I've got a server running Ubuntu. I installed openssh-server and wanted to use ssh key for login purposes. Everything works fine except one thing. On Ubuntu's community site is written "This massively improves your security, but makes it impossible for you to connect to your own computer from a friend's PC without pre-approving the PC [...]" (https://help.ubuntu.com/community/SSH/OpenSSH/Configuring).
I created the key pair on my server/at serverside. Then I added the public key to the authorized_keys and transfered the private key to my client pc and deleted the private key from server.
I'm able to log in from my pc with the private key. But I'm also able to login from any other computer or smartphone with this private key.
Is this behaviour correct? Because the above quote says, that I have to approve every new client, but in practice I havn't.