[AlexCTF] Ultracoded [crypto][50]

“Ultracoded” is a crypto challenge of 50 points from AlexCTF 2017 :

Challenge’s description :

Fady didn’t understand well the difference between encryption and encoding, so instead of encrypting some secret message to pass to his friend, he encoded it!
Hint: Fady’s encoding doens’t handly any special character

The file to decipher is :

ZERO ONE ZERO ZERO ONE ONE ZERO ZERO ZERO ONE ONE ZERO ONE ZERO ZERO ONE ZERO ZERO ONE ONE ZERO ZERO ZERO ZERO ZERO ONE ONE ZERO ZERO ONE ONE ONE ZERO ONE ZERO ZERO ONE ONE ZERO ZERO ZERO ONE ONE ZERO ONE ZERO ZERO ONE ZERO ZERO ONE ONE ZERO ZERO ZERO ZERO ZERO ONE ONE ONE ZERO ONE ZERO ONE ZERO ONE ZERO ZERO ONE ONE ZERO ZERO ZERO ONE ONE ZERO ONE ZERO ZERO ONE ZERO ONE ZERO ZERO ZERO ZERO ZERO ONE ZERO ONE ONE ONE ZERO ONE ZERO ONE ZERO ONE ZERO ZERO ONE ZERO ZERO ONE ZERO ONE ZERO ZERO ZERO ZERO ONE ONE ZERO ZERO ONE ONE ZERO ZERO ZERO ZERO ZERO ONE ONE ONE ZERO ONE ZERO ONE ZERO ONE ZERO ZERO ONE ONE ZERO ZERO ZERO ONE ONE ZERO ONE ZERO ZERO ONE ZERO ZERO ONE ONE ZERO ZERO ZERO ZERO ZERO ONE ONE ZERO ZERO ONE ONE ONE ZERO ONE ZERO ZERO ONE ONE ZERO ZERO ZERO ONE ZERO ONE ZERO ZERO ONE ONE ZERO ZERO ONE ONE ZERO ONE ZERO ZERO ZERO ONE ONE ONE ZERO ONE ZERO ZERO ZERO ONE ZERO ZERO ONE ONE ZERO ZERO ZERO ONE ONE ZERO ONE ZERO ZERO ONE ZERO ONE ZERO ZERO ZERO ZERO ZERO ONE ZERO ONE ONE ONE ZERO ONE ZERO ZERO ZERO ONE ZERO ZERO ONE ZERO ZERO ONE ZERO ONE ZERO ZERO ZERO ZERO ONE ONE ZERO ZERO ONE ONE ZERO ONE ZERO ZERO ZERO ONE ONE ONE ZERO ONE ZERO ONE ZERO ONE ZERO ZERO ONE ONE ZERO ZERO ZERO ONE ZERO ONE ZERO ZERO ONE ONE ZERO ZERO ONE ONE ZERO ONE ZERO ZERO ZERO ONE ONE ZERO ZERO ONE ONE ONE ZERO ONE ZERO ZERO ONE ONE ZERO ZERO ZERO ONE ZERO ONE ZERO ZERO ONE ONE ZERO ONE ZERO ZERO ZERO ZERO ZERO ONE ZERO ONE ONE ONE ZERO ONE ZERO ONE ZERO ONE ZERO ZERO ONE ONE ZERO ZERO ZERO ONE ONE ZERO ONE ZERO ZERO ONE ZERO ZERO ONE ONE ZERO ONE ZERO ZERO ZERO ONE ONE ONE ZERO ONE ZERO ONE ZERO ONE ZERO ZERO ONE ZERO ZERO ONE ZERO ONE ZERO ZERO ZERO ZERO ONE ONE ZERO ZERO ONE ONE ZERO ONE ZERO ZERO ZERO ONE ONE ONE ZERO ONE ZERO ZERO ZERO ONE ZERO ZERO ONE ONE ZERO ZERO ZERO ONE ZERO ONE ZERO ZERO ONE ONE ZERO ZERO ONE ONE ZERO ZERO ZERO ZERO ZERO ONE ONE ONE ZERO ONE ZERO