anonymity networks - trial lecturearyan/docs/thesis/trial.pdf · anonymity networks trial lecture...

Introduction Anonymity Networks SDN Applications in Anonymous Communication Proposal Summary

Anonymity NetworksTrial Lecture

Aryan TaheriMonfared

Department of Electrical Engineering and Computer ScienceUniversity of Stavanger

October 26, 2015


Outline1 Introduction

Privacy & Anonymity2 Anonymity Networks

Anonymous CommunicationTor: The Onion RouterTor Hidden ServicesTor AttacksTor Open Questions

3 SDN Applications in Anonymous CommunicationOverviewAnonyFlowOF-RHMNetwork Attributes RandomizationSNEACCloud Onion Routing

4 ProposalOur Proposal

5 Summary


Privacy & Anonymity






5 Summary


Privacy & Anonymity

Privacy

Cyber PrivacyBe Concerned About Your Cyber Privacy!

Common Answers:I have nothing to hide.Those, who are concerned, look suspicious.


Privacy & Anonymity

Privacy

How about privacy in other aspects of life?

Do you use curtains? Do you close the door?


Privacy & Anonymity

Anonymity

Anonymity → PrivacyAnonymity is one step toward privacy.You are not anonymous on the Internet.

Definition"The state of being not identifiable within a set of subjects,the anonymity set" Pfitzmann and Hansen 2008.


Privacy & Anonymity

Anonymity Types

UnlinkabilityRecipient anonymity: recipient & sent messageSender anonymity: sender & received messageRelationship anonymity: sender & receiver

Unobservability

Sender & Sent msgCover traffic

Recipient & Received msg


Privacy & Anonymity

Anonymity

Who needs anonymity?Citizens: privacyBusinesses: network securityGovernments: traffic analysis resistanceActivists: access


Anonymous Communication






5 Summary




Use-Cases

File sharingInstant messagingemail communication

CurrencyBrowsingHidden services

Design Criteria

LatencyAnonymity GuaranteesFlexibility

Supported protocolsTrust & Threat modelsCommunication model




Networks/Tools

Mix-NetBabelMix-masterMixminionFreedomThe Onion Router (Tor)AnonymizerJava Anon Proxy (JAP)

PipeNet

Tarzan

MorphMix

Hordes

Herbivore

P5

...


Tor: The Onion Router






5 Summary



Tor: What Others Say?

A Three-letter Agency

"the King of high-secure, low-latency Internet anonymity""no contenders for the throne in waiting""We will never be able to de-anonymize all Tor users all thetime""with manual analysis we can de-anonymize a very smallfraction of Tor users"



So, you googled "Tor"?Hah, you’re already a target....

And,That’s why you should be concerned about your privacy.



Original Tor Overview

Onion Routing 1st Generation – 1998Distributed overlay network.Designed to anonymize TCP-based applications.Clients choose a path to build a circuit.Each node only knows its predecessor and successor.Traffic flows in fixed-size cells.Unwrapped by a symmetric key at each node.



Original Tor Overview



Enhanced Tor Overview

Onion Routing 2nd Generation – 20041 Perfect forward secrecy:

Initiator negotiates keys with each node.

2 TCP streams share a circuit:Multiplex streams to improve efficiency and anonymity.

3 Leaky-pipe circuit topology:In-band signaling + traffic exits from the middle of circuit.

4 Variable exit policies:Defines hosts and ports that an exist node will connect.

5 Directory servers:Avoid state info flooding + signed directories of routers and states.

6 Rendezvous points & hidden services:Clients negotiate rendezvous points to connect with hidden services.



Enhanced Tor Overview – 2012

Attacks

Malicious OR OR IP blocking Protocol Blocking



Tor Design

Tor Goals1 Improve Deployability, Usability, and Flexibility.2 Simplify design.3 Resistance against traffic analysis.

Tor Non-Goals1 Not peer-to-peer.2 Not secure against end-to-end attacks.3 Not prevent traffic confirmation.



Tor Entities

Onion Router (OR)/RelayUser-level process.Connected to every other ORs using TLS.Exit node: terminating OR of a circuit.Exit node sends/receives data to/from destinations.

Onion Proxy (OP)/ClientFetches directories.Establishes circuits incrementally.Negotiates symmetric keys with each OR.Multiplexes TCP streams across several circuits.



