Transcript Tor Bruce Maggs relying on materials from

Tor
Bruce Maggs
relying on materials from
http://www.torproject.org
2
How Tor Works
3
How Tor Works
4
5
Encryption Keys in TOR
• Each relay has a long-term ``identity’’
•
•
public/private key pair used to sign TLS
certificates (public keys signed by directory)
Medium-term (one week) public/private ``onion’’
keys are used to decrypt requests to extend
circuits – so first node can’t spoof the whole
path
Short-term “connection” keys used to
negotiation TLS connections
6
How Tor Works
7
Bridge Relays (a.k.a. Bridges)
• Some ISPs/governments block all traffic
to relays that appear in the Tor
directory.
• Bridges are relays that don’t appear in
the directory.
• User has to solve the problem of finding
a bridge.
8
Solve a Captcha to get Bridge Address
9
10
Growth of Tor Network
11
Growth of Tor Network
12
Spike in Number of Users
13
Possible Explanation for Spike
• Botnet “Mevade.A” a.k.a. “Sefnit” a.k.a.
“SBC” is using Tor for connectivity
• http://blog.fox-it.com/2013/09/05/largebotnet-cause-of-recent-tor-networkoverload/
14
15
Tor Exit Nodes See Plaintext!
http://archive.wired.com/politics/security/news/2007/09/embassy_hacks?currentPage=all
16
Tor Browser
17
Tor Browser
18
19
Tor-Aware Web Servers
Connect directly to Tor, do not advertise their network addresses.
20
Establishing a Hidden Service
21
Establishing a Hidden Service
22
Finding a Hidden Service
23
Contacting a Hidden Service
24
Contacting a Hidden Service
25
Communicating with a Hidden Service
26
Using Tor as a SOCKS5 Proxy
• Can tunnel any TCP connection through
Tor (and DNS requests)
• First run the Tor browser, it will also act
as a SOCKS5 proxy and accept
connections
• Configure your application, e.g., chat, to
use 127.0.0.1 as SOCKS5 proxy
27
Configure HexChat to use Proxy
28
Now Chatting through Tor
29
4
30