Verify the host’s ECDSA signature

On the host machine:

ssh-keygen -l -f /etc/ssh/ssh_host_ecdsa_key.pub

That key should match the one you get when you attempt to login with ssh.

Automatic login

Imagine you want to login automatically from computer A / user a to computer B / user b.

First login to computer A as user a and generate authentication keys without entering a passphrase, i.e., just press enter when prompted for a passphrase. For example, on a@A do the following to setup automatic login to b@B:

ssh-keygen -t rsa -b 4096
ssh b@B mkdir -p .ssh
cat ~/.ssh/id_rsa.pub | ssh b@B 'cat >> .ssh/authorized_keys'

Now, you will be able to login from a@A into B as b@B without a passphrase using ssh b@B.