Released in June 2022
Are Blockchains Decentralized?
Unintended Centralities in Distributed Ledgers
Executive Summary
Over the past year, Trail of Bits was engaged by the Defense Advanced Research Project Agency (DARPA) to investigate the extent to which blockchains are truly decentralized. We focused primarily on the two most popular blockchains: Bitcoin and Ethereum. We also investigated proof-of-stake (PoS) blockchains and Byzantine fault tolerant consensus protocols in general. This report provides a high-level summary of results from the academic literature, as well as our novel research on software centrality and the topology of the Bitcoin consensus network. For an excellent academic survey with a deeper technical discussion, we recommend the work of Sai, et al.
Complete Paper
62af6c641a672b3329b9a480_Unintended_Centralities_in_Distributed_Ledgers.pdf (1.1 MB)