What Is Onion Routing



Routing is the process of selecting a path for traffic in a network or between or across multiple networks. Broadly, routing is performed in many types of networks, including circuit-switched networks, such as the public switched telephone network, and computer networks, such as the Interne


Types of Routing

Routing is a process which is performed by layer 3 (or network layer) devices in order to deliver the packet by choosing an optimal path from one network to another. 

There are 3 types of routing: 
1. Static routing – 
Static routing is a process in which we have to manually add routes in routing table. 
Advantages – 

  • No routing overhead for router CPU which means a cheaper router can be used to do routing. 
  • It adds security because only administrator can allow routing to particular networks only. 
  • No bandwidth usage between routers. 

 Default Routing – 
This is the method where the router is configured to send all packets towards a single router (next hop). It doesn’t matter to which network the packet belongs, it is forwarded out to router which is configured for default routing. It is generally used with stub routers. A stub router is a router which has only one route to reach all other networks. 
Configuration – 
Using the same topology which we have used for the static routing before. 

In this topology, R1 and R2 are stub routers so we can configure default routing for both these routers. 
Configuring default routing for R1: 

R1(config)#ip route

Now configuring default routing for R2: 

R2(config)#ip route

Onion routing is a technique for anonymous communication over a computer network. In an onion network, messages are encapsulated in layers of encryption, analogous to layers of an onion

It is also a method for anonymous communications over a wide area network such as the Internet. Onion routing hides the names of the parties that are communicating as well as the data by encrypting the payload in layers, with a different layer for each hop in the route

There is a large set of precautionary measures and best practices to make web browsing safer and more secure for users. Let’s say that you send an HTTPs request to a server and someone intercepts that request but that person can’t know what that message says because its encrypted. But you are still not satisfied with this level of security and want to take this to the next level i.e. you don’t even want anyone sniffing on your network to know which server you are contacting and if you are making any requests or not. This is where onion routing comes in.

 Dynamic Routing – 
Dynamic routing makes automatic adjustment of the routes according to the current state of the route in the routing table. Dynamic routing uses protocols to discover network destinations and the routes to reach it. RIP and OSPF are the best examples of dynamic routing protocol. Automatic adjustment will be made to reach the network destination if one route goes down. 

A dynamic protocol have following features: 

  1. The routers should have the same dynamic protocol running in order to exchange routes. 
  2. When a router finds a change in the topology then router advertises it to all other routers. 

Advantages – 

  • Easy to configure. 
  • More effective at selecting the best route to a destination remote network and also for discovering remote network. 

Disadvantage – 

  • Consumes more bandwidth for communicating with other neighbors. 
  • Less secure than static routing. 


The “onion” name refers to onion routing, the technique used by Tor to achieve a degree of anonymity.

What is the main feature that onion routing networks offer?

Onion routing creates and obscures a path between two computers such that there’s no discernible connection directly from a person to a website, but there still exists records of connections between computers.

How do you check the routing of an onion?

Detecting traffic from the Tor network using firewalls and gateways. Traffic from the Tor network can be detected by configuring a firewall or gateway to audit and log connections from Tor exit nodes.


How does onion routing work?

If you are browsing the internet on a normal web browser like chrome, firefox, etc you request webpages by making simple GET requests to servers without any intermediary. Its just a single connection between a client and a server and someone sniffing on your network can know which server your computer is contacting.

  • Onion routing does this differently. In onion routing, the connection is maintained between different nodes i.e. the connection hops from one server to another and when it reaches the last server on this circuit it is the server that we wanted to contact and it will process our request and serves us the desired webpage which is sent back to us using the same network of nodes.
  • Now you must thing why is it called the onion router. It is because the message we send and the responses we receive are encrypted with different keys, with a unique key for encryption for every different hop or server visit.
  • The client has access to all the keys but the servers only have access to the keys specific for encryption/decryption to that server.
  • Since this process wraps your message under layers of encryption which have to be peeled off at each different hop just like an onion that’s why its called an onion router.

How does it provide anonymity?

Imagine if there is sniffer listening in at the first connection(client – input node) all it can know is the address of the input node and a thrice encrypted message that doesn’t make sense. So all the attacker/sniffer knows that you are browsing tor.
Similarly if sniffing starts at the exit node all the sniffer sees is a server contacting another server but it can’t track the client or the source of the request generated.
But now you may think that if someone is listening in at Node 2 the will know the address of the input and exit and can trace the client and the destination server. But its not that simple, each of these nodes have hundreds of concurrent connections going on and to know that which one leads to the right source and destination is not that easy. In our circuit, the Node 2 is a middle node but it can be a part of another circuit on a different connection where it acts as the input node receiving requests or an exit node serving up webpages from various servers.

Vulnerability in Onion Routing

The only security flaw in onion routing is that if someone is listening in on a server at the same time and the matches the request at the destination to a request made by a client on the other side of a network by analyzing the length and the frequency of the characters found in the intercepted request or response at the destination server and using that to match with a same request made by a client a fraction of a second (time-stamps on requests and responses can also be helpful in deducing that) and then tracking them down and knowing their online activity and shattering the idea of anonymity. This is pretty hard to do but not impossible. But removing this flaw from Tor is virtually impossible.


What are the advantages of Tor browser?

Advantages of tor browser or onion routing

  • It’s free: Tor is free and open-source. …
  • Hides your information: It hides your IP and other data while browsing websites.
  • Network security: The websites you open in this network is secured and encrypted. …
  • Democratic activities: You can do democratic activities easily by using tor.


What is a disadvantage to using onion routing?

Disadvantages of Tor

  • Slow Connection. Since a single request goes through multiple layers or nodes, using the Tor network will really slow down your connection. …
  • Security Limited Only to Tor Browser. …
  • Potential Security Breach. …
  • Questionable Maintenance. …
  • Red Flag.

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Author: refuge_2020

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