A Lightweight True Random Number Generator Based on Chain-Coupled Oscillation Rings

ZHANG Yuan; YING Haixuan; GAO Kai; YE Jin; WANG Shuang; ZHANG Jiliang

doi:10.11999/JEIT260377

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ZHANG Yuan, YING Haixuan, GAO Kai, YE Jin, WANG Shuang, ZHANG Jiliang. A Lightweight True Random Number Generator Based on Chain-Coupled Oscillation Rings[J]. Journal of Electronics & Information Technology. doi: 10.11999/JEIT260377

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ZHANG Yuan, YING Haixuan, GAO Kai, YE Jin, WANG Shuang, ZHANG Jiliang. A Lightweight True Random Number Generator Based on Chain-Coupled Oscillation Rings[J]. Journal of Electronics & Information Technology. doi: 10.11999/JEIT260377

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A Lightweight True Random Number Generator Based on Chain-Coupled Oscillation Rings

doi: 10.11999/JEIT260377 cstr: 32379.14.JEIT260377

College of Integrated Circuit Science and Engineering, Nanjing University of Posts and Telecommunications, Nanjing 210023, China

Funds: National Natural Science Foundation of China under Grant No. U24A20289

Accepted Date: 2026-06-04
Rev Recd Date: 2026-06-04

Available Online: 2026-06-08

Abstract

Abstract

Objective With the rapid growth of the Internet of Things, 5G/6G, and satellite Internet, resource-constrained devices increasingly require high-quality random numbers for key generation, authentication, masking, and other security functions. Although pseudo-random number generators are efficient, their outputs may be predictable once the seed or internal state is compromised. True random number generators (TRNGs) offer a hardware root of trust by extracting entropy from physical randomness, but many existing designs rely on multiple entropy sources or complex post-processing, leading to increased area and power consumption. To address this issue, this paper proposes a lightweight TRNG based on chain-coupled oscillation rings for high-quality randomness with very low FPGA overhead. Methods Starting from the state evolution of a Galois oscillation ring (GARO), this work demonstrates that ideal matched-delay conditions can result in periodic and predictable oscillation. However, in practical circuits, delay mismatch, jitter, and process variation disturb the ideal evolution and can be exploited as entropy sources. On this basis, a compact delay-feedback XOR ring is proposed to enhance state uncertainty, introduce feedback competition, and improve randomness through inter-stage delay differences. In addition, a second-order oscillation ring is incorporated to eliminate the all-zero stop state and provide continuous excitation. Multiple rings are then chain-coupled, enabling adjacent rings to mutually interfere with one another and thereby generate stronger irregular oscillations. The proposed design is modeled in MATLAB and implemented on a Xilinx Artix-7 FPGA. Finally, we evaluate its performance by NIST SP 800-22, NIST SP 800-90B, bias, autocorrelation, and voltage-temperature robustness tests. Results and Discussions Simulation confirms that the proposed structure avoids stable periodic locking and produces sustained irregular oscillation. Experimental results show that the TRNG passes all NIST SP 800-22 tests and achieves an average minimum entropy of 0.9936 in NIST SP 800-90B test, outperforming conventional RO and GARO-based TRNGs under similar conditions. The measured bias is only 0.0228%, and the autocorrelation remains well below the threshold, indicating excellent statistical independence. The design also maintains high entropy over temperatures from 0 °C to 80 °C and supply voltages from 0.9 V to 1.1 V. Implemented on Artix-7, our proposed TRNG achieves 200 Mbps throughput using only 11 LUTs and 4 DFFs, with 0.108 W power consumption. Conclusions This paper presents a lightweight chain-coupled oscillation-ring TRNG that exploits delay mismatch, phase disturbance, and feedback competition to generate high-quality physical randomness. The theoretical analysis clarifies how practical nonidealities transform ideal periodic oscillation into irregular oscillation, providing a design basis for compact oscillator-based entropy sources. By combining delay-feedback XOR rings with chain-coupled mutual disturbance and continuous excitation, the proposed design enhances entropy while avoiding excessive hardware overhead and complex post-processing. FPGA implementation and statistical evaluations verify high entropy, low bias, and high randomness under voltage and temperature variations. Therefore, the proposed TRNG achieves high randomness quality and high throughput while effectively reducing hardware overhead, making it suitable for resource-constrained security applications such as IoT terminals, lightweight cryptographic modules, and embedded authentication systems.
- True Random Number Generator,
- chain-coupled oscillation ring,
- irregular oscillation,
- lightweight entropy source,
- hardware security

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References(31)

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