Trombe wrote:The insides of the box are put under pneumatic pressure. Obviously I don't want to use very high pressure because I don't want the box to explode, but it should be enough to trigger an alert when an internal pressure sensor detects the pressure drop, if the housing has been breached i.e. a drilling attempt. This would be difficult to pull off, because it would need a tight housing, and each smallest leak would cause the box to depressurite slowly. As an addition the box will have to be repressurize each time I want to open it myself. Also, if an attacker knew the box was under pressure, he could use a pressurized chamber to equalize the pressure and then open the box without triggering an alarm.
this would be a challenge.. the logistics of keeping it pressurized (holes for wire. small leaks etc) probably make this not feasible
Vibration sensor
I can install a small vibration sensor in the box. However how can the sensor differ between a real breakin attempt,
This is a good one.. you can detect drilling my the constant vibration pattern (say over 5 seconds.. you should not have a lock vibrating for 5 seconds in regular use)..
you can also use maximum G. look for a single high G impact. (you can differentiate this from a door slam by looking at the 5-10 seconds before.. a slam of a door will have a proceeding "open" of the door with vibration. where a hammer impact, "should" be pretty quiet just before.
Microphone
We can install a small mic to monitor the noise level. Surely a power drill or a saw produces the whole lot of racket that's not going to sit well with the mic's ears and will trigger an alarm. Obviously the box will have to be placed in a very quiet environment to avoid false positives.
for a drill the vibration will be best to detect it.. sound nearby might cause lots of false readings using sound.
Light sensor
A sensor that measures the amount of light can be installed. If the box is opened, it will trigger an alarm when there is sufficient light. The downside is that an attacker can simply open the box in a dark place. Or possibly use a light with a frequency that the sensor doesn't detect.
Accelerometer
I would need an extremely sensitive sensor. This can detect whenever the box is moved. So any movement will cause alarms. Again the box should be statically attached to some object for this to work.
Power loss
Okay, so how is my device supposed to work, if an attacker simply unplugs the device from power? Simple. If the power is lost, trigger an alarm. Need to implement a fail-secure mechanism. This however cannot differ between unplugs and real-life power cuts. Even a mains fuse can get blown in my appartment so...
That's about it from my side. Comments, ideas, suggestions?
how about a simple contact switch on the plug (to know when it's rotated) vs opening of the door (simple compression switch).. if the door opens, and neither the inside handle nor plug "rotate", then you can deduce a forced entry of some kind.
for "anti picking" you can look at something like a contact switch at the last pin (maybe for a SC4 core with SC1 keys) .. drill through the core/cylinder, and you can have a simple light barrier detector.. someone put "something" past the last pin which would not happen in normal use
an accelerometer should be able to detect the impact events (bumping/hammer) and you need to look at the impact(s) over time.. many in a small period (with the door open/close sensor showing that the door was not opened in the last 30 seconds.. ) you can deduce a break in.
you can also drill (sideways) through the cylinder, and and put a light barrier to detect is a pin was lifted to high (which would not be that high based on bitting/pins etc) a bumpkey/pick would put the pin to high then it would normally see.
I think that with a few simple things
1) light barrier
2) Accelerometer
3) plug rotation & door open/close
you can detect 95% of the ways the lock will be defeated..
This is not perfect, as there are ways around VATS, but I wont go into that here and most people wouldn't know anyways.
