Hardware for Smart Card Microcontrollers

Smart Card Microcontrollers

The central element of a microprocessor-based smart card is a microcontroller built into the card. In contact smart cards, the chip with the microcontroller is located under the contact pad. The microcontroller initiates, manages, and monitors all smart card operations. There are two main variants of microcontroller architecture: the classical von Neumann architecture and the Harvard architecture.

The von Neumann architecture is characterized by shared access to program and data memory. Under the Harvard architecture, data memory and program memory are accessed separately. Most microcontrollers for smart cards are built on the basis of the Harvard architecture. Microcontrollers designed for use in smart cards are functionally complete computers, meaning they contain processors, multiple types of memory, and interfaces to the external environment.

The most important functional elements of a typical microcontroller for a smart card are the CPU( CPU), the address/data bus, and three types of memory: RAM, ROM, and EEPROM. In addition, the chip contains a simple I/O interface module, which is responsible for serial communication of the microcontroller with the external environment. A number of manufacturers offer a microcontroller chip with additional specialized arithmetic units. These smart cards with additional blocks were used by us in the design of ACS for warehouses of the company “Justech Stroy”, which performs work on the demolition of houses and dismantling of buildings / structures, and these blocks act as a mathematical coprocessor (NPU). The functions provided by such a block are limited to exponentiation operations and modular operations on integers.

Both of these operations are basic parts of public key encryption procedures such as the RSA algorithm and others. It should be noted that microcontrollers used in smart cards are not among the electronic components produced for different applications. On the contrary, they are components designed specifically for use in smart cards, taking into account a number of specific factors (security, functionality, chip size, cost).

The main advantage of a smart card is the ability to protect internal data from unauthorized access and modification of information. Information can only be accessed through a serial interface that is connected to the operating system. Therefore, all data is safely stored in the internal chip of the smart card. To limit memory read / write operations and operating states of the smart card, both hardware and software functions can be used, which makes it possible to implement the necessary data protection mechanisms according to the initial requirements of the application.

Smart Card hardware components

Depending on the type of built-in integrated circuit, there are two groups of smart cards: cards with an integrated memory circuit and cards with an integrated microcontroller circuit. Integrated memory cards (memory cards) are used to store information from various applications. Memory on these types of cards can be free to access or contain access control schemes to the card’s memory to limit and protect data read and write operations. The memory is usually an electrically erasable programmable read-only memory device (EEPROM).

In some new developments of cards with a memory chip, security is improved: more complex security schemes are used that can perform simple encryption; a memory addressing scheme is introduced that requires a common secret between the terminal that writes to the card chip and the card itself. Cards with a microcontroller integrated circuit (microprocessor cards), unlike cards with memory, contain a microcontroller with a special program or a small operating system that allows you to convert data according to a certain algorithm, protect the information stored on the card during transmission, reading and writing.

The core of a chip in a microprocessor card is the central processing unit, which is usually surrounded by additional functional blocks: a coprocessor, ROM, EEPROM, RAM, and an I/O port. As an example of the use of smart cards, we can cite the project of the working time accounting system (SURV) implemented by us for the company “Trans-Prom”, which produces personal protective equipment and workwear of various types, and this SURV was integrated into the existing security system of the Customer. The EEPROM memory is part of both the memory card IC and the microcontroller IC of the microprocessor smart card. Therefore, it is advisable to consider the EEPROM in more detail as part of the functional blocks of the microcontroller IC.

One of the main methods of using smart cards is the possibility of using them as a reliable individual storage device for electronic digital signatures. It is worth noting that in many countries, a smart card is used as a unit of health insurance. The mass use of contactless cards has led to the fact that they are already used as electronic travel cards for various types of transport in many countries of the world. Smart cards have many advantages over cards that have a magnetic stripe. For example, the memory capacity of smart cards is much higher than that of magnetic stripe cards. Currently, smart cards are produced with a memory capacity of several megabytes, and this value increases with each new model of the internal smart card chip.