Author, Institution: Aušrys Kilčiauskas, Kaunas University of Technology
Science area, field of science: Natural Sciences, Informatics, N009
Research supervisor: Prof. Dr. Eligijus Sakalauskas (Kaunas University of Technology, Natural Sciences, Informatics, N009)
Dissertation Defence Board of Informatics Science Field:
Prof. Dr. Hab. Rimantas Barauskas (Kaunas University of Technology, Natural Sciences, Informatics, N009) – chairperson
Prof. Dr. Joerg Bruedern (University of Gottingen, Germany, Natural Sciences, Mathematics, N001)
Prof. Dr. Hab. Antanas Čenys (Vilnius Gediminas Technical University, Natural Sciences, Informatics, N009)
Prof. Dr. Vacius Jusas (Kaunas University of Technology, Natural Sciences, Informatics, N009)
Prof. Dr. Gintaras Palubeckis (Kaunas University of Technology, Natural Sciences, Informatics, N009)
Dissertation defence meeting will be at the Rectorate Hall of Kaunas University of Technology (K. Donelaičio 73-402, Kaunas)
The doctoral dissertation is available at the library of Kaunas University of Technology (Gedimino 50, Kaunas) and on the internet: A. Kilčiauskas el. dissertation.pdf
© A. Kilčiauskas, 2026 “The text of the thesis may not be copied, distributed, published, made public, including by making it publicly available on computer networks (Internet), reproduced in any form or by any means, including, but not limited to, electronic, mechanical or other means. Pursuant to Article 25(1) of the Law on Copyright and Related Rights of the Republic of Lithuania, a person with a disability who has difficulties in reading a document of a thesis published on the Internet, and insofar as this is justified by a particular disability, shall request that the document be made available in an alternative form by e-mail to doktorantura@ktu.lt.”
Annotation: This doctoral dissertation addresses a pressing challenge in private blockchain technologies: how to effectively reconcile transaction authenticity, user anonymity, and the requirements for independent auditing and regulatory compliance. Conventional approaches, such as Monero’s Linkable Spontaneous Anonymous Group (LSAG) signatures, provide a degree of anonymity but often incur high computational costs and struggle to balance confidentiality with the demands of external oversight. The primary aim of the research is to develop and investigate an integrated Transaction Authenticity and Anonymity System (TAAs) suitable for resource-constrained environments, including the Internet of Things (IoT). The proposed system employs additively-multiplicatively homomorphic ElGamal encryption within the Unspent Transaction Output (UTXO) paradigm. This enables network participants and audit authorities to verify transaction balance correctness without revealing actual amounts. Anonymization and deanonymization are achieved through Schnorr multi-signatures. In addition, the alternative method of anonymization based on Schnorr type signature realized by Matrix Power Function (MPF) is presented having a potential to be a hypothetic post-quantum cryptographic method. Theoretical analysis and experimental evaluations demonstrate that the TAAs system significantly outperforms Monero LSAG ring signatures in terms of operational efficiency and execution time, particularly as the number of participants increases. Practical implementations in a simulated private blockchain and a hybrid IoT confirm the system’s functionality under realistic conditions. The proposed methods maintain high security levels while minimizing computational and energy demands on constrained devices.
Keywords: private blockchains, transaction anonymity, deanonymization, ElGamal homomorphic encryption, Schnorr multi-signature, non-interactive zero-knowledge proofs, matrix power function.