@Maschell
Thanks for your reply!
It seems that JNUSTool and FunkiiU offer similar functionalities, although decrypting is also a functionality of JNUSTool.
What's the advantage of having a decrypted file instead of an encrypted one?
I was reading this on a website:
Wii U Common Key -
Used to decrypt the title key for every Wii U application. System titles and installable applications are decrypted at install time, disc-based games are decrypted at load time.