#!/usr/bin/env python3
from Crypto.Cipher import DES
import signal
import os

if __name__ == "__main__":
    signal.alarm(15)

    with open("flag", "rb") as f:
        flag = f.read()
    
    key = b'Dream_' + os.urandom(4) + b'Hacker'
    key1 = key[:8]
    key2 = key[8:]
    print("4-byte Brute-forcing is easy. But can you do it in 15 seconds?")
    cipher1 = DES.new(key1, DES.MODE_ECB)
    cipher2 = DES.new(key2, DES.MODE_ECB)
    encrypt = lambda x: cipher2.encrypt(cipher1.encrypt(x))
    decrypt = lambda x: cipher1.decrypt(cipher2.decrypt(x))

    print(f"Hint for you :> {encrypt(b'DreamHack_blocks').hex()}")

    msg = bytes.fromhex(input("Send your encrypted message(hex) > "))
    if decrypt(msg) == b'give_me_the_flag':
        print(flag)
    else:
        print("Nope!")

from pwn import *
from Crypto.Cipher import DES

io = process(["python3", "prob.py"])
# io = remote("host3.dreamhack.games", 18664)

io.recvuntil(b":> ")
hint = bytes.fromhex(io.recvline().decode())

conflict = dict()

for i in range(65536):
    b = i.to_bytes(2, "big")
    cipher = DES.new(b"Dream_" + b, DES.MODE_ECB)
    enc = cipher.encrypt(b"DreamHack_blocks")
    conflict[enc] = b"Dream_" + b

for i in range(65536):
    b = i.to_bytes(2, "big")
    cipher = DES.new(b + b"Hacker", DES.MODE_ECB)
    dec = cipher.decrypt(hint)

    if dec in conflict:
        key1 = conflict[dec]
        key2 = b + b"Hacker"
        break

cipher1 = DES.new(key1, DES.MODE_ECB)
cipher2 = DES.new(key2, DES.MODE_ECB)
encrypt = lambda x: cipher2.encrypt(cipher1.encrypt(x))
assert encrypt(b"DreamHack_blocks") == hint

io.sendlineafter(b'> ', encrypt(b"give_me_the_flag").hex().encode())

flag = eval(io.recvline())
io.close()

print(flag.decode())