Tor Bridges - Everything you need to know

Since the consensus list of relays is available to everyone it’s easy for a government, a law enforcement agency or any network or adversary to block you from using Tor by blocking all of the relays that are in the consensus. A Tor bridge is an unpublished relay to attempt to solve the problem of the tor relays being blocked; the bridge becomes your first relay instead of the guard relay. You might need to use a bridge if using Tor is blocked by censorship or using Tor is dangerous or illegal where you are or if it's considered suspicious to your adversaries. If you live in an uncensored area tor bridges are not necessarily more secure than using a normal entry guard

How to get Tor Bridges and Set them up

The bridges page on the tor website provides the details of a few bridges at a time to stop all the bridges from being known. You can get new bridges from the URL here. Click on get bridges and then you have the option to just get normal Bridges or Vanilla bridges as they call them by clicking on “just give me bridges”. If you want to use pluggable transports and bridges and or IPV-6 fill the advanced one below.

So let's click on the get bridges and fill the captcha and voila we get three bridges, the IP address the port that they use and their ID. For some reason, if you can't reach the URL then send an email from a G-mail or a Yahoo account (This only works for those currently) to bridges@torprojects.org with “get bridges” in the message body and they will send you some bridges like this-

Remember tor bridges are generally less reliable and slower than Guard relays. So now in order to use these, you must put these into your browser. Select and copy them and open up the Tor browser and go to the network settings and select “my internet service provider (ISP) blocks connections to the tor network and then select “enter custom Bridges” and paste the bridges there and that's it.

If your adversary was able to get a hold of the full bridge list they would effectively be able to block tor. if interested there are a couple of papers here and here about how that very thing might be done. The obvious way is to scan the whole internet continuously using tools like Zmap which makes the job quite easy. Zmap if you're not aware is an open-source network scanner that enables people to perform internet-wide network studies. This paper here reveals that one group was able to identify at one point 79 to 86 percent of the total tor bridges, the likes of the Chinese government and other censoring nations will likely be doing the same sort of tricks or will be doing it soon.

You can set up your own bridge to help yourself or others bypass censorship. Debian would be the best operating system to use and there's also Unix which we will go through in the future which is an option as it is built to be a relay and a bridge and of course is Debian. With Turnkey Linux you could up and down servers extremely fast to prevent your Bridges from being blocked or found. Turnkey as you probably know already is a service integrated with Amazon Web Services and you can deploy Bridges very quickly, literally in minutes and then take them down or stop them once you've finished using them.

A bit of a warning here, If someone offers to help you out of your censorship problem who you don't a hundred percent trust by giving you a tor bridge to help you access Tor be aware this could be a monitored bridge and a deliberate trap so avoid. If getting caught for using Tor has serious consequences for you where you are tor bridges are not recommended. They are only a short term workaround and any adversary of sophistication will identify that you're using a bridge if they happen to observe the traffic it’s not really that difficult for them. The other option is to bypass Tor being blocked which might be safer than using tor Bridges includes tunneling tor through all the privacy and anonymity services like VPNs, Nested VPNs or SSH or using an offsite connection which we cover in the future,  but only if using those has no consequences as well.

So that's tor bridges! They are unlisted relays to help avoid censorship and to enable you to use Tor If it is dangerous illegal or considered suspicious to do so where you are.