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Criteria:

  • Makes audio/video calls
  • Encrypts the whole traffic (using good encryption)
  • Is cross-platform (including Windows 7, etc.)
  • Runs on modern Linux distributions (Fedora, Ubuntu, etc.)
  • Runs on OpenBSD

Does anybody know a good Free and Open-Source alternative to Skype?

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Well, there's Skype, which comes in a Linux version and can be run in OpenBSD via the Linux emulation layer. Can you explain why you're looking for an alternative? –  mattdm Mar 20 '11 at 13:02
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And a related question: Skype encrypts traffic, but its probable that the company can intercept calls. Is that a problem, or do you mostly care about your neighbors eavesdropping? –  mattdm Mar 20 '11 at 13:04
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skype license = freeware - we don't know what's inside of it. that is the problem. –  LanceBaynes Mar 20 '11 at 13:21
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That's fine, I just wanted to be clear. So, having source is an important requirement? If so, that should be clearly listed. –  mattdm Mar 20 '11 at 13:28
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@mattdm: sounds like he wants something that is FOSS. I do too. –  Faheem Mitha Mar 20 '11 at 20:14

7 Answers 7

Well, there are Ekiga and its various cousins eg. Twinkle, which support the SIP standard. Unfortunately my experience is that they do not work as reliably as Skype. In particular, Ekiga seems to get upset by Flash. That is understandable. I also find Flash quite upsetting.

If you can get Ekiga to work, its rates via Diamondcard.us are a lot cheaper than Skype, particularly for SMS, if you use that. The cost of an SMS for the locations I checked is around a third of Skypes. The difference for regular calls is less dramatic but still significant. And it is free (as in freedom) software, and seems to be quite cross-platform.

I think Ekiga does not currently support encryption, so that would violate one of your criteria.

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Skype is a proprietary network so to get an open source client you must replace the entire Skype network.

The open source solutions are built around the Asterisk PBX/VOIP server. Asterisk supports SIP and its own IAX protocol. The IAX protocol has optional encryption and requires only one open port on firewalls. Pre-configured linux+asterisk distributions such as Trixbox will get you going. There exists asterisk service providers like teliax.com (and Diamondcard.us mentioned above) that host asterisk servers connecting to other networks (like cell, land lines). AFAICT nobody provides direct connectivity to Skype's network.

http://voip-info.org/ is the best source on asterisk-related VOIP technology.

Many VOIP clients listed here http://www.voip-info.org/wiki/view/Asterisk+IAX+clients . Some support video telephony via webcam, some are cross platform, proprietary and open source codecs must coexist. The setup of all this is truly hideous.

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https://palava.tv/ Is not the only free software alternative to Skype I ever saw to actually work, but it's also cross platform. Unfortunately it's Browser based, but OTOH it means it works on every OS with a modern browser (With WebRTC). You can call anybody without the need to convince them to install ${obscure software}, it's pretty real world feasible.

The Code is on Github, and stetting up one's own server is easy, it's however not required.

The calls are encrypted, however javascript crypto is nothing I'd put too much trust in.

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There's Speak Freely & a Windows only version, but development was halted many years ago (Windows7 did not exist, but there was a Windows and a Linux version). So if you fancy picking it up where it was left, that could be an option.

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There isn't any yet :( that's the correct answer. But Thank you!

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-1. Solutions for placing secure SIP calls on Linux exist. For example see unix.stackexchange.com/a/151402/55183 . –  landroni Aug 21 at 15:02

SFLphone (free, opensource from sflphone.org) can be compiled with a video option. It then includes phone calls (audio), video calls, and texting. (I have not persionally tried the video options, but I like the voice features.) It also features optional encryption. Use a good SIP provider (I use Callcentric.com) and it is as reliable as Skype. But it is all open source and non-proprietary.

As mentioned in another answer, there are several open source client options and a variety of SIP providers. If you wish to put in the effort, you can construct your own open alternative to Skype.

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It is very easy to use Linphone to place secure calls, using ZRTP encryption protocol and TLS transport.

Follow these steps:

  1. Choose a SIP provider that supports authenticating and transporting traffic through TLS (not all do), like Linphone SIP service or Ostel.

  2. Install Linphone 3.7.0, mainly because this version allows to "configure multiple proxy accounts with different transports (UDP, TCP, TLS)". But this of course is not a requirement, more like cosmetics, and older versions would do just fine.

  3. Add a SIP account in Linphone (using the above-mentioned providers) and for each account, in the SIP Account Configuration dialogue set Transport to TLS (instead of UDP).

  4. Lastly, in Options > Prefs > Network Settings set Media encryption type to ZRTP.

You can check that all works as expected by calling the Ostel Echo testing service sip:9196@ostel.co and verifying that you see the message:

Secured by ZRTP - [auth token: ab34]

As for the required criteria, Linphone:

  • supports placing audio/video calls,
  • allows encrypting the media stream using open standards,
  • runs on most modern Linux distributions (Fedora, Debian, Ubuntu, Gentoo, etc.),
  • apparently has some OpenBSD ports (but I have little experience with those),
  • is fully open-source, although the company behind it also provides commercial support

Also, Linphone has impressive cross-platform support:

Linphone has been launched in 2001. It was the very first open source application using SIP software on Linux. For more than 10 years, a lot of improvements have been done and Linphone has been ported on the main desktop, mobile and web platforms:

  • on Windows Desktop in 2006

  • on iOS and Android in 2010

  • on Blackberry OS5-7 in 2011

  • on Windows Phone 8 in 2013

  • on web browsers in 2013 (Chrome, Mozilla Firefox, Microsoft Internet Explorer, Apple Safari)


And lastly some personal impressions. I played around with many SIP Softphones (including Ekiga, Jitsi and others who simply crash and burn) and by far Linphone was the most reliable, especially in terms of audio and video throughput. It may be a little choppy wrt to the UI (where Jitsi is superior), even though recently they've made progress on that, but this is just a small nitpick compared to Linphone's technical reliability. It is available on most platforms you could think of, and it is subject to active development, namely wrt codec support (it supports VP8 and H264 video codecs, and Opus and Speex for audio, among others).

As for Skype being secure, I take issue with that. There is anecdotal evidence that Skype calls can be intercepted by the authorities, which implies that Skype keeps backdoors into its encryption mechanisms. I suspect that the NSA would have a harder time intercepting a ZRTP-encrypted Linphone call..

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