Abstract
Embedded systems that follow a secure and low-power design methodology are, besides keeping strict design constraints, heavily dependent on comprehensive test and verification procedures. The large set of possible test vectors and the increasing density of System-on-Chip designs call for the introduction of hardware-accelerated techniques to solve the verification time problem. As already described earlier, emulation-based methodologies based on FPGA evaluation platforms prove capable of providing a solution compared to traditional system simulation. This chapter gives an introduction into a multi-disciplinary emulation-based design evaluation and verification methodology that is based on various techniques that have been presented in chapter 5. Test and verification capabilities are enhanced by the augmentation of this approach using model-based analysis units: gate-level-based power consumption models, power supply network models, event-based performance monitors, and high-level fault modes. The feasible usage of this verification methodology in the field of contactlessly powered smart cards is finally demonstrated using several industrial case studies.
TopIntroduction
Semiconductor industry advances have led to technology capabilities permitting the integration of an increasing number of features on the same chip size. This comes along with a number of challenges, first, the increasing susceptibility of these systems to power and supply voltage variations translating to higher demands in system reliability. Second, a growing number of these highly integrated systems are deployed in security applications (electronic passports, electronic payment, etc.), yielding higher requirements in system security.
In recent years, however, the industry has faced a multitude of design challenges. First, the lack of rich design tools and effective design methodologies has caused an emerging productivity gap between the potential of presently available technology and the exploitation of its potential (ITRS Working Group, 2012, ITRS). Second, the late design phase applicability of many tools has blocked designers from investigating the potential design issues and introducing countermeasures early in the design phase. Early design phase monitoring of the following physical parameters such as, system performance, power and supply voltage, and security-relevant system behavior, is essential in order to reduce the productivity gap and to further push semiconductor advances.
Figure 1 illustrates a typical industrial near-field communication (NFC) system giving a prime example of contemporary power-constrained embedded systems. A smart-phone, a multi-feature and inherently power-constrained device, must provide power to the contactless smart card system (through a wireless air interface, e.g., ISO-14443 standard) by electromagnetic induction. This way of powering a device is described as a loosely power-coupled system. On the smart card end, power management is a critical issue due to the varying nature of its power supply and power consumption. While the strength of the electromagnetic field is set by the reader, the consumption is directly dependent on the smart card functions: it rises according to an increase in activity in its arithmetic and logic units and vice-versa. If power consumption is higher than power supply for a duration that cannot be compensated by draining the capacitor of its charge, then hazardous supply voltage drops can occur, which lead to operational failures. Contrarily, if power supplied is higher than power consumed for a duration that cannot be compensated by charging the capacitor up to its maximum voltage, then the excess energy is bled out of the system via the shunt resistor 
, which is depicted by a Zener diode in a simplified way. Its purpose is to protect the smart card electronics against power surges and to reduce side-channel information leakage.
Figure 1. Reader/smart card system and dedicated smart card power/voltage trends. Peak power consumption provokes hazardous supply voltage drops which may compromise the smart card’s operational stability.
In addition, smart card systems may be the target of security attacks. Such attacks must be countered by the smart card and, at the same time, it has to perform its normal functions in a reliable fashion and, whenever it is possible, with the best possible performance.
TopObjectives
Figure 2 shows our proposed comprehensive early design phase evaluation platform. It enables functional, power consumption and supply voltage, as well as performance and fault-attack investigations of power-constrained embedded systems.
Figure 2. Principle of the early design phase evaluation flow
Key Terms in this Chapter
Fault Attack: A fault attack is an intentional manipulation of the integrated circuit or its state, with the aim to provoke an error within the integrated circuit in order to move the device into an unintended state. The goal is to access security critical information or to disable internal protection mechanisms.
Fault: A fault constitutes a deviation of normal internal system states or signals. Such deviation could lead to the generation of wrong results, but it could also be masked by the current system state.
Power Emulation: Power emulation extends the hardware emulation technique with power sensors and corresponding power models in order to gather estimated power analysis data of the design-under-test.
Hardware Emulation: Hardware emulation is a technique that integrates a hardware design into a reconfigurable (e.g. FPGA-based) prototyping platform in order to allow the functional testing of a design-under-test including its firmware. This way both hardware and software can be evaluated in a realistic performance setting.
System-on-Chip: A System-on-Chip (SoC) is an integrated circuit integrating all circuits and electronics (such as analog, digital, mixed-signal, or RF components) necessary for a system on a single chip.
Error: An error describes a deviation from the expected system behavior caused by a fault. Therefore, an error is a final consequence after a fault was activated and the result is stored by internal or external resources.
Smart Card: A smart card is a device with an integrated circuit including its own memory and central processing unit. Besides a standard contact-based interface, it can also be powered contactlessly by means of an alternating and modulated magnetic field, through which contactless communication is also enabled.
Vulnerability: Vulnerability describes a certain inability of a system to withstand the effects of an attack in a hostile environment.