diff options
Diffstat (limited to 'pyecsca')
| -rw-r--r-- | pyecsca/ec/mod.py | 18 |
1 files changed, 6 insertions, 12 deletions
diff --git a/pyecsca/ec/mod.py b/pyecsca/ec/mod.py index 978b853..487dc03 100644 --- a/pyecsca/ec/mod.py +++ b/pyecsca/ec/mod.py @@ -767,23 +767,17 @@ if has_flint: return FlintMod(res, self._ctx, ensure=False) def is_residue(self) -> bool: - mod = self.n - if not _fmpz_is_prime(mod): - raise NotImplementedError - if self.x == 0: - return True - if mod == 2: - return self.x in (0, 1) - legendre_symbol = jacobi(int(self.x), int(mod)) - return legendre_symbol == 1 + res = self.sqrt() + return res is not None def sqrt(self) -> "FlintMod": mod = self.n if not _fmpz_is_prime(mod): raise NotImplementedError - if self.x == 0: - return FlintMod(self._ctx(0), self._ctx, ensure=False) - if not self.is_residue(): + try: + res = flint.fmpz(int(self.x)).sqrtmod(mod) + return FlintMod(self._ctx(res), self._ctx, ensure=False) + except ValueError: raise_non_residue() if mod % 4 == 3: |