class Security:

    def __init__(self):

        import os

        env = os.environ

        if env.has_key('PYTHON_KEYFILE'):

            keyfile = env['PYTHON_KEYFILE']

        else:

            keyfile = '.python_keyfile'

            if env.has_key('HOME'):

                keyfile = os.path.join(env['HOME'], keyfile)

            if not os.path.exists(keyfile):

                import sys

                for dir in sys.path:

                    kf = os.path.join(dir, keyfile)

                    if os.path.exists(kf):

                        keyfile = kf

                        break

        try:

            self._key = eval(open(keyfile).readline())

        except IOError:

            raise IOError, "python keyfile %s: cannot open" % keyfile

    def _generate_challenge(self):

        import random

        return random.randint(100, 100000)

    def _compare_challenge_response(self, challenge, response):

        return self._encode_challenge(challenge) == response

    def _encode_challenge(self, challenge):

        p, m = self._key

        return pow(long(challenge), p, m)