ZERO ZERO ONE ZERO ZERO ONE ZERO ZERO ONE ZERO ONE ZERO ZERO ZERO ZERO ONE ONE ZERO ZERO ONE ONE ZERO ONE ZERO ZERO ZERO ONE ONE ONE ZERO ONE ZERO ONE ZERO ONE ZERO ZERO ONE ONE ZERO ZERO ZERO ONE ONE ZERO ONE ZERO ZERO ONE ZERO ZERO ONE ONE ZERO ONE ZERO ZERO ZERO ONE ONE ONE ZERO ONE ZERO ONE ZERO ONE ZERO ZERO ONE ZERO ZERO ONE ZERO ONE ZERO ZERO ZERO ZERO ONE ONE ZERO ZERO ONE ONE ZERO ZERO ZERO ZERO ZERO ONE ONE ONE ZERO ONE ZERO ZERO ZERO ONE ZERO ZERO ONE ONE ZERO ZERO ZERO ONE ZERO ONE ZERO ZERO ONE ONE ZERO ONE ZERO ZERO ZERO ZERO ZERO ONE ZERO ONE ONE ONE ZERO ONE ZERO ONE ZERO ONE ZERO ZERO ONE ONE ZERO ZERO ZERO ONE ZERO ONE ZERO ZERO ONE ONE ZERO ZERO ONE ONE ZERO ZERO ZERO ZERO ZERO ONE ONE ONE ZERO ONE ZERO ZERO ZERO ONE ZERO ZERO ONE ONE ZERO ZERO ZERO ONE ZERO ONE ZERO ZERO ONE ONE ZERO ONE ZERO ZERO ZERO ZERO ZERO ONE ZERO ONE ONE ONE ZERO ONE ZERO ONE ZERO ONE ZERO ZERO ONE ONE ZERO ZERO ZERO ONE ONE ZERO ONE ZERO ZERO ONE ZERO ZERO ONE ONE ZERO ONE ZERO ZERO ZERO ONE ONE ZERO ZERO ONE ONE ONE ZERO ONE ZERO ZERO ONE ONE ZERO ZERO ZERO ONE ZERO ONE ZERO ZERO ONE ONE ZERO ZERO ONE ONE ZERO ZERO ZERO ZERO ZERO ONE ONE ONE ZERO ONE ZERO ZERO ZERO ONE ZERO ZERO ONE ZERO ZERO ONE ZERO ONE ZERO ZERO ZERO ZERO ONE ONE ZERO ZERO ONE ONE ZERO ONE ZERO ZERO ZERO ONE ONE ONE ZERO ONE ZERO ONE ZERO ONE ZERO ZERO ONE ONE ZERO ZERO ZERO ONE ONE ZERO ONE ZERO ZERO ONE ZERO ZERO ONE ONE ZERO ONE ZERO ZERO ZERO ONE ONE ONE ZERO ONE ZERO ONE ZERO ONE ZERO ZERO ONE ZERO ZERO ONE ZERO ONE ZERO ZERO ZERO ZERO ONE ONE ZERO ZERO ONE ONE ZERO ONE ZERO ZERO ZERO ONE ONE ONE ZERO ONE ZERO ONE ZERO ONE ZERO ZERO ONE ONE ZERO ZERO ZERO ONE ZERO ONE ZERO ZERO ONE ONE ZERO ONE ZERO ZERO ZERO ZERO ZERO ONE ZERO ONE ONE ONE ZERO ONE ZERO ONE ZERO ONE ZERO ZERO ONE ONE ZERO ZERO ZERO ONE ZERO ONE ZERO ZERO ONE ONE ZERO ZERO ONE ONE ZERO ZERO ZERO ZERO ZERO ONE ONE ONE ZERO ONE ZERO ONE ZERO ONE ZERO ZERO ONE ZERO ZERO ONE ZERO ONE ZERO ZERO ZERO ZERO ONE ONE ZERO ZERO ONE ONE ZERO ONE ZERO ZERO ZERO ONE ONE ONE ZERO ONE ZERO ONE ZERO ONE ZERO ZERO ONE ONE ZERO ZERO ZERO ONE ONE ZERO ONE ZERO ZERO ONE ZERO ZERO ONE ONE ZERO ZERO ZERO ZERO ZERO ONE ONE ONE ZERO ONE ZERO ZERO ZERO ONE ZERO ZERO ONE ZERO ZERO ONE ZERO ONE ZERO ZERO ZERO ZERO ONE