Runtime Analog Sanitization of NAND Flash Memory
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Solution Overview
Problem
Existing methods for deleting data from NAND flash memory do not effectively prevent recovery of sensitive information using conventional computer forensic techniques, as they only mark memory pages as unavailable without truly overwriting the data, leading to recoverable remnants due to differences in analog voltage levels over time.
Innovation Solution
Implementing a partial programming operation that accounts for relative voltage levels in memory cells to match and equalize voltage levels during data deletion, using a memory controller to determine and adjust for voltage leakage, ensuring that all memory cells have substantially matched voltage levels post-write operation, thereby preventing data recovery.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If conventional deletion methods are used that mark memory pages as unavailable, then ease of operation is improved, but data security deteriorates as sensitive information remains recoverable through forensic techniques
Solution Approach 1:
The patent changes the physical parameter (voltage level) of memory cells to achieve secure deletion. By forcing a program operation that alters the analog voltage state of cells, the original data becomes unrecoverable through conventional forensic means while maintaining operational simplicity for the user.
2Reliability
If forced program operation is applied during deletion to overwrite flash memory cells, then data security is improved, but device complexity increases due to additional control mechanisms needed
Solution Approach 1:
The memory controller automatically manages the complex task of voltage level matching and program operation timing without requiring external intervention. The system self-adjusts the partial programming parameters based on detected voltage levels, hiding the complexity from the user while achieving secure deletion.
3Reliability
If partial programming operation is performed to equalize voltage levels in memory cells, then data security is improved by preventing forensic recovery, but loss of time increases due to additional voltage matching steps
Solution Approach 1:
Instead of performing a complete program operation on all cells, the patent applies partial programming only to the extent necessary to equalize voltage levels and prevent forensic recovery. This partial action achieves the security goal without the full time cost of a complete overwrite operation.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Ensures secure and permanent deletion of data by preventing successful recovery using conventional forensic techniques, maintaining data integrity and security through analog sanitization.
Implementation Method 1
the memory controller is configured to detect a set of voltage levels corresponding to a set of memory cells
Implementation Method 2
a partial write operation is performed to overwrite a portion of the strong zero memory cells such that, upon completion of the partial write operation, the voltage levels in the memory cells substantially match one another
Data Source
AI summary
A memory system performs analog sanitization of memory using a partial programming operation to overwrite existing data taking into account the relative voltage levels in the memory cells. By taking into account the relative voltage levels, the timing of a partial programming operation can be controlled to provide matched voltage levels in the memory cells so that conventional computer forensic techniques for data recovery are ineffective.