In General, the task such. There is a program that can only connect to the server via FTP using login and password. With SFTP it can not work. Is the server to which you can connect only by SFTP with a username and an ssh-rsa key. While there is no way to "teach" the program to work with SFTP, nor to access the server via FTP. How can they "make friends"?
PS I mean some softinu under the "vendu" to make the tunnel FTP SFTP. The goal of the program is at certain points just to put on the server some reports. Would root access to the server - I'd just FTP up on it.