Software to send files and messages between PCs securely

I'm looking for something that will let me send and receive messages and files to and from my parents securely.

I want to avoid using encrypted email and passwords and just use something that creates a public/private keypair and after manually verifying each machine's identity once using a hash (ideally a human-friendly list of words we can read out over the phone), allows us to communicate securely, with a popup appearing on screen when there's a new message.

Is there …

files messages pcs privacy send software