Based on the ability to pass data wirelessly a few inches, near-field communications has opened a new world of technology. An entire ecosystem stands ready to support applications ranging from contactless payment cards to authentication between mobile devices. This ecosystem includes chips such as NFC-enabled microcontrollers, standards for wireless transactions, and protocol stacks for handling various communication tasks.
Already, contactless payment cards can be used at 51,000 merchant locations worldwide. NFC-enabled devices such as smartphones and tablets can emulate contactless payment cards. The devices can be used for services such as e-ticketing; e-couponing; secure file sharing; and access control in offices, homes and vehicles. Tapping both NFC and geotargeting technologies, the Google Wallet NFC payments program has lined up such partners as Citi, First Data, MasterCard and Sprint for a launch this summer in San Francisco and New York City.
Biometric passports, meanwhile, use contactless smart cards to enhance security. And so-called smart poster systems provide a different way to access location-based interactive advertising.
For the latter systems, the user initiates access by passing an NFC-enabled handset over the poster’s RFID tag. The handset then connects via the mobile network to the appropriate back-end server. Based on both the user and poster IDs, the server can send back information tailored to the user and the physical location. Users can get directions, learn about a product or offer, get coupons and make reservations.
To protect security, devices such as smart cards and secure-element ICs provide hardware tamper-resistance features, public key infrastructure (PKI) acceleration for authentication, and hardware encryption of the communication channel and/or contents. Those features address high-level EMV (Europay, MasterCard and Visa) security requirements. Supporting software ranges from drivers to middleware and software development kits.
Beyond the NFC hardware and software components is an ecosystem of mobile network operators and transaction service providers. A trusted service manager (TSM) links mobile network operators, banks, service providers and NFC mobile devices. Mobile network operators such as Isis (a joint venture among AT&T, T-Mobile and Verizon in North America) may provide the TSM functions.
NFC hardware architectures
Figure 1 shows one possible implementation of NFC in a handset. A contactless front end (CLF), such as the Renesas RF21 NFC controller, handles RF connectivity and interfaces to the handset’s application processor and subscriber identity module (SIM) card.
Figure 1. In one scenario, a handset can integrate near-field communications using a contactless front end (CLF) that connects to the subscriber identity module via a standard single wire protocol (SWP) interface. Next-generation, integrated implementations provide greater flexibility.
An alternative configuration (Figure 2), which improves flexibility, integrates the CLF within a secure microcontroller such as the Renesas RF21S. This next-generation approach allows the NFC functionality to work either independently of the SIM card or with the SIM card as required. The secure NFC microcontroller can handle all the functionality for applications such as EMV financial transactions, transit system payment cards, ticketing and ID cards.
Figure 2. In the next-gen NFC implementation, a microcontroller integrates the CLF and secure
element (SE) to enable versatile NFC transaction capabilities
using the internal SE or external SIM cards.
Additionally, the microcontroller supports an NFC modem capability that enables additional services via the SIM card or other secure elements in the handset. Because such an approach maximizes versatility, the microcontroller also suits apps in retail equipment, laptops and tablets.
Another configuration approach implements all NFC-related functionality in an SD card. With mobile devices that have an SD card slot, users can plug in the card to get immediate NFC capabilities. One issue with this implementation is the challenge of maintaining RF reception, but banks may favor it because it would preserve their independence from the handset ecosystem. The approach also allows non-NFC-enabled products to support NFC services, albeit mainly in card emulation mode for the time being.
A mobile handset, company ID or just about any other device can incorporate NFC functionality using a contactless sticker—a prelaminate inlay sandwiched into the device’s case during manufacturing.
Alternatively, an NFC-USIM inlay combines a secure NFC microcontroller with a flex RF antenna that can fit with the SIM card into the handset SIM slot and provide NFC services. The unit processes NFC functions locally and passes signals associated with the universal SIM to the host controller.
Three protocol stacks support different modes for communicating with NFC targets: the peer-to-peer stack, card emulation stack and reader/writer stack. Figure 3 shows how the stacks fit into the NFC architecture.
Figure 3. NFC can operate in three modes, each supported by a protocol stack on the device host.
Open NFC, available in an open-source edition sponsored by Inside Secure, provides a complete NFC middleware solution for use in developing mobile phones, embedded products and other devices. The stack covers functions ranging from low-level RF control to NFC Forum-specified tag handling. Developers can work with the stack on various platforms, from the core real-time OS applications to Open NFC for Android.
The main challenge of NFC is deciding just how to take advantage of the technology for the target product. Specific challenges include the need for careful design in handsets to avoid magnetic interference from other components. Similarly, given NFC’s growing popularity, developers will need to manage the complexities of combining multiple secure-element devices into one mobile product.
Ensuring NFC’s reliability, security and ease of use are crucial goals for any NFC solution, since consumer acceptance is at the heart of the technology’s success. As consumers have good experiences with NFC-enabled products, the scope of NFC applications should expand rapidly in coming years.
About the author
Nick Mori is a staff product marketing manager with Renesas Electronics America’s Consumer & Industrial Business Unit, where is he is responsible for product marketing of NFC secure microcontrollers.
Thanks for the detailed description and the architecture of NFC! I was always curious about the design circuit and you have me that. Appreciate the effort. NFC is that technology that is going to take the payment modes and other wireless activities by a storm!
David Patterson, known for his pioneering research that led to RAID, clusters and more, is part of a team at UC Berkeley that recently made its RISC-V processor architecture an open source hardware offering. We talk with Patterson and one of his colleagues behind the effort about the opportunities they see, what new kinds of designs they hope to enable and what it means for today’s commercial processor giants such as Intel, ARM and Imagination Technologies.