How Do Smart Key Fobs For Cars Work?

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Nowadays, smart key fobs for cars have become quite popular from the time they were first introduced by Mercedes-Benz in the year 1998. But how do these miniscule devices actually work? Let’s find out by going through the information mentioned below:


A smart fob typically contains a short range transmitter that works up to around 20 metres. The system at its core is quite similar to that used for opening electronic locks and garage doors. The transmitter sends signals in the form of radio waves along with a specific code. As soon as a match is found between the sent code and the code at receiver, a mechanism gets activated automatically.

Active Keys

These have been in existence ever since the 90s. They generally have a button which when pressed, initiates a transmission along with a code as well as a command that matches the button. That transmission then spreads in all directions, and this explains the reason why an active key can be pointed in any way for unlocking a car. The receiver and transmitter are linked so that they have corresponding codes and no other car in close proximity gets unlocked.

Passive Keys

Passive keys are newer additions to the lineup of keyless entry. They can easily authorise commands even without the press of any button. This is made possible by four to six LF (low frequency) antennas which extend around a car and generate a magnetic field. The fob itself generally stays inactive, but keeps a very low power detector active. It switches on only after detecting LF field around a car and immediately starts transmission of a code. The antennas receive the transmission and may even use varied signal strengths for determining location of the fob.

Encryption & Security

Security is the most important aspect of keyless entry. It needs to be impeccable enough for impeding transmission of code to another key as well as duplication. And this is ensured by a heavy-duty encryption. Every automobile manufacturer have their own method to encrypt keys. But in general, modern manufacturers make use of a 128-bit encryption key. This means that the code contains 128 characters or around 339 decillion combinations.

However, a car locksmith in Sydney also possess a great amount of skills in order to issue replacements or duplicates for smart key fobs. This is because the encryption of keyless entry is done on a rolling or changing basis, which renders them entirely unhackable.

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