Do you think that there is a really secure messenger? Can you recommend anything for personal usage? I am not happy with the fact, for example, that someone, somewhere could access my correspondence with a friend of mine.
You should check out Telegram messenger, it offers both mobile and a desktop app! The basic chats offers a level of encryption, while "secret chats" offer an increased amount of encryption, however it's only between 2 people and it cannot be with a group. Also secret chats can only be done in the mobile version of telegram so there's that.
However it is really user friendly, you can set up passwords for both your desktop and mobile app so that before you see any messages you have to provide a password. This can be done for both Android and iOS.
Although there are basics of encryption and authentification everything that comes out from our PC/Smartphone and is transmitted over the internet is potentially identifiable (see NSA, HackingTeam, etc).
It's hard to think of being totally safe when we write or receive messages.
Are the recipients of your messages being delivered to a device:
- running the latest operating system, security patches and fixes
- with strong encryption
- non-rooted mobile or tablet, genuine Windows, OS X or Linux (ie. not pirated)
- unique passwords
- non-shared passcodes
- not infected with malware
Telegram looks safe but if you send a Wireshark, you immediately understand that the messages you send go firstly to a server and after that to the receiver. Even if you send a message while the other part is offline and sign out from the messenger, as soon as he becomes online, he receives the message. This automatically means that there is a server in the middle.