I like to avoid having to remember and typing passwords when i log into things on the internet, hence why I use KeePass. I have the same mindset when it comes to logging onto servers. Luckily there exists something known as SSH Keys.

Generating a public-private key pair

We start by running the ssh-keygen utility:

ssh-keygen

Select where to save the key pair. (Press {Enter} to save in default location).

C:\Users\Arnav>ssh-keygen
Generating public/private rsa key pair.
Enter file in which to save the key (C:\Users\Arnav/.ssh/id_rsa):

If you wish to have additional security, you can add an optional passphrase:

C:\Users\Arnav>ssh-keygen
Generating public/private rsa key pair.
Enter file in which to save the key (C:\Users\Arnav/.ssh/id_rsa):
Enter passphrase (empty for no passphrase):

You key pair should now be generated:

C:\Users\Arnav>ssh-keygen
Generating public/private rsa key pair.
Enter file in which to save the key (C:\Users\Arnav/.ssh/id_rsa):
Enter passphrase (empty for no passphrase):
Enter same passphrase again:
Your identification has been saved in C:\Users\Arnav/.ssh/id_rsa.
Your public key has been saved in C:\Users\Arnav/.ssh/id_rsa.pub.
The key fingerprint is:
SHA256:1zuyJ2emb2f+lP9cFLosAmFdjMJIPsBvad7OBOpEHqM arnav@Jain10
The key's randomart image is:
+---[RSA 2048]----+
|  ....o   o.     |
|   .o. o....     |
|    .o.o..     . |
|   + *o .  .  . .|
|  + B o.S . ..  .|
| E + . o..  .....|
|  o   +  ...oo .o|
|   .   o  ooB.ooo|
|          oX.+..*|
+----[SHA256]-----+

C:\Users\Arnav>

To display the public key we can use the following commands:

*nix: cat ~/.ssh/id_rsa.pub
Windows (from the home directory): type .\.ssh\id_rsa.pub

C:\Users\Arnav>type .\.ssh\id_rsa.pub
ssh-rsa AAAAB3NzaC1yc2EAAAADAQABAAABAQDD1pYvyhKyiDSvbPSETiOeF0ORn9E3ePIGN35d+lJUKcRGW7lOW2tR3Sr8hDMkOSFIzVajOE/C1JKxbX1QNZKeHDFCDle0atCfRDCF9pHadZKqnJxp+8BnjdmE+GIptENpFGrHWiQShRx6RLy33crA/Wm62xNAqrlq10SCPNOUwQJNkBhah7B7lNEbcz6RkA6kmiBASqqM1sLuaWiQz90A+RvB2b8p02Xhprj0bSPX+EaXHcnBa9+NF19X5+kS879LYX7XlHxXBwuaifdmwPFLSGh9ZAMSePdBfi0q/EtyclS29vb+Wn+vFm7NL63bPQXlJol0WvMt8TF+UG12oAFB arnav@Jain10

C:\Users\Arnav>

The ssh-rsa AAAA/***/oAFB arnav@Jain10 is my public key.

Placing public key on remove server

Access the web-server in whichever way you find convenient. For me it’s ssh to my Pi I just set up.

ssh root@photon-rpi3.jain.lan

Firstly we need to ensure that the .ssh sub-directory exists in our home directory. We do this by the mkdir command:

mkdir -p ~/.ssh

We now need to add the public key (from above) as an authorised key. This is done by the following command:

echo «public_key_string» >> ~/.ssh/authorized_keys

Remember to replace «public_key_string» with the public key you displayed above. Note that the >> signifies that this command will:

if file exists the command will append the string to very end of the file.
if file does not exist the command will create a new text file with the string as a content.

root@photon-rpi3 [ ~ ]# mkdir -p ~/.ssh
root@photon-rpi3 [ ~ ]# echo ssh-rsa AAAAB3NzaC1yc2EAAAADAQABAAABAQDD1pYvyhKyiDSvbPSETiOeF0ORn9E3ePIGN35d+lJUKcRGW7lOW2tR3Sr8hDMkOSFIzVajOE/C1JKxbX1QNZKeHDFCDle0atCfRDCF9pHadZKqnJxp+8BnjdmE+GIptENpFGrHWiQShRx6RLy33crA/Wm62xNAqrlq10SCPNOUwQJNkBhah7B7lNEbcz6RkA6kmiBASqqM1sLuaWiQz90A+RvB2b8p02Xhprj0bSPX+EaXHcnBa9+NF19X5+kS879LYX7XlHxXBwuaifdmwPFLSGh9ZAMSePdBfi0q/EtyclS29vb+Wn+vFm7NL63bPQXlJol0WvMt8TF+UG12oAFB arnav@Jain10 >> ~/.ssh/authorized_keys
root@photon-rpi3 [ ~ ]#

That should be it.

Try out the passwordless logon

The response from the server when using password logon:

C:\Users\Arnav>ssh root@photon-rpi3.jain.lan
Password:
Last login: Sun Jun  2 17:00:40 2019 from 192.168.8.10
 18:01:52 up  1:03,  0 users,  load average: 0.01, 0.02, 0.00

root@photon-rpi3 [ ~ ]#

And the same when using SSH keys to logon:

C:\Users\Arnav>ssh root@photon-rpi3.jain.lan
Last login: Sun Jun  2 18:01:52 2019 from 192.168.8.10
 18:08:05 up  1:10,  0 users,  load average: 0.17, 0.06, 0.01

root@photon-rpi3 [ ~ ]#