OTP Memory Indirection and Hashing for PUF Security
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Solution Overview
Problem
Existing PUF circuits face challenges in securing access to integrated circuits as content stored in OTP memory devices can be discovered through reverse engineering, compromising security.
Innovation Solution
The implementation of an indirection process combined with hashing to hide content stored in OTP memory devices, generating a key for secure access, where the PUF device employs a PUF controller and OTP memory to transform input bits into hidden content, and subsequently a key for accessing SRAM, utilizing hash functions and indirection processes to obscure the content from external devices.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If content is stored directly in OTP memory device, then access is simple and direct, but security is compromised due to reverse engineering
Solution Approach 1:
The patent introduces an indirection mechanism where the OTP memory device does not directly store the secret key, but rather stores data that indirectly leads to the key through a computational process involving hash functions and indirection tables. This intermediary layer prevents direct access to the secret key, thereby improving security while maintaining manageable access complexity through structured processes.
Solution Approach 2:
The system performs preliminary actions by pre-computing hash values and indirection tables during system initialization or manufacturing. These pre-computed structures are stored in the OTP memory, so that during operation, the actual secret key derivation requires following the pre-established indirection paths rather than direct access, thus enhancing security without requiring complex real-time computation.
2Reliability
If indirection process with hashing is implemented to hide content, then security is improved against reverse engineering, but device complexity increases
Solution Approach 1:
The secret key storage is segmented into multiple components distributed across different memory locations via indirection tables. Instead of storing the complete key in one location, the system divides the key derivation process into segments that follow multiple indirection steps, making reverse engineering more difficult while keeping each individual step relatively simple and manageable.
Solution Approach 2:
The patent adds an additional dimension to the key access process by introducing indirection tables that map logical addresses to physical storage locations. This dimensional transformation converts a direct one-to-one mapping into a multi-hop indirect mapping, thereby enhancing security through increased access complexity without requiring fundamentally new hardware components.
3Reliability
If multiple indirection processes are applied to obtain hidden content, then security against reverse engineering is enhanced, but access time and complexity increase
Solution Approach 1:
The indirection tables and hash structures are pre-computed and stored during manufacturing or initialization. This preliminary action ensures that during operational key access, the system only needs to follow pre-established paths rather than performing complex real-time computations, thereby minimizing access time while maintaining the security benefits of multiple indirection steps.
Solution Approach 2:
The system dynamically adapts the number of indirection steps based on security requirements and performance constraints. By making the indirection process configurable and adaptable, the system can optimize the balance between security (more indirection steps) and access time (fewer steps), allowing flexibility in tuning the security-performance tradeoff for different application scenarios.
Data Source
AI summary
Disclosed herein is related to physical unclonable function (PUF) with enhanced security based on one time programmable (OTP) memory device. In one aspect, indirection process, hashing or a combination of them can be employed to hide a key for allowing access to an integrated circuit. Each indirection process may include identifying a subsequent address of the OTP memory device based on content stored by the OTP memory device at an address, and obtaining subsequent content stored by the OTP memory device at the subsequent address. Through a number of indirection processes, hidden content stored by the OTP memory device can be obtained. In one approach, hashing can be applied to input bits to obtain an address of the OTP memory device to apply. In one approach, hashing can be applied to the hidden content stored by the OTP memory device to generate the key.