Understanding the Tor Network - Tor v2 v3 and v4


The tor network is a fairly simple system that provides users with the ability to browse the internet while maintaining full anonymity. While on the surface the network is a basic way to route traffic through multiple different locations to prevent tracking, the method by which this is done does have a little bit more complexity. Over time, this network has been improved and upgraded to not only help ensure people’s privacy was protected, but also to make it more efficient, faster, and able to handle modern data.

Looking at Version History

Learning about how the versions of the tor network are established, and the difference between v2, v3, and v4 is important. This article will provide you with a high-level overview of the versions of the software and what it means for users of the tor network.

The Onion network, which is another name for the tor network, got its start in 2002, but the concepts behind it were being worked on for many years before that. As with almost all software, it went through many initial code versions, and tracking the various changes is very important. Because of this, the team working on the tor network followed (and continue to follow) standard code version tracking protocols.

In this case, that meant naming any releases with the format of ‘Tor 0.x.x.x.’ The X’s will change over time as new releases are made. For example, when the tor network first came out, it would be some version of Tor 0.1.x.x. The latest version, as of this writing, is Tor In general, people will only talk about the main version, so the latest option would just be referenced as Tor v4.

One of the great things about the tor network is that it can run smoothly even with multiple different versions being used in production. Of course, that backwards compatibility only goes so far.

Current Production Versions

While the latest version of the tor software is version 4, there are other versions that are commonly used. With over 6000 nodes on the onion network, and all of them being run by volunteers, having the ability to run multiple versions at once is important. Take a look at the main versions below to learn more about them:

Tor V2 (Depreciated)

Tor v2 was the standard used for many years. Even through to as recent as 2019 it was seen by many as the primary option. Unfortunately, due to advancements in tracking technologies and other factors, this version now has a number of shortcomings that make it no longer useful. This is why anyone who runs a tor router node should upgrade to either version 3 or 4. Some of the main issues that would be present if using this version today include:

  • Shorter names are used for the nodes. These names are simple hashes of an RSA public key for the onion service.
  • It is possible for malicious people to snoop on certain aspects of the traffic, which allows them to identify the address of a v2 onion service.
  • The cryptography used in version 2 is now sufficiently out dated that it is no longer considered fully secure by most people.

For those who are still interested in Onion v2, however, it is possible to create your own private onion service. Private services like this are generally still safe since it is unlikely that bad actors would be aware of their existence.

Tor V3

The Onion v3 continues to be a very popular option and is still seen as the default by many people. This option put in a variety of improvements that helped to allow for longer names, which were actual ed25519 keys and therefore more anonymous. In addition, this version has made it so users cannot snoop on the traffic of the onion services. This means that nobody can determine that a specific onion service even exists without the owner publishing it.

There were also advancements to the cryptography used in version 3 and general code cleanup, which takes place in every new version of any software. Tor v3 continues to be a secure option that works well with modern Tor browsers.

Tor V4

The earliest versions of Tor v4 were released in 2019. It is only just recently becoming a popular option for most people running nodes. While Tor v3 continues to be heavily used, it is almost certain that over the course of the coming years everyone will transition to version 4.

Some of the major upgrades that come with version 4 of the onion network include:

• Improved Electricity Management – When a node is not being used it can enter dormant node to limit network and CPU activity, saving on battery life and electricity usage.

  • Bootstrap Reporting – Improved reporting of the bootstrap progress including how connecting to things like proxies or pluggable transports are handled.
  • Introduction of Circuit Padding – The initial support for circuit or adaptive padding was added (though not heavily used at this point).
  • Error Handling – Version 4 has improved error handling, especially when it comes to things like empty ID/password fields and other handshake related issues.
  • Much More – As with any major version upgrade, there are going to be a variety of major and minor improvements throughout nearly every aspect of the platform.

Since this is the latest stable version, new sub-versions are released regularly. These are primarily for bug fixing and minor advancements within the current version.

Impact Tor Users

Understanding the versions used for the tor network is extremely important for those who manage these systems directly. For the average user of a tor browser, however, it is not typically necessary to have in-depth knowledge of how the back-end software works. It can be comforting, however, to see that the various teams that contribute to the tor network are constantly working on the system.

These version updates (both major and minor) are essential not only for protecting your privacy and anonymity, but also helping to ensure you have the best user experience possible. Of course, there is a lot more that one could learn about the differences between tor v2, tor v3, tor v4, and any future version, but that is typically best left to the developers.