Gain Cell Memory PUF Architecture for Simpler Chip Authentication
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Solution Overview
Problem
Existing PUF technologies for chip authentication are complex to implement and present security risks, such as offering a backdoor to the device being authenticated.
Innovation Solution
A physically unclonable function (PUF) structure is implemented using gain cells connected to multiplexers and a current sense amplifier, leveraging the inherent manufacturing variations in retention times of gain cells to generate unique identifiers without precise measurement of each cell's retention time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional PUF structures are used for chip authentication, then authentication functionality is provided, but the implementation becomes complicated and security risks arise
Solution Approach 1:
The PUF structure is segmented into multiple independent gain cells (e.g., 64 gain cells) that can be individually configured and read. Each gain cell operates independently with its own retention time characteristics, allowing the system to achieve high security through aggregation of many simple units rather than one complex unit.
Solution Approach 2:
Multiplexers are introduced as intermediary components to selectively connect groups of gain cells to the sense amplifier. This intermediary layer simplifies the read process by providing controlled access to multiple gain cells through a single amplifier, reducing the complexity of direct connections while maintaining security.
2Measurement precision
If precise measurement of each gain cell's retention time is performed, then unique identifiers can be generated, but the reading process becomes complex
Solution Approach 1:
Instead of precisely measuring retention times of all gain cells individually, the system uses a simplified approach where groups of gain cells are read collectively through multiplexers. The sense amplifier detects relative differences in retention times without requiring precise absolute measurements, achieving sufficient precision for authentication while greatly reducing reading complexity.
Solution Approach 2:
Multiple gain cells are merged into groups that are read simultaneously or sequentially through shared multiplexers and a single sense amplifier. This combining approach allows the system to leverage the unique retention time characteristics of individual cells without the complexity of reading each cell separately with dedicated measurement circuits.
3Ease of operation
If gain cells are connected to multiple multiplexers, then the reading process is simplified, but the device structure becomes more complex
Solution Approach 1:
The multiplexers are designed with universal functionality to handle multiple groups of gain cells. Each multiplexer can selectively connect different groups of gain cells to the sense amplifier, providing a unified interface for reading multiple cells. This multi-functional design simplifies the overall reading process while the modular multiplexer structure manages the device complexity.
Data Source
AI summary
A method is presented for employing a physically unclonable function (PUF) structure for chip authentication. The method includes connecting a plurality of gain cells to either a first multiplexer or a second multiplexer and receiving outputs from the first and second multiplexers by a current sense amplifier. The plurality of gain cells can be either two-transistor gain cell memories or three-transistor gain cell memories.