AngstromCTF_2018:

Category: Crypto Points: 40 Description:

We found these mysterious symbols hidden in ancient (1950s-era) ruins. We think a single byte may be key to unlocking the mystery. Can you help us figure out what they mean?

Write-up

This is just a single-byte XOR encryption.

import binascii

ciphertext = binascii.unhexlify("fbf9eefce1f2f5eaffc5e3f5efc5efe9fffec5fbc5e9f9e8f3eaeee7")
for key in range(255):
    plaintext = ""
    for c in ciphertext:
        plaintext += chr(c ^ key)
    if "ctf" in plaintext:
        print(plaintext)

In a script, we get our flag

$ ./script.py
actf{hope_you_used_a_script}

Therefore, the flag is actf{hope_you_used_a_script}.

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