Phase Change Memory PUF Key Generation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing physical unclonable functions for integrated circuits have limited variability, making them susceptible to bit errors due to slight changes in temperature or time, which compromises security, especially when analog values are close to threshold thresholds.
Innovation Solution
Embedding phase change memory with intentionally increased variability in resistance values by applying programming pulses or laser anneals, creating a wide range of unique physical properties that are used to derive cryptographic keys, reducing the likelihood of bit errors and enhancing security.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If phase change memory is used for physical unclonable functions, then device authentication capability is provided, but variability in resistance values causes bit errors under temperature or time changes
Solution Approach 1:
The patent applies parameter changes by intentionally modifying the resistance values of phase change memory cells through controlled programming pulses or laser annealing. This creates a deliberate distribution of resistance values that are sufficiently separated from threshold values, ensuring that temperature or time variations do not cause bit errors. The key insight is changing the parameter distribution (resistance values) to achieve both uniqueness for authentication and stability against environmental variations.
2Reliability
If cryptographic keys are stored in non-volatile memory, then authentication capability is enabled, but physical access allows key extraction attacks
Solution Approach 1:
The patent extracts the cryptographic key from static non-volatile memory storage and replaces it with a dynamic physical unclonable function based on phase change memory. Instead of storing the key directly, the system uses the unique resistance characteristics of phase change memory cells to generate authentication credentials on-the-fly. This extraction of the key from persistent storage eliminates the vulnerability to physical extraction attacks while maintaining authentication capability.
3Reliability
If phase change memory variability is increased for security, then resistance value distribution improves, but manufacturing precision requirements increase
Solution Approach 1:
The patent applies preliminary action by intentionally programming the phase change memory cells during manufacturing to achieve a desired resistance value distribution. Through controlled application of programming pulses or laser annealing, the manufacturing process pre-establishes resistance values that are optimally distributed for both security and stability. This preliminary configuration ensures that subsequent operational variations (temperature, time) do not compromise authentication reliability.
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
The increased variability in phase change memory properties results in more reliable and stable binary keys, reducing the risk of bit errors over time and temperature changes, providing greater security and a larger number of unique PUF values for various devices.
Implementation Method 1
embedding a phase change memory in the secure device, where the phase change memory includes a plurality of cells, and setting the phase change memory in a manner that results in a phase variation over the plurality of cells
Data Source
AI summary
A method of manufacturing a secure device having a physical unclonable function includes embedding a phase change memory in the secure device, where the phase change memory includes a plurality of cells, and setting the phase change memory in a manner that results in a phase variation over the plurality of cells, wherein the phase variation is the physical unclonable function. A method for retrieving a cryptographic key from an integrated circuit, wherein the cryptographic key is stored in the integrated circuit, includes measuring a property of a phase change memory embedded in the integrated circuit, wherein the phase change memory includes a plurality of cells and the property is a function of a phase variation over the plurality of cells, deriving a signature from the property, and deriving the cryptographic key from the signature.