permission

~: 755
~/.ssh: 700
- authorized_keys: 600, owned by user
- config: 600
- Private Key: 400
- *.pub: 644
- known_hosts: 600
/etc/ssh
- ssh[d]_config: 644
- Private Key: 400, owned by root
- *.pub: 644
- ssh_known_hosts: 644