NFC | Near Field Communication
Near Field Communication is a technology invented and developed by Sony and Philips in 2002. It was approved by ECMA (European Computer Manufacturers Association) on the date of its release, and in 2003 ISO/IEC (International Standards Organization / International Electrotechnical Commission) announced that it accepted this technology as a standard technology. ECMA-340 and ISO/IEC 18092 with NFCIP-1 (Near Field Communication Interface and Protocol-1) and ECMA-352 and ISO/IEC 21481 with NFClP-2 (Near Field Communication Interface and Protocol-2). and two separate NFC standards have been developed by ISO/IEC. In 2004, NFC Forum; NXP was founded by Sony and Nokia with the aim of improving and disseminating this technology.
NFC has been developed using RFID protocols, interfaces and infrastructure, so it can be said that it is a technology compatible with current RFID technology. This technology, which has a wireless communication distance of 4 centimeters, can provide contactless communication between 2 devices close to each other at a maximum speed of 424 kbps, at a frequency of 13.56 MHz. This technology realizes communication by pairing the magnetic module in 2 active, passive or two active devices.
It has an infrastructure that complies with ISO/IEC 14443 Contactless Smart Card Technology standards. Thanks to the aforementioned compatible infrastructure, it can provide easy connection, fast processing power and simple data sharing. NFC’s compatibility with other existing contactless infrastructures enables users to use a device in different systems. As mentioned, NFC technology is a technology derived from RFID.
However, what makes it different from RFID is that it provides more communication possibilities. Among these possibilities, the most characteristic feature that distinguishes NFC from RFID is the two-way data transfer between NFC devices. To enable communication between two NFC devices, it will be sufficient to bring the devices close to each other or touch them. Since this communication takes place in a short distance, there is an inherent security (inherent security).
The NFC protocol then automatically establishes a peer-to-peer connection where devices can be in passive or active mode. In passive mode, only one device generates a radio frequency field and the other device applies load modulation for data transmission. Devices that can create their own RF field are active devices and all leading devices are active devices. Devices that cannot create their own RF field are considered passive devices.
The core specification of NFC is that it complements many wireless technologies, key parameters, and elements of existing standards for contactless card technology. Working integrated with smartphones is one of the strongest features of NFC. With the use of this feature, many innovative and unique NFC services have emerged in a short time. Examples of this service are transportation applications, loyalty applications, smart poster applications, ticketing, access control, mobile payments. For this reason, NFC technology reduces the necessity of carrying many objects that people often need to use in their daily life, and enables all these services to be performed with smart phones equipped with NFC.
NFC Operation Modes
Within the scope of active and passive communication mode, NFC communication has three different operating modes. Three different working methods are revealed by touching or bringing the NFC-equipped Smartphone to an NFC reader or another NFC-compatible Smartphone or an NFC tag. These; It consists of Card Emulation, Peer-to-Peer and Read/Write methods.
In peer-to-peer mode, NFC devices are designed to communicate directly with each other, rather than being a contactless smart card reader or contactless smart card. Therefore, both the reader and card side protocol elements were combined in this mode and extended with higher layer protocols specific to peer-to-peer mode.
As seen in Figure 1, the protocol stack of the peer-to-peer mode of NFC is summarized. The lowest layer; It is the lowest level communication technology (NFC-A for 106 kbps and NFC-F for other data rates) that defines the modulation, encoding, framing and device detection procedure.
NFC-A and NFC-F are based on the ISO/IEC 14443 Type A and JIS X 6319-4 smart card protocols, respectively.
NFC Data Exchange Protocol (NFC-DEP) adds device activation and basic data exchange capabilities to NFC-A and NFC-F. Layers up to NFC-DEP are standardized in ISO/IEC 18092. In NFC-DEP, one device takes the role of Master (initiator) controlling the communication and one device takes the role of Slave (target). Also, the two devices can communicate in active mode or passive mode. In active mode, both initiator and target alternately generate their own High Frequency carrier signals. In passive mode, the initiator sends data using its High Frequency signal, while the target responds by modulating the payload in the High Frequency carrier signal sent from the initiator.
On top of NFC-DEP, connectionless end-to-end communication is provided for Logical Link Control Protocol (LLCP) connectivity. These communication endpoints can be used by services and applications on NFC devices and allow multiple communication channels at the same time. On top of LLCP is Simple NDEF Exchange Protocol (SNEP), a known and widely supported service. This protocol allows easy exchange of NDEF messages between applications. NDEF, the NFC Data Exchange Format, allows applications to exchange data regardless of the communication mode and communication technology used.
There are two protocols that provide security for each other mode of communication: NFCIP-1 Security and Service Protocol (NFC-SEC) and TLS over NFC LLCP.
NFC-SEC; NFC-DEP provides channel encryption and authentication between the LLCP layer, while LLCPS provides a TLS (Transport Layer Security) protocol layer similar to HTTPS for LLCP services. However, none of these security protocols are known to exist on NFC-equipped smartphones.
In Read/Write mode, NFC-equipped smartphone can read and write to tags. Contactless communication also supports this mode.
Figure 2 shows the protocol stack of NFC’s Read/Write mode. In Read/Write mode, NFC devices generally support three low-level communication technologies: NFC-A (based on ISO/IEC 14443 Type A), NFC-B (based on ISO/IEC 14443 Type B) and NFC-F (JIS X 6319 -4 base). Some NFC devices also support ISO/IEC 15693 based NFC-V. The ISO Data Exchange Protocol (ISO-DEP) layer is equivalent to the common transport protocol defined in ISO/IEC 14443-4.
Alongside these communication technologies, four standard tag platforms (Type 1–4) and several proprietary tag platforms (eg MIFARE Classic, Type V) define memory structures for storing NDEF messages in these tags. Tag platforms provide an abstraction layer that allows NFC applications to read and write NDEF messages regardless of actual tag hardware and memory layout.
Besides abstracting through NDEF, some device platforms also support direct communication with tags by exchanging commands using ISO-DEP or low-level communication protocols.
Card Emulation Mode
In Card Emulation mode, the NFC-equipped smartphone behaves as if it were a smart card. Figure 3 summarizes the protocol stack of NFC’s card emulation mode. Existing NFC devices with card emulation capabilities support one or more of the low-level communication protocols NFC-A, NFC-B, and NFC-F.
As a result, in card emulation mode, an NFC device can interact with existing contactless smart card readers. Card emulation is usually associated with the secure element (SE), or HCE, which is a secure smart card microchip connected to the device’s NFC controller that performs the actual emulation. In addition to access via the contactless interface, the SE or HCE can also be accessed by applications running on the NFC device’s application processor.