Abitti's "custom" .meb format (just a zip, nothing special), files are encrypted (just AES, nothing special, c'mon what were you expecting from "datanomi" people?). My script decrypts them.

1. Download the .jar file from releases.
2. Enter this into your command-line:

java -jar mebextractor.jar <password> <encrypted_file> <output>

In this website https://oma.abitti.fi/ you can create exams and download your own .meb files.

.meb file is just "rebreanded" zip archive, which contains encrypted files.

.bin files contained in the archive are encrypted, thus can be decrypted with this utility.

1. .meb = .zip. They're same
2. .bin files are encrypted with AES/CTR/NoPadding method
3. Key calculation is done using pbkdf2. Learn more in the code.