While there are many data collection and analysis tools for Ethereum - the largest smart contract blockchain by market capitalization, development of similar tools for other smart contract blockchains is lacking. Reasons for this are non-existent standards, changing specifications d ue t o rapid development, common usage of the off-chain storage, and lack of developers. One of such blockchains is Polkadot - a layer- zero blockchain featuring a single relay chain whose role is to secure smart contract transactions on multiple other parachains. In this paper we describe a data collection pipeline for Polkadot blockchain that we then use to perform an analysis of the bow-tie structure of its transfer network over time, with special emphasis on the role of nominators and validators in this structure. We find evidence that t he Polkadot ecosystem iss lowly maturing from a system dominated by nominators and validators, both of which require some technical skill as well as willingness to bond sufficient amount of funds, into a system increasingly populated by regular users using the financial services of Polkadot.

In this paper we present a prototype system for easy testing and visualization of the Bitcoin consensus protocol. The system consists of a modified version of the Bitcoin Core client which is intended to run on Raspberry PI machines, modified so that the latency in the block production and propagation can be manually introduced, which simulates network communication issues in the real Bitcoin network. Built-in LCD displays on each machine visualize current state of their local blockchains which allows easy visual observation of the consensus in the network. As machines are running fully capable Bitcoin Core clients, as well as mining clients for production of new blocks in the Proof of Work (PoW) consensus protocol, it is possible to investigate different configuration scenarios and when these lead to the break of the consensus.