Sensing Circuit for IC Protective Coating Tamper Detection
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing methods for protecting integrated circuits against tampering are sensitive to temperature variations and require complex measurement processes, making them less effective for secure applications like smartcards.
Innovation Solution
A sensing circuit that measures the impedance of a protective coating using a reference impedance, incorporated in an oscillator circuit with interdigitated comb structure electrodes, which reduces stray capacitances and provides a reliable secret key generation mechanism.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional capacitance measurement circuits are used to measure the impedance of the protective coating, then the measurement process becomes complex requiring multiple switches and transistors, but this increases device complexity and introduces temperature sensitivity
Solution Approach 1:
The patent extracts the impedance measurement function from complex switching circuits and implements it directly through the oscillator's natural frequency response. The oscillator circuit inherently responds to impedance changes without requiring external switching or transistors, thereby simplifying the device while maintaining measurement precision.
Solution Approach 2:
The patent replaces mechanical switching components (transistors and switches) with an oscillator-based electrical system. The oscillator's frequency naturally adapts to impedance changes, eliminating the need for mechanical or electronic switching mechanisms and reducing temperature sensitivity associated with transistor-based circuits.
2Reliability
If temperature compensation mechanisms are added to reduce temperature-induced variations, then measurement reliability improves, but device complexity increases
Solution Approach 1:
The oscillator circuit performs self-compensation for temperature variations. The resonant frequency of the oscillator naturally adjusts to environmental conditions without requiring external compensation circuits. This self-service mechanism maintains measurement reliability while avoiding additional complexity from temperature compensation components.
3Adaptability or versatility
If multiple security elements are measured sequentially using switches, then the number of measurable elements increases, but the measurement time and device complexity increase
Solution Approach 1:
The patent combines multiple security element measurements into a single oscillator circuit. By connecting security elements in parallel to the oscillator, multiple impedance values can be measured simultaneously or sequentially without requiring switching mechanisms, thereby reducing measurement time and eliminating the need for additional switching components.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution effectively detects tampering by minimizing temperature-induced variations and generating a secure key without the need for complex switching, enhancing the security of integrated circuits.
Implementation Method 1
a sensing circuit arranged to sense a first impedance of a part of the protective coating compared to a reference impedance
Implementation Method 2
The sensing circuit has an amplifier having a feedback loop, such that the impedance being sensed is in the feedback loop
Implementation Method 3
A sensing circuit that measures the impedance of a protective coating using a reference impedance, incorporated in an oscillator circuit
Data Source
Figure 1~3
Figure 4A~4B
Figure 5
AI summary
An integrated circuit has an inhomogeneous protective layer or coating over a circuit to be protected, and a sensing circuit (80) arranged to sense a first impedance of a part of the protective coating compared to a reference impedance (CO) located on the integrated circuit. The sensing circuit is able to measure a change in the first impedance, e.g. caused by tampering. The sensing circuit has an amplifier (OTA) having a feedback loop, such that the impedance being sensed is in the feedback loop. The sensing circuit can be incorporated in an oscillator circuit (OTA, Comp) so that the frequency depends on the impedance. Where the impedance is a capacitance, sensing electrodes adjacent to the protective layer or coating, form the capacitance. The electrodes can be arranged as selectable interdigitated comb structures, so that the protective layer or coating extends in between the teeth of the comb structures.