Telegram - Secret chats (end-to-end encrypted)

Telegram allows you to have end to end encrypted chats, which means only you and other parties in the chat can read the messages. No one else can decipher them without access to either your or the other party's device — not even Telegram. As we've written before, end to end encryption is an essential feature to help protecting the confidentiality and integrity of transmitted information. However, Telegram does not enable secret chats by default.
To start a secret chat, open the profile -- not an existing chat -- of the user you want to message and click on the three vertical dots in the top right corner, then click on Start secret chat. You can have multiple secret chats with the same contact. After the connection is established, Telegram generates a picture for both parties representing the encryption key between you. You should ensure — offline, or using another form of secure communication — that your images match. If not, your connection should not be considered secure as it might be compromised by an attacker.
After you start a secret chat, you can set your messages and media to self-destruct after a fixed period of time after they have been read or opened. The message will then disappear from both your and your friend's devices after that period.
Note that, unlike regular chats, secret chats in Telegram are only available on the device from which you start them, and are not backed up to the cloud. As such, if you log out of that device, or lose access to it, your chats will be lost.