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Technology Description:
Accord’s In-Chip Anti-Tamper Sensor Technology (ICAT) is an on-chip or in-chip package method for detecting physical attacks on semiconductor chips. The ICAT sensor detects artifacts of physical attack by flagging subtle changes in morphology of the physical structure. The sensor is effective whether or not it is powered when structure damage occurs, detecting any physical change of state of the protected infrastructure. Accord’s Phase I results demonstrated the feasibility of the ICAT intrusion sensor, showing very high sensitivity to chip or package structural change. Accord’s work indicates it is feasible to configure this sensor for applications such as chips executing critical technology software or logic, as well as protecting chip packages and buses in printed circuit boards. ICAT is compatible with chip manufacturing and assembly technology. A prototype can be built using laboratory technology available at many MEMS and Nano Tech laboratories.
Protection of legacy circuit boards involves bonding a sensor film to the top of a finished chip package. If protection is added during fabrication, a film is mounted inside the chip package and attached to the chip via matching or decoupling layers. Tamper detection monitors induced changes in sections of the structure which are coupled to the sensor. Laboratory processing uses regression analysis to determine the characteristic inflection points for the “standard” base structure.
Deployed sensor signal evaluation compares results with calibration measurements near critical characteristic inflection points. These inflections establish the “normal” structure response. Physical assaults are detected when sequential status signature measurements are observed to be significantly different. This structure personality assessment information is generated on demand, by a control circuit, thereby requiring no long-term retention of raw measurement data. Compensation for environmental effects on the structure and the sensor are incorporated into ICAT’s sensor analysis. The high sensitivity is obtained by its resonance characteristics over the frequency range of the random pattern oscillator. Laboratory experiments show these values to be sensitive to within one part in 108. The sensitivity is to any physical effects on chip surface, chip package, or the underlying board that modify the structural characteristics.
The Inside Chip Anti-tamper (ICAT) sensor has very small footprint, adding only a small layer to the chip or its package. The small size, weight, heat-added and power-used allows low-cost tamper resistance to be added to platform resources or mission operations. The key to the footprint advantage is its extreme sensitivity and processing simplicity.
Accord defined two approaches for processing the ICAT sensor signal; the first based on an in-phase-and-quadrature-detector bridge then using successive approximation techniques to determine the characteristic inflection points, and their differences, from the structure standard. The second approach is a free running oscillator that automatically matches itself to detect the characteristic inflection points. Thus event processing is reduced to a few small footprint computation chips . The digital circuitry consists of control, reference storage and detection processing using a small microcontroller (or a FPGA processor). The digital unit drives the detection bridge with a direct digital synthesis (DDS) driver. Reference storage memory includes calibration data tables as the structure characteristic baseline. Analog-to-digital and digital-to-analog units are mounted separately.
The micro-miniaturized design requires only an oscillator, an environment compensating sensor, and peak and valley detection logic and a counter to detect physical change to the chip or package structure. The sensor driver is controlled by digital logic which uses a temperature sensor to adjust the driving frequency naturally to compensate for temperature change. A simple counter it the only required sensor.
Detection does not require constant operation; a very low drain timer awakens the sensor, validates package integrity, and returns to sleep mode. When the protected circuits are taken from storage, the detection pace can be set to match mission parameters. When ICAT operates, the sensor driver generates a few micro-Watts of probe energy, (difficult to detect because it has a random pattern characteristics similar to noise). It is also difficult to detect using X-rays because of its appearance as a static protection film. This low detectability allows it to operate in distributed situations, requiring an attacker to have multiple copies to learn about ICAT.
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