Easy Peasy

Buka terminal kalilinux dan buat file python dengan nama easypeasy.py

touch easypeasy.py

Edit isi file dengan codingan berikut

from Crypto.Util.number import long_to_bytes

from pwn import *

conn = remote(‘mercury.picoctf.net’, 36981)

# Terima data sampai bagian flag terenkripsi

conn.recvuntil(“This is the encrypted flag!\n”.encode())

encrypted_flag = str(conn.recvline(), “ascii”).strip()

print(“Encrypted Flag:”, encrypted_flag)

flag_len = int(len(encrypted_flag) / 2)

padding = “a” * (50000 – flag_len)

# Kirim padding untuk mendapatkan key

conn.sendlineafter(“What data would you like to encrypt?”.encode(), padding.encode())

message = “a” * flag_len

conn.sendlineafter(“What data would you like to encrypt?”.encode(), message.encode())

conn.recvuntil(“Here ya go!\n”.encode())

encrypted_message = str(conn.recvline(), “ascii”).strip()

print(“Encrypted Message:”, encrypted_message)

# Ubah hex ke bytes dengan aman

encrypted_message_bytes = bytes.fromhex(encrypted_message)

encrypted_flag_bytes = bytes.fromhex(encrypted_flag)

# Hitung key

key = xor(encrypted_message_bytes, message.encode())

print(“Key:”, key)

# Decrypt flag

flag = xor(encrypted_flag_bytes, key).decode()

print(f”Flag: picoCTF{{{flag}}}”)

conn.close()

Bagian remote (yang ditandai kuning) sesuai di picoCTF

Install paket pycryptodome dan pwntools

source venv\bin\activate

pip install pycryptodome

pip install pwntools

Jalankan file python

python easypeasy.py

Maka didapatkan flag yang dibutuhkan