With other partners we have had no trouble getting a password to connect with. This is the code we use presently to connect via proxy partner's SFTP server using a password:
import paramiko
proxy_command = '/usr/bin/ssh ' + proxy_address + ' -p 22 /usr/bin/nc ' + host_address + ' ' + str(host_port)
proxy = paramiko.ProxyCommand(proxy_command)
transport = paramiko.transport.Transport(proxy)
transport.connect(username=username, password=password)
sftp = paramiko.sftp_client.SFTPClient.from_transport(transport)
Our newest partner will not share a password with us--the connection should rely solely on keys. How can we modify the above to implement the keys on the proxy and not be reliant on using a password to connect to the host?