"""

 Name: rsa - RSA encryption and decryption

 Description: RSA-based encryption and decryption of messages.

 Author: Eugen Sawin <sawine@me73.com>

 """

 MAX_PRIME = 120

 from random import choice

 def main():

     args = parse_args()

     if args.e:

         m, e, n = args.e

         print encrypt(m, e, n)

     elif args.d:

         c, d, n = args.d

         print decrypt(c, d, n)

     else:

         print create_keys()

 from prime import safe_is_prime as isprime

 def create_keys():

     primes = [p for p in xrange(3, MAX_PRIME) if isprime(p)]

     p = choice(primes)

     q = choice(primes)

     n = p * q

     pn = (p-1)*(q-1)

     e = choice(range(2, pn))

     (ggt, d, k) =[int(i) for i in extended_euclid(e, pn)]

     while ggt != 1 or d < 0:

         e = choice(range(2, pn))

         (ggt, d, k) = [int(i) for i in extended_euclid(e, pn)]

     return ((e, n), (d, n))

 def encrypt(m, e, n):

     c = m**e%n

     return c

 def decrypt(c, d, n):

     m = c**d%n

     return m

 from math import floor

 def extended_euclid(a, b):

     if b == 0:

         return (a, 1, 0)

     (ds, ss, ts) = extended_euclid(b, a%b)

     (d, s, t) = (ds, ts, ss - floor(a/b)*ts)

     return (d, s, t)    

 from argparse import ArgumentParser

 def parse_args():

     parser = ArgumentParser(description='Applies the Dijkstra algorithm for the single source shortest path problem.')

     parser.add_argument('-e', metavar=('M', 'K', 'N'), type=int, nargs=3, help='sequence of (u, v, c(u,v))')

     parser.add_argument('-d', metavar=('M', 'K', 'N'), type=int, nargs=3, help='source vertex')

     return parser.parse_args()

 if __name__ == "__main__":

     main()