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Secure FTP (SFTP)

Secure FTP (SFTP)

SSH File Transfer Protocol or SFTP is a network protocol that provides file transfer and manipulation functionality over any reliable data stream. It is typically used with the SSH-2 protocol to provide secure file transfer.

Compared to the earlier SCP protocol, which allows only file transfers, the SFTP protocol allows for a range of operations on remote files—it is more like a remote file system protocol. An SFTP client's extra capabilities compared to an SCP client include resuming interrupted transfers, directory listings, and remote file removal. For the same reason it is reasonable to implement a GUI SFTP client, but not a GUI SCP client.

SFTP attempts to be more platform-independent than SCP; for instance, with SCP, the expansion of wildcards specified by the client was up to the server, whereas SFTP's design avoids this problem. While SCP was mostly implemented on Unix platforms only, there now exist SFTP servers for most platforms.

A common misconception is that SFTP is simply FTP run over SSH (for which see FTP over SSH); in fact it is a new protocol designed from the ground up by the IETF SECSH working group. The protocol itself does not provide authentication and security; it expects the underlying protocol to secure this. SFTP is most often used as subsystem of SSH protocol version 2 implementations, having been designed by the same working group. However, it is possible to run it over SSH-1 (and some implementations support this) or other data streams. Running SFTP server over SSH-1 is not platform independent as SSH-1 does not support the concept of subsystems. An SFTP client willing to connect to an SSH-1 server needs to know the path to the SFTP server binary on the server side.