1. The Onion Router Hao-Lun Hsu
Taiwan Evolutionary Intelligence Laboratory
2017/3/13 Group Meeting Presentation

2. Outline Dark Web Onion Router Structure of the Internet
Content of dark web
Onion Router
Onion routing
Security issue

3. Dark Web
The Internet was not designed with things like anonymity and privacy.
In 1960s, U.S. navy (Naval Research Laboratory) began to develop The Onion Router (Tor).
Onion Routing is a system that allows for bi-directional communications over the Internet where the source and destination cannot be determined by a mid-point.
Tor的project負責人曾說：
不能只有美國政府在用這套系統，不然的話下次有人看到一條匿名的連線就會說”噢，又一個CIA探員在偷看我”

4. Structure of Internet
Deep Web/ Surface Web = 500
I2P Freenet
Source:

5. Content of Dark Web Hidden Services:
.onion e.g.
Black market e.g. Drug Market
Google會鎖 因為會判定為DDoS

7. Onion Router
Randomly selects 3 nodes from a list provided by a "directory node“.
These nodes are arranged into a path, called a “circuit”.
No node in a circuit can tell whether the node before it is the originator or another intermediary like itself.
Random select 但是有congestion control
Lannister
Stark
Baratheon
Bolton
Targaryen

8. Stark
Baratheon
Lannister
Bolton
Targaryen

9. Stark
Baratheon
Lannister
Bolton
Targaryen

10. Stark
Baratheon
Lannister
Bolton
Targaryen

11. Stark
Baratheon
Lannister
Bolton
Targaryen

12. Stark
Baratheon
Lannister
Bolton
Targaryen

13. Stark
Baratheon
Lannister
Bolton
Targaryen

14. Stark
Baratheon
Lannister
Bolton
Targaryen

15. Stark
Baratheon
Lannister
外部攻擊者必須
Bolton
Targaryen

16. Onion Router Each node only knows its next node and previous node.
The three nodes change every 10 minutes.
Unless all three nodes are compromised, the user cannot be traced. (Usually, the three nodes are in three different countries)
If the three nodes are compromised unfortunately, tracing the user is still hard since there are too many users.

17. Connection Establishment

18. Security Issue Exit node vulnerability Time analysis attack
SSL connection between exit node and destination server
Time analysis attack
NSA: 木馬將Tor導向NSA控制的節點

19. Pros & Cons Pros Cons Real anonymity Slow (high latency)
Rely on SSL connection between nodes and between a node and the destination

20. Reference
Roger Dingledine, Nick Mathewson, Paul Syverson, Tor: The Second-Generation Onion Router
Wikipedia: