Processing Unit Startup Protection Against Monotonic Counter Freezing
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Solution Overview
Problem
Existing methods for securing the startup of processing devices are vulnerable to external attacks, particularly glitch attacks, which can freeze the monotonic counter at a low isolation level, granting unauthorized access to sensitive data and codes.
Innovation Solution
A method and device that utilize a monotonic counter and protection circuit to increment a count value, comparing it to reference values at specific durations during the startup sequence, ensuring that the count value is updated to a secure reference value to prevent unauthorized access, and deactivating the protection circuit when a threshold is reached, thereby securing the startup process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a monotonic counter is used to protect the startup sequence, then security against replay attacks is improved, but the system becomes vulnerable to glitch attacks that can freeze the counter at a low isolation level
Solution Approach 1:
The protection circuit proactively monitors the monotonic counter and preemptively corrects its value before a glitch attack can exploit the frozen state. By continuously comparing the counter value with expected reference values and correcting deviations, the system prevents the vulnerability from materializing rather than reacting after the attack occurs.
Solution Approach 2:
The protection circuit implements a feedback mechanism that continuously monitors the monotonic counter value and compares it with reference values. When the counter is frozen at an incorrect value due to a glitch, the feedback loop detects the deviation and triggers a correction by loading the next expected reference value, thereby restoring security without requiring external intervention.
2Reliability
If the protection circuit continuously monitors and corrects the count value, then security against glitch attacks is improved, but device complexity increases
Solution Approach 1:
The protection circuit applies monitoring and correction only at critical moments during the startup sequence when the monotonic counter transitions between isolation levels. Instead of continuous full-system monitoring, the circuit focuses its protective actions locally at the counter and its immediate control logic, reducing overall system complexity while maintaining security effectiveness.
Solution Approach 2:
The protection circuit is designed to autonomously detect and correct counter value deviations without requiring external intervention or complex control systems. The circuit self-manages the monitoring, comparison, and correction functions using simple logic that loads pre-determined reference values when deviations are detected, thereby providing robust protection with minimal added complexity.
3Reliability
If the count value is frequently updated to reference values, then security is improved, but the startup sequence duration increases
Solution Approach 1:
The protection circuit performs monitoring and potential corrections at periodic intervals corresponding to the expected progression of the monotonic counter through reference values. Rather than continuous checking, the circuit samples the counter at predetermined moments in the startup sequence, allowing the system to maintain security while minimizing interruptions to the normal startup flow and reducing overall startup time.
Data Source
Figure 1A~1B
Figure 2
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AI summary
This description relates to a method comprising: - the protection (301,302) of a start-up sequence of a processing device by increments of a count value generated by a monotonic counter; - a first time after the start of the start-up sequence, the comparison (305, 305'), by the protection circuit, between the count value and a first reference value; and - if the count value is less than the first reference value, the modification (306, 306'), by the protection circuit, of the count value to the first reference value.