```
#!/usr/bin/env python3

from Crypto.Util.number import *
from Crypto.Cipher import AES
from Crypto.Util.Padding import unpad,pad
import os
import base64
import random
import socket

#FLAG regex is TFCCTF{[bdefgmnprsu012345_]+}

def server_unpad(ct,conn):
conn.send(ct.encode() + b'\n')
r = conn.recv(4096).strip()
return r

def my_unpad(ct,conn):
global req
ress = 0
for i in range(30):
if (server_unpad(ct,conn) == b'True'):
ress +=1
if (ress > 15):
return True

def decryption(iv, ct, conn):
alph = b'bdefgmnprsu012345_TFC{+}'
fl = b''
for _ in range(16):
for i in alph:
#print(i)
x = b''
x += bytes(a^(len(fl)+1) for a in (long_to_bytes(i)+fl))
ivmask = b'\x00'*(16-1-len(fl))+x
iv2 = bytes(a ^ b for a,b in zip(iv,ivmask))
give2 = base64.b64encode(iv2 + ct).decode()
if (my_unpad(give2,conn) == True):
fl = long_to_bytes(i) + fl
print('flag',fl)
break
return fl

if __name__ == '__main__':
with socket.create_connection(('challs.tfcctf.com', 31009)) as conn:
res = b''
res += conn.recv(4096)
line, _, _ = res.split(b'\n')
print(res)
give = line.replace(b'Lets see you decode this: ', b'').strip()
print(give)

try:
ct = base64.b64decode(give)
for p in range(0,3): #change 0 to 1,2 to find next parts of the key
print(ct[p*16:(p+1)*16], ct[(p+1)*16:(p+2)*16])
decryption(ct[p*16:(p+1)*16], ct[(p+1)*16:(p+2)*16],conn)
except:
print(Exception)
```