It's been a year and a month since I posted a topic about RFIDs --> Building antenna for ID-2 (RFID Reader) but nobody responded :'(
Anyway, my mom bought a car (Ford Ecosport) which have a keyless entry.
And I thought hmm... train of thought choo choo-ing
Long range means RFID not infrared.
But what range?
Is it active?
yes, it has a battery.
How come the battery doesn't wear down? Is it charging when I plug the car key in the ignition?
(Her old car has a fob key and it has been my long assumption that the battery charges when she puts the key on the car ignition haha) duh, push button ignition.
What? Why? How does fob keys work really?
both the car and key has a transceiver. The battery is only needed when I push a button.
Why other cars doesn't open when I push a button? Does it have a code like RFID tags? but I saw a hack and they can copy the id and they can open the door lock but why are they saying fob is secure?
Says they use rolling codes.
What? Read it here: How Remote Entry Works
">The transmitter's controller chip has a memory location that holds the current 40-bit code. When you push a button on your key fob, it sends that 40-bit code along with a function code that tells the car what you want to do (lock the doors, unlock the doors, open the trunk, etc.).
>The receiver's controller chip also has a memory location that holds the current 40-bit code. If the receiver gets the 40-bit code it expects, then it performs the requested function. If not, it does nothing.
>Both the transmitter and the receiver use the same pseudo-random number generator. When the transmitter sends a 40-bit code, it uses the pseudo-random number generator to pick a new code, which it stores in memory. On the other end, when the receiver receives a valid code, it uses the same pseudo-random number generator to pick a new one. In this way, the transmitter and the receiver are synchronized. The receiver only opens the door if it receives the code it expects."
They both have a random number generator? How do they sync if they generate both random numbers? random is random, right?
train stopped here
then again I remembered one time when she was in a hurry to go to a meeting and left my sister to drive the car it alarmed saying the key is out of range or outside the vehicle. we had to call her to get the key.
Well that changed everything. It means the car checks if the key is inside the vehicle. And it can only do so if the key emits an ID. But fob key only transmits if a button is pushed. Wait. There are cars that open when the key is inside the car bubble. Is the key and the car constantly looking for each other then? Why doesn't the battery wear down easily again?
train stopped here again
Can anyone kindly explain how the rolling codes works? I have read it is based on the clock and the initial 40 bit code but I'm still confused. Does the key have a clock? Are random numbers not that random if I will base the generated number from the initial code and time? Or is it really the transmitter that sends the random number? the receiver only stores the value then uses it on the transmitters next command?
Also, how do the key searching works? is the key constantly emitting rf for the car to recognise? I can't see any reading on this.