OTP Memory PUF Generation for Secure and Reliable Chip IDs
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Solution Overview
Problem
Existing Physically Unclonable Functions (PUFs) face challenges in meeting security, uniqueness, randomness, reliability, and implementation efficiency requirements, often requiring additional masks or processing steps, and are vulnerable to attacks and environmental variations.
Innovation Solution
The use of One-Time-Programmable (OTP) memory to create PUFs through reliable programming methods, including entropy sources, weak bit masking, and hash functions, ensuring data randomness and security without detectable program states, using standard CMOS processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of information
If traditional PUF methods (arbiter PUF, bi-stable PUF) are used to generate unique chip IDs, then uniqueness and randomness are improved, but security against attacks and reliability under environmental variations deteriorate
Solution Approach 1:
The patent applies preliminary action by pre-programming OTP memory cells during manufacturing to store challenge-response pairs. This pre-established storage mechanism ensures that the PUF data is fixed before the device is deployed, eliminating vulnerabilities to environmental variations and attacks that affect runtime-generated PUFs. The OTP cells are programmed once with unique manufacturing variations and maintain their state indefinitely, providing both uniqueness and reliability.
2Reliability
If additional masks or processing steps are added to enhance PUF security, then security is improved, but device complexity and manufacturing cost increase
Solution Approach 1:
The patent merges the PUF generation function with the existing OTP memory structure that is already part of standard CMOS manufacturing processes. By utilizing the OTP cells that are normally used for storing configuration data or calibration information, the invention combines security functionality with an existing memory component, eliminating the need for separate PUF hardware blocks and additional processing steps.
Solution Approach 2:
The OTP memory cells serve multiple functions: they act as both the PUF storage medium and the configuration memory for the device. This multi-functionality allows the same hardware structure to provide both security credentials and operational configuration, reducing overall device complexity while maintaining high security standards.
3Ease of manufacture
If standard CMOS processes are used to manufacture PUFs, then ease of manufacture and cost are improved, but the available PUF types are limited compared to specialized processes
Solution Approach 1:
The patent exploits parameter changes in the OTP memory programming process to generate PUF data. By varying programming conditions such as voltage thresholds, pulse widths, and temperature during the OTP programming stage, the invention creates unique resistance values in the OTP cells that serve as the PUF entropy source. This approach allows standard CMOS OTP memory to provide the same functionality as more complex PUF structures.
Data Source
AI summary
An electronic device and method of generating a Physically Unclonable Function (“PUF”) value is disclosed. An OTP memory with a plurality of OTP cells that can be reliably and deterministically programmed with a minimum and a maximum program voltage being selected for pre-conditioning. All OTP cells can be programmed at least once around the minimum program voltage to hide the program status. Data to be programmed into the OTP can be a fixed, time-varying voltage or data from an entropy source. The programmed OTP data can be masked for weak bits and further randomized to generate PUF output by compressing a bit stream into a single bit, e.g., single parity bit. The PUF output can be through a hash function and/or to generate keys.