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Topic: Alarm system and radio transmission (Read 1 time) previous topic - next topic

djjoshuad



@karlok - a rolling code can be defeated fairly easily once you recognize that it is being used.  A replay attack just replays the last message and would of course fail.  Actually determining the rolling key algorithm will allow you to modify the next message and "play" it with the right key.

Hello, I still am not able to beleive that. How would you do so. For me a rolling code is an always changing code that is created by using a secret key and a message(message = counter in this case).

And I am also interested in the outdoor cable idea where I drew the picture.

There isn't a /lot/ of information here, but go read http://en.wikipedia.org/wiki/KeeLoq - specifically the parts about the weaknesses.  This is not to say that it doesn't provide a good encryption mechanism, but it is certainly breakable and really not that difficult.  Without going into a full on crypto lesson, it suffices to say that any mechanism can be broken given enough time and a little luck.  An attacker needs far less luck when you use a standard mechanism.  If you are doing something very proprietary, there are no off-the-shelf tools available to break your code... so it takes far more intelligence and a lot more luck.

It makes me happy that you are considering using a wired solution.  That reduces your risk significantly, not to mention making power, range, and a whole host of other hurdles much easier to deal with.  It just takes a bit more work to implement :)

karlok

What do you think about the idea (http://arduino.cc/forum/index.php/topic,140776.msg1058205.html#msg1058205) to control whether the cable to the siren was cut? Can this method work - the idea is that there is a short circuit from Arduino GND to a pullupped Arduino Digital In, if the cable is cut anywhere - this is like a switch - it will be recognized. How to make the alarm then?
using Arduino Uno Rev 3

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