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use crate::{
bigint::Encoding as _,
ops::Invert,
rand_core::{CryptoRng, RngCore},
Curve, Error, FieldBytes, ProjectiveArithmetic, Result, Scalar,
};
use core::{convert::TryFrom, ops::Deref};
use ff::{Field, PrimeField};
use generic_array::GenericArray;
use subtle::{Choice, ConditionallySelectable, ConstantTimeEq, CtOption};
#[cfg(feature = "zeroize")]
use {crate::SecretKey, zeroize::Zeroize};
#[cfg_attr(docsrs, doc(cfg(feature = "arithmetic")))]
#[derive(Clone)]
pub struct NonZeroScalar<C>
where
C: Curve + ProjectiveArithmetic,
{
scalar: Scalar<C>,
}
impl<C> NonZeroScalar<C>
where
C: Curve + ProjectiveArithmetic,
{
pub fn random(mut rng: impl CryptoRng + RngCore) -> Self {
loop {
if let Some(result) = Self::new(Field::random(&mut rng)) {
break result;
}
}
}
pub fn from_repr(repr: FieldBytes<C>) -> Option<Self> {
Scalar::<C>::from_repr(repr).and_then(Self::new)
}
pub fn new(scalar: Scalar<C>) -> Option<Self> {
if scalar.is_zero() {
None
} else {
Some(Self { scalar })
}
}
}
impl<C> AsRef<Scalar<C>> for NonZeroScalar<C>
where
C: Curve + ProjectiveArithmetic,
{
fn as_ref(&self) -> &Scalar<C> {
&self.scalar
}
}
impl<C> ConditionallySelectable for NonZeroScalar<C>
where
C: Curve + ProjectiveArithmetic,
{
fn conditional_select(a: &Self, b: &Self, choice: Choice) -> Self {
Self {
scalar: Scalar::<C>::conditional_select(&a.scalar, &b.scalar, choice),
}
}
}
impl<C> ConstantTimeEq for NonZeroScalar<C>
where
C: Curve + ProjectiveArithmetic,
{
fn ct_eq(&self, other: &Self) -> Choice {
self.scalar.ct_eq(&other.scalar)
}
}
impl<C> Copy for NonZeroScalar<C> where C: Curve + ProjectiveArithmetic {}
impl<C> Deref for NonZeroScalar<C>
where
C: Curve + ProjectiveArithmetic,
{
type Target = Scalar<C>;
fn deref(&self) -> &Scalar<C> {
&self.scalar
}
}
impl<C> From<NonZeroScalar<C>> for FieldBytes<C>
where
C: Curve + ProjectiveArithmetic,
{
fn from(scalar: NonZeroScalar<C>) -> FieldBytes<C> {
Self::from(&scalar)
}
}
impl<C> From<&NonZeroScalar<C>> for FieldBytes<C>
where
C: Curve + ProjectiveArithmetic,
{
fn from(scalar: &NonZeroScalar<C>) -> FieldBytes<C> {
scalar.scalar.to_repr()
}
}
#[cfg(feature = "zeroize")]
#[cfg_attr(docsrs, doc(cfg(feature = "zeroize")))]
impl<C> From<SecretKey<C>> for NonZeroScalar<C>
where
C: Curve + ProjectiveArithmetic,
{
fn from(sk: SecretKey<C>) -> NonZeroScalar<C> {
Self::from(&sk)
}
}
#[cfg(feature = "zeroize")]
#[cfg_attr(docsrs, doc(cfg(feature = "zeroize")))]
impl<C> From<&SecretKey<C>> for NonZeroScalar<C>
where
C: Curve + ProjectiveArithmetic,
{
fn from(sk: &SecretKey<C>) -> NonZeroScalar<C> {
let scalar = sk.as_scalar_bytes().to_scalar();
debug_assert!(!scalar.is_zero());
Self { scalar }
}
}
impl<C> Invert for NonZeroScalar<C>
where
C: Curve + ProjectiveArithmetic,
{
type Output = Scalar<C>;
fn invert(&self) -> CtOption<Self::Output> {
ff::Field::invert(&self.scalar)
}
}
impl<C> TryFrom<&[u8]> for NonZeroScalar<C>
where
C: Curve + ProjectiveArithmetic,
{
type Error = Error;
fn try_from(bytes: &[u8]) -> Result<Self> {
if bytes.len() == C::UInt::BYTE_SIZE {
NonZeroScalar::from_repr(GenericArray::clone_from_slice(bytes)).ok_or(Error)
} else {
Err(Error)
}
}
}
#[cfg(feature = "zeroize")]
impl<C> Zeroize for NonZeroScalar<C>
where
C: Curve + ProjectiveArithmetic,
Scalar<C>: Zeroize,
{
fn zeroize(&mut self) {
self.scalar.zeroize();
}
}