Switch Isolation Circuit for Leakage Current Obfuscation
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Solution Overview
Problem
Existing power isolation techniques are inadequate in preventing leakage current detection, as information about power drawn by switches can still be determined through measurements, even with buffer circuits, due to vulnerabilities in current leakage through protected switches.
Innovation Solution
A switch isolation circuit is introduced, comprising a switch isolation charge store and a buffer circuit, which operates in synchronized modes with a timing signal to provide additional power obfuscation by isolating the charge store from the power input when the protected switch is open, making it difficult to measure leakage current at the power input.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a buffer circuit is used to isolate the power input from the protected switch, then power isolation is improved, but leakage current can still be detected through measurements
Solution Approach 1:
The power isolation circuit is divided into two independent charge stores: a power isolation charge store for isolating power consumption information, and a switch isolation charge store for isolating switch control signals. This segmentation creates multiple isolation layers that prevent leakage current detection more effectively than a single buffer circuit.
Solution Approach 2:
The switch isolation charge store acts as an intermediary between the timing signal and the protected switch, storing the control signal and releasing it to drive the switch. This intermediary layer obfuscates the relationship between the timing signal and switch operation, making leakage current measurements ineffective for determining power consumption.
2Loss of information
If a charge store is used to isolate power output from power input, then power obfuscation is improved, but the charge store remains connected to power input allowing leakage detection
Solution Approach 1:
The system uses two separate charge stores with distinct functions: the power isolation charge store handles power consumption obfuscation, while the switch isolation charge store handles switch control isolation. This segmentation ensures that the charge store connected to power input cannot be used to detect leakage current about power consumption.
Solution Approach 2:
The switch isolation charge store extracts the timing signal from the power input domain and stores it independently. By taking the control signal out of the direct power input connection and storing it separately, the system prevents leakage current measurements from revealing power consumption information.
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 significantly enhances power obfuscation, making it harder to determine current leakage through protected switches, thereby increasing the difficulty of detecting power drawn at the power output by measuring the power input, thus providing a higher level of isolation.
Implementation Method 1
a switch isolation circuit comprising a switch isolation charge store
Data Source
AI summary
There is provided an apparatus and method, the apparatus comprising a power input and a switch isolation circuit to provide isolation between the power input and a protected switch responsive to a timing signal. The switch isolation circuit comprises a switch isolation charge store, and a buffer circuit to receive power from the switch isolation charge store and coupled between the timing signal and the protected switch. The switch isolation circuit is configured to, in response to the timing signal having the first value, operate in a powered mode in which the switch isolation charge store receives power from the power input; and, in response to the timing signal having the second value, operate in an isolation mode in which the switch isolation charge store is isolated from the power input.