Encrypting in Transit: Tor

Anonymizing tools conceal your Internet activities so that no one will be able to trace or analyze where you go on the web. One powerful option for protecting data in transit is Tor [4], a sophisticated peer-based virtual private network designed to guard you and your information against profiling from any entity. Tor uses a distributed, peer-based network. Each computer that actively participates on the Tor network is called a relay. It is possible to connect to the Tor network as a mere user or as a relay.

With Tor, your network traffic is encrypted using public key encryption then routed and forwarded on a near-random basis through the Tor network. As a result, it is quite difficult for anyone to determine the sites you have visited. Ironically, Tor was created by the United States Navy. Called the "Onion Routing Project," Tor was designed to help protect Navy traffic from snooping.

A Tor network is a distributed virtual network designed to do two things: First, Tor encrypts traffic. Second, it randomizes traffic so that it is more difficult for any entity to analyze it. Tor is quite successful, and several government entities have gone on record recently, noting that the Tor network is quite good at randomizing and anonymizing traffic. Although governments regularly capture Tor-based traffic, they tend to find that traffic analysis and decryption of Tor data is fairly difficult.

How Does Tor Work?

Tor is the Napster or LimeWire of VPN servers: All you have to do is install some software, join with the Tor network, and you are on your way to encrypting and anonymizing your network.

You'll need to configure your web browser to access your system as you would any proxy server, such as Squid. Tor uses the SOCKS protocol for local network connections. This means when you configure your browser's proxy server settings, you'll want to use the SOCKS protocol and specify the port (usually TCP 9050).

The easy way to join up with a Tor network is to use the Tor Browser Bundle (TBB), which you can download from the Tor site. Simply download the software and participate in the Tor virtual private network scheme. The hard way is more interesting to me, because it allows you to contribute to the overall network. The hard way involves connecting to the Tor network as a relay, which helps add more randomization to the network.

To get started, download the Tor package using either the available tarball or the package available from your system repository. For example, I was able to download a copy of Tor using apt-get on my Ubuntu system without having to update any of the standard repositories. If you are using Tor to simply connect to the network, install the binary and use a system script to start the service (Listing  1).

When Tor runs in default mode, it listens for connections from your local machine on TCP port 9050. This port will accept only connections from your local machine. Once Tor is running, you should check its log files to make sure it has connected with the overall Tor network (Listing 2).

Listing 2 shows that Tor has gone out to find relays on the Internet. Because I made sure my firewall software wasn't blocking Tor-based connections, the process went quite quickly.

Your Browser as a Tor Client

To use Tor, you will need to configure your browser for a proxy server. In Firefox, go to Edit | Preferences. Then, click on the Advanced tab, then click on the Settings tab. You can then enter the SOCKS configuration information, as shown in Figure 3.

Figure 3: Configuring Firefox to use Tor.

The steps for configuring Opera, Chrome, or another browser are similar. Simply specify the correct SOCKS information. Once you have configured your browser, restart it. Then, point your web browser to the following URL to confirm that your system is communicating across Tor's relay network:

https://check.torproject.org

If your browser is not using the Tor network, you'll get a screen similar to Figure 4.

Figure 4: Message that you are not using Tor.

If your system and browser are properly configured and running, you will see the confirmation screen shown in Figure 5.

Figure 5: Confirmation that Tor is working in a browser.