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Merge pull request #260 from fabric-and-ink/ed-decompress-simplify

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Remove unneeded check for negativity in edwards point decompression
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Henry de Valence 2019-08-07 12:57:24 -07:00 committed by GitHub
commit b01888a929
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1 changed files with 3 additions and 4 deletions
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src/edwards.rs
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@ -190,11 +190,10 @@ impl CompressedEdwardsY {
if is_valid_y_coord.unwrap_u8() != 1u8 { return None; } if is_valid_y_coord.unwrap_u8() != 1u8 { return None; }
// Flip the sign of X if it's not correct // FieldElement::sqrt_ratio_i always returns the nonnegative square root,
// so we negate according to the supplied sign bit.
let compressed_sign_bit = Choice::from(self.as_bytes()[31] >> 7); let compressed_sign_bit = Choice::from(self.as_bytes()[31] >> 7);
let current_sign_bit = X.is_negative(); X.conditional_negate(compressed_sign_bit);
X.conditional_negate(current_sign_bit ^ compressed_sign_bit);
Some(EdwardsPoint{ X: X, Y: Y, Z: Z, T: &X * &Y }) Some(EdwardsPoint{ X: X, Y: Y, Z: Z, T: &X * &Y })
} }