When we try to sftp to a machine we get the error "keyboard-interactive authentication failure". The same setup on different machines works fine. The only difference between the two setups is the Citrix version. Could somebody explain what the error exactly means?
Keyboard-interactive authentication uses a password for authentication, just like password-based authentication. Internal to the SSH authentication protocol, it is implemented a bit differently and affords the opportunity for the server to request a password change. If no forced password changes are expected, then the AuthenticatePw method handles both password and keyboard-interactive authentication.
A "keyboard-interactive authentication failure" is basically just a "wrong password" failure.
If the server might force a password change, then an app can explicitly use keyboard authentication as demonstrated in this example: http://www.example-code.com/csharp/ssh_keyboardAuthentication.asp