saymrwulf/risc0-curve25519-dalek-source
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fixup! Properly handle exceptional points.

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This commit is contained in:
Henry de Valence 2017-02-27 23:15:39 -08:00
parent db53b58e89
commit 5d3d114628
1 changed files with 11 additions and 5 deletions
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16
src/curve.rs
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@ -462,7 +462,7 @@ impl ProjectivePoint {
let u = &Z_plus_Y * &Z_minus_Y.invert(); let u = &Z_plus_Y * &Z_minus_Y.invert();
if Z_minus_Y.is_zero() == 0u8 { if Z_minus_Y.is_zero() == 0u8 {
CompressedMontgomeryU(u.to_bytes()) Some(CompressedMontgomeryU(u.to_bytes()))
} else { } else {
None None
} }
@ -512,8 +512,14 @@ impl ExtendedPoint {
} }
} }
/// Compress this point to `CompressedMontgomeryU` format /// Convert this point to a `CompressedMontgomeryU`.
pub fn compress_montgomery(&self) -> CompressedMontgomeryU { /// Note that this discards the sign.
///
/// # Return
/// - `None` if `self` is the identity point;
/// - `Some(CompressedMontgomeryU)` otherwise.
///
pub fn compress_montgomery(&self) -> Option<CompressedMontgomeryU> {
self.to_projective().compress_montgomery() self.to_projective().compress_montgomery()
} }
} }
@ -1076,7 +1082,7 @@ mod test {
#[test] #[test]
fn test_basepoint_to_montgomery() { fn test_basepoint_to_montgomery() {
let bp = BASE_CMPRSSD.decompress().unwrap(); let bp = BASE_CMPRSSD.decompress().unwrap();
let bp_monty = bp.compress_montgomery(); let bp_monty = bp.compress_montgomery().unwrap();
assert_eq!(bp_monty, BASE_CMPRSSD_MONTY); assert_eq!(bp_monty, BASE_CMPRSSD_MONTY);
} }
@ -1106,7 +1112,7 @@ mod test {
#[test] #[test]
fn test_identity_to_monty() { fn test_identity_to_monty() {
let id = ExtendedPoint::identity(); let id = ExtendedPoint::identity();
assert!(id.compressed_montgomery().is_none()); assert!(id.compress_montgomery().is_none());
} }
/// Test round-trip decompression for the basepoint. /// Test round-trip decompression for the basepoint.