Secure Non-Volatile Memory Cell With Periodic State Flipping
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Solution Overview
Problem
Conventional non-volatile memory cells, such as ROM, are easily reconstructible through structural analysis, making them unsuitable for cryptography applications where the memory content needs to be secure and difficult to detect.
Innovation Solution
A secure non-volatile memory cell with a bistable flip-flop configuration and a mechanism to periodically flip its state using a flip signal, generated by a clock with a period shorter than an emission microscope's acquisition time, ensuring the state is hard to detect through structural analysis, employing cross-coupled inverting elements with similar physical structures but dissimilar transistor characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional non-volatile memory (ROM) is used, then the memory structure is simple and easy to manufacture, but the memory content is easily reconstructed through structural analysis
Solution Approach 1:
The patent applies periodic action by implementing a flip-flop circuit that periodically toggles its state at a frequency higher than the acquisition frequency of emission microscopes. This periodic switching prevents the microscope from capturing a stable state image, thereby securing the memory content against structural analysis while maintaining a simple underlying memory structure
Solution Approach 2:
The patent transforms the static memory structure into a dynamic system by introducing a flip-flop mechanism that continuously switches between states. This dynamic behavior ensures that the memory content cannot be reliably detected through static structural analysis, resolving the contradiction between manufacturing simplicity and detection difficulty
2Difficulty of detecting and measuring
If the memory state is periodically flipped to prevent detection, then the memory content becomes secure against emission microscope analysis, but the memory requires additional control circuitry
Solution Approach 1:
The patent achieves multi-functionality by designing a flip-flop circuit that simultaneously serves as both the memory storage element and the security mechanism. The same circuit that stores data also provides the periodic toggling for security, eliminating the need for separate control circuitry and reducing overall device complexity
Solution Approach 2:
The patent merges the memory storage function with the security function into a single integrated flip-flop structure. By combining these functions, the patent avoids adding extra control circuitry, thus maintaining relatively simple device architecture while achieving secure memory content
3Difficulty of detecting and measuring
If a flip-flop mechanism is implemented to periodically toggle memory state, then the memory becomes difficult to analyze, but the memory can no longer maintain a stable stored state
Solution Approach 1:
The patent uses periodic action at a controlled frequency higher than the microscope's acquisition frequency. This creates the illusion of instability during observation while the memory maintains functional stability for legitimate read operations, resolving the contradiction between analysis resistance and state stability
Solution Approach 2:
The patent ensures continuous useful action by maintaining the memory in a functional state that can be read when needed, while the periodic toggling occurs at a frequency that prevents detection. The memory continuously serves its purpose of storing and retrieving data while simultaneously providing security against analysis
Data Source
AI summary
A secure memory includes a bistable memory cell having a programmed start-up state, and means for flipping the state of the cell in response to a flip signal. The memory may include a clock for generating the flip signal with a period, for example, smaller than the acquisition time of an emission microscope.