Tags: reversing
Rating: 1.0
# Secret Array
Author: [thebongy](https://github.com/thebongy) and [roerohan](https://github.com/roerohan)
# Requirements
- Python
# Source
```
Get back to flag.
Author: KOOLI
```
# Exploitation
Since we have the AES key, it's got nothing much to do with that. We just have to reverse the shuffling properly.
```py
#!/usr/bin/python3
from Crypto.Cipher import AES
from Crypto.Util.Padding import pad
from Crypto.Util.number import long_to_bytes
from binascii import hexlify
import random
key = "very_awes0m3_k3y"
flag = "FwordCTF{xxx_xxx}" #REDACTED
# assert len(flag) == 62
# assert len(key) == 16
def to_blocks(text):
return [text[i*2:(i+1)*2].encode() for i in range(len(text)//2)]
def random_bytes(seed):
random.seed(seed)
return long_to_bytes(random.getrandbits(8*16))
def encrypt_block(block,key):
cipher = AES.new(key.encode(), AES.MODE_ECB)
plain_pad = pad(block, 16)
return hexlify(cipher.encrypt(plain_pad)).decode()
def encrypt(txt, key):
res = ""
blocks = to_blocks(txt)
for block in blocks:
res += encrypt_block(block, key)
return res
def decrypt(txt, key):
b = bytes.fromhex(txt)
flag = b''
for i in range(0, len(b), 16):
block = b[i:i+16]
cipher = AES.new(key.encode(), AES.MODE_ECB)
dec = cipher.decrypt(block)
flag += dec[:2]
return flag
def translate(txt,l,r):
return txt[:l]+txt[r:]+txt[l:r]
def reverse_translate(txt, l, r):
return txt[:l] + txt[-(r-l):] + txt[l:(-(r-l))]
def shuffle(txt):
seed=random.choice(txt)
random.seed(seed)
for _ in range(45):
l = random.randint(0, 15)
r = random.randint(l+1, 33)
txt = translate(txt, l, r)
return txt
def reverse_shuffle(txt, seed):
random.seed(seed)
vals = []
for _ in range(45):
l = random.randint(0, 15)
r = random.randint(l+1, 33)
vals.append((l,r))
vals = vals[::-1]
for i in range(45):
txt = reverse_translate(txt, vals[i][0], vals[i][1])
return txt
flag = shuffle(flag)
print (encrypt(flag, key))
hx = '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'
chars = decrypt(hx, key)
possible_seeds = list(map(chr, set(chars)))
for i in possible_seeds:
print(reverse_shuffle(chars, i))
```
Run the script with python.
```bash
$ python solve-tornado.py | grep Fword
```
The flag is:
```
FwordCTF{peekaboo_i_am_the_flag_!_i_am_the_danger_52592bbfcd8}
```
