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k256: remove Scalar::conditional_add_bit #431

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Merged
tarcieri merged 1 commit into from
Sep 14, 2021
Merged

k256: remove Scalar::conditional_add_bit #431

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10 changes: 0 additions & 10 deletions k256/src/arithmetic/scalar.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -353,16 +353,6 @@ impl Scalar {
Self(U256::from_be_slice(bytes))
}

/// If `flag` evaluates to `true`, adds `(1 << bit)` to `self`.
fn conditional_add_bit(&self, bit: usize, flag: Choice) -> Self {
debug_assert!(bit < 256);

// Construct Scalar(1 << bit).
// Since the 255-th bit of the modulus is 1, this will always be within range.
let w = Scalar(U256::ONE << bit);
Self::conditional_select(self, &(self.add(&w)), flag)
}

/// Raises the scalar to the power `2^k`.
fn pow2k(&self, k: usize) -> Self {
let mut x = *self;
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2 changes: 1 addition & 1 deletion k256/src/arithmetic/scalar/wide32.rs
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Expand Up @@ -227,7 +227,7 @@ impl WideScalar {

// Check the highmost discarded bit and round up if it is set.
let c = (l[(shift - 1) >> 5] >> ((shift - 1) & 0x1f)) & 1;
res.conditional_add_bit(0, Choice::from(c as u8))
Scalar::conditional_select(&res, &res.add(&Scalar::ONE), Choice::from(c as u8))
}

#[inline(always)] // only used in Scalar::mul(), so won't cause binary bloat
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2 changes: 1 addition & 1 deletion k256/src/arithmetic/scalar/wide64.rs
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Expand Up @@ -115,7 +115,7 @@ impl WideScalar {

// Check the highmost discarded bit and round up if it is set.
let c = (l[(shift - 1) >> 6] >> ((shift - 1) & 0x3f)) & 1;
res.conditional_add_bit(0, Choice::from(c as u8))
Scalar::conditional_select(&res, &res.add(&Scalar::ONE), Choice::from(c as u8))
}

#[inline(always)] // only used in Scalar::mul(), so won't cause binary bloat
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