Hello everyone, and welcome back to my posts :)
So, today's story is about security tags that are attached to clothes.
So, you buy a garment, go back home just to find that the cashier has forgotten to remove it!
Okay, not a problem, makes a good reverse engineering toy...
Firstly, I took apart the long compartment cover, let us have a look under the hood:
Awesome, this is the RFID tag which responds to the antennas on the store's exit doors. Now, let us have a look on the smaller compartment:
Note: The pin head is broken (that's the round shiny part on the bottom left of the above image).
It is basically a simple but smart lock. In normal condition, the spring pushes the ball holder (gray colored in the below demonstration) towards the casing (golden color). The balls therefore press against the pin and holds it tight. (There is actually a small notch on the pin to give more friction surface).
When the cashier places the tag against a strong magnet, the holder is pulled away from the casing:
Note that the spring is compressed, when the magnetic field is removed, the holder is pushed back to its original (locked) position.
Smart!
