Debug Access Control Using a Monotonic Counter
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Solution Overview
Problem
Debugging procedures for processing devices pose a risk to the security of sensitive data such as encryption keys and proprietary protocols stored in device memory, as existing methods do not adequately protect against unauthorized access during debugging.
Innovation Solution
A method utilizing a monotonic counter to generate and manage count values, which are compared against reference values to authorize or deny debug access, ensuring that sensitive data is only accessible at specific stages of the device's lifecycle.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If debug access is permitted during processing device operation, then debugging capability is improved, but security of sensitive data deteriorates
Solution Approach 1:
The patent applies preliminary action by checking the monotonic counter value before permitting debug access. The system pre-establishes security conditions (counter value comparisons) that must be satisfied before debugging operations can access sensitive data, thereby preventing unauthorized access while maintaining legitimate debugging capability
Solution Approach 2:
The patent introduces a monotonic counter and access control circuit as intermediary elements between the debug interface and sensitive data in memory. This intermediary mechanism mediates access requests by comparing counter values against reference values, allowing legitimate debugging while blocking unauthorized access to encryption keys and proprietary protocols
2Object-affected harmful factors
If monotonic counter value is checked against reference values, then security of sensitive data is improved, but complexity of access control increases
Solution Approach 1:
The patent applies parameter changes by using a monotonic counter that changes its value over time or through operational stages. The access control circuit compares this changing parameter (counter value) against reference values to dynamically control debug access, providing security through parameter evolution rather than static access control
Solution Approach 2:
The patent segments the access control process into distinct stages: generating monotonic counter values, comparing them against reference values, and selectively permitting or denying debug access based on comparison results. This segmentation simplifies the overall control logic by breaking down the security mechanism into manageable, modular operations
Data Source
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AI summary
This description relates to a method for debugging a processing device, the method comprising: - the generation, by a monotonic counter, of a first counting value; - the transmission (209), by the monotonic counter, of the first counting value to a debug access control circuit; - the comparison (211), by the debug access control circuit, of the first counting value with one or more reference values; and - the authorization (215) or prohibition (213) of access for debugging, by the debug access control circuit, on the basis of the comparison.