Reset Resilience via Unpredictable Storage Initialization
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Solution Overview
Problem
Existing processing circuits are vulnerable to attacks such as differential power analysis (DPA) and fault injection during reset events, as they typically reset storage elements to predictable values, allowing attackers to reproduce and compromise secure data.
Innovation Solution
The apparatus and method introduce update circuitry that stores data values in storage elements based on unpredictable obscuring data, generated frequently, such as pseudo-random numbers, making the data values stored upon reset unpredictable and inhibiting reproducibility of attack steps.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If storage elements are reset to predictable values, then the reset operation is simple and deterministic, but the apparatus becomes vulnerable to DPA and fault injection attacks
Solution Approach 1:
The patent changes the parameter of storage element initialization from predictable fixed values to unpredictable values derived from obscuring data. This parameter change makes the reset operation resistant to DPA and fault injection attacks while maintaining deterministic behavior through the use of a reset signal that triggers the update circuitry to store new obscuring data values in storage elements.
2Reliability
If obscuring data is updated frequently, then the unpredictability of stored values increases and attack resilience improves, but the device complexity and overhead increase
Solution Approach 1:
The patent applies preliminary action by having the update circuitry prepare and store new obscuring data values in storage elements during the reset operation. This preliminary action ensures that when normal operation resumes, the storage elements contain unpredictable values that have been pre-computed and stored, thereby achieving high unpredictability without requiring continuous complex operations during normal execution.
Solution Approach 2:
The patent extracts the obscuring data generation and storage function into a separate update circuitry component. This extraction allows the main processing logic to remain simple while the security function is handled by the dedicated update circuitry that operates during reset events, thereby achieving high security with minimal impact on overall device complexity.
Data Source
AI summary
An apparatus and method are provided for enhancing resilience to attacks on reset of the apparatus. The apparatus comprises at least one storage element, and update circuitry that is configured to receive obscuring data, and which is responsive to a reset event to store in each of the at least one storage element a data value that is dependent on the current value of the obscuring data. For each such storage element, this ensures that the data value stored in that storage element is unpredictable following each reset event, thereby preventing the reproducibility of certain steps that would typically be taken by an attacker during an attack on the apparatus.