Share how awesome the crack me was or where you struggle to finish it! Stay polite and do not spoil the solution/flag!
8:38 PM 03/04/2023
Pretty simple key checking algorithm, reverse it and generate a key for it - There exists many valid keys.
RainerZimmerman on 12:37 AM 03/08/2023: Just realized there is a very easy solution I forgot to remove! If you find it, please ignore it. :)