There are three different secure security protocols available with Core FTP Server: SSL/TLS, SSH2/SFTP, and HTTPS.
The main reason for using secure FTP connections is to protect your account information (which is passed in clear text across networks with standard FTP) and data from being seen by 'unwanted' or 'prying' eyes on networks.
SSL and TLS are the more commonly used secure FTP options for transferring files. This option will protect your login information from being displayed, as well as your files. SSL and TLS connections are established after the request has been issued by an FTP client. This option is enabled by default. You can disable SSL or specify that only SSL connections be allowed, in the domain setup screen.
The SSL direct option involves a direct SSL connection with all data being encrypted as soon as a connection is established.. To enable this option, select the 'SSL direct' option in the domain setup screen.
SSH2/SFTP is a less common form of security used for secure FTP transfers, but offers the benefit of only one connection for transfers (whereas SSL/TLS involves two with the data channel often using a multitude of ports). This can often be easier to implement when configuring firewalls or routers to allow secure FTP connections to pass through.
It generally offers a wider span of encryption ciphers, as well as higher levels of encryption.
To enable SSH2/SFTP encryption, simply check the SSH/SFTP option in
the domain setup screen.
(If you are using private/public key pairs, Core FTP Server uses the OpenSSH format).
HTTPS transfers are also supported (typically on port 443), check the HTTPS option in the domain setup screen.