Exploit the block cipher more to recover the secret

enterprise_grade_encryption.py

#!/usr/bin/env python

from Crypto.Cipher import AES
from binascii import hexlify
from base64 import b64decode


KEY = b64decode("WUVMTE9XIFNVQk1BUklORQ==")
cipher = AES.new(KEY, AES.MODE_ECB)


def pad(plaintext, block_size=AES.block_size):
    """PKCS#7 Padding"""
    num_pad = block_size - (len(plaintext) % block_size)
    return plaintext + bytearray([num_pad for x in range(num_pad)])


def enterprise_grade_encryption(username):
    """You can see the key and postfix here, but don't cheat ;)"""
    global cipher
    secret = "ZWNiX3N1Y2tz"
    return hexlify(cipher.encrypt(bytes(pad(username + ':' + b64decode(secret)))))


username = "A" * 14
known_string = ":"

# Encrypt username to get the first letter of the secret
# For every byte value 0 to 255
    # Add this value to the end of your username and encrypt
    # Check if this value matches the ciphertext that has the byte of the secret

# Repeat above steps again now knowing one more byte of the secret