Microcontroller Self-Test for FIB Manipulation Detection
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Solution Overview
Problem
Security controllers, such as micro-controllers, are vulnerable to permanent modifications via focused ion beam (FIB) attacks, which can compromise their functionality, and existing detection methods like user mode security life control (UmSLC) require additional hardware and significant downtime, making them impractical for integration in all scenarios.
Innovation Solution
The proposed solution involves utilizing the initial clock cycles after a reset signal to execute self-test instructions within the micro-controller, checking for signal path manipulations by shifting a test value through the arithmetic logic unit, and using a control unit to detect deviations from expected values, thereby enabling internal hardware-based security checks without additional hardware or downtime.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If user mode security life control (UmSLC) is used to detect permanent manipulations, then detection capability is improved, but additional hardware is required and considerable downtime is needed for testing
Solution Approach 1:
The processing unit performs self-testing using its own existing hardware resources (ALU, registers, control unit) without requiring external testing equipment or additional dedicated testing hardware. The system tests itself by executing test instruction sequences that utilize normal operational paths to detect manipulations.
Solution Approach 2:
Existing hardware components are made multi-functional by using them for both normal operational tasks and security testing. The ALU, registers, and control unit serve dual purposes: processing normal instructions and executing test instruction sequences to detect manipulations, eliminating the need for dedicated testing hardware.
2Reliability
If user mode security life control (UmSLC) is used to detect permanent manipulations, then detection capability is improved, but considerable downtime is required for testing
Solution Approach 1:
Testing is performed periodically at predetermined intervals during normal operation rather than requiring continuous or extensive dedicated testing time. The control unit executes test instruction sequences at scheduled moments, allowing the system to remain operational while periodically self-testing for manipulations.
Solution Approach 2:
The system maintains continuous operational functionality while integrating testing into the normal operational flow. By using existing operational paths and components for both processing and testing, the system minimizes interruptions and maintains productivity while performing security checks.
3Reliability
If traditional testing methods are used, then detection capability is improved, but integration is sometimes impossible due to hardware requirements
Solution Approach 1:
The processing unit autonomously performs manipulation detection using its own internal resources without requiring external testing equipment or additional hardware interfaces. The control unit executes test instruction sequences that utilize existing ALU and register resources, making the solution universally applicable to any processing unit with basic computational capabilities.
Data Source
AI summary
A processing unit having a control unit configured to execute after a reset phase a sequence of test instructions to detect a manipulation of the processing unit before the control unit decodes a first instruction for a normal operation.