The paper examines the problem of ensuring Byzantine fault tolerance in smart city distributed ledger systems. To improve the security of distributed ledgers, it is proposed to use the hashgraph distributed consensus protocol, in which events are organized as a directed acyclic graph, and nodes exchange “gossip about gossip”. The traditional hashgraph protocol has been supplemented with the developed trust model that reduces the impact of malicious devices when reaching consensus in digital infrastructures of a smart city.