{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2025,12,29]],"date-time":"2025-12-29T11:10:00Z","timestamp":1767006600991,"version":"build-2065373602"},"reference-count":15,"publisher":"MDPI AG","issue":"9","license":[{"start":{"date-parts":[[2021,9,5]],"date-time":"2021-09-05T00:00:00Z","timestamp":1630800000000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/501100001691","name":"Japan Society for the Promotion of Science","doi-asserted-by":"publisher","award":["20K23327"],"award-info":[{"award-number":["20K23327"]}],"id":[{"id":"10.13039\/501100001691","id-type":"DOI","asserted-by":"publisher"}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Entropy"],"abstract":"<jats:p>A cloud service to offer entropy has been paid much attention to. As one of the entropy sources, a physical random number generator is used as a true random number generator, relying on its irreproducibility. This paper focuses on a physical random number generator using a field-programmable gate array as an entropy source by employing ring oscillator circuits as a representative true random number generator. This paper investigates the effects of an XOR gate in the oscillation circuit by observing the output signal period. It aims to reveal the relationship between inputs and the output through the XOR gate in the target generator. The authors conduct two experiments to consider the relevance. It is confirmed that combining two ring oscillators with an XOR gate increases the complexity of the output cycle. In addition, verification using state transitions showed that the probability of the state transitions was evenly distributed by increasing the number of ring oscillator circuits.<\/jats:p>","DOI":"10.3390\/e23091168","type":"journal-article","created":{"date-parts":[[2021,9,6]],"date-time":"2021-09-06T13:15:56Z","timestamp":1630934156000},"page":"1168","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":6,"title":["Consideration for Affects of an XOR in a Random Number Generator Using Ring Oscillators"],"prefix":"10.3390","volume":"23","author":[{"ORCID":"https:\/\/orcid.org\/0000-0001-9166-4336","authenticated-orcid":false,"given":"Ryoichi","family":"Sato","sequence":"first","affiliation":[{"name":"Graduate School of Natural Science and Technology, Okayama University, Okayama 700-8530, Japan"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Yuta","family":"Kodera","sequence":"additional","affiliation":[{"name":"Graduate School of Natural Science and Technology, Okayama University, Okayama 700-8530, Japan"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Md. Arshad","family":"Ali","sequence":"additional","affiliation":[{"name":"Department of Computer Science and Engineering, Hajee Mohammad Danesh Science and Technology University (HSTU), Dinajpur 5200, Bangladesh"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Takuya","family":"Kusaka","sequence":"additional","affiliation":[{"name":"Graduate School of Natural Science and Technology, Okayama University, Okayama 700-8530, Japan"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Yasuyuki","family":"Nogami","sequence":"additional","affiliation":[{"name":"Graduate School of Natural Science and Technology, Okayama University, Okayama 700-8530, Japan"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Robert H.","family":"Morelos-Zaragoza","sequence":"additional","affiliation":[{"name":"Department of Electrical Engineering, San Jos\u00e9 State University, One Washington Square, San Jos\u00e9, CA 95192, USA"}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"1968","published-online":{"date-parts":[[2021,9,5]]},"reference":[{"key":"ref_1","unstructured":"(2021, July 05). Entropy as a Service, Available online: https:\/\/csrc.nist.gov\/projects\/entropy-as-a-service."},{"key":"ref_2","first-page":"219","article-title":"Randomness in digital cryptography: A survey","volume":"13","author":"Marton","year":"2010","journal-title":"Rom. J. Inf. Sci. Technol."},{"key":"ref_3","doi-asserted-by":"crossref","first-page":"426","DOI":"10.1587\/transinf.E95.D.426","article-title":"FPGA Implementation of Metastability-Based True Random Number Generator","volume":"E95.D","author":"Hata","year":"2012","journal-title":"IEICE Trans. Inf. Syst."