Tor Entities

Directory ServersDSs:I A small group of redundant, well-known ORs.I Track topology and node state (e.g. keys, exit policies).I Avoid link-state routing protocols.I Generate a signed description of the network state.I Work as HTTP servers.

ORs publish signed states to DSs.Clients:I Are pre-loaded with a list of DSs and their keys.I Fetch network state, routers list, etc from DSs.



Tor Keys

Long-term Identity Keys

OR: signs TLS certs, router descriptor (keys, address, bw,exit policy, etc.).DS: signs directories.

Short-term Onion KeysDecrypts users’ requests for circuit establishment.Ephemeral key negotiation.Rotated periodically.



Tor Details


Tor Hidden Services






5 Summary


Tor Hidden Services

Tor Rendezvous Points & Hidden Services

Hidden ServicesEnsuring service provider anonymity.Concealing service IP address.


Tor Hidden Services

Tor Hidden Services


Tor Attacks






5 Summary


Tor Attacks

Tor Attacks

Passive Attacks

Observing patterns/content.

Option distinguishability.

End-to-end timing/size.

Website fingerprinting.

Active Attacks

Compromise keys.

Hostile recipient/OP/OR.

DoS OR/Introduce Timing.

Smear/Protocol attack.

Directory Attacks

Destroy, subvert DSs.DS dissent through operators.

Persuade DS to accepthostile/malfunctioning OR.

Rendezvous Point AttacksDisrupt IP operation by DoS, direct attack, compromise.

Compromise a rendezvous point.


Tor Open Questions






5 Summary


Tor Open Questions

Tor Open Questions and Future Directions

Circuit rotate frequency and length.Scalability:I OR verification.I Global view distribution to clients.I State synchronization between DSs.I Central authority (DSs) reliability .I Node failure tolerance.

Bandwidth classes.Cover traffic.Caching at exit nodes.Multi-system interoperability.Wide-scale deployment.


Tor Open Questions

Tor Statistics

metrics.torproject.org

Users: 2 M (Max: 5 M)Relays: 6.5 K, Bridges: 3.5 kRelay Advertised BW: 140 GbpsRelay Used BW: 60 GbpsGuard Advertised BW: 35 GbpsExit nodes BW: 5 Gbps,Hidden services traffic: 800 Mbps







5 Summary


SDN Related Work

1 A Flexible In-Network IP Anonymization Service,Mendonca et al. 2012

2 OpenFlow Random Host Mutation: Transparent MovingTarget Defense using Software Defined Networking,Jafarian et al. 2012

3 SNEAC: Scalable Network Emulator for AnonymousCommunication, Singh et al. 2014

4 Techniques for the Dynamic Randomization of NetworkAttributes, Chavez et al. 2015

5 Hiding Amongst the Clouds: A proposal for Cloud-basedOnion Routing, Jones et al. 2011


AnonyFlow






5 Summary


AnonyFlow

AnonyFlow

A Flexible In-Network IP Anonymization ServiceCurrent approaches have low performances.Assumption: Trust in infrastructure providers.Reactive SDN programming.Intercepting the first packet of all flows.

Goals

Endpoint privacy.Low overhead.

Network-based design.Easy deployment.

Non-Goals

Data security.Steganography.

Complete anonymity.


OF-RHM






5 Summary


OF-RHM

OF-RHM Overview

OpenFlow Random Host MutationStatic network configurations introduce significant threats.Hosts’ IPs mutation is a novel proactive defense.

ApproachUse OpenFlow to mutate hosts’ IPs frequently andunpredictably.Named hosts are reachable through virtual IPs.vIPs are chosen from unused IPs in the subnet.vIPs are obtained via DNS.Address allocation is formalized as a multi-constraintsatisfaction problem.


Network Attributes Randomization






5 Summary


Network Attributes Randomization

Network Attributes Randomization Overview

Techniques for the Dynamic Randomization of NetworkAttributes

Critical Infra. Control Systems are vulnerable.CICSs use predictable paths and static configuration.Attractive and easy targets for attacks.

ApproachAutomatic reconfiguration of network settings.CICS → Moving Target Defense.SDN: IP/port/route randomization.


