Package Substrate PUF Circuitry Using Random Impedance Paths
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Solution Overview
Problem
Existing silicon-based physically unclonable function (PUF) circuits in integrated circuit (IC) chips face security risks due to commonality among chips of the same lot, making them vulnerable to reverse-engineering, and have design challenges related to variability over voltage and temperature changes.
Innovation Solution
Implementing PUF circuit structures on an organic substrate coupled to an IC chip, using a high-throughput additive manufacturing (HTAM) process like cold spray deposition to create randomly varying impedance-based structures, which generate repeatable pseudo-random numbers for cryptographic keys and authentication codes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If PUF circuits are implemented on silicon IC chips, then manufacturing precision and integration are improved, but security vulnerability increases due to commonality among chips of the same lot
Solution Approach 1:
The patent introduces an organic substrate as an intermediary layer between the silicon IC chip and the external environment. This organic substrate contains the PUF circuit structures with randomly varying impedances, physically separating the PUF functionality from the silicon chip. This mediator approach allows the PUF circuits to have unique physical characteristics while maintaining connection to the chip, thereby improving security without sacrificing manufacturing precision.
Solution Approach 2:
The patent changes the physical medium from silicon-based to organic substrate-based PUF circuits. By using organic materials with inherently random impedance variations created through high-throughput additive manufacturing, the physical parameters of the PUF structures differ fundamentally from traditional silicon PUFs. This parameter change ensures that each chip has unique electrical characteristics that are not replicated across production lots, enhancing security while maintaining manufacturing efficiency.
2Ease of manufacture
If traditional fuse-based encryption keys are used, then manufacturing simplicity is improved, but security vulnerability increases due to probing attacks and insider threats
Solution Approach 1:
The PUF circuits on the organic substrate generate encryption keys autonomously through their inherent physical variations. Each PUF structure naturally exhibits unique impedance characteristics that deterministically generate specific pseudo-random sequences. This self-service mechanism eliminates the need for external key programming processes, removing the security vulnerabilities associated with fuse-based key distribution while maintaining manufacturing simplicity.
3Productivity
If PUF circuits use silicon-based implementation, then manufacturing scalability is improved, but design complexity increases due to variability over voltage and temperature changes
Solution Approach 1:
The patent transitions from silicon-based to organic substrate-based PUF circuits, fundamentally changing the physical and electrical parameters of the PUF structures. Organic materials exhibit different electrical characteristics with potentially lower sensitivity to voltage and temperature variations. This parameter change maintains high-volume manufacturing capability through additive manufacturing processes while reducing the complexity of managing environmental variability in PUF circuit behavior.
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 solution provides highly randomized and repeatable impedance variations, enhancing security by reducing commonality-based vulnerabilities and addressing design challenges related to variability across different operational conditions.
Implementation Method 1
using a high-throughput additive manufacturing (HTAM) process like cold spray deposition to create randomly varying impedance-based structures
Implementation Method 2
generate repeatable pseudo-random numbers for cryptographic keys and authentication codes
Data Source
AI summary
Techniques and mechanisms for providing physically unclonable function (PUF) circuitry at a substrate which supports coupling to an integrated circuit (IC) chip. In an embodiment, the substrate comprises an array of electrodes which extend in a level of metallization at a side of the insulator layer. A cap layer, disposed on the array, is in contact with the electrodes and with a portion of the insulator layer which is between the electrodes. A material of the cap layer has a different composition or microstructure than the metallization. Regions of the cap layer variously provide respective impedances each between a corresponding two electrodes. In other embodiments, the substrate includes (or couples to) integrated circuitry that is operable to determine security information based on the detection of one or more such impedances.