Blockchain, as a distributed database, offers security, transparency and decentralization, with cryptocurrencies, such as bitcoin, being the most famous example of its application, therefore it is necessary to provide a comprehensive overview of blockchain technology. Technical aspects such as hash functions, Merkle trees and roots that ensure data inviolability are analyzed so the first part of the paper focuses on the history of blockchain and its technological development, starting from the initial concepts in the 90s to the expansion of its application in various industries. Types of blockchain systems are discussed, including public, private, consortium and hybrid. Various questions related to misuse arise with the stages of money laundering using cryptocurrencies and the use of technological tools such as mixers to conceal the true sources of illegally obtained funds being presented. A special emphasis of the thesis relates to legal aspects with a focus on the regulation of cryptocurrencies and crypto-assets in the Republic of Croatia and the European Union. Sources such as Regulation (EU) 2023/1114 on crypto-asset markets and Directive (EU) 2018/843, which seek to establish clear guidelines for the use and misuse of crypto-assets and the protection of users, are analyzed in detail. The challenges of aligning blockchain technology with the General Data Protection Regulation (GDPR) are discussed, especially in the context of the indelibility of data on blockchain. In conclusion, the paper highlights the potential of blockchain technology for transforming society, but also the need for a responsible approach, as the sustainable development of this technology requires continuous adaptation of legal, technical and social aspects.