ONE ZERO ZERO ONE ONE ZERO ONE ZERO ZERO ZERO ONE ONE ONE ZERO ONE ZERO ZERO ZERO ONE ZERO ZERO ONE ONE ZERO ZERO ZERO ONE ONE ZERO ONE ZERO ZERO ONE ZERO ONE ZERO ZERO ZERO ZERO ZERO ONE ZERO ONE ONE ONE ZERO ONE ZERO ZERO ZERO ONE ZERO ZERO ONE ONE ZERO ZERO ZERO ONE ZERO ONE ZERO ZERO ONE ONE ZERO ZERO ONE ONE ZERO ZERO ZERO ZERO ZERO ONE ONE ZERO ZERO ONE ONE ONE ZERO ONE ZERO ZERO ONE ONE ZERO ZERO ZERO ONE ONE ZERO ONE ZERO ZERO ONE ZERO ZERO ONE ONE ZERO ONE ZERO ZERO ZERO ONE ONE ONE ZERO ONE ZERO ONE ZERO ONE ZERO ZERO ONE ONE ZERO ZERO ZERO ONE ONE ZERO ONE ZERO ZERO ONE ZERO ZERO ONE ONE ZERO ONE ZERO ZERO ZERO ONE ONE ZERO ZERO ONE ONE ONE ZERO ONE ZERO ZERO ONE ONE ZERO ZERO ZERO ONE ONE ZERO ONE ZERO ZERO ONE ZERO ONE ZERO ZERO ZERO ZERO ZERO ONE ZERO ONE ONE ONE ZERO ONE ZERO ZERO ZERO ONE ZERO ZERO ONE ONE ZERO ZERO ZERO ONE ONE ZERO ONE ZERO ZERO ONE ZERO ZERO ONE ONE ZERO ZERO ZERO ZERO ZERO ONE ONE ONE ZERO ONE ZERO ONE ZERO ONE ZERO ZERO ONE ZERO ZERO ONE ZERO ONE ZERO ZERO ZERO ZERO ONE ONE ZERO ZERO ONE ONE ZERO ONE ZERO ZERO ZERO ONE ONE ONE ZERO ONE ZERO ZERO ZERO ONE ZERO ZERO ONE ONE ZERO ZERO ZERO ONE ONE ZERO ONE ZERO ZERO ONE ZERO ONE ZERO ZERO ZERO ZERO ZERO ONE ZERO ONE ONE ONE ZERO ONE ZERO ONE ZERO ONE ZERO ZERO ONE ONE ZERO ZERO ZERO ONE ONE ZERO ONE ZERO ZERO ONE ZERO ZERO ONE ONE ZERO ONE ZERO ZERO ZERO ONE ONE ONE ZERO ONE ZERO ZERO ZERO ONE ZERO ZERO ONE ONE ZERO ZERO ZERO ONE ZERO ONE ZERO ZERO ONE ONE ZERO ONE ZERO ZERO ZERO ZERO ZERO ONE ZERO ONE ONE ONE ZERO ONE ZERO ZERO ZERO ONE ZERO ZERO ONE ZERO ZERO ONE ZERO ONE ZERO ZERO ZERO ZERO ONE ONE ZERO ZERO ONE ONE ZERO ZERO ZERO ZERO ZERO ONE ONE ONE ZERO ONE ZERO ZERO ZERO ONE ZERO ZERO ONE ONE ZERO ZERO ZERO ONE ZERO ONE ZERO ZERO ONE ONE ZERO ONE ZERO ZERO ZERO ZERO ZERO ONE ZERO ONE ONE ONE ZERO ONE ZERO ZERO ZERO ONE ZERO ZERO ONE ZERO ZERO ONE ZERO ONE ZERO ZERO ZERO ZERO ONE ONE ZERO ZERO ONE ONE ZERO ZERO ZERO ZERO ZERO ONE ONE ONE ZERO ONE ZERO ONE ZERO ONE ZERO ZERO ONE ONE ZERO ZERO ZERO ONE ONE ZERO ONE ZERO ZERO ONE ZERO ZERO ONE ONE ZERO ZERO ZERO ZERO ZERO ONE ONE ZERO ZERO ONE ONE ONE ZERO ONE ZERO ZERO ONE ONE ZERO ZERO ZERO ONE ZERO ONE ZERO ZERO ZERO ONE ZERO ZERO ONE ONE ONE ONE ZERO ONE ZERO ZERO ONE ONE ONE ONE ZERO ONE

