## 4 Intelligent Sensors Model for IT Security Development Process  
The paper is focused on intelligent sensors (sensor nodes, motes), not on sensor networks or control- and SCADA systems, although connectivity aspects will be considered too. To discuss the security features of the intelligent sensor, a common, generalized sensor model should be elaborated. It will be used for security consideration according to the Common Criteria methodology. To develop the generalized intelligent sensor model, another group of publications, presenting different sensors architectures, ought to be reviewed. The paper [25] discusses the architecture and features of wireless intelligent sensors with complete systems on a chip, integrated low-power communication facility, and integrated low-power transducers. The presented example of an intelligent sensor, used to measure temperature and light, consists of a microcontroller (MCU) with internal memories: flash program memory, data SRAM and data EEPROM. It is connected to a set of sensors and actuators. The intelligent sensor also includes LEDs (connected to I/O ports displaying digital values or status), a low-power radio transceiver (for external communication), analogue photo-sensor, digital temperature sensor (A/D converter connected by means of I\({}^{2}\)C, _i.e._, Inter-Integrated Circuit interface), serial port (UART), and a small coprocessor unit. This unit is connected by SPI, _i.e._, Serial Peripheral Interface, to allow sensor reprogramming by transferring data from the network into the coprocessor EEPROM. As an operating system, TinyOS is applied allowing concurrency handling in a very limited memory space. Because the presented intelligent sensor is a prototype for evaluation and further development, physical security (a case, seal, _etc._) was not considered for it. The device is simply implemented on a small printed circuit board, convenient for experimentation. Hardware solutions for sensor nodes (called motes) used for permanent monitoring of long-term care patients are presented in [10]. One of the used hardware platforms was Crossbow MICA [26]. MICA (as well as IRIS), operating on TinyOS, consists of: Atmel(r) ATMega128 MCU (8-bit microcontroller with 128 K Bytes In-System Programmable Flash, digital and analog I/O) [27], RF transceiver, flash data logger memory (storing data and measurements, over-the-air reprogramming under TinyOS), power source (batteries), and sensor board interface (to connect peripheral sensors and data acquisition boards or base station, including connections for: A/D converter, UARTs, I\({}^{2}\)C, digital I/Os). The latest IRIS is equipped with the ZigBee standard [28], ready radio frequency transceiver (of better range), and sensor ID facilities. Many advanced solutions were developed according to this proprietary standard, including network processors [29] with implemented protocols. The paper [30] describes another new general-purpose wireless sensor node architecture designed for experimentation, educational projects and preliminary deployment in industrial environments. It is based on the OKI ARM ML67Q500x microcontroller and Chipcon CC2420 ZigBee-compliant communication subsystem. Four-layer software architecture was applied, encompassing: sensor drivers, preprocessing and measurement storage, localization algorithms, and sensor network applications. Echelon FT 5000 Smart Transceivers/ Neuron(r)5000 [31] is another representative example of a platform for intelligent sensors. The Neuron chip series, provided with multiple processors, ROM, RAM, communication and I/O subsystems, is able to perform key functions necessary to process inputs from sensors and control devices, and to propagate control information across different kinds of network media. Neuron contains three processors to manage the operations of the chip, the network, and the user application. At higher clock rates, it is additionally equipped with a separate processor to handle interrupts.