Open source advent calendar: Tor and its ecosystem

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This is an advent calendar for techies. In the fully commercialized digital world, almost everything belongs to a large Internet corporation. Their software is neither open nor free. As an alternative, there is this small island of the open source world: software whose code is publicly visible and can be independently checked for possible security gaps and backdoors. Software that can be freely used, distributed and improved. Often the drive for work is simply the joy of providing something useful to society.

Short portraits of open source projects will be published on heise online from December 1st to December 24th. These are about the functions of the respective software, the pitfalls, the history, the background and the financing. Some projects are backed by an individual, others by a loosely organized community, a tightly managed foundation with full-time employees or a consortium. The work is entirely voluntary, or it is financed through donations, cooperation with Internet companies, government funding or an open source business model. Regardless of whether it is a single application or a complex ecosystem, whether a PC program, app or operating system – the diversity of open source is overwhelming.

Short portraits of open source projects will be published on heise online from December 1st to December 24th. These are about the functions of the respective software, the pitfalls, the history, the background and the financing.

The onion is a versatile kitchen vegetable. The anonymization technology Tor, named after the onion, is just as diverse. A look at six programs beyond the Tor browser.

The best known application of “The Onion Router” technology is the Tor browser. It allows you to surf the World Wide Web anonymously and free of censorship; the browser also enables access to Darknet addresses with the extension .onion. There are also a number of other onion-based programs that can be used to exchange files, chat or run all of the data on a PC and smartphone via Tor.

Some of the programs use a “simple” Tor channel, as we know it from the Tor browser: data is sent from the device to the target via three obfuscation stations. Other programs use the “double” Tor mode of Darknet addresses: the data travels over three nodes to a kind of dead mailbox. The Darknet address picks them up there via three of their own Tor stations.

Onionshare creates an .onion address on the PC, which is suitable for different purposes can be used: as a download station, as a mailbox, as a chat room or as the basis for a static darknet website. The other person calls up the .onion address generated by Onionshare with the Tor browser – to download a document that has been made available, to upload a document, to chat or to call up the darknet page that has been created.

The respective Darknet addresses are available as long as Onionshare is running and online. A timer function can be used to limit availability. By default, access is protected by a 52-digit password, but this can be deactivated. A linked term is currently in progress.

Ricochet Refresh is a minimalist, Darknet-based PC program for text chats and file sharing. The 56-digit .onion address generated by the program corresponds to the chat profile.

Also the Android app Briar works with darknet addresses. Communication takes place directly between the .onion addresses on the users’ smartphones. Briar allows you to send text messages and pictures. The standard communication channel is Tor. If two devices are in the vicinity or in the same WLAN, they can alternatively communicate via Bluetooth or WiFi. A nice gimmick is a social network function: you can use it to set up minimalist blogs and forums and share them with contacts.

As with Onionshare and Ricochet Refresh, communication is only possible when both sides are online at the same time. However, the Briar team is working on one Mailbox function, which should be ready by the end of 2022: If you are offline, the messages are temporarily parked on a second cell phone that is at home and is permanently connected to the Internet.

Tails, an acronym for “The Amnesic Incognito Live System”, is a live operating system for PC: You start it temporarily from a USB stick or DVD. By default, Tails routes the traffic of all programs through Tor. There is only one way to communicate past Tor – through a program called Unsafe Browser. The use of Tails does not leave any traces of data on the computer or the USB stick. There is, however, the option of creating a “persistent” folder. Tails is based on Linux Debian and provides a specific one Selection of open source software including the Tor browser, the Thunderbird mail program, the LibreOffice office suite, the KeePassXC password manager, the Elecrum bitcoin wallet and the MAT program for removing metadata.

The left-wing technology collective Capulcu publishes an extensive German-language version for each version PDF instructions.

Another operating system based on Tor is Whonix. In contrast to Tails, it is run “within” a stationary operating system, as a virtual machine using software such as VirtualBox. The actual computer use takes place in the “Whonix Workstation”. All traffic is directed to the “Whonix Gateway”, which feeds it into the Tor network. Whonix is ​​also based on Linux Debian and brings various open source software With.

The VPN app Orbot routes the data traffic of selected or all apps on an Android smartphone via Tor. This also applies to system applications. What sounds good in theory is not always easy in practice: Commercial apps often have a hard time dealing with data traffic suddenly passing through Tor. You can use the menu to specify which nodes you want to use or exclude. With the help of Orbot you can also operate a small Tor node on your own smartphone and use this side application of Tor technology to enlarge the onion network a bit.

The work on the series of articles is based in part on a “Neustart Kultur” grant from the Federal Government Commissioner for Culture and the Media, awarded by VG Wort.

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