Ditch Skype for your audio, video and text chats

Signal

Signal [18] has had a series of well known fans during the last few years. These include the cryptography and IT security specialist Bruce Schneier; Matthew Green, who is a professor for cryptography at Johns Hopkins University; and the whistleblower Edward Snowden to mention just a few. All of the fans want to see a completely free messenger. The program was developed in the non-profit software group Open Whisper Systems, which was founded by Moxie Marlinspike [19]. Previously, the group had developed TextSecure and RedPhone, which are apps for encrypting SMS and telephone conversations.

Signal is strongly reminiscent of WhatsApp and other instant messengers used primarily on smartphones (Figure 5). Therefore, a smartphone is the kind of device to use with this program. The service relies on the mobile phone number for authentification. Alternative methods for registration are being discussed [20], as is instant registration using an email address. However, implementations for these features are still far down the road. The Signal desktop version is only available as a browser app for Chrome and Chromium [21]. Therefore, installation merely involves installing an extension.

Figure 5: Many users recognize Signal from smartphones. The service has come to the Linux desktop as a browser extension.

Although Signal does not run as a standalone application, the program appears in the application menu of the desktop environment. Signal synchronizes news and contact lists via the Internet. This means that you can start a chat on your smartphone and then continue it on your PC. In addition to purely text-based chats, the program also offers telephone conversations but currently only via smartphone clients. With Signal, the communication includes end-to-end encryption. Even so, the service can collect metadata on its central server; therefore it has the potential to know who was in contact with whom and also when. Also, Signal refuses to release its source code for the server components. This has made it lose credibility with the Linux crowd over time.

Tox

Tox [22] is one of the trailblazers among the P2P chat clients. The program originated with a discussion about the personal privacy of Skype users in the notorious 4chan forum [23]. Since the time that this discussion took place, the project has advanced a lot. Tox supports group chats, data transfers, audio and video calls, as well as offline news. The program distinguishes between the client and the core library, which provide the protocol and the API. Therefore, there are a series of different Tox programs that, depending on their development status, support just a portion or all of the features mentioned above.

The most advanced and mature Tox clients are uTox [24] and qTox [25]. The latter (Figure 6) is frequently found in the package sources of mainstream distributions. You can also install an updated version using the official package sources for the developer. Listing 3 shows how this works for Debian 8 and Ubuntu 16.04 [26].

$ sudo sh -c ,echo "deb https://pkg.tox.chat/debian/ nightly release" > /etc/apt/sources.list.d/tox.list'
$ wget -qO - https://pkg.tox.chat/debian/pkg.gpg.key | sudo apt-key add -?$ sudo apt update
$ sudo apt install qtox

Figure 6: Tox works without registration and without having a central server. It offers a full set of capabilities with text, audio, and video chats.

You will need to set up a Tox profile when you start the program for the first time. The profile consists of various private and public keys. Tox stores the data locally. The public key corresponds to your Tox ID. You can share the key for chatting with your contacts as a text or as a QR code. An option is available for registering the key and your email address in the Toxme register. This lets you find friends more easily over the Tox network [27].

In practice, Tox proves itself to be adept when working together with qTox. Adding contacts using the public key was easy. Chats and data transfers work out of the box. Currently, screen shares are only available on uTox. However, qTox lets the user take screenshots of the desktop and individual programs and send them to chat partners. Audio and video chats worked instantly. However, they don't come near to having the level of quality offered by Skype or WebRTC conferencing.

A large number of Tox client programs originate with the separation between back-end and front-end. In addition to qTox and uTox, you will find Tox clients for the command line, and a plugin for the multiprotocol messenger Pidgin. There are also Tox clients for Android and iOS in the form of Antox [28] and Antidote [29]. However, the developers for Antox are still working on getting rid of errors in the audio and video functions.