You might or might not have seen the recent buzz around the security problems with hotel locks. There are of course quite a few people out there that believe in "security through obscurity" and the problem is that not everybody thinks like that -- more specifically the "Black Hat" community. Keeping that in mind, you should really, REALLY not leave any valuables in hotel rooms (the safe isn't that safe after all, but that's another topic), but that will be reinforced if you get a chance to do some "light" reading on the topic. The first link is a paper on how the Onity HT locks are designed and their vulnerabilities. It's somewhat heavy on the technical aspects of the encryption, but suffice it to say that the system is extremely insecure, as you can easily read the hotel's sitecode and make yourself a master key if you simply have physical access to one of the locks. http://demoseen.com/bhpaper.html The second link is worse, as it's basically an extension of the first... someone takes the information and puts it into practice by taking all the knowledge and squeezing the components into an Arduino device concealed as a dry erase marker. http://blog.spiderlabs.com/2012/10/pentesting-hotels-with-pens.html In theory, if you happened to be evil enough, you could book yourself a room at a hotel that uses these locks and go through your floor opening doors and grabbing valuables. So yeah... I suppose the bottom line is don't try this at home, but also make sure you are aware of what's possible so you're not surprised that pretty much anyone with enough knowledge can break into your room on a whim.