Sunday, 26 February 2012

The Onion Router


      TOR stand for The Onion Router and is a freeware software that is one of the best anonymity, privacy and unblocking tools available on the internet. Tor has thousands of volunteer relay servers in different parts of the world through which a user's data is routed and tunnelled in encrypted format with the intention of keeping it completely anonymous. Not only does it protect your freedom on the Internet, it keeps all your communications on the Internet completely secure. It can be downloaded free of cost from

       A number of organizations and governments like to monitor the Internet by performing something known as traffic analysis. For example, imagine your company could be running a data sniffer on the company network to look at the traffic on the network to figure out what websites and servers employees are accessing. At a bigger level, the government could be running a data sniffer on all major ISP's networks with the intention to record, monitor and analyse traffic of all users in a country. This information could then be used to block access to certain websites as well.

   Typically, all data i being transmitted  on the internet in the form of data packets. Each data packet has two parts:

  • Data: This is the actual data that is being transmitted in the data packet. It could be a part of an email, file or webpage.
  • Header: This contains important information about thee source and destination computers that is used to route the data through the Internet.
   There are a lot of ways in which the data being transmitted on the Internet can be encrypted. For example, it is possible to encrypt an email using PGP encryption and then send it out on the Internet. However, encrypting the actual data does not hide the header of a data packet. This means that somebody who is using a data sniffer at your ISP or company or college network could still easily read the header part of the data transfer and figure out valuable information about the source and destination of the data packets. For every data communication on the Internet, there are multiple such intermediaries that could be monitoring and spying on your data communication like your college, company, ISP or even the government. In other words, imagine that you want to communicate with your bank, then typically something like the following communication route is established:

      YOUR COMPUTER->COMPANY or COLLEGE Network->ISP Network->ISP Backbone->Bank's ISP->BANK

  Obviously, in a communication like the above, your computer and your bank will know everything about both the data and the data header. But based on how Internet routing works, all intermediaries along the way(like your company/college)

    One of the powerful data sniffers is a free software called Wireshark ( that allows criminal or system administrators to monitor all data packets being sent and received across the entire network. Even if a user has encrypted the actual data being sent on internet, Wireshark can be used to analyse the header informatiom to figure out valuable details about the source and destination involved in the data transfer.


     This is where Onion Routing comes into the picture. It is an anonymous communication mechanism that ensures that the intermediaries can read neither the data nor the data header that they are transmitting, hence giving complete anonymity to both the sender and destination sustems.

     Typically in Onion Routing, the entire data is repeatedly encrypted with multiple layers of encryption(just the way an onion has multiple layers of skin) and these encryption layers are slowly peeled until data reaches the destination computer. Once the data is encrypted at the source computer it is then routed through multiple intermediate nodes called onion routers. Whenever data reaches an onion router it will peel a layer of encryption to reveal information about the next onion router node to which the data has to be forwarded. The next onion router will follow and repeat the same procedure and peel the next layer of encryption, forward the data again and so on.. This process is repeated until all the encryption layers are peeled and the data reaches the destination computer. Such a multilayer-ed encryption and routing machanism ensures that none of the intermediaries know anything about the contents of the data, the source or the destination. the best part is that no intermediary onion router knows the complete path. Each intermediary onion router will only know where it got the data from and the next system it is supposed to send the data to. The destination system(recipient system) will think that all the data originated at the lat onion router and not the source system.

  TOR is a fantastic free utility that uses onion routing to provide users with a secure, anonymous and encrypted communication channel for all their data transfer needs. Once installed, all applications on your computer can be configured to communicate on the internet through the TOR relay servers(onion routers) in different parts of the world. According ti the TOR project's website(, TOR works in the following steps:

STEP 1: 
Let us assume that you want to connect to through an encrypted communication channel that is completely secure and anonymous at the same time. You need to install TOR on your computer and make sure you have configured your browser to connect to the internet through TOR. Once TOR receives your request to connect to the, it will first connect to the TOR directory server and download a list of all available TOR relay nodes(onion routers) that it can potentially connect to.

TOR will now create a secure encrypted connection between you and the by routing the connection through any three randomly selected TOR relay nodes one after the other. This path that the TOR creates is known as a TOR circuit. TOR will make use of Onion Routing principals while establishing this encrypted secure TOR circuit. TOR always connects to a minimum of three randomly selected TOR relay routers in any part of the world before connecting the user to the destination system, hence ensuring adequately randomized anonymity. The advantage of TOR over a proxy server is that TOR ensures that you are always routed via a minimum of three different TOR relay servers. On the other hand, in case of a proxy server, you are normally routed only through one system.

Once a TOR circuit has been created, it will continue to be used for all connections for 10 minutes or so, after which all new connections will be given completely new TOR circuits. It is also possible to force TOR to change its circuit sooner than 10 minutes if required. Whenever TOR changes its circuit, your identity on the internet also changes.

