enigma.py

#enigma machine
#---------------
# Usage:
# to encypt use python enigma.py string-text int-key1 int-key2 int-key3 encrypt
# to decrype use python enigma.py string-text int-key1 int-key2 int-key3 decrypt
#
# when encrypting set keys to 0 to select random key
#
#
#------
import random
import sys
#global vars
key1 = 0
key2 = 0
key3 = 0
alpha = ['a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j', 'k', 'l', 'm', 'n', 'o', 'p', 'q', 'r', 's', 't', 'u', 'v', 'w', 'x', 'y', 'z']

def input_string(mode, T):
    T = T.lower()
    RT = [] # creating a list for later
    LT = list(T)
    print LT
    for a in range(0, len(LT)): # remove spaces
        if LT[a] == " ":
            LT[a] = '' #---
    for a in range(0, len(LT)):
        if mode == "encrypt":
            RT.append(encrypter(LT[a])) #encryps each letter and appends it to a new list
        elif mode == "decrypt":
            RT.append(decrypter(LT[a])) #encryps each letter and appends it to a new list

    return RT

def key_increment():
    global key1
    global key2
    global key3
    key1 +=1
    if key1 > 25:
        key1 = 0
        key2 += 1
        if key2 > 25:
            key2 = 0
            key3 += 1
            if key3 >25:
                key3 = 0

def encrypter(L):
    global key1
    global key2
    global key3
    global alpha
    encryption = key3 * key2 * key1 # creates a number between 0 and 15625
    pos = alpha.index(L) # finds the position of the letter in the alphabet
    eL = alpha[(pos + encryption)%26] # adds the result of the keys to the position of the letter while looping arround the alphabet
    key_increment() #increments the key by 1
    return eL # returns the now encrypted letter


def decrypter(L): # same as encrypt
    global key1
    global key2
    global key3
    global alpha
    encryption = key3 * key2 * key1
    pos = alpha.index(L)
    eL = alpha[(pos - encryption)%26] # simply reverses the modulo rather than adding it
    key_increment()
    return eL

def main(mode, T, k1, k2, k3):
    global key1
    global key2
    global key3
    enT = input_string(mode, T)
    print("input is %s k1 = %s k2 = %s k3 = %s and output is %s" %(T, k1, k2, k3, enT))

if __name__ == "__main__":
    try:
        T = sys.argv[1] #gathering system variables
        key1 = int(sys.argv[2])
        key2 = int(sys.argv[3])
        key3 = int(sys.argv[4])
        mode = sys.argv[5]#---
    except:
        print("incorerct format. please read code for correct format.")
        sys.exit()
    if(key1 == 0 and key2 == 0 and key3 == 0): # sets keys to random values if set to 0
        key1 = random.randint(1, 25)
        key2 = random.randint(1, 25)
        key3 = random.randint(1, 25)#---
    #try:
    main(mode, T, key1, key2, key3)
    #except:
    #   print("error in main()")