Keep your chat history away from prying eyes by locking it with encryption! This feature is only available on QQ International for Windows.
First of all you need to open your settings menu from the Main Panel:
Go to “Security” and select “Message History”, then activate the option as below. You’ll need to set a standalone password to encrypt your message history: please keep it safe because if you lose it you won’t be able to recover your history in any way.