Cross-Coupled Ring Oscillators for On-Chip True Random Numbers
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Solution Overview
Problem
Conventional hardware true random number generators (TRNGs) face challenges when integrating into low-power digital chips due to the need for analog circuits, leading to off-chip fabrication and vulnerability to side-channel attacks, especially when communicating with microprocessors.
Innovation Solution
A semiconductor device featuring cross-coupled ring oscillators that self-correct frequency mismatches and utilize digital counters and comparators to generate true random numbers based on frequency differences, enabling on-chip integration compatible with digital CMOS technology.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional hardware TRNGs use analog circuits to generate random numbers, then true random number generation is achieved, but integration into low-power digital chips becomes difficult and off-chip fabrication is required
Solution Approach 1:
The patent replaces analog circuitry with a fully digital implementation using ring oscillators and digital logic gates. The random number generation is achieved through digital frequency measurements and comparisons rather than analog signal processing, enabling seamless integration with digital CMOS technology while maintaining true random number generation capability
Solution Approach 2:
The patent changes the operating parameters by using frequency-domain measurements of ring oscillator outputs instead of time-domain analog signals. By measuring frequency differences and using digital counters to capture these differences, the system achieves random number generation in the digital domain, resolving the integration conflict with digital chips
2Reliability
If conventional TRNGs are fabricated off-chip to avoid analog integration issues, then true random number generation is maintained, but vulnerability to side-channel attacks increases during communication with microprocessors
Solution Approach 1:
The patent merges the TRNG functionality directly into the digital chip by integrating ring oscillators and digital logic circuits on the same substrate. This eliminates the need for off-chip communication between the TRNG and microprocessor, thereby removing the communication channel that would be vulnerable to side-channel attacks while maintaining true random number generation
Solution Approach 2:
The patent introduces digital counters and frequency measurement circuits as intermediaries between the ring oscillators and the output register. These digital intermediaries process the oscillator signals entirely within the digital domain, preventing any analog or mixed-signal communication paths that could be exploited by side-channel attacks
3Stability of the object's composition
If cross-coupled ring oscillators are used to self-correct frequency mismatches, then frequency stability is improved, but device complexity increases
Solution Approach 1:
The patent implements cross-coupling between ring oscillators where the output of one oscillator feeds back to influence the operation of another. This feedback mechanism enables automatic frequency matching and stabilization without external control, as the oscillators self-adjust their frequencies through the mutual coupling, achieving frequency stability while using only simple digital logic gates
Solution Approach 2:
The ring oscillators are designed to self-correct their frequency mismatches through the cross-coupling mechanism without requiring external calibration or control circuits. The system serves itself by using the inherent properties of the coupled oscillators to automatically achieve frequency synchronization, thereby maintaining simplicity while improving stability
Data Source
AI summary
The semiconductor device comprises a first ring oscillator and a second ring oscillator. An input of the first ring oscillator is an end output of the first ring oscillator and an output of the second ring oscillator and wherein an input of the second ring oscillator is an end output of the second ring oscillator and an output of the first ring oscillator.