CTF for CyberHub and Programming Club (2022-12)

ctf-dec.py

## Capture the Flag - Cypto Beginners - Basic Cypher 
#  authors: Nauman (recluze) / Sohail 
#  Effat University, Jeddah, KSA 


#  Information availble to perform cryptanalysis: 
#  - Message is in the English language 
#  - Message is approximately (but not exactly) 10 words long


cypher_text = "1012,981,924,968,980,985,974,985,914,924,1023,979,978,987,974,989,968,969,976,989,968,981,979,978,975,924,979,978,924,984,985,991,974,965,972,968,981,978,987,924,968,980,985,924,983,985,965,925,924,1012,985,974,985,923,975,924,965,979,969,974,924,986,976,989,987,902,924,906,907,909,990,901,906,900,989,911,986,985,904,908,910,901,900,901,910,906,909,986,910,984,905,909,991,990,991,901,908,904,906,985,909,990,901,989,904,905,910"
key = 1

def decrypt(msg, key): 
    
    decrypted_message = "" 
    
    for c in msg.split(","):   # each character gets decrypted separately 
        if c.strip() == "": continue 
    
        c_bin = int(c)
        c_decrypted = c_bin ^ key 
        c_decrypted  = chr(c_decrypted)
        
        decrypted_message += c_decrypted 
        
    return decrypted_message


if __name__ == "__main__": 
    for key in range(10_000): 
        decrypted = decrypt(cypher_text, key) 

        # add a check here to "detect" if the key is the rigth one! 
        if True: 
            print(decrypted)
            break