Challenge Title: XOR (Strangely enough…)
Platform: pwn.college
Category: Cryptography
Difficulty: Easy
Tag: bitwise, beginner, XOR, python

đź“ť Description

Strangely enough, we’ll start our crypto journey with the humble Exclusive Or (XOR) operator.

XOR is a bitwise operator — it compares each bit of two numbers and returns 1 if the bits are different, and 0 if they are the same.

For example:
9 (1001) XOR 5 (0101) = 1100 (which is 12 in decimal).

What makes XOR useful in cryptography is that it is self-inverse:

  • If A ^ B = C, then C ^ B = A.

This means if we XOR a message with a key to encrypt it, XORing it again with the same key will decrypt it.

In this level, you will learn to XOR!
We’ll give you a shared key, XOR a secret number with it, and expect you to recover the number.

đź’ˇ HINT

Use Python’s ^ operator to XOR integers.

🧪 Challenge Walkthrough

Let’s understand this through an example session:

hacker@cryptography~xor:~$ python
Python 3.12.11 (main, Jun  3 2025, 15:41:47) [GCC 14.2.1 20250322] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> 250 ^ 143
117
>>> exit()

We’re simply XORing two numbers. Now, let’s try solving the actual challenge: ```hacker@cryptography~xor:~$ /challenge/run The key: 119 Encrypted secret: 49 Decrypted secret? 70 CORRECT! Your flag: pwn.college{8i1fbZRWfamOen__vOIWhimMl.QX3IzN5wSM0IzMyEzW}

### Decryption logic:
Since Encrypted = Secret ^ Key, then
Secret = Encrypted ^ Key
=> Secret = 49 ^ 119 = 70
---
## Flag

pwn.college{8i1fbZRWfamOen__vOIWhimMl.QX3IzN5wSM0IzMyEzW} ``` —