SSH access with key

Create Public & Private Key

$ ssh-keygen -t rsa

$ ls -l
id_rsa  <-- private key
id_rsa.pub  <-- public key

Create .ssh directory. Change ownership
$ mkdir /home/<user>/.ssh

$ cat id_rsa.pub >> /home/<user>/.ssh/authorized_keys

$ chmod 700 /home/<user>/.ssh

$ chmod 600 /home/<user>/.ssh/authorized_keys

Copy id_rsa private key file to Windows computer.

Use Puttygen.exe to convert from id_rsa.private to id_rsa.ppk

Configure Putty.exe to use SSH key id_rsa.ppk to access server (instead of password)