Nous ecrivons un script pour remplacer les ZERO et ONE par 0 et 1,nous décodons la chaîne en binaire pour obtenir une chaîne en base64 que nous decodons encore une fois , nous obtenons finalement un message en morse :

Let’s write a script to replace ZERO by 0 and ONE by 1, then we translate from binary to character, this give us a base64 strings, let’s decode it :

#!/usr/bin/env python

import binascii
import base64


with open('./zero_one', 'r') as content_file:
    bin_text = content_file.read()

bin_text = bin_text.replace("ZERO","0")
bin_text = bin_text.replace("ONE","1")
bin_text = bin_text.replace(" ","")
bin_text = bin_text.strip()
print("Binaire : "+ bin_text)
b64 = ''.join(chr(int(bin_text[i:i+8], 2)) for i in range(0, len(bin_text), 8))
print("Base 64 : "+ b64)
print("morse : " + base64.b64decode(b64).decode('utf-8'))
decrypt.py
neolex@neolex-pc> crypto1:Ultracoded[crypto50]_DONE$./expl.py 
Binaire : 0100110001101001001100000110011101001100011010010011000001110101010011000110100101000001011101010100100101000011001100000111010101001100011010010011000001100111010011000101001100110100011101000100110001101001010000010111010001001001010000110011010001110101010011000101001100110100011001110100110001010011010000010111010101001100011010010011010001110101010010010100001100110100011101000100110001010011001100000111010001001001010000110011010001110101010011000110100100110100011101010100100101000011001100000111010001001100010100110100000101110101010011000101001100110000011101000100110001010011010000010111010101001100011010010011010001100111010011000101001100110000011101000100100101000011001101000111010101001100011010010011010001110101010010010100001100110100011101010100110001010011010000010111010101001100010100110011000001110101010010010100001100110100011101010100110001101001001100000111010001001001010000110011010001110100010011000110100101000001011101000100110001010011001100000110011101001100011010010011010001110101010011000110100100110100011001110100110001101001010000010111010001001100011010010011000001110101010010010100001100110100011101000100110001101001010000010111010101001100011010010011010001110100010011000101001101000001011101000100100101000011001100000111010001001100010100110100000101110100010010010100001100110000011101010100110001101001001100000110011101001100010100010011110100111101
Base 64 : Li0gLi0uLiAuIC0uLi0gLS4tLiAtIC4uLS4gLSAuLi4uIC4tLS0tIC4uLi4uIC0tLSAuLS0tLSAuLi4gLS0tIC4uLi4uIC4uLSAuLS0uIC4uLi0tIC4tLiAtLS0gLi4uLi4gLiAtLi0uIC4tLiAuLi4tLSAtIC0tLSAtIC0uLi0gLQ==
morse : .- .-.. . -..- -.-. - ..-. - .... .---- ..... --- .---- ... --- ..... ..- .--. ...-- .-. --- ..... . -.-. .-. ...-- - --- - -..- -

It looks like morse code, let’s go to http://www.dcode.fr/morse-code and get the string  “ALEXCTFTH15O1SO5UP3RO5ECR3TOTXT”

This flag is ALEXCTF{TH15_1S_5UP3R_5ECR3TOTXT}

Leave a Reply

Your email address will not be published.