Pick anything illegal in Germany, such as a pirate Mein Kampf text. Disclaimer: I don't support non-civic nationalism.

Xor the text file bytes, key made from /dev/urandom and base64. Use split to get 20 pieces.. Run sha512sum on all the pieces, pipe it to a text file.

Rename all the files to a random pattern with vidir+vim or dired under Emacs.

Now you have total junk files and nothing illegal. Still, reversing that up it's trivial by renaming the files matching the sha512sum (easy with AWK), and with cat you will get the illegal file back.

If any, you can add (with dd) a fake GB ROM or NES ROM header and rename them as "test ROMs". With dd you recover the files back like nothing, it has options to skip an amount of bytes while copying data.

And, technically, we didn't use dedicated encryption tools, at all.

Or thousands of public school teachers protected by schoolboards and principals.