def encode(key, string):
encoded_chars = []
for i in xrange(string):
key_c = key[i % len(key)]
encoded_c = chr(ord(string[i]) + ord(encoded_c) % 256)
encoded_chars.append(encoded_c)
encoded_string = "".join(encoded_chars)
return base64.urlsafe_b64encode(encoded_string)
