Challenge Title: XORing Hex
Platform: pwn.college
Category: Cryptography
Difficulty: Easy
Tags: bitwise, XOR, hexadecimal, python

📝 Description

As you’ve already learned in earlier challenges, XOR is a key concept in cryptography.
Now we take things one step further by working with hexadecimal representations — the typical format for bytes in memory and cryptographic operations.

In this challenge, you’ll be given a random key and an encrypted secret, both in hex format.
Your task is to decrypt the secret by XORing the key and the encrypted value.

📚 Quick Recap: XOR and Hex

XOR still works the same way with hex — it’s just that you’re now looking at the values in base 16 rather than base 10.

# Example:
>>> hex(0x4e ^ 0x46)
'0x08'

So:

  • key = 0x4e
  • cipher = 0x46
  • secret = 0x4e ^ 0x46 = 0x08

#!/opt/pwn.college/python

import random import sys

for n in range(10): print(f”Challenge number {n}…”)

key = random.randrange(1, 256)
plain_secret = random.randrange(0, 256)
cipher_secret = plain_secret ^ key

print(f"The key: {key:#04x}")
print(f"Encrypted secret: {cipher_secret:#04x}")
answer = int(input("Decrypted secret? "), 16)
print(f"You entered: {answer:#04x}, decimal {answer}.")
if answer != plain_secret:
    print("INCORRECT!")
    sys.exit(1)

print("Correct! Moving on.")

print(“CORRECT! Your flag:”) print(open(“/flag”).read())


### Example Run
Here’s what a sample session looks like:
```bash
Challenge number 0...
The key: 0x4e
Encrypted secret: 0x46
Decrypted secret? 0x8
You entered: 0x08, decimal 8.
Correct! Moving on.

Challenge number 1...
The key: 0x3d
Encrypted secret: 0x53
Decrypted secret? 0x6e
You entered: 0x6e, decimal 110.
Correct! Moving on.

...

Challenge number 9...
The key: 0x0b
Encrypted secret: 0x78
Decrypted secret? 0x73
You entered: 0x73, decimal 115.
Correct! Moving on.

CORRECT! Your flag:
pwn.college{4h3zyQYsFWqwrwbL2T5GTokZSM1.QXwMzN5wSM0IzMyEzW}

Flag

pwn.college{4h3zyQYsFWqwrwbL2T5GTokZSM1.QXwMzN5wSM0IzMyEzW}