Challenge Title: XORing ASCII
Platform: pwn.college
Category: Cryptography
Difficulty: Easy
Tags: ascii, bitwise, XOR, character encoding, python

📝 Description

Much of cryptography involves text encryption. Text in computers is represented as bytes, using encoding standards like ASCII or UTF-8.

In this challenge, we stick to ASCII, where each character has a fixed byte value (0–127).

Using XOR on characters becomes easy:

  • Convert the character to its ASCII code (via ord() in Python).
  • XOR it with a given key.
  • Convert the result back to a character (via chr()).

You will be given an encrypted character and an XOR key. Your task is to decrypt it — that is, find the original character before encryption.

💡 ASCII Recap

Here’s how to view ASCII codes:

man ascii

Or use Python interactively:

>>> ord('A')      # Get ASCII code
65
>>> chr(0x40)     # Get character from ASCII code
'@'

Example:

Encrypted Character: A
XOR Key: 0x01

ord('A') = 0x41  
0x41 ^ 0x01 = 0x40 → chr(0x40) = '@'

Answer: @

Example Session

Challenge number 1...
- Encrypted Character: r
- XOR Key: 0x2a
- Decrypted Character? X
Correct! Moving on.

Challenge number 2...
- Encrypted Character: h
- XOR Key: 0x4e
- Decrypted Character? &
Correct! Moving on.

...

Challenge number 9...
- Encrypted Character: [
- XOR Key: 0x18
- Decrypted Character? C
Correct! Moving on.

You have mastered XORing ASCII! Your flag:
pwn.college{wdhDQFWHhHscYIG5U5f7ZYFUCKo.QX4IzN5wSM0IzMyEzW}

Flag

pwn.college{wdhDQFWHhHscYIG5U5f7ZYFUCKo.QX4IzN5wSM0IzMyEzW}