SNEAC






5 Summary


SNEAC

SNEAC Overview

Scalable Network Emulator for Anonymous CommunicationAnonymous communication technologies require reliabletestbeds.Tor testbeds are not scalable.

ApproachNetwork emulation testbed for Tor.Uses Mininet and Open vSwitch to build the core.


Cloud Onion Routing






5 Summary


Cloud Onion Routing

COR Overview

Hiding Amongst the Clouds: A proposal for Cloud-based OnionRouting

Tor has limitations: low performance, inadequate capacity,prone to wholesale blocking.Cloud characteristics can help.

ApproachLeverage large capacity, robust connectivity, EoS in Cloud.Cloud increases the censorship cost (collateral damage).Establishes several Anonymity Service Providers onmultiple Cloud services.


Our Proposal






5 Summary


Our Proposal

Our Proposal

Building Tor Using SDN mechanisms

Faithful reproduction of Tor circuits using SDN.DS Authorities → Global cluster of SDN controllers.Onion Proxy/Client software → User SDN controller.Onion Router/Relay → SDN-capable switches.


Our Proposal

Proposal Tradeoffs

Advantages

Flexibility.Scalability.BW classes.Interoperability.Open/Standard protocols.

HW & SW support.Large community.Separation of concerns:network management/keymanagement.

Disadvantages

Complexity.Maturity.

SDN-related attackvectors.


Summary

Take-Away Lesson1 Be concerned about your cyber-privacy.2 Anonymization plays an important role in privacy.3 SDN mechanisms can tackle many open problems in

anonymous communication.


Thank you! Questions? & Answers!


References I

Adrian Chavez, William Stout, and Sean Peisert, Techniques for the dynamic randomization of networkattributes, Proceedings of the 49th Annual International Carnahan Conference on Security Technology, 2015.

Roger Dingledine, Nick Mathewson, and Paul Syverson, Tor: The second-generation onion router,Proceedings of the 13th Conference on USENIX Security Symposium - Volume 13 (Berkeley, CA, USA),SSYM’04, USENIX Association, 2004, pp. 21–21.

Matthew Edman and Bülent Yener, On anonymity in an electronic society: A survey of anonymouscommunication systems, ACM Comput. Surv. 42 (2009), no. 1, 5:1–5:35.

Staale Freyer, Figure 3.

Nicholas Jones, Matvey Arye, Jacopo Cesareo, and Michael J. Freedman, Hiding amongst the clouds: Aproposal for cloud-based onion routing.

Jafar Haadi Jafarian, Ehab Al-Shaer, and Qi Duan, Openflow random host mutation: Transparent movingtarget defense using software defined networking, Proceedings of the First Workshop on Hot Topics inSoftware Defined Networks (New York, NY, USA), HotSDN ’12, ACM, 2012, pp. 127–132.

Eng Keong Lua, J. Crowcroft, M. Pias, R. Sharma, and S. Lim, A survey and comparison of peer-to-peeroverlay network schemes, Communications Surveys Tutorials, IEEE 7 (2005), no. 2, 72–93.

Damon McCoy, Kevin Bauer, Dirk Grunwald, Tadayoshi Kohno, and Douglas Sicker, Shining light in darkplaces: Understanding the tor network, Privacy Enhancing Technologies (Nikita Borisov and Ian Goldberg,eds.), Lecture Notes in Computer Science, vol. 5134, Springer Berlin Heidelberg, 2008, pp. 63–76 (English).


References II

Stefano De Sabbata Mark Graham, Geographies of Tor, Creative Commons Attribution-Share Alike 4.0International.

M. Mendonca, S. Seetharaman, and K. Obraczka, A flexible in-network ip anonymization service,Communications (ICC), 2012 IEEE International Conference on, June 2012, pp. 6651–6656.

A. Ruiz-Martinez, A survey on solutions and main free tools for privacy enhancing web communications,Journal of Network and Computer Applications 35 (2012), no. 5, 1473 – 1492, Service Delivery Managementin Broadband Networks.

Jian Ren and Jie Wu, Survey on anonymous communications in computer networks, Comput. Commun. 33(2010), no. 4, 420–431.

Sukhbir Singh, Large-scale emulation of anonymous communication networks.

Clayton Tang, Portable potty on top of a mountain in china, Creative Commons Attribution-Share Alike 3.0Unported.

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