{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2025,10,28]],"date-time":"2025-10-28T05:57:07Z","timestamp":1761631027448,"version":"build-2065373602"},"reference-count":35,"publisher":"MDPI AG","issue":"2","license":[{"start":{"date-parts":[[2023,5,10]],"date-time":"2023-05-10T00:00:00Z","timestamp":1683676800000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"name":"FEDER\/Junta de Andaluc\u00eda-Consejer\u00eda de Transformaci\u00f3n Econ\u00f3mica, Industria, Conocimiento y Universidades\/Proyecto","award":["B-TIC-588-UGR20"],"award-info":[{"award-number":["B-TIC-588-UGR20"]}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Cryptography"],"abstract":"<jats:p>The generation of random numbers is crucial for practical implementations of cryptographic algorithms. In this sense, hardware security modules (HSMs) include true random number generators (TRNGs) implemented in hardware to achieve good random number generation. In the case of cryptographic algorithms implemented on FPGAs, the hardware implementation of RNGs is limited to the programmable cells in the device. Among the different proposals to obtain sources of entropy and process them to implement TRNGs, those based in ring oscillators (ROs), operating in parallel and combined with XOR gates, present good statistical properties at the cost of high area requirements. In this paper, these TRNGs are revisited, showing a method for area optimization independently of the FPGA technology used. Experimental results show that three ring oscillators requiring only three LUTs are enough to build a TRNG on Artix 7 devices from Xilinx with a throughput of 33.3 Kbps, which passes NIST tests. A throughput of 50 Kbps can be achieved with four ring oscillators, also requiring three LUTs in Artix 7 devices, while 100 Kbps can be achieved using an structure with four ring oscillators requiring seven LUTs.<\/jats:p>","DOI":"10.3390\/cryptography7020026","type":"journal-article","created":{"date-parts":[[2023,5,11]],"date-time":"2023-05-11T01:37:24Z","timestamp":1683769044000},"page":"26","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":5,"title":["Revisiting Multiple Ring Oscillator-Based True Random Generators to Achieve Compact Implementations on FPGAs for Cryptographic Applications"],"prefix":"10.3390","volume":"7","author":[{"ORCID":"https:\/\/orcid.org\/0000-0001-8126-1146","authenticated-orcid":false,"given":"Luis","family":"Parrilla","sequence":"first","affiliation":[{"name":"Departamento de Electr\u00f3nica y Tecnolog\u00eda de Computadores, Centro de Investigaci\u00f3n en Tecnolog\u00edas de la Informaci\u00f3n y las Telecomunicaciones CITIC-UGR, Universidad de Granada, 18071 Granada, Spain"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-3533-4660","authenticated-orcid":false,"given":"Antonio","family":"Garc\u00eda","sequence":"additional","affiliation":[{"name":"Departamento de Electr\u00f3nica y Tecnolog\u00eda de Computadores, Centro de Investigaci\u00f3n en Tecnolog\u00edas de la Informaci\u00f3n y las Telecomunicaciones CITIC-UGR, Universidad de Granada, 18071 Granada, Spain"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-6476-8105","authenticated-orcid":false,"given":"Encarnaci\u00f3n","family":"Castillo","sequence":"additional","affiliation":[{"name":"Departamento de Electr\u00f3nica y Tecnolog\u00eda de Computadores, Centro de Investigaci\u00f3n en Tecnolog\u00edas de la Informaci\u00f3n y las Telecomunicaciones CITIC-UGR, Universidad de Granada, 18071 Granada, Spain"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-0334-0863","authenticated-orcid":false,"given":"Juan Antonio","family":"L\u00f3pez-Villanueva","sequence":"additional","affiliation":[{"name":"Departamento de Electr\u00f3nica y Tecnolog\u00eda de Computadores, Centro de Investigaci\u00f3n en Tecnolog\u00edas de la Informaci\u00f3n y las Telecomunicaciones CITIC-UGR, Universidad de Granada, 18071 Granada, Spain"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-8130-9963","authenticated-orcid":false,"given":"Uwe","family":"Meyer-Baese","sequence":"additional","affiliation":[{"name":"Department of Electrical and Computer Engineering, FAMU-FSU College of Engineering, Tallahassee, FL 32310-6046, USA"}]}],"member":"1968","published-online":{"date-parts":[[2023,5,10]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"230","DOI":"10.1137\/1004061","article-title":"Random number generators","volume":"4","author":"Hull","year":"1962","journal-title":"SIAM Rev."},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"357","DOI":"10.1145\/356789.356795","article-title":"Quasi-random number sequences from a long-period TLP generator with remarks on application to cryptography","volume":"11","author":"Bright","year":"1979","journal-title":"Acm Comput. 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