March 20, 2013

first of all install sshd : “sudo apt-get install openssh-server”
then start sshd : “sudo /etc/init.d/ssh start” and try to connect from SSH Secure Shell with username/password

If it works, we have to know that username/password authentication is not secure!
So we will disable authentication with username/password and allow only keys authentication.
We have to edit sshd config file: sudo vi /etc/ssh/ssh_config
ensure that lines bellow are not commented and have such values:

• RSAAuthentication yes
• PubkeyAuthentication yes
• AuthorizedKeysFile      %h/.ssh/authorized_keys
  and disable username/password auth:
• PasswordAuthentication no
  save sshd_config and restart sshd : sudo /etc/init.d/ssh restart

now if you try to connect from SSH Secure Shell with username/password you will be refused. you must generate and put public and private keys.

ssh-keygen -t dsa mykey.ossh
will create private and public keys

cat mykey.ossh.pub » ~/.ssh/authorized_keys
will authorize person having keys to login

if you will connect from open ssh client you just have to copy keys in your .ssh home directory
if you will connect from SSH Secure Shell you must before that convert open ssh keys to ssh2

ssh-keygen -e -f mykey.ossh > mykey
ssh-keygen -e -f mykey.ossh.pub > mykey.pub
then use mykey and mykey.pub from SSH SecureShell

connect with specified private key

ssh -i path/to/your/private_key user@server.domain_or_ip
transfer myfile to server
scp -i path/to/your/private_key myfile user@server.domain_or_ip:/path_in_server/