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Re: [Discuss-gnuradio] Car alarms and garage door openers

From: Marcus Leech
Subject: Re: [Discuss-gnuradio] Car alarms and garage door openers
Date: Mon, 05 Jun 2006 16:38:50 -0400
User-agent: Thunderbird (X11/20060516)

Matt Ettus wrote:

After the Wired article today, I've received a couple of email from people who are concerned that the USRP could be used to clone their keyfob transmitters for car alarms and garage doors. I'm not concerned, since there are already many ways to do this (just check the back of pupular science magazine). However, I am curious about it. I know that we can capture and play back any rf signal. The question is whether that replayed signal would result in the door being unlocked. I was under the impression that most of those systems allow an unlock code to only be used once, but does anyone out there know for sure?

Most, but not all, such devices now use a "rotating code sequence", based on a not-very-long pseudo-random sequence. Certainly for the impatient burglar, merely replaying won't work in most cases. I don't know how they maintain synchronization between the key and the lock, and it's likely that there are weaknesses there.

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