XOR School

Cryptography 100 pts standard

Story: A student tried to “encrypt” the flag using XOR with a single byte.

Given: cipher.bin

Goal: Identify XOR encryption

Recover the key

Decrypt flag

Difficulty: Easy

↓ cipher.bin

        
          View Hint : Hints

Hints:

Hint 1: XOR is a symmetric operation. If $A \oplus B = C$, then $A \oplus C = B$.

Hint 2: There are only 256 possible values for a single byte. Why not try them all?

Hint 3: You know the flag starts with HackCTF{. What happens if you XOR the first byte of the file with the letter H?