Financial Cryptography and Data Security

The Bitcoin scheme is the most popular and talked about alternative payment scheme. One of the most active parts of the Bitcoin ecosystem was the Silk Road marketplace, in which highly illegal substances and services were traded. It was run by a person who called himself Dread Pirate Roberts (DPR), whose bitcoin holdings are estimated to be worth hundreds of millions of dollars at today’s exchange rate. On October 1-st 2013, the FBI arrested a 29 year old person named Ross William Ulbricht, claiming that he is DPR, and seizing a small fraction of his bitcoin wealth. In this paper we use the publicly available record to trace the evolution of his holdings in order to find how he acquired and how he tried to hide them from the authorities. In particular, we trace the amounts he seemingly received and the amounts he seemingly transferred out of his accounts, and show that all his Silk Road commissions from the months of May, June and September 2013, along with numerous other amounts, were not seized by the FBI. This analysis demonstrates the power of data mining techniques in analyzing large payment systems, and especially publicly available transaction graphs of the type provided by the Bitcoin scheme.