Byzantine-tolerant Distributed Grow-only Sets: Specification and Applications

Abstract

Blockchains (as termed by Nakamoto in [14]) or Distributed Ledger Technologies(DLTs) (as used in [7] and [15]) became one of the most trendy data structures following the introduction of crypto-currencies [14] and their recent application in finance and token-economy. Despite their early wide adoption, little was known initially about the fundamental construction and semantic properties ofDLTs. A number of research groups attempted to provide rigorous definitions to characterise the fundamental properties of DLTs as those used in Bitcoin and beyond [1, 7, 8]. Among those, Fernández Anta et al. [7], was the first to identify and provide a formal definition of a reliable concurrent object, termedDistributed Ledger Object(DLO), which conveys the essential building block form any DLTs.With a growing amount of works dedicated to the Distributed Ledger formalization, it was shown in [10] that cryptocurrencies do not need consensus to be implemented. From a theoretical point of view, it was shown in [9] that, assuming one process per account, the consensus number of cryptocurrencies is 1. A non-sequential specification of money transfer was introduced in [2]. It follows that Byzantine transactional systems do not necessarily need consensus, but rather can be implemented on top of less powerful data structures. That’s one of the reason why we focused on providing a lighter tool that gets rid of the strict ordering information of the elements that are added to the system.