> Technically, sftp is not a 'secure shell' (its a secure service),
> and yet it is included.
And, just in case Darren's response is insufficient for your purposes.
Read up on RFC2228 - ftps - aka - FTP over TLS/SSL.
sftp is Secure SSH's implementation of ftp, which runs over an SSH
connection.
From what I have found, it is still in IETF format.
Here's a little light reading to help, from someone who appears to be deeply
involved in the ftps world.
http://www.ford-hutchinson.com/~fh-1-pfh/ftps-ext.html
Favorite comment from that page - "sftp is nothing to do with FTP over SSL,
it
is a way of doing file transfer over SSH which has nothing to do with FTP (RFC
959)."
For info on the FTP over SSH (aka SFTP) read
http://www.ietf.org/internet-drafts/draft-ietf-secsh-filexfer-06.txt
Hope this helps.