noname

I have Noname; I am but two days old.

File #1: volga2020-encrypted
File #2: volga2020-encryptor.py

Recon

From volga2020-encryptor.py:

key = md5(str(int(time.time()))).digest()

The key uses time(), bruteforce should be straightforward.

Solution

from Crypto.Cipher import AES  # pip install pycrypto
import time
from hashlib import md5
from base64 import b64decode

t = 1585323501

with open('encrypted', 'r') as f:
    data = b64decode(f.read())

for i in range(t, 0, -1):
    if not i % 10000:
        print(f'Trying {i}..')
    key = md5(str(i).encode()).digest()
    aes = AES.new(key, AES.MODE_ECB)
    dec = aes.decrypt(data)
    if b'VolgaCTF' in dec:
        print(dec)
        break

Trying 1585320000..
Trying 1585310000..
Trying 1585300000..
Trying 1585290000..
Trying 1585280000..
Trying 1585270000..
Trying 1585260000..
Trying 1585250000..
VolgaCTF{5om3tim3s_8rutf0rc3_i5_th3_345iest_w4y}\x10\x10\x10

Flag

VolgaCTF{5om3tim3s_8rutf0rc3_i5_th3_345iest_w4y}