Exploring Anonymity on The Silk Road and TOR

The Silk Road: An Online Marketplace By Adam Cronin

Project Overview Main goal: Research The Silk Road and how it provides anonymity Mechanisms for providing anonymity Failures in anonymity

What is The Silk Road? An anonymous online marketplace created to facilitate the online sales of both legal and illegal items People around the world can trade with each other without divulging their identity A means of circumventing buying and selling restrictions that may be in effect due to geographic location

Anonymity in a Marketplace Requirements for an anonymous online marketplace Accessing the site Ability to post/advertise items for sale Ability to browse available items Transactions Sending item from seller to buyer

The Silk Roads Solution Requirements for an anonymous online marketplace Accessing the site Tor Ability to post/advertise items for sale Register Account Ability to browse available items Register Account Transactions Bitcoin Sending item from seller to buyer Still have to give an address

Tor The Tor browser is essentially a means of anonymously sending network data Data is sent through a series of nodes Each node is a volunteer Each node only knows the previous node and the next node so single compromised node isn t a huge issue

How Tor Works Tor installs an Onion Proxy onto the user s computer The OP creates a virtual circuit that defines the path through the Tor nodes that leads to the user s end destination Tor downloads list of all potential Tor nodes in the network Uses the list to choose an Entry node, an Intermediate node, and an Exit node

How Tor Works (Contd) Creates a Transport Layer Security (TLS) connection between itself and the Entry Node Uses encryption to prevent eavesdropping, tampering, or message forgery Then starts the process of creating the virtual circuit To create a VC, can send three commands: create, extend, and delete

Tor Destination Server Onion Proxy

Create TLS Connection (Transport Layer Security) Destination Server Onion Proxy TLS, K1

Create Command on Entry Node Create Destination Server Onion Proxy

Create Command on Intermediate Node Create Destination Server Onion Proxy Extend

Create Command on Exit Node Extend Destination Server Onion Proxy Create

Send Message Extend Destination Server Onion Proxy Create

Traditional Online Transactions Traditional online transaction requires a middle man Buyer Bank Seller Disadvantages of trusted third-party Access to user s money Knowledge of all transactions and who with Transactions can be disputed and reversed

Bitcoin A peer-to-peer electronic cash system Goal: move away from the traditional form of cash exchange Remove trusted third-party (ex: banks) Instead of third-party, broadcast every transaction to all nodes on the Bitcoin network Transactions can t be reversed or disputed

Bitcoin Each user holds their Bitcoins in a wallet which is referenced during transactions Bitcoin characterized as a chain of digital signatures Each user has a public and private key so that only the owner of a wallet can transfer Bitcoins During a transaction, a signature is created and added to the coin Private key used to generate signature Public key used to verify the signature

Failures in Anonymity Tor by itself doesn t encrypt data leaving the exit node or returning to the exit node A passive attacker who watches both the sender and the receiver could link the two with high probability Compromised TLS key for Onion Proxy could lead to impersonation Receiver of package must still give an address

Failures in Anonymity The Silk Road has been shut down twice and the people running the site were arrested A new clone is started up every time The Silk Road gets shut down

References [1] Christin, Nicolas. "Traveling the Silk Road: A Measurement Analysis of a Large Anonymous Online Marketplace." (2012): n. pag. Carnegie Mellon, 30 July 2012. Web. 12 Oct. 2015. <https://www.cylab.cmu.edu/files/pdfs/tech_reports/CMUCyLab12018.pdf>. [2] Dingledine, Roger, Nick Mathewson, and Paul Syverson. "Tor: The Second- Generation Onion Router." (n.d.): n. pag. Web. 5 Oct. 2015. < https://svn.torproject.org/svn/projects/design-paper/tor-design.pdf>. [3] Dierks, T. & C. Allen. The TLS Protocol Version 1.0. January 1999. (6 November 2015) [4] Nakamoto, Satoshi. "Bitcoin: A Peer-to-Peer Electronic Cash System." (n.d.): n. pag. Web. 5 Oct. 2015. <https://bitcoin.org/bitcoin.pdf>. [5] Biryukov, Alex, and Ivan Pustogarov. "Bitcoin over Tor Isn't a Good Idea." 2015 IEEE Symposium on Security and Privacy(2015): n. pag. 8 Jan. 2015. Web.