Secure Mobile Messengers

On this page I try to shed some light on the jungle of mobile messaging apps out there. I have also written blog articles about this:

And also some talks:

I focus solely on applications with automatic contact discovery here, because I want to stay close to the SMS or WhatsApp analogy. While there are valid reasons for choosing messengers with custom identifiers like XMPP (I use and recommend Conversations on Android), the barrier to reaching a large audience is much higher. For more background please see the above links.

I try to keep this page up-to-date, but if you see that something is outdated or incorrect, please contact me!

Trust

Crypto Client trust
E2EE E2EE default E2EE group chats Forward secrecy Free Software 3rd Party audit
WhatsApp Yes Yes Yes Yes No ?
Telegram Yes No No Yes Yes Yes
Threema Yes Yes Yes Not on E2EE No Yes
Signal Yes Yes Yes Yes mostly Yes
Wire Yes Yes Yes Yes mostly Yes
Allo Yes No No Yes No ?
Kontalk Yes Yes experimental No Yes ?

This table gives an overview over how much trust you can put into the application regarding the confidentiality of your messages. You definitely want End-to-End-Encryption (E2EE) to be sure that intercepted messages cannot be read and you also want a Free Software client so that chances are lower they are intercepted before being sent / after being received. Third party audits increase the level of trust, but only if the app is also Free Software. Forward secrecy protects you in the long-term.

Currently Telegram and Kontalk are trustworthy, although both have drawbacks. Signal and Wire both have improved on their Client trust and the clients work on Google-free Android phones, now, but the builds still contain some proprietary dependencies and cannot be included in e.g. F-Droid. Once this gets solved, they would be superior choices.

Metadata and Availability

Free Software server Federated system Notify method Proxy/TOR support(client) Alternative Identifiers
WhatsApp No No GCM/APNS only? No No
Telegram No No Poll optional No No
Threema No No Poll optional No? Custom; E-Mail
Signal Yes No WebSocket optional No No
Wire Yes No WebSocket optional No E-Mail
Allo No No GCM/APNS only? No? No
Kontalk Yes partly Poll optional Yes JID

This table indicates whether you are forced to entrust a single party with your metadata, whether this party shares metadata with Google/Apple and how resilient the system is to failure and/or censorship.

Signal and Wire have improved greatly in this area in recent times. Both now have completely free server implementations that you can host yourself.
However you would loose the ability to contact users on other instances, because there is no federation, something we really need in the long run.
Kontalk has some benefits here, although its federation still has limitations, e.g. encryption doesn’t work with clients outside the official server. Wire and Threema also offer different-than-phone-IDs.

Other features

Desktop/Web-Client Multi-Device support Voice Message Audio-Calls Video-Calls
WhatsApp Yes ? Yes Yes Yes
Telegram Yes Not for E2EE Yes No No
Threema Experimental ? via plugin No No
Signal Yes limited Yes Yes Yes
Wire Yes Yes Yes Yes Yes
Allo No ? Yes No No
Kontalk Yes Yes Yes No No

This table shows some features that are not immediately related to security, but might be important to many users.

Leave a Reply