Tor2web is a gate to Tor Hidden Services

1. tor2web
Past, Present and Future of Tor Hidden Services
Sunday, September 4, 2011

2. What is tor2web?
• Gate to hidden services
• Allows people to access HTTP(s) Hidden
Services without Tor
Sunday, September 4, 2011

3. Tradeoff
• --Client Anonymity
• ++Usability
Sunday, September 4, 2011

4. Tor Hidden Services
• am4wuhz3zifexz5u.onion
• Anonymity for the Server
• DoS protection
• End-To-End encryption
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11. Why use HS
• Avoid retaliation for what you publish
• Securely host and serve content
• Stealth Hidden Service
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12. Tor2web
• Works for HTTP(s) HS
• Promote Tor HS
• HS can impact the whole web!
Sunday, September 4, 2011

13. Tor2web 1.0
• Started by Aaaron Swartz in 2008
• Now part of GlobaLeaks
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14. Tor2web 1.0 Issues
• Exposed to abuse complaints
• Misuse of HS to spread illegal material
• No disclaimer
• This leads to Server Takedown
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15. First iteration
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16. Solved problems
• Tell the audience no content is hosted on
the server
• Abuse and problem complaint form
• Dynamic URL rewriting
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17. Kharon
• Complementary to tor2web
• Firefox and Chrome plugin
• https://github.com/hellais/kharon
• rewrites hidden services to tor2web and
i2p
• Done by evilaliv3, hellais and vecna
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18. Unsolved problems
• Responsibility not distributed
• Links directly serve the content
• High risk of takedown
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19. Future tor2web 3.0
• Discussed with Paul Syverson
• Further reduce the risk of takedown
• Distribute responsibility across multiple
actors
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20. Scenarios
• Spammer links to *.tor2web.org site hosted
on HS
• Illegal content hosting
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21. Definitions
User
Node
B
Node
A
Hidden Service
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22. Node A
• Landing page
• Accept disclaimer
• Does not serve content
• Generates a unique, temporary access URL
for the User
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23. Properties of the URL
• Usable once
• Only Node A’s can make them
• Usable only by who generated it
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24. The unique URL
H( nonce
timestamp
the_user (maybe the IP)
onion_address )
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25. The unique URL
Signed nonce
Node Node
A B
verifies the
Hash signature
User
computes the H(...)
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26. Node B
Node B is in different ISP and/or country
content
Node
User
B
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27. What have we
achieved?
• Distribute responsibility across two actors
in two different jurisdictions
• Avoid direct serving of content
• URL’s are unique per user
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28. New problems
• How to handle caching?
• The issue is the delay in connecting to HS
• Cache is used only after connection has
been established
• What are the flaws in this solution?
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29. Questions?
• Wiki: http://wiki.tor2web.org
• Mailing list: tor2web-talk@lists.tor2web.org
• IRC: #tor2web on irc.oftc.net
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30. Thanks for listening!
Sunday, September 4, 2011