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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
Tor, a quick overview Linus Nordberg <linus@torproject.org> - - PowerPoint PPT Presentation
Tor, a quick overview Linus Nordberg <linus@torproject.org> - - PowerPoint PPT Presentation
Tor, a quick overview Linus Nordberg <linus@torproject.org> The Tor Project https://torproject.org/ 1 What is Tor Online anonymity: 1. software, 2. network, 3. protocol Open source, freely available Community of researchers,
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- 501(c)(3) non-profit
- rganization dedicated
to the research and development of tools for online anonymity and privacy
The Tor Project, Inc.
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Estimated 400,000 daily tor users
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Anonymity serves different interests for different user groups
Anonymity?
Private citizens “It's privacy”
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Anonymity serves different interests for different user groups
Anonymity?
Private citizens Businesses “It's network security” “It's privacy”
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Anonymity serves different interests for different user groups
Anonymity?
Private citizens Businesses “It's network security” “It's privacy” Governments “It's traffic-analysis resistance!”
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Anonymity serves different interests for different user groups
Anonymity?
Private citizens Governments Businesses “It's traffic-analysis resistance!” “It's network security” “It's privacy” Blocked users “It's reachability!”
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Encryption alone doesn't protect against traffic-analysis
Alice Bob
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10 Sick Alice Web serarch Vårdguiden.se Netdoktor.se
Regular citizens don't want to be watched and tracked
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11 8-year-old Alice Web services
Regular citizens don't want to be watched and tracked
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12 Blogger Alice Blog site
Regular citizens don't want to be watched and tracked
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13 Employed Alice Web search Vårdguiden.se Netdoktor.se
Regular citizens don't want to be watched and tracked
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14 Consumer Alice Amazon.com Cdon.se Bokus.com Prisjakt.nu Pricerunner.se
Regular citizens don't want to be watched and tracked
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15 Alice Corp Competitor
Business need to keep trade secrets
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16 Alice Corp Web search Suppliers Customers Media
Business need to keep trade secrets
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17 Police Alice Suspected Bob
Law enforcement needs anonymity to get the job done
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18 Police Alice Bob, selling illegal drugs
Law enforcement needs anonymity to get the job done
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19 Police Alice Bob Corleone
Law enforcement needs anonymity to get the job done
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20 Witness Alice Police tip line
Law enforcement needs anonymity to get the job done
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21 Alice with protected identity Online news Internet shops Web forums
Law enforcement needs anonymity to get the job done
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22 Ambassador Alice abroad Foreign ministry at home
Governments need anonymity for their security
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23 Agent Alice Defence agency
Governments need anonymity for their security
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24 Alice the source Bob the journalist
Journalists and their sources need Tor for their personal safety
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25 Alice the journalisten Suspicious company
Journalists and their sources need Tor for their personal safety
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26 Censored Alice Filtered web site
Journalists and their sources need Tor for their personal safety
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27 Alice the dissident Surveiled web site
Journalists and their sources need Tor for their personal safety
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The simpler systems use only one relay
Bob2 Bob1 Bob3 Alice2 Alice1 Alice3 Relay E(Bob3,“X”) E(Bob1, “Y”) E ( B
- b
2 , “ Z ” ) “Y” “Z” “X”
(For example relax.se, dold.se and ipredator.se)
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The simpler systems put all the eggs in the same basket
Bob2 Bob1 Bob3 Alice2 Alice1 Alice3 E(Bob3,“X”) E(Bob1, “Y”) E ( B
- b
2 , “ Z ” ) “Y” “Z” “X”
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A single relay is also an attractive target
Bob2 Bob1 Bob3 Alice2 Alice1 Alice3 Relay E(Bob3,“X”) E(Bob1, “Y”) E ( B
- b
2 , “ Z ” ) “Y” “Z” “X” Trafic and timing analysis will reveal which Alice is talking to which Bob.
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So, add multiple relays so that no single one can betray Alice
Bob Alice R1 R2 R3 R4 R5
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A corrupt first hop can tell that Alice is talking, but not to whom
Bob Alice R2 R3 R1 R4 R5
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A corrupt final hop can tell that somebody is talking to Bob, but not who
Bob Alice R1 R2 R3 R4 R5
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The first hop is protected by three layers of encryption, then each hop peels off one layer, onion routing
R1 R2 R3 R4 R5 Alice Bob1 Bob2
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