Dynamic Row Hammering Threshold for Memory Security
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Solution Overview
Problem
Memory devices are vulnerable to row hammering attacks, where malicious actors can exploit the refresh operations by incrementing activate commands to exceed thresholds, leading to security risks and data corruption, as the existing static thresholds do not effectively mitigate such attacks within a short time span.
Innovation Solution
Implementing a dynamic row hammering threshold that adjusts based on the quantity of rows exceeding the threshold and the total activate operations during the refresh duration, reducing the threshold to prevent a large number of refresh operations from occurring simultaneously, thereby increasing the time for rows to be refreshed and reducing the likelihood of a successful attack.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a static row hammering threshold is used, then the memory device can detect row hammering attacks, but attackers can overwhelm the system by incrementing many rows to near-threshold values and then exceeding the threshold simultaneously
Solution Approach 1:
The patent implements a dynamic threshold mechanism where the row hammering threshold is not fixed but adjusts based on the current state of the memory system. Specifically, the threshold is modified based on the number of rows that have exceeded the threshold within a rolling time window, allowing the system to adapt to attack patterns and prevent overwhelming simultaneous refresh operations
Solution Approach 2:
The system continuously monitors the number of rows exceeding the threshold and uses this feedback to dynamically adjust the threshold value. When many rows are near the threshold, the system increases the threshold to prevent attackers from triggering a large number of simultaneous refresh operations, thereby maintaining system performance under attack conditions
2Reliability
If the threshold is reduced to prevent simultaneous refresh operations, then security is improved, but refresh operations occur more frequently consuming additional time and resources
Solution Approach 1:
Rather than using a permanently reduced threshold, the patent employs a dynamic threshold that temporarily adjusts based on attack conditions. The threshold is only modified when the system detects a pattern consistent with row hammering attacks, and the modification is temporary, allowing the system to maintain security while minimizing unnecessary refresh operations during normal operation
Solution Approach 2:
The system changes the threshold parameter dynamically based on operational conditions. When the number of rows exceeding the threshold within the rolling time window exceeds a certain limit, the threshold parameter is adjusted to prevent overwhelming refresh operations. This parameter change is reversible and adaptive, allowing the system to optimize between security and performance based on real-time conditions
Data Source
AI summary
Methods, systems, and devices for a dynamic row hammering threshold for memory are described. A memory device may implement a dynamic threshold, such as a threshold quantity of activate operations or a row hammering threshold, for a set of multiple rows of the memory device. For example, the memory device may determine a quantity of rows which exceed a row hammering threshold during a refresh duration and a total quantity of activate operations performed across the set of rows during the refresh duration, and may alter the dynamic threshold based on the quantity of rows, the quantity of activate operations, or both. By altering the dynamic threshold, the memory device may decrease a likelihood that a relatively large quantity of refresh operations for rows that are close to being hammered occur within a short time span.