},{"key":"ref_4","unstructured":"Coppock, W.R., and Philbrook, C.R. (2021, August 22). A Mathematical and Physical Analysis of Circuit Jitter with Application to Cryptographic Random Bit Generation. Available online: http:\/\/citeseerx.ist.psu.edu\/viewdoc\/download?doi=10.1.1.434.8264&rep=rep1&type=pdf."},{"key":"ref_5","doi-asserted-by":"crossref","unstructured":"Saarinen, M.J.O. (2021). On Entropy and Bit Patterns of Ring Oscillator Jitter. arXiv.","DOI":"10.1109\/AsianHOST53231.2021.9699508"},{"key":"ref_6","doi-asserted-by":"crossref","first-page":"1365","DOI":"10.1142\/S0218127410026538","article-title":"Digital Control as Source of Chaotic Behavior","volume":"20","author":"Stepan","year":"2010","journal-title":"Int. J. Bifurc. Chaos"},{"key":"ref_7","doi-asserted-by":"crossref","first-page":"1365","DOI":"10.1007\/s11071-019-05268-z","article-title":"Twofold quantization in digital control: Deadzone crisis and switching line collision","volume":"98","year":"2019","journal-title":"Nonlinear Dyn."},{"key":"ref_8","doi-asserted-by":"crossref","first-page":"109","DOI":"10.1109\/TC.2007.250627","article-title":"A Provably Secure True Random Number Generator with Built-In Tolerance to Active Attacks","volume":"56","author":"Sunar","year":"2007","journal-title":"IEEE Trans. Comput."},{"key":"ref_9","doi-asserted-by":"crossref","unstructured":"WOLD, K., and TAN, C.H. (2008, January 3\u20135). Analysis and enhancement of random number generator in FPGA based on oscillator rings. Proceedings of the 2008 International Conference on Reconfigurable Computing and FPGAs, Cancun, Mexico.","DOI":"10.1109\/ReConFig.2008.17"},{"key":"ref_10","doi-asserted-by":"crossref","first-page":"1","DOI":"10.1155\/2010\/879281","article-title":"True-randomness and pseudo-randomness in ring oscillator-based true random number generators","volume":"2010","author":"Bochard","year":"2010","journal-title":"Int. J. Reconfigurable Comput."},{"key":"ref_11","first-page":"296","article-title":"Implementation of non-periodic sampling true random number generator on FPGA","volume":"44","author":"Tuncer","year":"2015","journal-title":"Inf. MIDEM"},{"key":"ref_12","doi-asserted-by":"crossref","first-page":"2987","DOI":"10.1049\/iet-ipr.2019.0168","article-title":"Ring oscillator as confusion\u2013diffusion agent: A complete TRNG drove image security","volume":"14","author":"Sivaraman","year":"2020","journal-title":"IET Image Process."},{"key":"ref_13","doi-asserted-by":"crossref","first-page":"54638","DOI":"10.1109\/ACCESS.2019.2912903","article-title":"Current-Starved Cross-Coupled CMOS Inverter Rings as Versatile Generators of Chaotic and Neural-Like Dynamics Over Multiple Frequency Decades","volume":"7","author":"Minati","year":"2019","journal-title":"IEEE Access"},{"key":"ref_14","doi-asserted-by":"crossref","first-page":"445","DOI":"10.1007\/s10470-019-01568-x","article-title":"Design, FPGA implementation and statistical analysis of chaos-ring based dual entropy core true random number generator","volume":"102","author":"Koyuncu","year":"2019","journal-title":"Analog. Integr. Circuits Signal Process."},{"key":"ref_15","unstructured":"(2021, July 05). Nexys A7\u2122 FPGA Board Reference Manual. Available online: https:\/\/reference.digilentinc.com\/_media\/reference\/programmable-logic\/nexys-a7\/nexys-a7_rm.pdf."}],"container-title":["Entropy"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/1099-4300\/23\/9\/1168\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2025,10,11]],"date-time":"2025-10-11T06:56:40Z","timestamp":1760165800000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/1099-4300\/23\/9\/1168"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2021,9,5]]},"references-count":15,"journal-issue":{"issue":"9","published-online":{"date-parts":[[2021,9]]}},"alternative-id":["e23091168"],"URL":"https:\/\/doi.org\/10.3390\/e23091168","relation":{},"ISSN":["1099-4300"],"issn-type":[{"type":"electronic","value":"1099-4300"}],"subject":[],"published":{"date-parts":[[2021,9,5]]}}}