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I would like to know if there is any group chat solution that can be used today with reasonable confidence that the content of the conversations will remain private. So far, these are the solutions I'm aware of:

  • IRC with SSL, plus FiSH: I'd rather avoid this, not only because it involves setting up an IRC server, but also because it employs Blowfish, which isn't recommended anymore even by it's creator.

  • Private XMPP server, with SSL: It's relatively easy to set up an XMPP server, which allows one to keep control over his data. The downside is that the messages themselves are not encrypted: I've seen some discussions and some papers about an mpOTR protocol, but no implementation. (this is what I'm currently using)

  • Tox: As far as I understand, being a peer-to-peer protocol the risk of leaking information should be minimal, plus it employs modern cryptographic primitives (curve25519, xsalsa20, and poly1305, from the NaCl crypto library). On the other hand, it is still in its infancy, and I wonder if there have been any audits or studies on the actual security it provides. Can Tox be considered reasonably safe or is it too early to tell?

Finally, did I miss some other interesting solution?


Update: Several other solutions have been proposed in the answers below, and some of them look promising. On the other hand, two of those are actually outside the scope of this question, and I would like to point out why because they are the most referenced I found on the internet, including this site.

  • Any protocol (usually XMPP), plus OTR: For one-on-one conversations OTR is great, and the de-facto standard. On the other hand, it doesn't support group chats, which are the focus of this question. The only multi-party OTR implementation I am aware of is Cryptocat's but... see below. (this covers Jitsi, ChatSecure, and many other clients)

  • Cryptocat: It was a great solution, but the project has been inactive (and unavailable) since February 2014. Its creator mentioned a big rewrite and upgrade in the works, but it is unclear when or if this will be available. See the notice on the project's homepage.

migrated from security.stackexchange.com Mar 18 '16 at 22:25

This question came from our site for information security professionals.

  • Is being Desktop compatible a hard requirement? Because Signal does a really good job... – SEJPM Mar 18 '16 at 21:47
  • "Private XMPP server, with" TLS. ​ ​ – Ricky Demer Mar 18 '16 at 22:17
  • @RickyDemer That's a good point, thanks for reminding me. – A.P. Mar 18 '16 at 22:23
  • @SEJPM Yes, being desktop compatible is very desirable for me. – A.P. Mar 18 '16 at 22:23
  • For which operating system(s)? – unor Mar 18 '16 at 23:59
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Now as for the security side of things, I cannot openly advise you on this. Here is a brief list of programs you can use.

I will not go into details about protocols etc.; I'll leave this all for you to research/review.

Wickr

Some information sourced from their Homepage:

  1. Wickr username, application ID and device ID are cryptographically hashed with multiple rounds of salted SHA256;
  2. Data at rest and in transit is encrypted with AES256;
  3. As part of Perfect Forward Secrecy, each message has a new encryption key that is deleted as soon as message is decrypted;
  4. Message encryption keys are encrypted with a key produced using ECDHE;
  5. Messages are bound to both the receiver’s application and device;
  6. No password or password hashes ever leave user device;
  7. All user content is forensically wiped from the device after it expires;
  8. Your UDID (Unique Device Identifier) is never uploaded to our servers so you are always anonymous to us;
  9. Wickr’s Secure Shredder forensically erases all deleted data on your device so it cannot be recovered;
  10. All user communications are cleared of any metadata.

Platform Supported

  • Windows
  • Android
  • List item
  • OSX
  • iOS
  • Linux

CryptoCat

  • OTR key pair
  • XMPP (Extensible Messaging and Presence Protocol) username and password (both are random alphanumeric 256 bytes long). These are used to register a new user on the XMPP server using XEP-0077
  • Chat rooms are XMPP MUC (Multi User Conference) instances (XEP-0045).

Supported Platforms

  • Windows
  • iOS
  • Android

Jitsi

The following are features of the program:

  • 100% open source
  • Encrypted by default
  • HD audio with Opus - Audio, Video, Desktop Streaming, Call Recording, Call Encryption (SDES/SRTP and ZRTP), OTR Encryption
  • No account needed
  • Presentations and desktop sharing
  • Integrated chat - SIP, Google, XMPP (Jabber), Facebook (XMPP), .NET Messenger Service (MSN), Yahoo. AIM and ICQ

Supported Platforms

  • Windows
  • iOS
  • Linux

RetroShare

Review the documentation here.

See here about the IP/DHCP questions. An alarming part to the document is the security section, "TODO"

Supported Platforms

  • Windows
  • iOS
  • Linux

Telegram

Features:

  • MTProto
  • End-To-End Encryption with Perfect Forward Secrecy
  • End-To-End TL

Supported Platforms

  • Windows
  • Android
  • List item
  • OSX
  • iOS
  • Linux

Hope this provides you with a decent list of apps to run off and play with. Personally I have used Wickr and find it just screams distrust (you can google all the reports) but they seem okay - just don't trust closed sourced apps for this sort of stuff.

Anywhoo point out any issues in comments please.

  • Thank you for your answer. I should point out that Jitsi is outside of the scope of this question and that Cryptocat is unavailable indefinitely (see my edit). The other solutions seem interesting, though. Telegram's "secure chats" are almost what I'm looking for, if it weren't that to chat with someone you have to share your phone number. Similarly, Wickr is almost perfect: I am concerned that they employ a closed protocol and closed source software, but the security audits are somewhat reassuring. – A.P. Mar 19 '16 at 15:14
  • They also seem to store some metadata indefinitely, but determining exactly what they collect is a bit hard, because their privacy policy is somewhat contradictory in this regard. Finally, I wasn't yet available to assess RetroShare in a satisfactory manner. – A.P. Mar 19 '16 at 15:16
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    I was hoping for some actual security advice, which is why this question was originally posted on Security.SE. I may end up accepting this answer, but I will wait a couple of days in case someone has some security advice in this matter. – A.P. Mar 19 '16 at 15:19
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    @A.P., in the security community, Telegram has a pretty bad image, because they are a bunch of mathematicans who rolled their own crypto (protocol) and didn't use the established (and well-trusted) standard (OTR). Also see the canonical Telegram question on Sec.SE – SEJPM Mar 21 '16 at 17:29
  • @SEJPM Yes, both Wickr and Telegram have implemented questionable protocol. – DankyNanky Mar 21 '16 at 20:19

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