That’s right, using the combination of SCP, SSH key authentication, and ssh-agent works well. This will keep you from having to type that SSH key password every time you issue the SCP command.

The Secure Shell — SSH — allows you to send secure, encrypted, communications between computers that is nearly impossible to crack. Here's how to use it in macOS.

PuTTY, a free and open-source telnet and SSH client, supports setting the acceptable authentication methods per connection and can be saved for future use.

How to generate SSH (Secure Shell) keys in Mac OS X using the Terminal app and Command Line.