Ring Oscillator Tap Alternation for Attack-Resistant RNGs
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing random-number generators and ring oscillators are vulnerable to various security threats, including fault-injection and side-channel attacks, which compromise their reliability in cryptographic applications.
Innovation Solution
The design incorporates a cascade of inverters with multiple feedback taps and alternation circuitry, utilizing a multiplexer and Linear Feedback Shift Register to alternate between feedback taps, creating rapid and unpredictable oscillation frequency changes, making the system resilient against attacks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a standard ring oscillator is used for random-number generation, then the circuit is simple and operates at a fixed frequency, but the system becomes vulnerable to fault-injection and side-channel attacks
Solution Approach 1:
The patent applies dynamics by making the ring oscillator's loop delay variable rather than fixed. The alternation circuitry dynamically switches between different feedback taps, changing the oscillator's frequency and timing characteristics in real-time. This dynamic behavior prevents attackers from predicting or exploiting fixed timing patterns, thereby enhancing security resilience against fault-injection and side-channel attacks while maintaining reasonable circuit complexity through systematic design
Solution Approach 2:
The patent changes the loop delay parameter of the ring oscillator by switching between multiple feedback taps with different delay characteristics. The alternation circuitry modifies the effective loop delay by selecting different tap combinations, creating variable oscillation frequencies. This parameter variation ensures that the oscillator does not operate at a predictable fixed frequency, making cryptographic operations resistant to timing attacks and fault injection while managing circuit complexity through controlled parameter switching
2Reliability
If multiple feedback taps with alternation circuitry are added to create variable loop delays, then security resilience against attacks is improved, but the device complexity increases
Solution Approach 1:
The patent segments the feedback path into multiple discrete taps, each providing a different loop delay. Instead of a single feedback path, the oscillator circuit is divided into segments with distinct delay characteristics. The alternation circuitry selectively connects different segments, enabling variable oscillation frequencies. This segmentation approach enhances attack resistance by creating unpredictable timing variations while managing circuit complexity through modular, systematic segmentation of the feedback path
Solution Approach 2:
The alternation circuitry serves multiple functions: it switches between different feedback taps, varies the loop delay, controls oscillation frequency, and enables secure cryptographic operations. This multi-functional component reduces overall circuit complexity by consolidating several security-enhancing functions into a single versatile switching mechanism, thereby improving attack resistance without proportionally increasing device complexity
Data Source
AI summary
An oscillator circuit includes a plurality of inverters connected in a cascade, at least first and second feedback taps, and alternation circuitry. The at least first and second feedback taps are configured to feed-back at least respective first and second output signals taken from at least respective first and second points in the cascade. The alternation circuitry is configured to derive an input signal from at least the first and second output signals by alternating between at least the first and second feedback taps, and to apply the input signal to an input of the cascade.