ReRAM PUF Key Generation via Low-Current Ephemeral Path Formation
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Solution Overview
Problem
Conventional encryption and authentication systems rely on key-based schemes that are vulnerable to compromise and side-channel attacks, and challenge-response methods are susceptible to interception, compromising security in communication channels.
Innovation Solution
The use of unformed ReRAM cells to generate physical unclonable functions (PUFs) for cryptographic key generation, where low current injection induces ephemeral conductive path formation and measurement, providing unique and secure cryptographic keys without altering the cells' state, and categorizing cells into rugged and vulnerable populations to detect unauthorized characterization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional key-based encryption schemes are used, then encryption and authentication can be performed, but the system becomes vulnerable to compromise and side-channel attacks
Solution Approach 1:
The ReRAM cells generate their own unique resistance characteristics that serve as cryptographic keys, eliminating the need for external key distribution and management infrastructure. Each cell's inherent physical properties provide the security foundation, making the system self-sufficient and resistant to traditional attacks.
Solution Approach 2:
The patent utilizes the natural resistance value parameter of ReRAM cells, which varies uniquely for each cell due to manufacturing variations. By measuring and utilizing these resistance parameters directly as cryptographic keys, the system transforms a manufacturing imperfection into a security feature, making each device's keys unique and unclonable.
2Reliability
If pre-formed ReRAM cells are used for memory storage, then digital memory bits can be stored, but the cells undergo irreversible forming process that lowers resistance permanently
Solution Approach 1:
The patent performs the forming action preliminarily during manufacturing, creating ReRAM cells with controlled resistance characteristics. These pre-formed cells are then used in their formed state for PUF operations, eliminating the need for repeated forming cycles and maintaining stable resistance values for cryptographic key generation.
Solution Approach 2:
Instead of using unformed cells with extremely high resistance, the patent inverts the conventional approach by utilizing pre-formed cells with lower, stable resistance values. This inversion allows the cells to maintain their composition stability while still providing unique resistance characteristics for PUF functionality.
3Measurement precision
If high current is injected through ReRAM cells to measure resistance, then accurate measurements can be obtained, but conductive path formation occurs that permanently alters cell state
Solution Approach 1:
The patent changes the current parameter to a low level that is sufficient for measurement purposes but below the threshold that would trigger conductive path formation. This parameter optimization allows accurate resistance measurements to be taken without altering the cell's conductive path structure or permanent state.
Solution Approach 2:
The patent applies partial action by using only the minimum necessary current level required for resistance measurement. This partial current injection is sufficient to obtain measurement data while avoiding the excessive current that would cause conductive path formation and permanent cell state changes.
4Reliability
If cryptographic keys are exchanged over communication channels, then secure communication can be established, but the keys become susceptible to interception
Solution Approach 1:
The patent extracts the cryptographic key generation process from the communication protocol and embeds it directly within the ReRAM device. Instead of exchanging keys over communication channels, each device independently generates its own keys from its unique physical characteristics, eliminating the vulnerable key exchange step entirely.
Solution Approach 2:
The ReRAM cell's unique resistance characteristics serve as an intermediary that enables secure communication without direct key exchange. The physical properties of the ReRAM cell mediate the generation of cryptographic keys, allowing two parties to establish secure communication through their respective device characteristics rather than through vulnerable communication channels.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach enhances security by generating a large number of unique cryptographic keys with low power consumption, resisting side-channel attacks and allowing secure communication without exchanging keys over insecure channels, while maintaining the cells' quasi-pristine state for repeated use.
Implementation Method 1
Nucleation is when clumps of ions begin to group together at one of the contact points
Implementation Method 2
cations (e.g., Cu or other active metal ions) migrate from the first (active) electrode into the dielectric material to form one or more essentially permanent, but breakable or dissolvable, conductive paths
Implementation Method 3
After measurement, the resistance values return to the original high resistance values of the pristine states (typically 100 MΩ or higher). Thus, the resistance of the cells measurable with small current injection is ephemeral and reversible.
Data Source
AI summary
A system and method of secure communication between computing devices based on physical unclonable functions such as memories having dissolvable conductive paths is provided. The method involves enrolling a client device, the client device having a PUF such as a pristine ReRAM. The PUF is enrolled in a secure environment by reading and storing the resistances of the PUF's addressable memory cells. The cells are categorized into “rugged” and “vulnerable” categories on the basis of their resistance, the vulnerable cells being those more likely to be permanently altered during the generations of PUF responses. The rugged cells are used for the generation of PUF responses for cryptographic key generation, but the vulnerable cells may be inspected to detect unauthorized 3rd party access to the PUF.