And how is that hostel called, Dachau? And which parent made you go there? Why are you putting up with that, even in North Korea you'd have more liberties, and you know what they say about people that would easily trade their liberties...

Not to mention that while some place might ban some equipment, they cannot confiscate it permanently, nor could they sell it on an auction, and especially they cannot fiddle with it, in almost any country in the world. Please tell us that you live in North Korea?

On to the topic, once somebody has a physical access to the device, most protections will fail, especially top level ones (e.g. locked screen and such). You can store files as root on ext3fs with 600 flag which will stop anyone from reading them without a root password, and you can encrypt files with Blowfish/AES, but those are not bullet-proof methods. The best option would be to keep really secret files on some cloud, encrypted with big keys, so if you have something special to hide (i.e. info how to escape from that concentration camp ) that's the way you should go with.