Most car key systems today are what are known as transponder keys. The fob that you carry with your car keys contains a tiny radio transmitter. When you push a button on the key fob, the transmitter sends a coded signal to the receiver inside the car that is tuned to the same frequency as the transmitter. Most systems transmit signals in the 300 to 400 MHz frequency range.
So how come you can't click "unlock" in a crowded Chicago parking lot and open a bunch of other cars? Back in the early days of automatic garage door openers, the systems were so simple that you actually could open garage doors with most any opener remote, so as these systems became more common, manufacturers had to come up with security measures to prevent this. Similar security systems are used with modern car keys.
It's easy enough to get your hands on a radio scanner, so it would seem that you could capture the code transmitted by a key fob and use it to open a car. However, the controller chip in today's key systems uses what are known as rolling codes to secure your car. The so-called 40-bit rolling code algorithm can generate around a trillion random codes.
The transmitter's controller chip holds the current 40-bit code in its memory, and when you push a button on the key fob, it sends that code plus a function code that "tells" your car what to do (like lock or unlock the doors). The receiver's controller also has a memory device that holds the current 40-bit code. If it receives the code it expects, it performs the action. If it doesn't, it doesn't do anything.
Both transmitter and receiver use the same pseudo-random number generator so that when the transmitter sends the current 40-bit code, the random number generator picks a new code and stores it in memory.
Then, the receiver stores the same new code. Transmitter and receiver are synchronized so that the proper transmitter always sends the expected code to the receiver.
Using this type of signal and random number generator, there is only the most miniscule chance of being able to open someone else's car doors, particularly since car manufacturers all use different systems. Code capturing using a radio scanner won't work with this type of system either, because there's not way to predict which random number the transmitter and receiver have chosen next.
So how do you get replacement car keys with such a system? You could call your car dealer, or you could call a trusted Chicago area locksmith. Both do the same job, but a car locksmith charges far less. Your Chicago locksmith has software and hardware that can reprogram new transponder keys, getting you moving again usually within half an hour.
If you discover that you've lost your car keys calling a Chicago local locksmith is much more cost-effective than calling your car dealer to replace your keys. A trained automotive locksmith understands how today's transponder key systems work, and can program new ones for virtually any make or model car quickly and with less overhead. Today's key systems are designed with robust security, but a trained locksmith knows how to get you moving again with new keys just as secure as the originals.