backend.py 文件源码

def _bn_to_int(self, bn):
        assert bn != self._ffi.NULL
        if six.PY3:
            # Python 3 has constant time from_bytes, so use that.
            bn_num_bytes = self._lib.BN_num_bytes(bn)
            bin_ptr = self._ffi.new("unsigned char[]", bn_num_bytes)
            bin_len = self._lib.BN_bn2bin(bn, bin_ptr)
            # A zero length means the BN has value 0
            self.openssl_assert(bin_len >= 0)
            return int.from_bytes(self._ffi.buffer(bin_ptr)[:bin_len], "big")
        else:
            # Under Python 2 the best we can do is hex()
            hex_cdata = self._lib.BN_bn2hex(bn)
            self.openssl_assert(hex_cdata != self._ffi.NULL)
            hex_str = self._ffi.string(hex_cdata)
            self._lib.OPENSSL_free(hex_cdata)
            return int(hex_str, 16)