This has been asked already, or similarly..
http://www.daemonforums.org/showthread.php?t=2014
There is much confusion between SFTP and FTPS, the former is a method of transferring files over the SSH protocol, the latter being a secure variant of the FTP protocol.
SFTP is a feature of OpenSSH, FTPS is a feature of a FTP daemon...
As with the topic above, please clarify... are you talking about a secure variant of "FTP" (RFC 4217) or an independent secure file transferring service over the SSH protocol. (
Which doesn't have a published RFC, but this is quite close..).
http://en.wikipedia.org/wiki/FTPS
http://en.wikipedia.org/wiki/SSH_file_transfer_protocol