Memory Controller Read Lock Management for Nonvolatile Data Security
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Solution Overview
Problem
Existing memory systems lack secure data access control mechanisms, particularly in nonvolatile memory systems, where data written before power supply initiation becomes unreadable after power is restarted, compromising data security and user convenience.
Innovation Solution
A memory system with a controller that manages read and write permissions using a management table and read lock flags, allowing data to be locked or unlocked based on power supply states, ensuring secure data access and user convenience by differentiating between system files and user files.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If data is made readable after power restart for user convenience, then ease of operation is improved, but data security deteriorates
Solution Approach 1:
The patent segments data into two distinct categories: system files and user files. This segmentation is implemented through separate management table entries that track read permission flags for each file type independently. System files maintain persistent read permissions across power cycles, while user files have their read permissions cleared after power restart, thereby achieving both security and convenience goals through differentiated treatment.
Solution Approach 2:
The patent applies local quality by assigning different security attributes to different parts of the data storage system. Specifically, system files are granted permanent read permission flags that persist across power cycles, while user files are assigned temporary read permission flags that are cleared after power restart. This localized differentiation of security properties allows the system to simultaneously maintain security for user data and accessibility for system operations.
2Ease of operation
If read permission flags are maintained across power cycles for all files, then ease of operation is improved, but data security worsens
Solution Approach 1:
The patent divides the file system into system files and user files with distinct permission management. The management table contains separate entries for each file type, allowing independent control of read permission flags. This segmentation enables system files to maintain continuous accessibility while user files are protected by clearing their permission flags after power restart, thus preventing unauthorized access to user data.
Solution Approach 2:
Instead of maintaining read permissions for all files across power cycles (the conventional approach), the patent inverts the logic by clearing read permissions for user files after power restart. This inversion ensures that user data is protected by default, and only system files retain continuous accessibility. The management table is designed to automatically clear user file permissions while preserving system file permissions.
3Reliability
If read permission flags are cleared after power restart for security, then data security is improved, but ease of operation deteriorates
Solution Approach 1:
The patent segments file access permissions into two independent management paths: one for system files and one for user files. The management table maintains separate read permission flag states for each category. System files have their read permission flags preserved across power cycles, ensuring continuous accessibility for system operations. User files have their read permission flags cleared after power restart, ensuring security. This segmentation resolves the contradiction by allowing both secure and convenient access patterns to coexist.
Solution Approach 2:
The management table structure serves multiple functions simultaneously: it tracks read permission flags for both system and user files, manages power cycle state transitions, and enforces different security policies for different file types. This multi-functionality allows a single data structure to handle both security requirements and operational convenience needs without requiring separate mechanisms.
Data Source
AI summary
According to one embodiment, a memory system includes a nonvolatile memory and a controller. When power supply is started with respect to the controller, the controller reads file allocation data indicative of an allocation position of a file stored in the nonvolatile memory from the nonvolatile memory, generates information indicating that the controller is permitted to read a system file stored in the nonvolatile memory, and generates information indicating that the controller is not permitted to read a first user file already written in the nonvolatile memory before the power supply, and generates information indicating that the controller is permitted to read a second user file written in the nonvolatile memory after the start of the power supply.