Supposing you refer to SSH public key authentication.
From your first post, I've understood, that you are the server-side, while your client is a client-side. In that case, the client (they) should provide you public part of their key, in format recognised by your SSH server.

Hi Martin

Sorry, got it slightly wrong -

They have suggested I send them our public Key (created in GnuPGP) and use Key exchange authentication rather than a password.

Best Regards
Crysitn

Sorry, I do not understand what is gnupgp good for in this scenario. Can you explain it in more details?

Hi

We have a client that I collect files from using the WinSCP application for sftp.

I want to automate this process, and the client has suggested public key encryption using the gnupgp public key that I sent them.

Does WinSCP support this functionality?

Best Regards
Crystin Slade