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TUCoPS :: Hardware Hacks :: anti-tmp.txt

Easy-to-make Anti Tampering Circuits




      
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| \        _______ _______ ____________
|  \     |\\__  __\\   _  \\   __     /
|   \    | \  ||    | | | | | |_/    /
|    \   |  \ ||    | | | | |       /
|     \  |  | ||    | | | | |  ____/
| |\   \ |  | ||    | |_| | | |
| | \   \|  | ||    |_____| |_|
|_|  \      | 
      \     | National Telco
       \    | Opposition Party
        \   | ----------------
         \  | irc.xnet.org #TeenYack
          \ | 1999
           \| 
---------------------------

Easy-to-make Anti-tampering circuits
by HaPpYKiLL

-

Ever built anything that you dont want anyone to see the inside of?
Got a brand new box that you dont want the telco to see? Read on...

For anti-tampering circuits, you have 4 methods for triggering an event.

1: Disconnection

 Gonna put this in a fone box? good idea, as you know the fone line has
DC current flowing thru it all the time. This provides us with an easy way to
trigger something when the box is disconnected from the power source.
Use a normally closed relay, the power from the line holds the relay open,
but if the clips are taken off the line, the relay throws, connecting current thru
your device.

<ASCII schematic>

   o R  o T
   |    |
  |RELAY |
  |______|
   | | |
   o o o
     | |
     | |_____o <-- Contacts going to your device. (See "The Payload")
     |_______o      Stick a battery in there, i couldnt figure out how to
                    make a battery in ascii

</ASCII schematic>

2: Motion Sensor

 Another good one, either go to rat shack and pick up a mercury switch, or
go garage sale hopping in the hopes of finding a thermostat. Im not going to do a
schematic for this one, since its fairly simple and straightforward. Position the
merc switch in your box so the connection is open when its in a position that it will
stay in. If someone picks up your box and moves it around, it closes the connection
and triggers the device.

3: Light Sensor

 Photocells can be put to good use here. Find plans for a simple optioisolator
(I had some, but theyre gone). If anyone removes the cover on your device, the light
triggers the optioisolator, triggering the device.

4: Hangup Switch

 Seen those new fones with the special hangup switch? it looks like a black
box with a silver tongue of metal on the top. Press the lever down and the connection
is broken. Perfect for an anti-tampering device. Super-glue the switch near the top of your
box, so when the lid is put on the box, the switch is held down (open). If anyone
removes the lid from your box, the switch closes, triggering your device.

The Payload

 Here is where a demented mind can run rampant. The question is, what do you
want to happen when one of the above methods triggers?

1: Meltdown

 Go to your local hobby store and buy a small model rocket engine and an electrical
ignitor for it. Fit the engine in your box so the trigger will light the engine up,
slagging the contents of your box very effeciently

2: ZAP!

 Ever seen a stun gun? what it is is a big capacitor wired to 2 poles, releasing a
high voltage low amperage current thru the victims body. Go buy a cheapass 1-time-use
camera with a flash. Remove the flash bulb, solder wires onto the poles where the
bulb was. Now remove the crappy trigger switch for the camera flash, wire that into
your trigger. Now, get one of those project cases from rat shack with the metal plate
covering 1 top piece. Hell buy 2, now take the metal plate off the second box and 
anchor it to the opposite side of your case. Now solder 1 wire from the flash securely 
to one metal plate, solder the oher one to the other metal plate. Now whenever joe
telephone lineman messes with your box, he gets a healthy dose of electricity to the hand.

NOTE: be sure you charge the "flash" before using your box or else it wont do shit.

3: BOOM!

 I dont reccomend doing this as it will get you in lots of trouble. But technically
you could stick a co2 bomb in the box, with a model rocket ignitor, and wire that to your
trigger. KABOOM!

-

 Other

You will probly want a way to disarm your device if you need to recover the box. Heres
a few ideas.

1: A switch

 Duh...only problem is, someone else will most likely figure out that the switch on the
side of the box disarms the device.

2: Knife switch

 I read this a long time ago, Leave a slot on the side of your box, add 2 metal contacts
inside where a metal strip (knife, piece of steel) will contact them. Use it as a switch to
add a bypass to the device (put a resistor on the trigger so the resistance on the trigger
circuitry is less then the resistance between the knife switch.)

hard to explain, but it does the job.

-HaPpYKiLL
zonehead@xnet.org


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