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Consensus Robustness and Transaction De-Anonymization in the Ripple Currency Exchange System
Adriano Di Luzio, Alessandro Mei and Julinda Stefa
Sapienza University of Rome, Sapienza University of Rome, Sapienza University of Rome

Distributed financial systems are radically changing the way we do business and spend our money. Ripple, in particular, is unique in its kind. It is built on consensus and trust among its peers and, differently from many other systems, it allows exchanging both fiat currencies and goods. It does so by storing the accounts of its users, their balances, and all the transactions in a distributed ledger, publicly accessible. In this paper we perform for the first time an in-depth study of the Ripple exchange system and its public distributed ledger. We analyze payments, the structure of payment paths, and the role of important peers in the system such as Gateways (the equivalent of Banks) and Market Makers that allow cross-currency exchange among users. To complete the study of the ecosystem we analyze the internal stream of events in Ripple and show that the whole system relies on a surprisingly small number of active validators, raising several concerns on the robustness and on the actual fairness of the system. Finally, we show how distributed financial systems can jeopardize the privacy of their users. By examining the first 3 years of Ripple history (more than 500 GB of data), we show that even approximate information on a single payment can uncover, with incredible accuracy, the whole financial life of the user. For example, this allows anyone who overhears our order for a Latte at our favourite bar to gain complete and unlimited access to our balance, our previous and future payments, our monthly income, as well as the places where we shop and the people we trust.