Simple generated key-pair using ssh key gen vs user created passowrd. If you have cloud images like Ubuntu cloud:https://cloud-images.ubuntu.com/ Firstly, generated a keypair and then initiating an instance by this command: nova boot --image IMAGE_NAME --flavor FLAVOR_NAME --key_name KEYPAIR INSTANCE_NAME. (e.g nova boot --image Ubuntu 13.10 --flavor m1.small --key_name id_rsa myFirstInstance). After that you should find out the ip address of that instance, then ssh to it. (ssh unbuntu@x.x.x.x , or root@x.x.x.x ). Then you should be prompted for the passphrase you entered for the keypair.

Most cloud images support public key authentication rather than conventional username/password authentication. Before launching an instance, you must generate a public/private key pair using ssh-keygen and add the public key to your OpenStack environment.

If your host does not contain the public/private key pair created in an earlier step, SSH prompts for the password associated with the user.

Please refer- http://docs.openstack.org/icehouse/install-guide/install/apt-debian/content/launch-instance-neutron.html (http://docs.openstack.org/icehouse/in...)