Remove sgn0 method

k256/src/arithmetic/field.rs

@@ -265,14 +265,6 @@ impl FieldElement {
  pub fn modulus_as_biguint() -> BigUint {
  Self::one().negate(1).to_biguint().unwrap() + 1.to_biguint().unwrap()
  }
-
- /// Return the parity of the field
- /// 1 == negative
- /// 0 == non-negative
- pub fn sgn0(&self) -> Choice {
- let bytes = self.to_bytes();
- (bytes[31] & 1).into()
- }
 }
 
 impl ConditionallySelectable for FieldElement {

k256/src/arithmetic/hash2curve.rs

@@ -46,7 +46,7 @@ impl FromOkm for FieldElement {
 
 impl Sgn0 for FieldElement {
  fn sgn0(&self) -> Choice {
- FieldElement::sgn0(self)
+ self.is_odd()
  }
 }
 
@@ -126,7 +126,7 @@ impl OsswuMap for FieldElement {
  // if e2, y = y1, else y = y2
  let mut y = Self::conditional_select(&y2, &y1, e2);
 
- y.conditional_assign(&-y, self.sgn0() ^ y.sgn0());
+ y.conditional_assign(&-y, self.normalize().sgn0() ^ y.normalize().sgn0());
  (x, y)
  }
 }

p256/src/arithmetic/field.rs

@@ -194,7 +194,8 @@ impl FieldElement {
  ///
  /// If odd, return `Choice(1)`. Otherwise, return `Choice(0)`.
  pub fn is_odd(&self) -> Choice {
- self.sgn0()
+ let bytes = self.to_bytes();
+ (bytes[31] & 1).into()
  }
 
  /// Returns self + rhs mod p
@@ -465,14 +466,6 @@ impl FieldElement {
  (&sqrt * &sqrt).ct_eq(self), // Only return Some if it's the square root.
  )
  }
-
- /// Return the parity of the field
- /// 1 == negative
- /// 0 == non-negative
- pub fn sgn0(&self) -> Choice {
- let bytes = self.to_bytes();
- (bytes[31] & 1).into()
- }
 }
 
 impl Add<FieldElement> for FieldElement {

p256/src/arithmetic/hash2curve.rs

@@ -48,7 +48,7 @@ impl FromOkm for FieldElement {
 
 impl Sgn0 for FieldElement {
  fn sgn0(&self) -> Choice {
- FieldElement::sgn0(self)
+ self.is_odd()
  }
 }