Big data analytics in blockchains and search for associated transactions

Blockchains are gaining a significant interest in general public as well as in scientific community, especially after the successful implementation of cryptocurrencies, particularly Bitcoin as the first of them. As the blockchains in the form implemented for the cryptocurrencies are not suitable for storing large quantities of data, there is a vivid development of solutions for this purpose going on. Blockchains are extended in two ways. Some extensions allow access only to the user that has stored the data originally. On the other hand, much attention is paid to technologies that would allow the cloud-storage vendors to perform an aggregated analysis, of course with a due respect for privacy of data owners and possibly enabling their control of the data usage, i.e. those who are permitted to use their data when such use is allowed. Analysis of the basic data constituting a blockchain is of a considerable scientific interest as well. Since a blockchain does not provide an analytic tool itself, it is necessary to use an external one. In order to find closely related transaction participants, we chose a graph database, ingested the Ethereum blockchain data into two different data models and found such communities by searching for tours in the graph. © 2019 Electrotechnical Society of Slovenia. All rights reserved.