Real-Time Entropy Health: How On-Chip Monitoring Secures Cryptographic Keys

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Cryptographic security relies heavily on the unpredictability of random number sources. These components generate the essential bits for key generation and data encryption. Physical hardware imperfections such as voltage fluctuations or device aging can degrade randomness quality. This degradation introduces bias that attackers may exploit. Standards like NIST SP 800-90B require continuous health testing. Traditional methods often provide only binary results. They lack the nuance needed to distinguish between transient glitches and persistent threats.

A new on-chip entropy-quality supervisor addresses these limitations by monitoring output streams in real time. This framework offers a source-independent diagnostic approach. It analyzes non-overlapping 1024-bit windows of data. A shared feature extraction engine calculates key statistics once per window. This efficiency allows multiple modules to reuse figures without duplicating logic. The result is significantly reduced hardware overhead.

The system incorporates tests beyond standard Repetition Count Tests. It uses a Low-Toggle Test to detect insufficient transitions. Two novel indicators analyze two-bit pattern concentration and first-order conditional transitions. These tools identify complex degradation modes like periodic patterns. An Exponentially Weighted Moving Average module tracks trends over time. This helps differentiate isolated anomalies from sustained entropy degradation.

The output provides actionable data for embedded security policies. It generates a 0 to 100 quality score and four supervisory states. A seven-bit alarm bitmap adds further granularity. Upper-level systems can make informed decisions based on this data. Options include logging events or switching to backup entropy sources. Implemented on an Artix-7 FPGA, the core requires minimal resources. It uses just 1009 LUTs and 276 flip-flops. This demonstrates that robust monitoring fits into resource-constrained environments. The advancement supports more resilient cryptographic hardware capable of adapting to dynamic challenges.