Malte Moeser General Exam Presentation - May 16, 2018 at 5:00pm - CS402 Title: Anonymous Alone? On the Challenge of Anonymity in Cryptographic Currencies Abstract: Cryptographic currencies balance two seemingly contradictory goals: radical transparency of the ledger and anonymity of users. A variety of privacy-enhancing techniques have been developed to strengthen users’ anonymity using obfuscation and cryptography, yet to this day their adoption remains limited. A closer look at existing deployments shows how in practice these techniques often fall short of their promises due to inherent complexity and dependence on user behavior. One such example is Monero, a privacy-centric cryptocurrency that allows users to obfuscate the true origin of the coin they are spending by including other chaff coins. Analyzing the Monero blockchain, we found several significant weaknesses in it’s design that allowed to retroactively deanonymize users’ transactions. This is one further example that cryptocurrency privacy is hard: the data is necessarily public forever, and often a user’s actions can negatively influence the anonymity of others. Based on the insights from the analysis of Monero and other privacy-preserving techniques, I’ll put forward a set of recommendations for protocol designers and discuss options for policy makers to regulate cryptographic currencies based on their inherent linkability. Barbara A. Mooring Interim Graduate Coordinator Computer Science Department Princeton University