HackTheBox Optimus Prime Writeup

Explore the basics of cybersecurity in the Optimus Prime Challenge on Hack The Box. This easy-level Challenge introduces encryption reversal and file handling concepts in a clear and accessible way, perfect for beginners.

#!/usr/bin/env python3
from math import gcd
from pwn import remote, sys

def get_process():
    try:
        host, port = sys.argv[1].split(':')
        return remote(host, int(port))
    except IndexError:
        print(f'Usage: python {sys.argv[0]} <ip:port>')
        exit(1)

def get_public_key(p) -> int:
    p.sendlineafter(b'Enter the option: ', b'4')
    p.recvuntil(b'PUBLIC KEY: ')
    return int(p.recvline())

def get_encrypted_password(p) -> int:
    p.recvuntil(b'ENCRYPTED PASSWORD: ')
    return int(p.recvline())

def main():
    try:
        r = get_process()
        n1 = get_public_key(r)
        c1 = get_encrypted_password(r)
        r.close()
        r = get_process()
        n2 = get_public_key(r)
        c2 = get_encrypted_password(r)
        px = gcd(n1, n2)
        p2 = n2 // px
        e = 65537
        phi_n2 = (px - 1) * (p2 - 1)
        d2 = pow(e, -1, phi_n2)
        m = bytes.fromhex(hex(pow(c2, d2, n2))[2:])
        r.sendlineafter(b'Please use it to proceed: ', m)
        r.recvuntil(b'ACCESS GRANTED: ')
        print(r.recvline().decode())
        r.close()
    except KeyboardInterrupt:
        print("\nInterrupted by user.")
        try:
            r.close()
        except:
            pass

if __name__ == '__main__':
    main()

Summary

Optimus Prime on Hack The Box teaches beginners how to reverse encryption and handle files programmatically, guiding them through decrypting a password and understanding public key factorization, all within a robust, interruption-resistant script.