Onion routing provides anonymity to users on the internet. It works by encrypting data multiple times and routing it through several intermediate servers, known as onion routers, hiding the origin and destination from each router. When a user wants to communicate anonymously, onion routing first establishes a encrypted circuit through the routers. It then opens a stream through this circuit to send data back and forth between the user and destination while preserving anonymity. Each router only knows the previous and next hops in the circuit, not the complete path. Periodically, new circuits are formed to further improve anonymity.

2. IMPORTANT BENEFIT OF ONION

3. ONION AND COMPUTERS
 PROVIDES FREEDOM TO USERS OF COMPUTER

4. ANONYMITY ↔ GOSSIPS

5. WHY ANONYMITY IS PRACTICED IN
NETWORKS ?
 Privacy
 Intelligence sectors
 Data Security

6. Anonymous Communication Protocols
 Mix Networks (1981)
 Dining cryptographers (1988)
 Onion routing (1999)
 Anonymous buses (2002)
 Crowds (1998)
 PipeNet (1998)
 Xor-trees (2000)
4
 Hordes (2002)
 Salsa (2006)
 ISDN,pool,
Stop-and-Go,
timed,cascade
mixes
 etc.

7. HOW ONION ROUTING WORKS ?
 CORE IDEA: MIX NETWORKS
ONION ROUTING PHASES:
 Setup
 Transmission
 Teardown
ONION ROUTING HIDES SENDING HOST AND THE RECEIVING HOST
THIS IS ANONYMITY !!!

8. SETUP PHASE
1. CREATE from U /CREATED (ACK from 1)
2. EXTEND/EXTENDED
3. [Repeat with layer of encryption]
[l2,CREATED]
u 1 2 3
15

9. TRANSMISSION PHASE
 Exchanging messages in the path setup during the setup phase

10. TEARDOWN PHASE
 After the successful delivery of message, the setup path will be destroyed.
 FOR EACH BLOCK OF MESSAGE, A NEW CIRCUIT IS FORMED BETWEEN THE
SOURCE AND THE DESTINATION.

11. How Onion Routing Works
User u running client Internet destination d
Routers running servers
u d
1 2
3
4
5
9

12. How Onion Routing Works
u d
1. u creates l-hop circuit through routers
1 2
3
4
5
9

13. How Onion Routing Works
u d
1. u creates l-hop circuit through routers
1 2
3
4
5
9

14. How Onion Routing Works
u d
1. u creates l-hop circuit through routers
1 2
3
4
5
9

15. How Onion Routing Works
u d
1. u creates l-hop circuit through routers
2. u opens a stream in the circuit to d
1 2
3
4
5
9

16. How Onion Routing Works
u d
1. u creates l-hop circuit through routers
2. u opens a stream in the circuit to d
3. Data are exchanged
{{{m}3}4}1
1 2
3
4
5
9

17. How Onion Routing Works
u d
1. u creates l-hop circuit through routers
2. u opens a stream in the circuit to d
3. Data are exchanged
{{m}3}4
1 2
3
4
5
9

18. How Onion Routing Works
u d
1. u creates l-hop circuit through routers
2. u opens a stream in the circuit to d
3. Data are exchanged
{m}3
1 2
3
4
5
9

19. How Onion Routing Works
u d
1. u creates l-hop circuit through routers
2. u opens a stream in the circuit to d
3. Data are exchanged
m
1 2
3
4
5
9

20. How Onion Routing Works
u d
1. u creates l-hop circuit through routers
2. u opens a stream in the circuit to d
3. Data are exchanged
m’
1 2
3
4
5
9

21. How Onion Routing Works
u d
1. u creates l-hop circuit through routers
2. u opens a stream in the circuit to d
3. Data are exchanged
{m’}3
1 2
3
4
5
9

22. How Onion Routing Works
u d
1. u creates l-hop circuit through routers
2. u opens a stream in the circuit to d
3. Data are exchanged
{{m’}3}4
1 2
3
4
5
9

23. How Onion Routing Works
u d
1. u creates l-hop circuit through routers
2. u opens a stream in the circuit to d
3. Data are exchanged
{{{m’}3}4}1
1 2
3
4
5
9

24. How Onion Routing Works
u d
1. u creates l-hop circuit through routers
2. u opens a stream in the circuit to d
3. Data are exchanged.
4. Stream is closed.
1 2
3
4
5
9

25. How Onion Routing Works
u
1. u creates l-hop circuit through routers
2. u opens a stream in the circuit to d
3. Data are exchanged.
4. Stream is closed.
5. Circuit is changed every few minutes.
1 2
3
4
5
d
9

26. THANK YOU
For more information visit my blog pingtheprotocols.blogspot.com