Dual Protection Word Memory Locking for Transponder Data Integrity
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Solution Overview
Problem
Conventional methods for locking words in non-volatile memory of transponders are prone to errors and data protection failures due to interruptions during the locking process, leading to potential unauthorized access and loss of protection word content.
Innovation Solution
The method employs a dual protection word system where the active and inactive protection words alternate during locking, ensuring that each new lock operation writes the updated content to the inactive protection word, which then becomes active, and includes steps to verify successful writing to prevent data loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single protection word is used for locking memory words, then the locking mechanism is simple, but the system is vulnerable to data loss if the protection word content is corrupted or the process is interrupted
Solution Approach 1:
The protection register is divided into two separate protection words (first protection word and second protection word) instead of using a single protection word. Each protection word can independently store lock bit information, creating redundancy that prevents data loss if one protection word becomes corrupted or the writing process is interrupted. This segmentation resolves the contradiction by increasing reliability without significantly complicating the overall protection mechanism.
Solution Approach 2:
The two protection words have different functional states - one is active while the other is inactive. The inactive protection word serves as a backup that can be activated if needed. This local differentiation in quality (active vs. inactive state) allows the system to maintain simple operation while ensuring reliability through the standby protection word.
2Ease of manufacture
If the protection word content is deleted before writing new content, then the write operation is simplified, but the system risks losing protection if power is interrupted during the process
Solution Approach 1:
Before deleting the content of the active protection word, the system first writes the new protection word content to the inactive protection word. This preliminary action ensures that a valid protection word is already in place before the old one is deleted, preventing any gap in protection even if power is interrupted during the deletion process.
Solution Approach 2:
The inactive protection word acts as a cushion or backup before the active protection word is deleted. If the deletion process is interrupted or fails, the inactive protection word remains as a valid backup, cushioning against the potential loss of protection. This beforehand cushioning resolves the contradiction by maintaining protection continuity while allowing simplified write operations.
3Reliability
If locking is made definitive and irreversible for security reasons, then security is improved, but the system loses flexibility to modify protection settings
Solution Approach 1:
The protection system dynamically switches between two states: programming mode where lock bits can be modified, and locked mode where protection is definitive. The dual protection word structure enables this dynamic behavior - during programming, the system can modify the inactive protection word while the active one remains unchanged, providing flexibility. Once locked, the system can switch to using the other protection word, making the change irreversible and providing security. This dynamics principle resolves the contradiction between security and flexibility.
Data Source
AI summary
The electronic device, in particular a transponder, includes a non volatile memory (EEPROM) having a plurality of words 1 to N whose read and/or write access can be locked. The protection register (22) is formed of two protection words A and B these two protection words are alternately active and inactive during the successive locking of words 1 to N of the programmable memory (16). The state of the protection register is defined by the active word. An initially active word is not deleted until the content thereof has been copied into the inactive word. Once the content has been altered in accordance with the lock command, the initially inactive word becomes the active word of the protection register.