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NFC locking systems

Wooden door with modern intercom with NFC function

NFC locking systems / NFC locks

Electronic payment in the form of NFC-based EC or credit cards demonstrates that NFC is also a suitable technology for security-critical systems. Electronic door locks are another application where security is a primary point. This article first explains the basic principle of electronic locks. Then goes on to discuss the use of NFC and finally summarizes the advantages of NFC locking systems and introduces a number of using examples.

Locking systems

The mechanical lock can look back on a long and varied history that goes back to the Bronze Age. Simplified, a lock consists of two elements: The locking mechanism and a key with which the mechanism can be locked or opened. In a typical door lock, for example, the locking mechanism ensures that a bolt is extended, thus preventing the door from opening. Opening and closing is normally made possible by a mechanical movement (turning), for which the appropriate key must be used. Electronic door locks promise to modernise this basic principle.

Electronic lock and electronic key

Electronic locks are locking systems, that replace the mechanical key with a digitized version. The mechanics for opening and closing are independent of each other and can be manual (e.g. by turning a knob) or electro-mechanically assisted (e.g. by a motor that operates the bolt). A non-mechanical key is giving the release whether the lock may be opened or closed. The key information is therefore available in digital form and must be exchanged between the key and the lock in order to have the lock check it and grant or refuse release. The challenge is therefore to digitally map the key and exchange the information with the lock - this is where NFC comes in as a suitable technology.

NFC door locks and NFC keys

With the help of NFC, data can be transmitted over short distances without configuration. As described in the basic article, communication takes place either between an active and a passive NFC transmitter or between two active transmitters. In this case, the typical NFC door lock takes on the role of an active NFC transmitter. This means that the locking system is extended with electronic components (logic and NFC antenna) so that it can communicate with other NFC transmitters - in this case the counterpart to the NFC lock, the NFC key. 

In simple terms, there is a secret on the NFC key. If the NFC key is held close to the NFC lock, the NFC lock reads/checks the secret and, if it is the correct key, releases the access and thus enables the lock to be opened/closed. Of course, the procedures are much more complex in reality and usually use advanced cryptographic methods and encryption, which will not be discussed in detail here. Instead, the aspect of the key will be examined in more detail.

NFC smartphone or NFC tag as key for NFC locking systems 

The key for an NFC locking system can be either an NFC smartphone or a passive NFC chip. In the case of a NFC smartphone, an app from the lock manufacturer is typically installed on the device and connected to the lock, e.g. via an account or by entering key information. The NFC smartphone can then be used by holding it in front of the NFC lock. To find out whether an NFC lock can also be unlocked with the NFC smartphone, please refer to the function list of the relevant provider. For example, BMW supports the unlocking of some models with the Android NFC smartphone. Apple will also make it possible to use the iPhone as an NFC key starting with iOS 14 - with BMW as one of the first implementations for opening the car via iPhone with NFC. However, since the smartphone must be charged and unlocked for use as a key, the battery-free NFC tags can show their strength. 

In the case of an NFC tag, the energy of the NFC lock is used to read and check the contents. Typically, these NFC tags are delivered in form of a key fob and are appropriately robust and waterproof encapsulated to withstand environmental influences. However, not every NFC tag can be used as a key for an NFC locking system. Several parameters must be fulfilled: 

Firstly, the chip type must match the locking system used and its security mechanism. For example, many older systems work exclusively with the MIFARE Classic chipset, whereas newer systems increasingly rely on DESFire EV1 or equivalent chips with appropriate security procedures. On the other hand, it is very important that the lock is supporting the learning of new keys. Whether and how NFC tags from other manufacturers can be taught in can be found out from the manufacturer information of the NFC door lock. You are welcome to share your experience with other customers at this point.

Advantages and application examples of NFC locking systems and locks

Although mechanical locking systems will continue to represent the majority of locking systems in practice for the foreseeable future due to their simplicity combined with robustness, there are some advantages that may make electronic alternatives the preferred choice. The use of electronic keys in combination with modern cryptographic procedures can provide security levels that cannot be achieved by mechanical keys. Properly implemented cryptography effectively prevents the copying of keys. In addition, lost keys can be blocked, which in mechanical systems would only be possible by a complete replacement of the locking system. Central, IT-supported control systems for key allocation also facilitate the management of access rights in buildings and form the basis for modern security concepts. But NFC locking systems can also bring advantages in private use - for example, suitable systems can be used to create keys themselves or to issue access rights flexibly, for example at specific times. When choosing a suitable system, it is therefore important to compare your own requirements with those of the respective suppliers. The IKEA NFC locking system and Doorbird are given below as examples.

NFC locking systems for cupboards and lockers 

The NFC lock ROTHULT from Ikea is an example of an electromechanical locking system based on NFC. It consists of a lock body with a pin that moves in / out by motor, provided the correct key card has been scanned. The energy in the form of batteries is thus used both to communicate with the key and to open / close the lock. Due to its design and the matching IKEA system, the lock can be used for office cabinets and lockers. Two NFC cards are included in the delivery. However, new NFC tags can be connected to the NFC locking system - but cards with chip X are required.

An instruction manual for learning new NFC tags for the NFC lock is available here.

NFC interfon from DoorBird

The modern intercom systems for the front door of DoorBird allow you to experience the events in front of the door live via microphone and camera. It is also possible to connect the smartphone to open the door from any location. The DoorBird system uses RFID/NFC-based transponders as keys. Since the system can learn its own transponders, new keys can be created for DoorBird itself. Instructions are available here.

Conclusion and summary

NFC as a basic technology is also increasingly used in the area of locking systems. The high degree of standardisation of NFC and the spread of NFC smartphones and their resulting suitability as keys can be cited as reasons. Systems such as ROTHULD from Ikea or Doorbird show how NFC locking systems are also becoming more and more widespread outside building complexes with complex security management requirements. When choosing an NFC locking system, we recommend that you make sure that even new key tokens can be generated. This opens up a wide range of possibilities for generating your own NFC keys - for example in the form of bracelets or your own, more creative pendants.

First published: 25.07.2023 / Updated: 06.05.2024 2023-07-25 2024-05-06