How to decrypt the encrypted string coming from python? - ios

Question

I get a encrypted base64 string from python. The format is AES 256 CBC. But when I try to decrypt using iOS Swift it return decrypted string as nil.
# coding=utf-8
import base64
from random import choice
from string import letters
try:
from Crypto import Random
from Crypto.Cipher import AES
except ImportError:
import crypto
import sys
sys.modules['Crypto'] = crypto
from crypto.Cipher import AES
from crypto import Random
class AESCipher(object):
def __init__(self, key):
self.bs = 32
self.key = key
def encrypt(self, raw):
_raw = raw
raw = self._pad(raw)
print raw, ';'
print _raw, ';'
iv = "".join([choice(letters[:26]) for i in xrange(16)])
print " iv :", iv
cipher = AES.new(self.key, AES.MODE_CBC, iv)
return base64.b64encode(iv + cipher.encrypt(raw))
def decrypt(self, enc):
enc = base64.b64decode(enc)
iv = enc[:AES.block_size]
cipher = AES.new(self.key, AES.MODE_CBC, iv)
return self._unpad(cipher.decrypt(enc[AES.block_size:])).decode('utf-8')
def _pad(self, s):
a = (self.bs - len(s) % self.bs)
b = chr(self.bs - len(s) % self.bs)
return s + a * b
#staticmethod
def _unpad(s):
return s[:-ord(s[len(s) - 1:])]
def encrypt(k, t):
o = AESCipher(k)
return o.encrypt(t)
def decrypt(k, t):
o = AESCipher(k)
return o.decrypt(t)
def main():
k = "qwertyuiopasdfghjklzxcvbnmqwerty"
s1 = "Hello World!"
d2 = encrypt(k, s1)
print " Password :", k
print "Encrypted :", d2
print " Plain :", decrypt(k, d2)
if __name__ == '__main__':
main()
iOS
Here I use AES256CBC Lib https://github.com/SwiftyBeaver/AES256CBC
let decrypted = AES256CBC.decryptString("Ymdqc3ZqdmZ1cXdsZG1sZenhgr4Xt0+ceARYRh1n40QkNDV/dyKbQjYLcbiXBBeO", password: "qwertyuiopasdfghjklzxcvbnmqwerty")
print("decrypted: \(String(describing: decrypted))") // here I get nil
when python run I get this Logs
iv : bgjsvjvfuqwldmle
Password : qwertyuiopasdfghjklzxcvbnmqwerty
Encrypted : Ymdqc3ZqdmZ1cXdsZG1sZenhgr4Xt0+ceARYRh1n40QkNDV/dyKbQjYLcbiXBBeO
Plain : Hello World!
I don't know why python and iOS not same in AES. Anyone solve this issue please put answer below. Thanks in advance.

Answer 1

I think you need to decode your base64 string first.
Maybe this will work (just googled it, I'm not a iOS dev, so I'm sorry to eventual errors)
let decodedData = NSData("Ymdqc3ZqdmZ1cXdsZG1sZenhgr4Xt0+ceARYRh1n40QkNDV/dyKbQjYLcbiXBBeO": base64String, options:NSDataBase64DecodingOptions.fromRaw(0)!)
let decodedString = NSString(data: decodedData, encoding: NSUTF8StringEncoding)
let decrypted = AES256CBC.decryptString(decodedString, password: "qwertyuiopasdfghjklzxcvbnmqwerty")
print("decrypted: \(String(describing: decrypted))")
It's also stated in the documentation