ACE Seminar: Secure and Anonymous Decentralized Bitcoin Mixing

Speaker: Jan Henrik Ziegeldorf

Date/Time: 08-Oct-2015, 15:00 UTC

Venue: Birbeck B30



The decentralized digital currency Bitcoin presents an anonymous alternative to the centralized banking system and indeed enjoys widespread and increasing adoption. 
Recent works, however, show how users can be re-identified and their payments linked based on Bitcoin’s most central element, the blockchain, a public ledger of all transactions. 
Thus, many regard Bitcoin’s central promise of financial privacy as broken.
In this talk, we analyze mixing services that help users re-establish their financial privacy. We distill desirable properties for mixing services and identify short-comings in the existing approaches.
We then propose CoinParty, an efficient decentralized mixing service that allows users to reestablish their financial privacy in Bitcoin and related cryptocurrencies.
CoinParty, through a novel combination of decryption mixnets with threshold signatures, takes a unique place in the design space of mixing services, combining the advantageous of previously proposed centralized and decentralized mixing services in one system. 
Especially, it achieves anonymity sets by orders of magnitude higher than related work as we quantify by analyzing transactions in the actual Bitcoin blockchain. We conclude with a brief discussion of the applicability of our design to other areas (in Bitcoin).


Jan Henrik Ziegeldorf is a researcher and PhD student at the Chair of Communication and Distributed Systems (COMSYS) at RWTH Aachen University, Germany. He holds a Diploma degree (equiv. M.Sc.) in Computer Science from RWTH Aachen University. He previously worked as a security researcher for Philips Research at Eindhoven, NL, and as a freelance data analyst for Zalando GmbH, Berlin, Germany. His research focuses on anonymity technologies (e.g, Differential Privacy), secure two/multiparty computations and lightweight cryptography and their application to engineering;privacy preserving protocols, e.g., for digital currency schemes, anonymous communications and participatory sensing.

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