Decentralization in open quorum systems: Limitative results for ripple and stellar

Citation

Bracciali A, Grossi D & de Haan R (2021) Decentralization in open quorum systems: Limitative results for ripple and stellar. In: Anceaume E, Bisiere C, Bouvard M, Bramas Q & Casamatta C (eds.) 2nd International Conference on Blockchain Economics, Security and Protocols, Tokenomics 2020, volume 82. Open Access Series in Informatics (OASIcs), 82. 2nd International Conference on Blockchain Economics, Security and Protocols (Tokenomics 2020), Toulouse, France, 26.10.2020-27.10.2020. Dagstuhl, Germany: Schloss Dagstuhl- Leibniz-Zentrum fur Informatik, pp. 5:1-5:20. https://doi.org/10.4230/OASIcs.Tokenomics.2020.5

Abstract
Decentralisation is one of the promises introduced by blockchain technologies: fair and secure interaction amongst peers with no dominant positions, single points of failure or censorship. Decentralisation, however, appears difficult to be formally defined, possibly a continuum property of systems that can be more or less decentralised, or can tend to decentralisation in their lifetime. In this paper we focus on decentralisation in quorum-based approaches to open (permissionless) consensus as illustrated in influential protocols such as the Ripple and Stellar protocols. Drawing from game theory and computational complexity, we establish limiting results concerning the decentralisation vs. safety trade-off in Ripple and Stellar, and we propose a novel methodology to formalise and quantitatively analyse decentralisation in this type of blockchains.