null - Mumbai June 2012 Meet

1. THE ONION ROUTER
DHARAMVIR BISHT

2. Who needs Anonymity
• Government Organization ?
• Private Organization?
• Hackers
• And yes !!!Criminals? But they already have it
• What About YOU

3. TOR
• Onion routing is an anonymous communication
technique over a computer network. Messages
are constantly encrypted and then sent through
several network nodes called onion routers
which creates a circuit of nodes

4. Anonymous Connection and
Onion Routing

5. Who is Talking to Whom ?
In a Public Network
>Packet headers identify recipients
>Packet routes can be tracked

6. Traffic Analysis Reveals
Identities
>Who is searching a public database?
>Which companies are collaborating?
>What are you talking to via-Email?
>What do you shop online?

7. Objectives
Design an infrastructure that
>Makes traffic analysis hard
>Separates identification from routing
Our goals is anonymous connections, not
anonymous communication.
An infrastructure, Onion Routing, has been
implemented.

8. Steps for Onion Routing
> Define the route
>Construct the anonymous connection
>Move and encrypt the data through the
connection
>Destroy the anonymous connection

9. Tor in brief – 1/3
Step 1: Alice‘s Tor client obtains a list of Tor
nodes from a directory server

10. Tor in brief – 2/3
Step 2: Alice‘s Tor client picks a random path to
destination Server. Green links are encrypted, red
links are in the clear.

11. Tor in brief – 3/3
Step 3: If the user wants access to another site, Alice‘s
Tor client selects a second random path. Again, green
links are encrypted, red links are in the clear.

12. Example
Let onion routers 4, 3, and 5 be randomly selected by
the onion proxy

13. Onion Sent by Client to 4
Router 4 will decrypt the E{4u} layer using
Its private key, to find the next router’s Ip address,
and encrypted

14. Onion Sent by 4 to 3
Router 3 will decrypt the E{3u} layer using
Its private key, to find the next router’s Ip address,
and encrypted

15. Onion Sent by 3 to 5
Router 5 will decrypt the E{5u} layer using
Its private key, to just find unencrypted data packet
Data Sent by 5 to Target

16. TOOLS
• TOR BROWSER
• TOR GATEWAY
• TOR WORK STATION
• JANUSVM

17. References
• https://www.torproject.org/about/overview.h
tml.en
• http://www.onion-router.net/
• http://ntrg.cs.tcd.ie/undergrad/4ba2.05/grou
p10/index
• http://en.wikipedia.org/wiki/Onion_routing