Best secure mobile messaging apps - Telegram
Launched by two Germany-based brothers in 2013 Telegram’s distinctiveness is its multi-platform support, including not only and Android and iPhone but Windows Phone as well as Windows OS X and even Linux. With the ability to handle a wide range of attachments, it looks more like a cloud messaging system replacing email as well as secure messaging for groups up to 200 users with unlimited broadcasting.
There are some important differences between Telegram and the other apps covered here, starting with the fact that users are discoverable by user name and not only number. This means that contacts don’t ever have to know a phone number when using Telegram, a mode of communication closer to a social network. The platform is also open to abuse, if that's the correct term, including reportedly being used by jihadists for propaganda purposes, which exploit its broadcasting capablity. This is not the fault of the developer but does bring home how such apps can be mis-used in ways that are difficult to control.
The sign up asks for an optional user name in addition to the account mobile number, and requires the user verify the number by receiving and entering an SMS code. The app is polite enough to ask for access to the user’s phone book and other data, which can be refused, and handily notices which contacts within that list already have signed up for the app.
Security: uses the MTProto protocol, 256-bit symmetric AES encryption, RSA 2048 encryption and Diffie–Hellman secure key exchange
Pro: multi-platform support including desktop computers, access files from anywhere
Con: More a cloud platform than an app, also reportedly been abused by violent jihadists which could spell an image problem for the app