Characterizing the Bitcoin network topology with Node-Probe

In blockchain networks, topology discovery is a prerequisite when investigating the network characteristics (e.g., performance and robustness), which can provide a deeper comprehension of the behavior of the nodes and topology dynamicity. In this paper, we conduct a longitudinal study on the Bitcoin topology by collecting network snapshots from 2018 to 2022 with Node-Probe, our topology discovery technique that uses recursive scanning to find all reachable nodes in the Bitcoin network. Using Node-Probe, we have collected 5-week-long snapshots (36-day-long snapshots) of the Bitcoin main network and analyzed the network properties, community structure, and topology dynamicity. We confirm that our approach achieves a precision of 99% with a recall of 98% in inferring the topology. Analytical results on community structure show that the Bitcoin network has $\times 4$ more communities than what should be expected from a random network. Meanwhile, analytical results on dynamicity indicate that the topology stands firmly on heavy and long-running nodes. Improving the propagation mechanism using master nodes could improve the propagation delay by proximity $\times 25$ compared with the Bitcoin default protocol. Considering a K-anonymity attack, any transaction from one of the autonomous systems containing only a single Bitcoin node can easily be linked to real users' IP information.