In this exercise we will setup basic open-ssh authentication with public keys. Scenario will be next, you will use user marry for generate a public key for her on client machine and than will be distribute it trough network.
You should to login like anna and generate a public ssh key, on next way:

[anna@security2 ~]$ ssh-keygen -t rsa

After this you should transfer that key on security1, and setup proper permissions for him: Login as root you should setup proper permissions on server side. Make directory .ssh with file authorized_keys which will has 600 permissions, and will be owned by proper user, in this case this will be anna.

[anna@security2 ~]$ scp .ssh/ anna@security1:~
[root@security1 anna]# mkdir .ssh
[root@security1 anna]# mv .ssh/authorized_keys
[root@security1 anna]# chmod 600 .ssh/authorized_keys
[root@security1 anna]# chown anna:anna -R .ssh/

OK, now you can ssh to security1 but you will be prompted for passphrase any time. So this can be annoying sometimes. So if anna is logged in through a X, you should remember passphrase for her session. Do next:

[anna@security2 ~]$ exec ssh-agent /bin/bash
[anna@security2 ~]$ ssh-add

So you will never until anna is loged in in system will be prompt for password. If you want to remove her key from this role do next:

[anna@security2 ~]$ ssh-add -D