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primefield: remove shr support #1320

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Merged
tarcieri merged 1 commit into from
Jul 21, 2025
Merged

primefield: remove shr support #1320

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2 changes: 1 addition & 1 deletion Cargo.lock
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50 changes: 1 addition & 49 deletions p521/src/arithmetic/scalar.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -18,7 +18,7 @@ use self::scalar_impl::*;
use crate::{FieldBytes, NistP521, U576};
use core::{
iter::{Product, Sum},
ops::{Add, AddAssign, Mul, MulAssign, Neg, Shr, ShrAssign, SubAssign},
ops::{Add, AddAssign, Mul, MulAssign, Neg, SubAssign},
};
use elliptic_curve::{
Curve as _, Error, FieldBytesEncoding, Result,
Expand Down Expand Up @@ -305,32 +305,6 @@ impl Scalar {
res
}

/// Right shifts the scalar.
///
/// Note: not constant-time with respect to the `shift` parameter.
#[cfg(target_pointer_width = "32")]
pub const fn shr_vartime(&self, shift: u32) -> Scalar {
Self(fiat_p521_scalar_montgomery_domain_field_element(
u32x18_to_u64x9(
&U576::from_words(u64x9_to_u32x18(self.as_limbs()))
.wrapping_shr_vartime(shift)
.to_words(),
),
))
}

/// Right shifts the scalar.
///
/// Note: not constant-time with respect to the `shift` parameter.
#[cfg(target_pointer_width = "64")]
pub const fn shr_vartime(&self, shift: u32) -> Scalar {
Self(fiat_p521_scalar_montgomery_domain_field_element(
U576::from_words(self.into_limbs())
.wrapping_shr_vartime(shift)
.to_words(),
))
}

/// Borrow the inner limbs of this scalar.
pub(crate) const fn as_limbs(&self) -> &[u64; 9] {
&self.0.0
Expand Down Expand Up @@ -551,28 +525,6 @@ impl IsHigh for Scalar {
}
}

impl Shr<usize> for Scalar {
type Output = Self;

fn shr(self, rhs: usize) -> Self::Output {
self.shr_vartime(rhs as u32)
}
}

impl Shr<usize> for &Scalar {
type Output = Scalar;

fn shr(self, rhs: usize) -> Self::Output {
self.shr_vartime(rhs as u32)
}
}

impl ShrAssign<usize> for Scalar {
fn shr_assign(&mut self, rhs: usize) {
*self = *self >> rhs;
}
}

impl PrimeField for Scalar {
type Repr = FieldBytes;

Expand Down
66 changes: 0 additions & 66 deletions primefield/src/lib.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -197,22 +197,6 @@ macro_rules! field_element_type {

res
}

/// Right shifts the [`
#[doc = stringify!($fe)]
/// `].
pub const fn shr(&self, shift: u32) -> Self {
Self(self.0.wrapping_shr(shift))
}

/// Right shifts the [`
#[doc = stringify!($fe)]
/// `].
///
/// Note: not constant-time with respect to the `shift` parameter.
pub const fn shr_vartime(&self, shift: u32) -> Self {
Self(self.0.wrapping_shr_vartime(shift))
}
}

impl $crate::ff::Field for $fe {
Expand Down Expand Up @@ -323,56 +307,6 @@ macro_rules! field_element_type {
}
}

impl ::core::ops::Shr<u32> for $fe {
type Output = Self;

#[inline]
fn shr(self, rhs: u32) -> Self {
Self::shr(&self, rhs)
}
}

impl ::core::ops::Shr<u32> for &$fe {
type Output = Self;

#[inline]
fn shr(self, rhs: u32) -> Self {
Self::shr(self, rhs)
}
}

impl ::core::ops::ShrAssign<u32> for $fe {
#[inline]
fn shr_assign(&mut self, rhs: u32) {
*self = Self::shr(self, rhs)
}
}

impl ::core::ops::Shr<usize> for $fe {
type Output = Self;

#[inline]
fn shr(self, rhs: usize) -> Self {
Self::shr(&self, rhs as u32)
}
}

impl ::core::ops::Shr<usize> for &$fe {
type Output = Self;

#[inline]
fn shr(self, rhs: usize) -> Self {
Self::shr(self, rhs as u32)
}
}

impl ::core::ops::ShrAssign<usize> for $fe {
#[inline]
fn shr_assign(&mut self, rhs: usize) {
*self = Self::shr(self, rhs as u32)
}
}

impl ::core::fmt::Debug for $fe {
fn fmt(&self, f: &mut ::core::fmt::Formatter<'_>) -> ::core::fmt::Result {
write!(f, "{}(0x{:X})", stringify!($fe), &self.0)
Expand Down