mul<&'b Scalar> for &'a RistrettoBasepointTable
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impl<'a> Mul<EdwardsPoint> for &'a Scalar
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impl Mul<EdwardsPoint> for Scalar
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impl<'a> Mul<MontgomeryPoint> for &'a Scalar
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impl Mul<MontgomeryPoint> for Scalar
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impl<'a> Mul<RistrettoPoint> for &'a Scalar
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impl Mul<RistrettoPoint> for Scalar
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impl<'a> Mul<Scalar> for &'a Scalar
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impl Mul<Scalar> for Scalar
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impl<'a> Mul<Scalar> for &'a MontgomeryPoint
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impl Mul<Scalar> for MontgomeryPoint
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impl<'a> Mul<Scalar> for &'a EdwardsPoint
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impl Mul<Scalar> for EdwardsPoint
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impl<'a> Mul<Scalar> for &'a RistrettoPoint
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impl Mul<Scalar> for RistrettoPoint
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impl<'b> MulAssign<&'b Scalar> for Scalar
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impl<'b> MulAssign<&'b Scalar> for MontgomeryPoint
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impl<'b> MulAssign<&'b Scalar> for EdwardsPoint
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impl<'b> MulAssign<&'b Scalar> for RistrettoPoint
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impl MulAssign<Scalar> for Scalar
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impl MulAssign<Scalar> for MontgomeryPoint
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impl MulAssign<Scalar> for EdwardsPoint
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impl MulAssign<Scalar> for RistrettoPoint
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impl<'a> Neg for &'a Scalar
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impl<'a> Neg for Scalar
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impl PartialEq<Scalar> for Scalar
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impl<T> Product<T> for Scalar where
T: Borrow<Scalar>,
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T: Borrow<Scalar>,
impl<'a, 'b> Sub<&'b Scalar> for &'a Scalar
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impl<'b> Sub<&'b Scalar> for Scalar
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impl<'a> Sub<Scalar> for &'a Scalar
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impl Sub<Scalar> for Scalar
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impl<'b> SubAssign<&'b Scalar> for Scalar
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impl SubAssign<Scalar> for Scalar
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impl<T> Sum<T> for Scalar where
T: Borrow<Scalar>,
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T: Borrow<Scalar>,
impl Zeroize for Scalar
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Auto Trait Implementations
impl RefUnwindSafe for Scalar
impl Send for Scalar
impl Sync for Scalar
impl Unpin for Scalar
impl UnwindSafe for Scalar
Blanket Implementations
impl<T> Any for T where
T: 'static + ?Sized,
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T: 'static + ?Sized,
impl<T> Borrow<T> for T where
T: ?Sized,
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T: ?Sized,
impl<T> BorrowMut<T> for T where
T: ?Sized,
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T: ?Sized,
impl<T> ConditionallyNegatable for T where
T: ConditionallySelectable,
&'a T: for<'a> Neg,
<&'a T as Neg>::Output == T,
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T: ConditionallySelectable,
&'a T: for<'a> Neg,
<&'a T as Neg>::Output == T,
impl<T> From<T> for T
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impl<T, U> Into<U> for T where
U: From<T>,
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U: From<T>,
impl<T> Same<T> for T
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type Output = T
Should always be Self
impl<T> ToOwned for T where
T: Clone,
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T: Clone,
impl<T, U> TryFrom<U> for T where
U: Into<T>,
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U: Into<T>,
impl<T, U> TryInto<U> for T where
U: TryFrom<T>,
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U: TryFrom<T>,