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Created 02 May 2004
Modified 09 Jul 2013

Article 189

What is the difference between Implicit SSL and Explicit SSL?

FTP over SSL (Explicit) Explicit security requires that the FTP client issues a specific command to the FTP server after establishing a connection to establish the SSL link. In explicit SSL (or in TLS) the FTP client needs to send an explicit command ( i.e. "AUTH SSL" or "AUTH TLS") to FTP server to initiate a secure control connection. The default FTP server port is used. This formal method is documented in RFC 2228.

FTP over SSL (Implicit) Implicit security is a mechanism by which security is automatically turned on as soon as the FTP client makes a connection to an FTP server. In this case, the FTP server defines a specific port for the client (990) to be used for secure connections. FTP over SSL Implicit has been deprecated and should no longer be used.

Keywords
SSL, Implicit, Explicit