Tags: crypto
Rating: 4.5
# Sonic // Writeup
## Problem
*Gotta go fast*
*nc chal.tuctf.com 30100*
## Solution
On that problem there was differents ways to solve it. For example, you can send every plaintext for each shift key ( 0 -> 26 ).
Or you can decode the message with the same shift key and do it until you got the flag :
```python
from pwn import *
import codecs
while True:
conn = remote('chal.tuctf.com' , 30100)
full_message = str(conn.recv())[301:]
LIST = list(full_message)
search=0
while search < len(LIST):
if LIST[search] == '\n':
for i in range(30):
try:
del LIST[search]
except:
pass
search += 1
encoded_message = ''.join(LIST)
rot13_message = codecs.encode(str(encoded_message) , 'rot_13')
conn.sendline(str(rot13_message))
recv = conn.recv()
if 'TUCTF' in recv:
print(recv)
break
conn.close()
```
**FLAG**: `TUCTF{W04H_DUD3_S0_F4ST_S0N1C_4PPR0V3S}`
