Flash Memory Secure Erase via Obscure Operation
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Solution Overview
Problem
Current methods for securely erasing data from flash-based memory, such as overwriting with patterns of 1s, 0s, or random combinations, do not effectively ensure complete inaccessibility of data, especially in high-security environments, and are inefficient due to the granularity of erase operations in flash memory, leading to persistence of old data until entire blocks are reclaimed.
Innovation Solution
A secure erase technique that performs an 'obscure' operation by reprogramming affected sectors to an all '0's state, allowing for immediate deletion without requiring migration or erasure cycles, and operates in a 'secure mode' to force overwrite operations, ensuring data is obscured and recycled through garbage collection or wear leveling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional deletion methods (deleting pointers and directory information) are used, then the operation is simple and fast, but the data remains resident in NVM and is not completely inaccessible
Solution Approach 1:
The patent applies preliminary action by performing an obscure operation on the old version of data before the new version is stored. This proactive obscuration ensures that even if the old data remains in physical locations, it is transformed into an inaccessible state (all 0's or all 1's patterns) before potential recovery attempts can occur, thus achieving complete data security without requiring complex post-deletion verification processes
2Reliability
If secure erase systems overwrite data multiple times with patterns of 1s, 0s, or random combinations, then data security is improved, but the erasure process becomes time-consuming and inefficient due to flash memory erase granularity
Solution Approach 1:
The patent segments the data erasure process into two distinct phases: (1) an immediate obscure operation that transforms old data into an inaccessible state at the logical level, and (2) a background recycling process that eventually reclaims the physical space. This segmentation allows the security-critical obscuration to occur instantly while the resource-intensive physical recycling happens asynchronously, resolving the contradiction between security and time efficiency
Solution Approach 2:
The obscure operation is performed as a preliminary action immediately when new data is to be stored, transforming the old data into an inaccessible state before the new data writing completes. This preliminary obscuration provides immediate security without waiting for the time-consuming physical recycling process to complete, thus achieving both security and time efficiency
3Reliability
If entire blocks are reclaimed through migration or erasure cycles to delete old data, then data security is improved, but performance is significantly impacted due to the granular nature of flash erase operations
Solution Approach 1:
The patent introduces an intermediary obscure operation layer between the logical data storage and the physical flash memory blocks. This intermediary transformation converts old data into an inaccessible state without requiring the complex migration or erasure cycles that would normally be needed to physically delete data from flash blocks, thus maintaining performance while achieving security
Solution Approach 2:
The obscure operation is performed as a preliminary action immediately when new data is to be stored, transforming the old data into an inaccessible state before the new data writing completes. This preliminary obscuration provides immediate security without waiting for the time-consuming physical recycling process to complete, thus achieving both security and time efficiency
Data Source
AI summary
A method is used in securely erasing flash-based memory. A new version of data is received for a logical location of a flash-based memory. An old version of the data of the logical location is stored in a first physical location in the flash-based memory. The old version of the data is caused to be subject to an obscure operation. The new version of the data is caused to be stored in a second physical location in the flash-based memory.