Memory Control Circuit With Randomized Row-Hammer Mitigation
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Solution Overview
Problem
External attackers can exploit the threshold values and access counts in memory devices to initiate row-hammer attacks, which overwhelm the memory device and reduce its efficacy.
Innovation Solution
A memory control circuit with a reset circuit, counter, and comparator that resets count values to a predetermined value and sets them to random values when necessary, making it difficult for attackers to determine the mitigation operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the memory device uses a fixed threshold value and count value for mitigation operations, then the mitigation operation can be performed efficiently, but external attackers can obtain and exploit these values to initiate row-hammer attacks
Solution Approach 1:
The patent applies dynamics by making the count value changeable over time through randomization. The count value is initialized to a random value and incremented dynamically with each access, rather than being a fixed static value. This dynamic behavior prevents attackers from predicting when mitigation will trigger, while still allowing the mitigation operation to function efficiently when the randomized threshold is reached.
Solution Approach 2:
The patent changes the parameter of the count value from a fixed predetermined value to a randomized value. By initializing the count value to a random number between 0 and the threshold value, and by randomizing the threshold value itself, the system alters the parameters that attackers would otherwise exploit. This parameter randomization maintains mitigation efficiency while preventing predictable attack patterns.
2Adaptability or versatility
If the count value is reset to a predetermined value after refresh command, then the count value can be reused for subsequent accesses, but attackers can predict the count value pattern and target specific memory cell rows
Solution Approach 1:
The patent makes the count value dynamic by randomizing it upon reset instead of using a fixed predetermined value. Each time a refresh command is received, the count value is reinitialized to a new random value rather than a static predetermined value. This dynamic randomization prevents attackers from predicting future count values while still allowing the count value to be reused for subsequent accesses.
Solution Approach 2:
The patent applies preliminary action by randomizing the count value in advance before accesses occur. The count value is initialized to a random number at the beginning of each refresh cycle, so that when attackers attempt to predict or exploit the count value pattern, the randomized initial value already prevents them from knowing what to expect. This preliminary randomization occurs before any access patterns can be exploited.
3Reliability
If the memory device performs mitigation operation frequently to prevent row-hammer events, then memory cell rows are protected, but the memory device becomes busy and efficacy decreases
Solution Approach 1:
The patent applies partial action by using randomized thresholds and count values to trigger mitigation operations only when necessary, rather than performing frequent mandatory mitigation. The randomized approach allows the system to maintain protection while reducing the frequency and predictability of mitigation operations, thereby improving overall device efficacy while maintaining adequate protection levels.
Data Source
AI summary
A memory control circuit and a control method of the memory device are provided. The control logic circuit includes a reset circuit, a counter and a comparator. The reset circuit resets a count value corresponding to an accessed memory cell row among memory cell rows of a memory array to a predetermined value. The counter sets the count value to a random value when the count value is equal to the predetermined value. When the count value reaches to a threshold value, the memory control circuit arranges memory cell rows nearby the accessed memory cell row into a mitigation operation.