Challenge archive: Google CTF 2024 - desfunctional

Challenge: desfunctional
Event: Google CTF - 2024 qualifiers
Year: 2024
Category: Cryptography
Authors: deuterium
Mode: interactive
Article: https://deut-erium.github.io/challenges/google-ctf-2024/desfunctional/
Text: https://deut-erium.github.io/challenges/google-ctf-2024/desfunctional/challenge.txt
JSON: https://deut-erium.github.io/challenges/google-ctf-2024/desfunctional/challenge.json

Original description:
A newbie friend of mine was trying to implement a secure server
for DES encryption and decryption but there seem to be some errors
unexpectedly creeping in the key. It is getting frustrating, please help

Notes:
- The original remote service is retired. Browser practice runs locally with the public dummy reward practice{local_dummy_reward}; it does not award an event solve.
- The original remote service is retired. Browser practice runs locally with the public dummy reward practice{local_dummy_reward}, not an event flag or authoritative score. No TCP endpoint is provided.

Browser practice: https://deut-erium.github.io/challenges/google-ctf-2024/desfunctional/#browser-practice
Runtime: desfunctional
Variants: default (first is default)
Mode describes the original interactive I/O. Start practice from the article, not a TCP client.

Challenge files (primary):
- chall.py (chall.py; handout)
  URL: https://deut-erium.github.io/assets/challenges/google-ctf-2024-desfunctional/chall.py
  Bytes: 2770
  SHA-256: f8fd36aa22a93dfab66e2961f0c5ef3ad0a8ac610e71f52306a3b8f477e92799
  Upstream provenance: https://raw.githubusercontent.com/google/google-ctf/067421eb7e918c29e39f187fac5a0f0d72a6ab83/2024/quals/crypto-desfunctional/attachments/chall.py

Licenses (local copies):
- Apache-2.0: https://deut-erium.github.io/assets/challenges/licenses/Apache-2.0.txt
  Bytes: 11358
  SHA-256: cfc7749b96f63bd31c3c42b5c471bf756814053e847c10f3eb003417bc523d30
  Upstream provenance: https://raw.githubusercontent.com/google/google-ctf/067421eb7e918c29e39f187fac5a0f0d72a6ab83/LICENSE

SPOILERS - organizer files and solutions
Spoilers: organizer files and upstream source, archive, or solution links may reveal answers. Modified downloads are identified below.
Source: https://github.com/google/google-ctf/blob/067421eb7e918c29e39f187fac5a0f0d72a6ab83/2024/quals/crypto-desfunctional/metadata.yaml
Archive: https://github.com/google/google-ctf/tree/067421eb7e918c29e39f187fac5a0f0d72a6ab83/2024/quals/crypto-desfunctional
Solution: https://github.com/google/google-ctf/blob/067421eb7e918c29e39f187fac5a0f0d72a6ab83/2024/quals/crypto-desfunctional/challenge/solve.py