Trends for the digital transformation of metrology and regulation of metrology through IT have some keywords in common with the main properties of the blockchain, such as traceability, immutability, and machine-readable documents. The possible applicability of the blockchain as an innovative IT solution for metrology regulation is known in the scientific community. Still, blockchain implementation must consider the entire metrology pyramid—the technical aspects and the legal framework intrinsic to metrology. This is also valid for possible IoT blockchain applications. In resolving the issues, this paper applies a bottom-up approach, starting from IoT devices analyzed as oracles and building up to the sole definition of measurement units, thereby discussing technical aspects concerning relevant standardization documents. The resulting trust model concept encompasses the vertical and horizontal traceability of the measurement results (oracle data), where normative standards and legal requirements are crucial for building trust. Conclusively, for practical implementations, it will be necessary to analyze blockchain properties and applicability with a view to the standard requirements, as shown for WELMEC.

With advances in Information and Communication Technologies (ICT) in convergence with blockchain technology, cities have been given the opportunity to improve their services, efficiently use resources, and, thus, become Smart Cities. The main properties of blockchain technology like decentralization, immutability, transparency, consensus, and robustness are qualities needed for Smart City. In this paper, we propose a digitalization strategy for the City of Osijek. Smart City digitalization strategy aims to solve problems of emerging urbanization, improve administration by reducing energy and water consumption, carbon emissions, pollution, and city waste management. To develop an information system based on blockchain technology, the administration structure and the current state of information systems are analyzed, and new solutions are presented.

Smart City public services need detailed and relevant public information to increase their efficiency. To have relevant information, collecting and processing the data about its previous uses are crucial. Clustering is one of the most powerful, yet computationally demanding, tools that can be used to process such information. Since public services data are vast, but usually not accurate, the objects clustered are considered as uncertain. In this paper, we propose a novel clustering method for uncertain objects called Improved Bisector Pruning (IBP), which uses bisectors to reduce the number of computations. We combine IBP with a modified segmentation of a data set area (SDSA) method that enables the parallelization of the clustering process. In the experiments, we show that IBP-SDSA is superior in performance to the most used clustering method UK-means combined with Voronoi or MinMax pruning, regardless of the problem size. We applied IBP-SDSA on clustering the public services data in the city of Osijek and show that the acquired data can be used to improve public services logistics.

In modern communication systems, one of the most challenging tasks involves the implementation of adequate methods for successful and secure transfer of confidential digital information over an unsecured communication channel. Many encryption algorithms have been developed for protection of confidential information. However, over time, flaws have been discovered even with the most sophisticated encryption algorithms. Each encryption algorithm can be decrypted within sufficient time and with sufficient resources. The possibility of decryption has increased with the development of computer technology since available computer speeds enable the decryption process based on the exhaustive data search. This has led to the development of steganography, a science which attempts to hide the very existence of confidential information. However, the stenography also has its disadvantages, listed in the paper. Hence, a new method which combines the favourable properties of cryptography based on substitution encryption and stenography is analysed in the paper. The ability of hiding the existence of confidential information comes from steganography and its encryption using a coding table makes its content undecipherable. This synergy greatly improves protection of confidential information.

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