XOR 1 - 20 points

Writeup by poortho

Problem Statement: My friend Miles sent me a secret message. He said he encoded it with an XOR cipher. Can you figure out what his message “KGZFK\qZFG]qA\qZFOZ” means?

Hint:

The key is only one digit long

Writeup

As the problem states, the text is encrypted using single-byte XOR. To solve this, we can simply write a program to brute force all possible keys.

def sxor(s1,s2):    
    return ''.join(chr(ord(a) ^ ord(b)) for a,b in zip(s1,s2))

s = "KGZFK\qZFG]qA\qZFOZ"
for x in range(128):
    print sxor(chr(x)*len(s),s)

Scrolling through the output, we see the flag.

Flag

either_this_or_that