PUF Memory Anti-Aging and Freezing Attack Countermeasures
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Solution Overview
Problem
Physical Unclonable Functions (PUFs) based on electronic memories are vulnerable to freezing attacks, where the memory state can be temporarily fixed and examined, allowing attackers to access and replicate the PUF pattern.
Innovation Solution
A system that includes a memory used as a PUF with re-writable memory locations and an overwriting mechanism to obscure the response pattern, making it difficult for attackers to access and replicate the PUF pattern by overwriting a portion of the memory locations with random or fixed values.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the memory state is made readable and stable for identification purposes, then the PUF pattern can be accessed and used for device identification, but the system becomes vulnerable to freezing attacks where attackers can temporarily fix and examine the memory state to replicate the PUF pattern
Solution Approach 1:
The system performs preliminary overwriting of memory locations with the inverse pattern before a freezing attack can occur. This preventive action ensures that even if an attacker manages to freeze the memory, they will only capture the obscured inverse pattern rather than the actual PUF pattern, thereby neutralizing the attack vector while maintaining normal PUF functionality during operation
Solution Approach 2:
The patent applies inversion by storing the inverse of the PUF pattern in the memory locations. When the memory is frozen, attackers capture this inverted state instead of the original PUF pattern. The system can later recover the original pattern through bitwise inversion, while the inverted storage obscures the data from attackers attempting freezing attacks
2Reliability
If the memory locations are overwritten with random or fixed values to obscure the response pattern, then freezing attack resistance is improved, but the information content and identification capability are reduced
Solution Approach 1:
Instead of overwriting with random or fixed values that would permanently destroy information, the system overwrites with the inverse of the PUF pattern. This inversion obscures the data from attackers (since they capture the inverted state during freezing attempts) while preserving the ability to recover the original pattern through bitwise inversion, thus maintaining full information content and identification capability
Solution Approach 2:
The system changes the parameter of memory content from the original PUF pattern to its inverse. This parameter transformation maintains the structural integrity and information content of the data while fundamentally altering its observable state, thereby protecting against freezing attacks that rely on capturing the original pattern state
3Reliability
If the memory is repeatedly activated to maintain PUF functionality, then the identification capability is preserved, but the memory becomes more susceptible to aging effects that degrade the response pattern
Solution Approach 1:
The system performs preliminary overwriting with the inverse pattern at designated intervals before significant aging can occur. This proactive maintenance approach resets the memory state and prevents cumulative degradation effects, thereby extending the operational lifespan of the PUF while maintaining its identification capability throughout the extended period
Solution Approach 2:
The patent implements periodic overwriting of the memory locations with the inverse pattern at predetermined intervals or after a certain number of activations. This periodic maintenance action counteracts the cumulative aging effects that occur during repeated use, thereby extending the functional lifespan of the PUF system while maintaining its identification capability
Data Source
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AI summary
Systems for generating an identifying response pattern comprising a memory (120) used as a physically unclonable function configured for generating a response pattern dependent on physical, at least partially random characteristics of said memory may be vulnerable to freezing attacks and to aging. A memory-overwriting device (110) configured for overwriting at least a first portion of the plurality of memory locations to obscure the response pattern in the memory avoids freezing attacks. An anti-degradation device (160) configured to write to each respective location of a second portion of the plurality of memory locations an inverse of a response previously read from the memory reduces the effects of aging.