Set-up SSH keys

Set-up SSH keys

Introduction:

Setting up SSH based security to access your server is a much more effective way than the use of a manual root password. Cracking the security system of a VPS depending on SSH keys is nearly impossible since it secures your VPS in a more sophisticated way by the use of encoded keys.

How do SSH keys work:

  • A key pair will be generated on your local PC.
  • Generating a key pair provides you with two long string of characters: a public and a private key.
  • The public key will be added to your VPS.
  • The corresponding private key pair will be saved on your local PC.
  •  Every time you access your VPS, the SSH system will look up for the private key pair of the public key added to it. The system will unlock only when the two keys match.
  • You can also disable the root password after the SSH keys are set up.

[ht_message mstyle="danger" title="Secure the private key" " show_icon="" id="" class="" style="" ]Make sure that you add the public key to the servers and the private key is saved in a secure location on your PC.[/ht_message]

Follow the below given steps to set up SSH keys:

Step One—Create the RSA Key Pair:

Open the Terminal on your PC

Enter the following command in the terminal:

ssh-keygen -t rsa

Step Two—Save the Keys and Passphrase

The above key generating command will follow up with a couple of questions:

Enter file in which to save the key (/home/user/.ssh/id_rsa):

You can hit Enter, which will save the keys to the user home.

Enter passphrase (empty for no passphrase):

In this step, you will be asked for a passphrase for protecting your private key. We recommend you to add a passphrase since the whole point of setting up SSH is security. You will need to enter the passphrase every time you use the key pair.

If you do not want a passphrase associated with your private key, then simply hit enter leaving the passphrase field empty.

This will complete the key generation process:

ssh-keygen -t rsa
Generating public/private rsa key pair.
Enter file in which to save the key (/home/demo/.ssh/id_rsa): 
Enter passphrase (empty for no passphrase): 
Enter same passphrase again: 
Your identification has been saved in /home/demo/.ssh/id_rsa.
Your public key has been saved in /home/demo/.ssh/id_rsa.pub.
The key fingerprint is:
4a:dd:0a:c6:35:4e:3f:ed:27:38:8c:74:44:4d:93:67 demo@a
The key's randomart image is:
+--[ RSA 2048]----+
|          .oo.   |
|         .  o.E  |
|        + .  o   |
|     . = = .     |
|      = S = .    |
|     o + = +     |
|      . o + o .  |
|           . o   |
|                 |
+-----------------+

In the above example:

The private key's location: /home/demo/.ssh/id_rsa

The public key's location: /home/demo/.ssh/id_rsa.pub

Step Three—Copy the Public Key to your VPS

Now, you can add your public key to the VPS you want to set up SSH on.

Enter the following command to copy your public key to your VPS:

ssh-copy-id user@xxx.xx.xx.xx

This will copy your public key to the authorized_keys file on your server.

[ht_message mstyle="info" title="" " show_icon="" id="" class="" style="" ]Make sure to replace xxx.xx.xx.xx with your actual Ip address and replace user with your actual username in the above command.[/ht_message]

Once you enter the ssh-copy-id command, you will see information similar to this:

The authenticity of host 'xx.xx.xx.xx (xx.xx.xx.xx)' can't be established.
RSA key fingerprint is b1:2d:33:67:ce:35:4d:5f:f3:a8:cd:c0:c4:48:86:12.
Are you sure you want to continue connecting (yes/no)? yes
Warning: Permanently added '12.34.56.78' (RSA) to the list of known hosts.
user@12.34.56.78's password: 
Now try logging into the machine, with "ssh 'user@12.34.56.78'", and check in:

  ~/.ssh/authorized_keys

to make sure we haven't added extra keys that you weren't expecting.

Step Four—Modifying permissions

Directory .ssh should have 700 permissions and authorized_keys file should have 400 or 600 permissions. To change the permissions, use the following commands:

$ cd
$ mkdir .ssh && touch .ssh/authorized_keys
$ chmod 700 .ssh/ && chmod 600 .ssh/authorized_keys
$ cat id_rsa.pub >> .ssh/authorized_keys && rm id_rsa.pub

Now log into the remote server using ssh or scp/sftp:

$ ssh username@< server-ip >

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