Multiple success and failure stories, research data and user preferences analyses lead us to the following conclusions about what a messenger should be like:
All the top leaders to a greater or lesser extent meet these requirements:
Excluing some national projects and the social network Snapchat from this list we come to the top five: WhatsApp; Facebook Messenger; Skype, Viber; Telegram.
We immediately note that the first three services are using the Signal protocol. Its implementation deserves trust, there are audit results available, no known examples of successful attacks.
Viber uses its own protocol based on that same Double Ratchet algorithm, but unlike Signal, the protocol of Viber was written from scratch. Telegram is using its own original protocol. These two messengers can also be regarded as encrypted if we speak about the technical side of the matter.
Let’s go back to the requirements listed above.
As far as convenience goes we opt for Telegram and WhatsApp.
The fastest ones are Telegram and WhatsApp. They are the least high-runners as well.
Telegram and WhatsApp promptly fix their critical mistakes.
Multi-platform — all of them except Facebook Messenger (no desktop version).
And the main question coming from an ordinary user, let’s say from a ‘housewife’: where can I find most of my contacts? Well, clear leaders here are Facebook Messenger and WhatsApp including markets of India and Brazil. The only exception is China where the absolute reign belongs to national services WeChat and QQ.
Now let’s remind ourselves of which messengers are cooperating with authorities and in what way they are doing so. Based on the open source data we learn the following: Skype and Viber used to provide data upon requests from special agencies without any court decisions. Facebook Messenger, Telegram and WhatsApp did not. However Telegram used to get negative feedbacks from its users after it was blocking groups and channels upon requests from the authorities and without any court decisions.
Seeking no glory in the shadow of the researchers’ laurels and having conducted even this superficial analysis of the TOP 5 we end up with one and the only leader: WhatsApp (including several excuses due to development of clients for various platforms, vulnerabilities for spammers and dealing with files).
Taking into consideration that the service does not store users’ data and therefore cannot present them upon somebody’s request (which was very well demonstrated during its conflict with the Brazilian authorities) – the offspring of Jan Koum is exactly what a user needs today.
However, this is only one side of the same coin. What happens to the information stored on user’s devices? What are the rules for the formation of user backups, how do they get transferred, where are they stored? Is this service resistant to various types of attacks? And what about those backdoors again, the ones the world mass media were writing about?
You can find it out in the next article.
 A Formal Security Analysis of the Signal Messaging Protocol \\ as of November, 2017
 WhatsApp design feature means some encrypted messages could be read by third party \\ as of January, 13 2017