csaw21

Writeups for CSAW 2021 CTF

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Save the Tristate

Writeup by: USERNAME

Team: OnlyFeet

Writeup URL: GitHub


So it was just another day in Danville when Phineas and Ferb were making a new device to communicate with Meep as he travels across the galaxy. To make a device suitable for galatic communication and secure enough to be safe from alien hackers, they decide to protect their device with QKD! Unfortunately, due to Phineas & Co singing their usual musical numbers about their inventions, Doofenshmirtz has caught wind of this technology and wants to use it to take over the Tristate area, using his brand new Qubit-Disrupt-inator. Naturally I, Major Monogram, have to send you, Perry the Platypus, on a mission to stop Doofenshmirtz from disrupting Phineas and Ferb's qubits with his diabolical inator. So grab your tiny fedora and doo-bee-doo-bee-doo-ba-doo your way over to stop Doofenshmirtz! Mission:

- Receive # of qubits that translate to the flag
- Measure qubits in your own basis
- Monogram tells you how many qubits were measured correctly, but not which ones
- Go back and fix it
- Get it right

nc misc.chal.csaw.io 5001

Initial Research

Word.

$ echo 'thingz'
thingz

Version Mismatches

Wordsz.

some output

Ancient History or Stegosarus Time

Moar Words

$ cat commands.txt
commands1
$ nmap 1.2.3.4
...

Victory

Submit the flag and claim the points:

flag{flag-goes-here}