Tor, a quick overview

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1 Tor, a quick overview Linus Nordberg <linus@torproject.org> The Tor Project 1

2 What is Tor Online anonymity: 1. software, 2. network, 3. protocol Open source, freely available Community of researchers, developers, users and relay operators Funding from US DoD, Electronic Frontier Foundation, Voice of America, Google, NLnet, Human Rights Watch and more 2

3 The Tor Project, Inc. 501(c)(3) non profit organization dedicated to the research and development of tools for online anonymity and privacy 3

4 Estimated 400,000 daily tor users 4

5 Anonymity serves different interests for different user groups Anonymity? It's privacy Private citizens 5

6 Anonymity serves different interests for different user groups Anonymity? Businesses It's privacy Private citizens It's network security 6

7 Anonymity serves different interests for different user groups It's traffic-analysis resistance! Governments It's privacy Anonymity? Private citizens Businesses It's network security 7

8 Anonymity serves different interests for different user groups It's traffic-analysis resistance! Governments It's privacy Blocked users Anonymity? Private citizens It's reachability! Businesses It's network security 8

9 Encryption alone doesn't protect against traffic-analysis Alice Bob 9

10 Regular citizens don't want to be watched and tracked Sick Alice Web serarch Vårdguiden.se Netdoktor.se 10

11 Regular citizens don't want to be watched and tracked 8-year-old Alice Web services 11

12 Regular citizens don't want to be watched and tracked Blogger Alice Blog site 12

13 Regular citizens don't want to be watched and tracked Employed Alice Web search Vårdguiden.se Netdoktor.se 13

14 Regular citizens don't want to be watched and tracked Consumer Alice Amazon.com Cdon.se Bokus.com Prisjakt.nu Pricerunner.se 14

15 Business need to keep trade secrets Alice Corp Competitor 15

16 Business need to keep trade secrets Alice Corp Web search Suppliers Customers Media 16

17 Law enforcement needs anonymity to get the job done Police Alice Suspected Bob 17

18 Law enforcement needs anonymity to get the job done Police Alice Bob, selling illegal drugs 18

19 Law enforcement needs anonymity to get the job done Police Alice Bob Corleone 19

20 Law enforcement needs anonymity to get the job done Witness Alice Police tip line 20

21 Law enforcement needs anonymity to get the job done Alice with protected identity Online news Internet shops Web forums 21

22 Governments need anonymity for their security Ambassador Alice abroad Foreign ministry at home 22

23 Governments need anonymity for their security Agent Alice Defence agency 23

24 Journalists and their sources need Tor for their personal safety Alice the source Bob the journalist 24

25 Journalists and their sources need Tor for their personal safety Alice the journalisten Suspicious company 25

26 Journalists and their sources need Tor for their personal safety Censored Alice Filtered web site 26

27 Journalists and their sources need Tor for their personal safety Alice the dissident Surveiled web site 27

28 The simpler systems use only one relay Alice1 E(Bob3, X ) Y Bob1 E(Bob1, Y ) Relay Z Alice2 E(Bob2, Z ) X Bob2 Alice3 Bob3 (For example relax.se, dold.se and ipredator.se) 28

29 The simpler systems put all the eggs in the same basket Alice1 E(Bob3, X ) Y Bob1 E(Bob1, Y ) Z Alice2 E(Bob2, Z ) X Bob2 Alice3 Bob3 29

30 A single relay is also an attractive target Alice1 E(Bob3, X ) Y Bob1 E(Bob1, Y ) Relay Z Alice2 E(Bob2, Z ) X Bob2 Alice3 Bob3 Trafic and timing analysis will reveal which Alice is talking to which Bob. 30

31 So, add multiple relays so that no single one can betray Alice Alice R1 R3 Bob R4 R2 R5 31

32 A corrupt first hop can tell that Alice is talking, but not to whom Alice R1 R3 Bob R4 R2 R5 32

33 A corrupt final hop can tell that somebody is talking to Bob, but not who Alice R1 R3 Bob R4 R2 R5 33

34 The first hop is protected by three layers of encryption, then each hop peels off one layer, onion routing Alice R1 R3 Bob1 Bob2 R4 R2 R5 34

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Online Anonymity & Privacy. Andrew Lewman The Tor Project

Online Anonymity & Privacy. Andrew Lewman The Tor Project Online Anonymity & Privacy Andrew Lewman The Tor Project https://torproject.org/ Outline Why anonymity? Crash course on Tor Future Informally: anonymity means you can't tell who did what Who wrote this