{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2025,10,10]],"date-time":"2025-10-10T00:58:37Z","timestamp":1760057917939,"version":"build-2065373602"},"reference-count":43,"publisher":"MDPI AG","issue":"3","license":[{"start":{"date-parts":[[2025,2,27]],"date-time":"2025-02-27T00:00:00Z","timestamp":1740614400000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"name":"Vlatacom Institute of High Technologies","award":["#164 EEG_Keys"],"award-info":[{"award-number":["#164 EEG_Keys"]}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Symmetry"],"abstract":"<jats:p>This paper presents an autonomous perfectly secure low-bit-rate voice communication system (APS-VCS) based on the mixed-excitation linear prediction voice coder (MELPe), Vernam cipher, and sequential key distillation (SKD) protocol by public discussion. An authenticated public channel can be selected in a wide range, from internet connections to specially leased radio channels. We found the source of common randomness between the locally synthesized speech signal at the transmitter and the reconstructed speech signal at the receiver side. To avoid information leakage about open input speech, the SKD protocol is not executed on the actual transmitted speech signal but on artificially synthesized speech obtained by random selection of the linear spectral pairs (LSP) parameters of the speech production model. Experimental verification of the proposed system was performed on the Vlatacom Personal Crypto Platform for Voice encryption (vPCP-V). Empirical measurements show that with an adequate selection of system parameters for voice transmission of 1.2 kb\/s, a secret key rate (KR) of up to 8.8 kb\/s can be achieved, with a negligible leakage rate (LR) and bit error rate (BER) of order 10\u22123 for various communications channels, including GSM 3G and GSM VoLTE networks. At the same time, by ensuring perfect secrecy within symmetric encryption systems, it further highlights the importance of the symmetry principle in the field of information-theoretic security. To our knowledge, this is the first autonomous, perfectly secret system for low-bit-rate voice communication that does not require explicit prior generation and distribution of secret keys.<\/jats:p>","DOI":"10.3390\/sym17030365","type":"journal-article","created":{"date-parts":[[2025,2,28]],"date-time":"2025-02-28T04:28:18Z","timestamp":1740716898000},"page":"365","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":1,"title":["A Class of Perfectly Secret Autonomous Low-Bit-Rate Voice Communication Systems"],"prefix":"10.3390","volume":"17","author":[{"ORCID":"https:\/\/orcid.org\/0000-0003-4895-5730","authenticated-orcid":false,"given":"Jelica","family":"Radomirovi\u0107","sequence":"first","affiliation":[{"name":"Vlatacom Institute of High Technology, Milutina Milankovica 5, 11070 Belgrade, Serbia"},{"name":"School of Electrical Engineering, Belgrade University, Bulevar kralja Aleksandra 73, 11120 Belgrade, Serbia"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-9630-804X","authenticated-orcid":false,"given":"Milan","family":"Milosavljevi\u0107","sequence":"additional","affiliation":[{"name":"Vlatacom Institute of High Technology, Milutina Milankovica 5, 11070 Belgrade, Serbia"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-9249-2660","authenticated-orcid":false,"given":"Sara","family":"\u010cubrilovi\u0107","sequence":"additional","affiliation":[{"name":"Vlatacom Institute of High Technology, Milutina Milankovica 5, 11070 Belgrade, Serbia"},{"name":"School of Electrical Engineering, Belgrade University, Bulevar kralja Aleksandra 73, 11120 Belgrade, Serbia"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-5296-1378","authenticated-orcid":false,"given":"Zvezdana","family":"Kuzmanovi\u0107","sequence":"additional","affiliation":[{"name":"Vlatacom Institute of High Technology, Milutina Milankovica 5, 11070 Belgrade, Serbia"},{"name":"School of Electrical Engineering, Belgrade University, Bulevar kralja Aleksandra 73, 11120 Belgrade, Serbia"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-7945-5571","authenticated-orcid":false,"given":"Miroslav","family":"Peri\u0107","sequence":"additional","affiliation":[{"name":"Vlatacom Institute of High Technology, Milutina Milankovica 5, 11070 Belgrade, Serbia"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-8195-8576","authenticated-orcid":false,"given":"Zoran","family":"Banjac","sequence":"additional","affiliation":[{"name":"Vlatacom Institute of High Technology, Milutina Milankovica 5, 11070 Belgrade, Serbia"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-2556-8212","authenticated-orcid":false,"given":"Dragana","family":"Peri\u0107","sequence":"additional","affiliation":[{"name":"Vlatacom Institute of High Technology, Milutina Milankovica 5, 11070 Belgrade, Serbia"}]}],"member":"1968","published-online":{"date-parts":[[2025,2,27]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"656","DOI":"10.1002\/j.1538-7305.1949.tb00928.x","article-title":"Communication theory of secrecy systems","volume":"28","author":"Shannon","year":"1949","journal-title":"Bell Syst. 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