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3.5.2 Test non-canonical from_repr

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Unfortunately, G::from_bytes doesn't require canonicity so that still can't
be properly tested for. While we could try to detect SEC1, and write tests
on that, there's not a suitably stable/wide enough solution to be worth it.
This commit is contained in:
Luke Parker 2023-03-07 04:05:56 -05:00
parent a053454ae4
commit ed056cceaf
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1 changed files with 18 additions and 0 deletions
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18
crypto/ff-group-tests/src/prime_field.rs
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@ -70,6 +70,24 @@ pub fn test_encoding<F: PrimeField>() {
test(F::one(), "1");
test(F::one() + F::one(), "2");
test(-F::one(), "-1");
// Also check if a non-canonical encoding is possible
let mut high = (F::zero() - F::one()).to_repr();
let mut possible_non_canon = false;
for byte in high.as_mut() {
// The fact a bit isn't set in the highest possible value suggests there's unused bits
// If there's unused bits, mark the possibility of a non-canonical encoding and set the bits
if *byte != 255 {
possible_non_canon = true;
*byte = 255;
break;
}
}
// Any non-canonical encoding should fail to be read
if possible_non_canon {
assert!(!bool::from(F::from_repr(high).is_some()));
}
}
/// Run all tests on fields implementing PrimeField.