"""

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()