# Possible Blockchain Solutions According to a Smart City Digitalization Strategy
## 1 Introduction  
Today cities tend to become Smart Cities and improve life quality in every city area. The characteristics of a Smart City are innovative public services such as Smart Governance [1], Smart Health, Smart Economy, Smart Mobility, Smart Environment, Smart People, and Smart Living [2]. Smart Mobility implies that Information and Communication Technology (ICT) is used to support and integrate transport and logistics systems. It requires that the users have relevant and real-time public information about the public services (such as emergency services, public transportation, water supply network, waste management, etc.) and vice versa to improve commuting/collection efficiency, save time, and reduce costs and CO\({}_{2}\) emissions. Smart City strategy aims to solve the problems of emerging urbanization and rising population growth by reducing energy and water consumption, carbon emissions, pollution, traffic jam, and city waste. IEEE has already developed standards for different components of Smart Cities like smart grids, IoT, Healthcare, and Intelligent Transportation Systems (ITS). ISO 37120 standard defines 100 performance indicators for education, economy, education, energy, and environment. City governance should use these indicators to grade their services and compare them to other cities. A Smart City produces an immense amount of data at a particular time about all public services. Up to date information is crucial to improve public services and provide feedback to its users. A Smart City should ensure an interactive information system to create different participation methods in public life and call citizens to become active users. The active users should be able to provide their real-time data to the Smart City information system and be involved in decision making [3]. To acquire up-to-date information about the public services, it is important to have a good information system for collection and to store relevant data, such as traffic data, air quality, water resources, high-density populated areas, areas inaccessible to certain infrastructure, status of city infrastructure, etc. In the digitalization strategy for city governance, implementing IoT sensors and devices is an excellent way to collect data and improve public services management asshown in Figure 1. IoT devices can be integrated into the information system to increase city governance transparency, include citizens in political decisions and city problems, improve healthcare, the well-being of the city, and other aspects of human life [4]. To achieve these goals, trust in city governance and transparency is mandatory; thus, we propose blockchain technology to store and maintain public service data. Blockchain technology has desired properties for this task, such as decentralization, reliability, transparency, and security. There are numerous blockchain solutions that are helpful for different Smart City tasks, such as authentication and trust management [5], healthcare [6; 7], waste management [8], and IoT sensors [9]. However, existing literature does not offer a comprehensive overview of the whole city system; it just showcases particular solutions (Table 1). Thus, the contribution of this paper is a presentation of the whole topic of the digital transformation of a city and the peculiarities of possible application of blockchain in each instance. In doing so, it was beneficial to collaborate with the City of Osjiek, with a goal to define the digitalization strategy document as the basis for later implementation.