Intercept

Writeup for Intercept (Rev) - HackTheBox Cyber Apocalypse CTF (2021) 💜

Video Walkthrough

Challenge Description

Intercept We managed to covertly spy on some of the elves' communications, as well as obtain partial code for their experimental encryption algorithm. Can you find where they're planning their next meeting?

Solution

from pwn import *

enc = unhex(b'5b2fedd4801914e7eb765119d4fe6223f1d1984638a9816b5419dac07b27eed9d35e09fdef65521ac5877a24eed19b0c0ae9f16d4c02cc86773bfaa8924a2ae9a12a2f1dd7923d39eea78d5909f9f57b2a16ddc87d33ada58f1208d4f737755283da1168a3e6cc075e8ce920774ef88d483fb1bb8a440884af7d69e2c5874b3bb3be695d4fd5a97b27e7d7d0572cf0bf665405dbfe4225e19b824813e4b96a4e178a95776fe1d8800b0bf7f0705719c0c37834a8f7a26f1febbe3d7119dad66427d5f58b4259eabc3f3626ded46621d3b0ca441afce552274bd6da1f2a')

dec = b''

for i, byte in enumerate(enc):
    dec += xor(chr((55 * i + 19) % 256), byte)

success(dec.decode())

Flag: HTB{pl41nt3xt_4sm?wh4t_n3xt_s0urc3_c0d3?}