EasyCTF_2018: xor

Category: Cryptography Points: 50 Description:

A flag has been encrypted using single-byte xor. Can you decrypt it? File.

Write-up

As a single-byte xor, this challenge is much more easily solved with a simple Python script.

for i in range(255):
    plaintext = ""
    for c in data:
        plaintext += chr(c ^ i)

    if "easyctf" in plaintext:
        print(plaintext)

Full script available here.

root@ctf:~/downloads# ./solve.py 
easyctf{nsbtbzlfudpixosinwqfckqrx}

Therefore, the flag is easyctf{nsbtbzlfudpixosinwqfckqrx}.