Memory Row Hammer Mitigation via Dynamic Refresh Thresholds
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Solution Overview
Problem
Existing memory sub-systems are vulnerable to row hammer attacks, which cause data corruption due to voltage leakage between adjacent memory rows, and current detection methods are either ineffective or resource-intensive, leading to potential data loss and security breaches.
Innovation Solution
Implementing a refresh circuitry with a memory decrease counter (CDC) and row hammer threshold (RHT) to determine when to refresh rows, using a content addressable memory (CAM) to track access counts and limit memory usage, thereby reducing false positives and power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If row hammer detection methods are implemented, then data corruption is detected, but resource consumption increases and false positives occur
Solution Approach 1:
The patent applies partial action by implementing row hammer detection only for specific rows that are identified as high-risk through access pattern analysis, rather than monitoring all rows uniformly. This selective approach reduces resource consumption while maintaining effective detection for the most vulnerable memory locations.
Solution Approach 2:
The system implements feedback mechanisms by continuously monitoring access patterns and adjusting detection thresholds dynamically. The row hammer threshold (RHT) is adjusted based on observed access behavior, allowing the system to reduce false positives while maintaining detection accuracy for actual attacks.
2Reliability
If frequent row refreshing is performed, then data corruption is prevented, but power consumption increases
Solution Approach 1:
The patent implements dynamic refreshing strategies where the refresh threshold is adjusted based on real-time access patterns. Rows with high access counts are prioritized for refreshing, while less active rows are refreshed less frequently. This dynamic approach maintains data integrity for critical rows while reducing overall power consumption.
Solution Approach 2:
The system changes the refresh parameter dynamically by adjusting the row hammer threshold (RHT) based on observed access patterns. When access patterns indicate potential row hammer attacks, the threshold is lowered to trigger more frequent refreshing. When access patterns are normal, the threshold is raised to reduce unnecessary refreshing and power consumption.
3Reliability
If access counting for all rows is implemented, then row hammer attacks are detected, but memory usage increases
Solution Approach 1:
The patent segments the memory array into groups of rows and maintains access counts only for the most frequently accessed rows or high-risk rows identified through analysis. Instead of tracking all rows uniformly, the system divides the monitoring task to focus resources on the most critical segments, reducing memory usage while maintaining effective attack detection.
Solution Approach 2:
The system applies partial monitoring by implementing access counting only for a subset of rows that are identified as high-risk through initial analysis. This selective counting approach reduces the memory required for tracking while maintaining detection capability for the most vulnerable rows that are most susceptible to row hammer attacks.
Data Source
AI summary
Systems, methods, and apparatus for memory device security and row hammer mitigation are described. A control mechanism may be implemented in a front-end and/or a back-end of a memory sub-system to refresh rows of the memory. A row activation command having a row address at control circuitry of a memory sub-system and incrementing a first count of a row counter corresponding to the row address stored in a content addressable memory (CAM) of the memory sub-system may be received. Control circuitry may determine whether the first count is greater than a row hammer threshold (RHT) minus a second count of a CAM decrease counter (CDC); the second count may be incremented each time the CAM is full. A refresh command to the row address may be issued when a determination is made that the first count is greater than the RHT minus the second count.