vigenere cipher

vigenere-cipher.py

# encoding: utf8
# vigenere cipher
# https://stackoverflow.com/a/2490718/1675586

def encode(key, string):
    encoded_chars = []
    for i in range(len(string)):
        key_c = key[i % len(key)]
        encoded_c = chr(ord(string[i]) + ord(key_c) % 256)
        encoded_chars.append(encoded_c)
    encoded_string = ''.join(encoded_chars)
    return encoded_string

def decode(key, string):
    encoded_chars = []
    for i in range(len(string)):
        key_c = key[i % len(key)]
        encoded_c = chr((ord(string[i]) - ord(key_c) + 256) % 256)
        encoded_chars.append(encoded_c)
    encoded_string = ''.join(encoded_chars)
    return encoded_string

e = encode('a key', 'a message')
d = decode('a key', e)
print([e])
print([d])

# python 3
# ['Â@ØÊìÔ\x81ÒÊ']
# ['a message']

# python 2
# ['\xc2@\xd8\xca\xec\xd4\x81\xd2\xca']
# ['a message']


#--------------------------------------------------
# this version makes it also base64:


import six, base64

def encode(key, string):
    encoded_chars = []
    for i in range(len(string)):
        key_c = key[i % len(key)]
        encoded_c = chr(ord(string[i]) + ord(key_c) % 256)
        encoded_chars.append(encoded_c)
    encoded_string = ''.join(encoded_chars)
    encoded_string = encoded_string.encode('latin') if six.PY3 else encoded_string
    return base64.urlsafe_b64encode(encoded_string).rstrip(b'=')

def decode(key, string):
    string = base64.urlsafe_b64decode(string + b'===')
    string = string.decode('latin') if six.PY3 else string
    encoded_chars = []
    for i in range(len(string)):
        key_c = key[i % len(key)]
        encoded_c = chr((ord(string[i]) - ord(key_c) + 256) % 256)
        encoded_chars.append(encoded_c)
    encoded_string = ''.join(encoded_chars)
    return encoded_string

e = encode('a key', 'a message')
d = decode('a key', e)
print([e])
print([d])

# python 3
# [b'wkDYyuzUgdLK']
# ['a message']

# python 2
# ['wkDYyuzUgdLK']
# ['a message']