# [Easy] Identify Yourself (100 points)
> The smart city is implementing a digital identity to keep sensitive data away from the AI. Can you confirm that it is securely implemented?>> Author information: This challenge is developed by [Bob@DeloitteBe](https://www.linkedin.com/in/bob-van-der-smissen/).
- Decompile the APK- AES CBC mode- Initialisation Vector present- 4 digit pin repeated four times to create AES key- Bruteforcing all 4 digit positions -> 10^4 total combinations
```pyimport base64import string
from Crypto.Util.number import *from Crypto.Cipher import AES
with open('session.raw') as file:  content = file.read().strip()
enc_key = base64.b64decode(content.split(':')[0])enc_data = base64.b64decode(content.split(':')[1])iv = b'1234567812345678'
for a in range(0, 10):  for b in range(0, 10):    for c in range(0, 10):      for d in range(0, 10):        pin = str(a) + str(b) + str(c) + str(d)        key = pin * 4        cipher = AES.new(key.encode(), AES.MODE_CBC, iv)        dec = cipher.decrypt(enc_key)        cipher = AES.new(dec[:32], AES.MODE_CBC, iv)        dec = cipher.decrypt(enc_data)         if b'CTF' in dec:          print('Pin:', pin)          print(dec.decode())
```