TOR: HUMAN FACTORS AND POLICY

CONSIDERATIONSSteven I. Davis

University of Maryland, University College

CSEC 620, E181

OVERVIEW

• The Onion Router (TOR): open source software to enable secret

communications

• Estimated 2 million users

• Information travels through distributed Internet Exchange Points (IXP)

and Anonymous Systems (AS)

• Public key encryption used to exchange symmetric keys with multiple nodes

• Each node-key pair in the path of a packet is another “layer in the onion”

• Removes identity-IP link increasing difficulty of “hot spot” law enforcement

• Geographic distribution of IP addresses complicates extradition

• Deep Web vs Dark Web

• See also I2P and Freenet

2

HISTORY

• 20 SEP 2002 – Early version of TOR released by Naval Research Laboratory to protect overseas

operatives and dissidents

• 29 JUN 2009 - Assistance during disputed Iranian elections

• 1 JUN 2011 – Gawker publishes expose on Silk Road, accessible via TOR with Bitcoin (BTC)

payments the norm

• 1 AUG 2013 – Arrest of Irish child pornography facilitator coincides with shutdown of large parts of

darknet, possibly part of FBI sting using Firefox vulnerability

• 4 AUG 2013 – Institute for National Security Studies in Israel reports high-level al-Qaeda leaders

use”deepnet, blacknet, or darknet” to communicate. 21 U.S. embassies closed.

• 1 OCT 2013 – FBI shuts down Silk Road and arrests Dread Pirate Roberts (Ross William Ulbricht).

$1.2 billion sales 2011-2013

• 4 OCT 2014 – Guardian reports NSA able to exploit TOR using side channel attacks3

LEGAL AND LIABILITY

• Facilitates human trafficking, assassinations, drugs, weapons

• Use of Bitcoin (BTC) to anonymize financial transactions

• No guarantee of promised goods due to anonymity

• Hop point functionality used to obtain sensitive data passed to wikileaks

• Loss of proprietary information in corporate environments

• Disclosure of military and national intelligence

4

VULNERABILITIES

• Fact that person using TOR not hidden, only

• Side channel attacks

• Plugins (JavaScript, Java, ActiveX) weaken user

protection

• Limited number of onion routers (~3,000)

• Passive surveillance timing (requires global

reach)

• Active watermarking and delay insertion

(requires malicious nodes)

• Cookies may persist on system after TOR

session ends

5

ANONYMITY

• Access to restricted news

• Open discussion of politics free of reprisal

• Protect journalists and sources

• Support groups (addictions, abuse survivors)

• Evade cyberstalkers

• Transaction Remote Release (TRR) methods can

be applied to Bitcoin transactions to harden

against attacks

• Transmission of validated e-ballots

6

POLICY CONTROL –NODE CONSORTIUM

• Governments, organizations, and individuals contribute to an independent fund to

finance onion router nodes

• Participating node operators are paid on regular basis (daily, monthly, yearly) based

on amount of exit traffic

• Anonymous cryptocurrency used

• Terms of service explicitly forbid examining exit traffic for content

• Increased number of nodes decreases effectiveness of surveillance techniques

7

POLICY CONTROL – PROPRIETARY INFORMATION

• Protect research and development from competitors

• Traffic analysis from corporate IP addresses

• Outwit tailored search results

• See what your customers are seeing

• Conduct research on competitors surreptitiously

8

POLICY CONTROL – DATA CLASSIFICATION

• Security needed in corporate, government, and academic settings

• Protects against over exposure and document exfiltration by malicious insiders

• Low security environment – application blacklisting

• Complicated by raw executable, no installation needed

• Medium security – application whitelisting

• High security – virtualized environment with protected execution stack

• All on site generated documents contain unique user signature

9

POLICY CONTROL - CRYPTOCURRENCY

• Regulate and track moneychangers as traditional currency exchange

• Apply accounting laws to all businesses grossing over $10,000 or equivalent

• May lose effectiveness as market grows to encompass more goods

10

HUMAN FACTORS

• Unconditional anonymity stimulates abusive behavior

• Endowment effect

• Information obtained secretly is worth more

• Illusion of control

• Communications intercepted by other means

• All the information we need can be gotten through TOR

11

REFERENCES

Abbott, R. (2010). AN ONION A DAY KEEPS THE NSA AWAY. Journal Of Internet Law, 13(11), 22-28.

Aguilera, L. (2011). An implementation of accountable anonymity (Master’s thesis). Iowa State University, Ames, IA.

Basarici, S., Rana, A., & Zincir, I. (2015). The Security and the Credibility Challenges in e-Voting Systems. Proceedings Of The

European Conference On E-Learning, 229-232.

Castillo-Pérez, S., & Garcia-Alfaro, J. (2013). Onion routing circuit construction via latency graphs. Computers &

Security, 37197-214. doi:10.1016/j.cose.2013.03.003

Eissa, T., & Gihwan, C. (2015). Lightweight Anti-Censorship Online Network for Anonymity and Privacy in Middle Eastern

Countries. International Arab Journal Of Information Technology (IAJIT),12(6A), 650-657.

Esguerra, R. (2009, June 29). Help Protestors in Iran: Run a Tor Bridge or a Tor Relay [Web log post]. Electronic Frontier

Foundation. Retrieved from https://www.eff.org/deeplinks

Fu, X., Jia, W., Ling, Z., Luo, J., Yu, W., & Zhao, W. (2013). Protocol-level attacks against Tor. Computer Networks, 57869-886.

doi:10.1016/j.comnet.2012.11.005

Fu, X., Jia, W., Ling, Z., Luo, J., Xuan, D., & Yu, W. (2012). A New Cell-Counting-Based Attack Against Tor. IEEE/ACM Transactions

On Networking, 20(4), 1245-1261. doi:10.1109/TNET.2011.217803612

REFERENCES (CONT.)

Kerner, S. M. (2013). Snowden Leaks Show NSA Targets Tor. Eweek, 8.

Kerner, S. M. (2014). Kickstarter Suspends Anonabox Security Appliance Project. Eweek, 2.

Kerner, S. M. (2014). Linux Lands on NSA Watch List. Eweek, 6.

Lawrence, D. (2014). Spy Vs. Spy. (cover story). Bloomberg Businessweek, (4364), 42-47.

McCormick, T. THE DARKNET. Foreign Policy, (203), 22-23.

Mehlman-Orozco, K. (2015). TOR AND THE BITCOIN. Diplomatic Courier, 9(2), 78-81.

Phelps, A., & Watt, A. (2014). I shop online - Recreationally! Internet anonymity and Silk Road enabling drug use in

Australia. Digital Investigation, 11(4), 261-272. doi:10.1016/j.diin.2014.08.001

ShenTu, Q., & Yu, J. (2015). Transaction Remote Release (TRR): A New Anonymization Technology for Bitcoin. ATR Defense

Science & Technology., Shenzhen University, Shenzhen, China.

Watson, K. D. (2012). THE TOR NETWORK: A GLOBAL INQUIRY INTO THE LEGAL STATUS OF ANONYMITY

NETWORKS. Washington University Global Studies Law Review, 11(3), 715.13