   Now that we have understood how TOR circuits are established and how TOR works, let us put this knowledge now to use and actually use it to anonymously and safely unblock a blocked website on the internet:

Download the TOR browser bundle, which is available as a free download on
The TOR  browser bundle is a self-contained executable file that can be run directly from a USB pendrive or even a camera SD Card without the need for any installation or configuration. It comes with a copy of the Firefox Portable Browser preconfigured and allows users to establish a secure encrypted connection esily and quickly without any hassles of configuration.


 STEP 2:
After downloading the TOR browser bundle, you need to extract it to a folder of your choice. It could be anywhere on your hard drive or even on an external USB peb drive. To launch TOR, you just need to go to the respective folder and double click on the Start Tor Browser icon.

As soon as you double click on the Start Tor Browser icon, the Vidalia Control Panel will open. At this stage, TOR will connect to its directory server and download a list of available TOR relay servers(onion routers) and then try to establish a secure encrypted TOR circuit through any three different randomly selected TOR relay servers. This entire process of establishing a TOR circuit should not take more than a few seconds. As soon as a secure TOR circuit has been established, a new Mozilla Firefox browser window will automatically open.

      Once Mozilla Firefox launches, it means that the secure TOR circuit has been established and you can start browsing on the internet securely and anonymously. The Firefox Mozilla window that opens will also say Congratulations. Your browser is configured to use Tor, letting you know that TOR is now ready to be used. 

Let us quickly test the TOR circuit by opening the website to check if our connection is anonymous or not. In this case if you look at the screenshot below, you will notice that TOR has routed our connection through a United States -based relay server whose IP address is ;)

     It is important to note that the TOR Browser bundle only works with the portable Firefox browser that it automatically opens once the TOR circuit gets established. All other applications, including other browsers installed on your system, will not automatically start connecting to the TOR circuit. For example, if you simultaneously open both Google Chrome and Mozilla Firefox portable browser to, then you will get two different IP addresses and two different locations in two different browsers at the same time!

  Let us assume that after sometime you get bored of being in United States and want to reroute your secure TOR circuit through some other country. All you need to do is in the Vidalia control panel you need to click on the Use a New Identity option and within a few seconds TOR will create a brand new TOR circuit for you, giving you a completely new location and IP Address.

  Now if you were to open in the Mozilla Firefox browser, then you will notice that your IP address has changed to and your new location to Sweden!

  Typically at any given point of time, TOR will have a few thousand different volunteer TOR servers/Onion routers(while typing this 928 relay servers were online) in different parts of the world. It is possible for a user to view all the TOR relay servers online at any given point of time by opening the Vidalia Control Panel and clicking on the View the Network link to display the TOR network Map:

   Within this TOR Network Map window, in the right bottom pane, information about all the three TOR relay servers throughwhich your computer has currently established a circuit is available.
currently my computer's TOR circuit is as follows:

Computer --> TOR Relay Server 1 in the United States --> TOR Relay Server 2 in Bulgaria --> TOR Relay Server 3 in Russia --> Internet

Celestra (Online)
Location: United States
IP Address:
Platform: Tor (git-c55c166e73d500af) on Linux x86_64
Bandwidth: 20.34 MB/s
Uptime: 108 days 7 hours 53 mins 30 secs
Last Updated: 2012-02-25 14:09:58 GMT

abgtor (Online)
Location: Bulgaria
IP Address:
Platform: Tor (git-4f42b0a93422f70e) on Linux x86_64
Bandwidth: 807.35 KB/s
Uptime: 1 days 22 hours 3 mins 21 secs
Last Updated: 2012-02-25 20:24:31 GMT

RedLantern (Online)
Location: Russia
IP Address:
Platform: Tor (git-1fbce83f8c56d9c6) on Linux x86_64
Bandwidth: 4.02 MB/s
Uptime: 33 days 14 hours 32 mins 6 secs
Last Updated: 2012-02-25 13:10:51 GMT

     Sometimes, your company, college or government will block access to the Tor Project website trying to prevent users from being able to download and use TOR. The good news is that it is possible to download TOR through email as well! Just sent an email to from any mail account that can accept large attachments (like Gmail or Ymail). Make sure you type help in the body of the email and they will get back to you with instructions on how to download a relevant TOR package via email:


      As described in their instructions email, if you want to receive the TOR browser bundle for windows, you need to send an email to them at with the keyword windows in the body of the email. Within a few seconds they will send you a detailed email with the TOR Browser Bundle for Windows attached. As simple as that!

1 comment:

  1. How To Use Block Sites On Google Chrome?
    How To Use Block Websites On Mozilla Firefox?


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