Secrets of intercom keys.

The secrets of intercom keys. Which one will open any door? Everyone has their own door phone keys in their pocket. We understand how they work and whether they can be demagnetized, and whether there is one key to all the doors.

Types of keys for intercoms

There are several families of intercom keys.
1. “Tablets”. Officially, the standard is called Touch Memory (TM) or iButton, these are contact keys in the MicroCAN package. The “tablets” use the 1-Wire protocol, but the formats are different.
In the Russian Federation, these are mainly Dallas model keys, which Vizit, Eltis, Z-5R, S2000-2, etc., Cyfral (keys DC2000A and Tsifral-KP1, etc.), Metakom are working with.
Quite rarely resistive “pills” are found – they have resistance read.
2. “Droplets”. RFID tags in a plastic case of a round, oval or drop-shaped form. Sometimes they come in the form of bracelets or cards.
Inside – RFID-tag, as in the subway cards, “beeper” on the goods in supermarkets and other similar things. Basically, the “droplets” can be short-range (Proximity, read at a distance of 10-15 cm), since the more “long-range” Vicinity tags, which operate at a distance of up to 1 m, are unsafe in this case.
In the RF, EM-Marin Proximity-keys are most often used, but there are also older HID-tags or newer MiFare, as in metro maps.
3. Optical. Real dinosaurs. Somewhere in the provinces are still preserved. Such a key is a metal plate in which holes are drilled in a certain order.
Inside the intercom there is a photocell that recognizes if holes are drilled in the correct order.
Security is below the baseboard, forging a key is a trifling matter, and some intercoms with optical keys were successfully and without a trace opened with a nail file.
How does the intercom determine if the key fits?
At the factory or at the company that installs intercoms, a special code is written into each key. Then it is also stored in the memory of the intercom.
When you bring the key to the doorphone, it reads the code and compares it with the values ​​from its memory. If the key value is there, the door opens.
By the way, you can open several door phones with one key. It is only necessary to register the code of this key in all the necessary intercoms. It is clear that intercoms must be compatible with the key.
Moreover, there are special modules that allow you to save all the keys from one intercom and transfer them to another.
That’s how you reinstall the intercom in your doorway, and you won’t have to change the keys. Although, of course, the intercom installer may well try to make money on it.
The exception is, perhaps, only MiFare keys. They include a rewritable memory area, in which the unique code of the intercom is copied.
When the master “from the stall” clones such a key, it copies only the factory code, but not the intercom code. As a result, the intercom can reject such a key – the anti-clone protection system will work. Copy the factory code can only service company.
How to make a copy of the key?
Usually for this take a blank – an empty blank without a code. Then the master reads the code from your key and writes it to the disc.
As a result, you get two identical keys. And since the code of the original key is already stored in the intercom, then its clone will open the door.
The blanks are rewritable and non-rewritable. If you remember the word “finalization” when burning discs, take a pie from the shelf, here it also applies.
Technically, you yourself can collect a duplicator (programmer) of keys based on Arduino or Raspberry Pi, and then make copies of the key for all occasions. There are plenty of instructions on the Internet, as well as offers to buy a duplicator for a thousand or other rubles.
The main thing – do not miss with the type of intercom and key.
So, some keys are designed for a frequency of 125 kHz, others at 13.56 MHz, and so on. In addition, they can be of different types. Remember about clone protection that can be supported by your intercom.