I am running Chilkat Dot Net 4.0 and need to update a working SFTP app from password authentication to certificates. Does the product I have do that? Would I only need to change the syntax to provide the key and user information? If so, is there example code as a reference?
See the example here: http://www.example-code.com/csharp/sftp_pubkeyAuthenication.asp
SSH/SFTP does not use digital certificates for public-key authentication. Rather, the public/private keys themselves are used. A digital certificate is something more, and it contains a public key, and is associated with a corresponding private key.
To use public-key SSH/SFTP authentication (instead of password authentication), you would install the public-key on your SSH server under the user-account. Your client-side app would use the corresponding private key to authentication. The idea is that you could provide your public-key to many different servers, and always use the same private key to authenticate. Only you (the client) has the private key, just like only you have the password for password-based authentication.
There is also the option to use public key authentication and password both. But the server on the other end has to have that option set.