Onion Protocol

Anshu Raj

Table of Contents

Overview Anonymity and its need Need for anonymous routing What is Onion Routing Implementation as TOR How TOR works? TOR Browser Conclusion References

Overview

Onion protocol also known as Onion Routing is a technique for anonymous communication over a computer network.

Onion routing was developed in the mid-1990s at the U.S. Naval Research to protect U.S. intelligence communications online.

It was further developed by the defence Advanced Research Projects Agency (DARPA) and patented by the Navy in 1998.

Currently it is best implemented as The Onion Routing project aka TOR

What is Anonymity?

Anonymity is the state of being unidentifiable within a set of subjects. Hiding your activities among other’s activities is anonymous activity. On the internet you are not anonymous. Your IP address can be linked

directly to you. Your browsing is being tracked. Cookies, flash cookies, HTML5 storage,

cache are some of the techniques by which browser is being tracked known as browser fingerprinting.

Need for anonymity

To protect privacy and avoid tracking by advertising companies. Protection from prosecution. Not every country guarantees free speech. To prevent chilling-effects. It’s easier to voice unpopular or controversial

opinions if you are anonymous. ISP’s store communication records usually for several years. Law

enforcement agencies can subpoena these records even after years. Your activities on the web can be used to identify you by the unique

websites you use and type of links you click.

Need for anonymous routing

Traditionally, the right to privacy of communications has been one of the natural rights in most countries of the world.

Unfortunately, no such regulations exist for the Internet. Even more worryingly, there is a global trend towards organised logging of information pertaining to individuals' activities online.

Keeping a record of a person's activities online is a stone's throw away from infringing on the natural right of that person to privacy.

Therefore good ways are needed to protect the privacy of communications against observers. And there comes onion routing.

What is Onion Routing?

Onion routing is an anonymous communication technique over a computer network.

Messages are constantly encrypted and then sent through several network nodes called onion routers which creates a circuit of nodes.

Each onion router removes a layer of encryption with its symmetric key to reveal routing instructions, and sends the message to the next router where this is process is repeated.

Thus the analogy “onion router”. This prevents these intermediary nodes from knowing the origin, destination, and contents of the message.

Onion Routing The system consists of a number of machines, called onion routers .

Routers communicate with each other over TCP. Some routers can also serve as entry funnels, they can accept connections from the clients of the network.

Some routers can server as exit funnels, they can create TCP connections leaving the network to the actual Internet services that are being accessed through the Onion Routing network. Such services can be world wide web, e-mail, peer-to-peer applications, etc.

When a client application wishes to establish an anonymous connection to a server, it first of all connects to an application proxy.

An application proxy accepts protocol-specific connections from applications, and converts them into a generic protocol. The packets are then forwarded to an onion proxy.

Onion Routing continued… The onion proxy creates a route over the onion network and then

constructs a special data structure, an onion. An onion is a multiply encrypted layered structure, with information

about the route through the network being spread across the layers. The onion is then passed on to an entry funnel.

When an entry funnel receives an onion, it decrypts it, which reveals a layer containing information about the next hop in the route constructed by the onion proxy. This layer is then stripped off and the onion is forwarded on to this next hop.

Eventually, the onion reaches an exit funnel. The decrypted packet is identical to the packet that was produced by the application proxy at the beginning of the connection. This packet will then be sent to the destination TCP host.

Onion Router and Analogy

Tor, An Implementation of Onion Routing

Tor is currently the most advanced implementation of Onion Routing in use today. Tor is currently deployed on the Internet.

What is TOR? It was originally developed for primary purpose of protecting

government communications. Today, it is an open source software project used everyday for wide

variety of purposes by normal people, the military, journalists, law enforcement agencies and activists.

It is a distributed anonymous network. It reduce the risks of both simple and sophisticated traffic analysis by distributing transactions over several places on the Internet.

Data packets on the Tor network take a random pathway through several relays.

No observer at any single point can tell where the data came from or where it's going.

TOR overview, deployment and statistics It introduces Hidden services. Servers which can only be accessed via

the TOR overlay. It is the largest, most well deployed anonymity preserving service on the

internet. It is publically available since 2002. It is continuous in development.

Currently, ~5000 Tor relays are present around the world. All relays are run by volunteers. It is suspected that some are controlled by intelligence agencies.

TOR network can be accessed by using TOR browser.

How TOR works? Tor provides anonymity by bouncing your Internet traffic around a

distributed network of encrypted relays run by volunteers around the world.

How TOR works?

How TOR works?

Tor Browser

Tor Browser

Onion Address Onion addresses starts with .onion It is only accessible via a TOR network. onion is a pseudo-top-level domain host suffix designating an

anonymous hidden service reachable via the TOR network. Example of onion url is

http://3g2upl4pq6kufc4m.onion/ – DuckDuckGo Search Engine http://zqktlwi4fecvo6ri.onion/wiki/index.php/Main_Page – Uncensored Hidden

Wiki

Conclusion Onion Routing protects the anonymity of a user and hide the

destinations of all communications initiated by the user. Any outside observers will not be able to tell whom the user is

communicating with and for how long. Onion Routing uses Public Key Encryption to put multiple layers of

encryption around the original data packet, thus creating an object called an onion.

This onion will follow a specific route through the network, and at each route a layer of encryption will be peeled off. Once the onion reaches its destination it will have been reduced to the original data packet.

When a router decrypts the onion using its private key it will only get the address of the next router along the path. So no router will ever know the full path that is travelled by the onion.

Since no outside observer will be able to follow an onion while it is travelling through the network, the communication is completely anonymous.

References

http://ntrg.cs.tcd.ie/undergrad/4ba2.05/group10/#1 http://www.makeuseof.com/tag/what-is-onion-routing-exactly-makeuseof

-explains/

http://tor.eff.org/ http://thehiddenwiki.org/ https://www.deepdotweb.com/how-to-access-onion-sites/

THANK YOU

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