Today I was told that there is a company that makes electronic tumbler locks.
The selling point of this thing is that the key presumably powers the circuitry located in the tumbler, checking the validity of the key and allowing to unlock the door based on the exchange. In theory the part where you power a chip using a key is not so hard, you just have to isolate a part of the tumbler so that you won't have a short. The part that is interesting is how do they move a mechanical part (I suppose is still a pin, or maybe more) in such a confined space. At first I was thinking that you can use an electro-magnet, however I'm not sure it would do the job, since there should be some kind of springs so that you won't be able to turn the lock when it's not powered.
What is your opinion on this topic, what would be the most reliable way to build such a thing?
PS: sadly I won't be able to get my hands on it anytime soon since it costs 260 euro/piece and it is out of my budget.