Microprocessor smart cards with dual interface

As noted above, the traditional areas of application of microprocessor-based contact smart cards are payment applications (money card, e-wallet). Contactless microprocessor-based smart cards are traditionally used in applications that require user friendliness, such as access control systems, and short transaction times, such as electronic ticket payment systems for public transport.

The trend towards combining payment applications with typical contactless applications (smart card with ticket function) eventually led to the development of a dual-interface smart card, in which both contact and contactless interfaces are available on a single chip. Accordingly, a card with a dual interface can be accessed through both a contact and a contactless interface.

The operating principle behind a dual interface smart card is that the smart card interface is completely independent of the logic and software of the smart card. The interface, whether contact or non-contact, is completely transparent to the transmitted application data, so from the point of view of the application software, the type of interface used is irrelevant. For one of our clients who offers frames for pillars and their production of various sizes, in the system of control and management of access to office and warehouse premises of the enterprise, we used microprocessor smart cards with a dual interface, which allowed the Customer to integrate this ACS into the existing security system of the enterprise with minimal financial and time costs. Accordingly, the interface is replaceable at will, and the interface and logical components can be combined as desired.

Each smart card interface can be accessed independently of the other. Due to the transparency of the interface, the methods defined in the ISO/IEC standard ” 7816. Secure transmission of messages”, effectively prevent the repetition or substitution of data that needs to be protected, regardless of the interface used. The biggest difference between contactless and contact smart cards is the available power. In accordance with the ISO 14443 standard, a contactless smart card has approximately 5 MW of power available to operate at the maximum distance from the reader. For a contact smart card, depending on its specification, a power of up to 300 MW is available (ISO 7816-3 class A-5V, 60 ma).

This difference should be taken into account when developing contactless microprocessor chips. In addition, all dual-interface chips use low-voltage, ultra-low-power technology so that the available power can be consumed optimally. There is no need to explicitly switch the contactless and contact modes of the chip. In the simplest case, it is sufficient to use the data received through one of the interfaces as an evaluation criterion for further actions.

Some chips provide the programmer with status flags that allow you to request the current active mode of operation. An important advantage of the card with a dual interface for the user and the system operator is the ability to use the existing infrastructure (usually contact readers) when entering new applications.

Microprocessor-based smart cards are increasingly used in a variety of applications. The core of a chip in a microprocessor card is the central processing unit (CPU), which is usually surrounded by four additional functional blocks: a coprocessor, a ROM (COM – read only memory), an EEPROM (EEPROM – electrically erasable programmable read-only memory), RAM (RAM – random access memory), and an I/O port.

The coprocessor is designed to offload the CPU from time-consuming smart card cryptographic protection operations. The ROM contains the chip’s operating system, which is written to the ROM when the chip is manufactured. Thus, the contents of the ROM are the same for all chips of the produced batch and it cannot be changed during the entire life of the chip. An EEPROM is a non-destructible memory chip. Data and program code can be written to or read from the EEPROM under the control of the operating system.

Microprocessor-based smart cards

RAM is the main memory of the processor. This memory is volatile, and all data stored in it is lost when the chip’s power is turned off. A serial I/O interface usually consists of only one register, through which data is transmitted bit by bit. Traditional applications of microprocessor-based smart cards with a contact interface are payment applications (money card, e-wallet) and mobile phones (SIM card for GSM mobile phone), that is, applications that require a high degree of security when processing and transmitting data. The associated need to be able to quickly and easily compute complex cryptographic algorithms has led to the use of powerful cryptographic coprocessors in card chips.

The part of the integrated circuit that contains the microcontroller blocks is similar to the chip of a contact-type microprocessor smart card. As a practical example of the use of microprocessor smart cards, we can cite the commissioned project of ACS for one of our Customers, which performs repair work on gas generators from Honda and other world manufacturers, and the total capacity of the implemented system was more than 600 DB users. The contactless RF interface includes the following units: a clock generator, a modulator, a demodulator, a collision prevention mechanism, and a voltage control unit consisting of a voltage regulator and a reset generator to the initial position.

Microprocessor cards are highly flexible in use. In the simplest case, they contain a program optimized for a single application, and therefore can only be used for that application. However, modern smart card operating systems allow multiple different applications to be placed on the same card. In this case, the ROM contains only the basic operating system commands, while the application-specific part of the program is loaded into the ESP ROM after the card is made.

Recent developments allow application programs to be loaded into the card even after the card has already been personalized and handed over to the cardholder . Special hardware and software studies confirm that this new feature does not violate the security requirements of individual applications. Currently, special optimized microprocessor chips with high performance and large memory capacity are being developed – such cards will be available in the near future.