hotp.py 文件源码

def _dynamic_truncate(self, counter):
        ctx = hmac.HMAC(self._key, self._algorithm, self._backend)
        ctx.update(struct.pack(">Q", counter))
        hmac_value = ctx.finalize()

        offset = six.indexbytes(hmac_value, len(hmac_value) - 1) & 0b1111
        p = hmac_value[offset:offset + 4]
        return struct.unpack(">I", p)[0] & 0x7fffffff