XOR Message Encryption

#XOR encryption mode
#keeps messages from existing in plaintext form by encrypting them immediately. Generates random key which can be #written to a file and stored elsewhere otherwise they can never be opened!


#!/usr/bin/env python2

from os import urandom

#generates xor key and string variable
def genkey(length):
    """Generate key"""
    return urandom(length * 2)

def xor_strings(s,t):
    """xor two strings together"""
    return "".join(chr(ord(a)^ord(b)) for a,b in zip(s,t))

#checks input to match encrypt or decrypt option
while True:
    user_input = raw_input('(E)ncrypt or (D)ecrypt? ')
    if user_input in ['E', 'D', 'e', 'd']:
        break
    else:
        print('That is not a valid option!')

if user_input in ['E', 'e']:
    #prompts for message and opens appropriate filenames
    message =raw_input(b"What is your message? ")
    file1=open(raw_input(b"Enter the full filepath to write to: "), 'w')
    file2=open(raw_input(b"Enter a filepath for the key: "), 'w')
    print 'message:', message
    #prints key
    key = genkey(len(message))
    print 'key:', key
    #prints code and key to files
    cipherText = xor_strings(message, key)
    coded = cipherText
    print 'cipherText:', cipherText
    file1.write(coded)
    file1.close()
    file2.write(key)
    file2.close()

    # verifies code and key
    if xor_strings(cipherText, key) == message:
        print 'Encode passed'
    else:
        print 'Encode failed'

elif user_input in ['d', 'D']:
    #opens encrypted file
    file1=open(raw_input("What is the full filepath of the file containing the message? "))
    file2=open(raw_input("What is the full filepath of the file containing the key? "))
    #reads encrypted file
    message=file1.read()
    key=file2.read()
    #prints decrypted message/contents
    print 'decrypted:', xor_strings(message, key)