Cybersecurity has been a central topic since the very beginning of the Internet era. Now, blockchain technology and, in particular the Bitcoin protocol, has demonstrated the potential of new security algorithms to substitute old paradigms of intermediation. A system based on a decentralised, possibly open, protocol has to regard with further attention on the role played by the properties of the network of communication, e.g. speed of information transmission, heterogeneity of connections, clustered sets of nodes. I’m interested in understanding what are the limitations and possibilities that are unlocked by the blockchain technology and especially by the role of the network of communication between the nodes of a decentralised system.