1. class CaptchaStore(models.Model):
    2.     id = models.AutoField(primary_key=True)
    3.     challenge = models.CharField(blank=False, max_length=32)
    4.     response = models.CharField(blank=False, max_length=32)
    5.     hashkey = models.CharField(blank=False, max_length=40, unique=True)
    6.     expiration = models.DateTimeField(blank=False)
    8.     def save(self, *args, **kwargs):
    9.         self.response = self.response.lower()
    10.         if not self.expiration:
    11.             self.expiration = timezone.now() + datetime.timedelta(
    12.                 minutes=int(captcha_settings.CAPTCHA_TIMEOUT)
    13.             )
    14.         if not self.hashkey:
    15.             key_ = (
    16.                 smart_text(randrange(0, MAX_RANDOM_KEY))
    17.                 + smart_text(time.time())
    18.                 + smart_text(self.challenge, errors="ignore")
    19.                 + smart_text(self.response, errors="ignore")
    20.             ).encode("utf8")
    21.             self.hashkey = hashlib.sha1(key_).hexdigest()
    22.             del key_
    23.         super(CaptchaStore, self).save(*args, **kwargs)
    25.     def __str__(self):
    26.         return self.challenge
    28.     def remove_expired(cls):
    29.         cls.objects.filter(expiration__lte=timezone.now()).delete()
    31.     remove_expired = classmethod(remove_expired)
    33.     @classmethod
    34.     def generate_key(cls, generator=None):
    35.         challenge, response = captcha_settings.get_challenge(generator)()
    36.         store = cls.objects.create(challenge=challenge, response=response)
    38.         return store.hashkey