Cornerstone uses public key security through Secure Sockets Layer (SSL), which is incorporated into several file transfer protocols, including FTPS, HTTPS, and WebDAVS. SSL offers a higher level of security by optionally accepting connections with only authorized certificates.

To configure your Cornerstone server to utilize public key authentication, start by running your Cornerstone MFT Server administrator. Launch the New Server Wizard and follow the steps.

1. Select the file transfer protocols this server will handle. Enable FTP access if you are using FTPS with explicit SSL (also known as AUTH SSL). If you will only be using Implicit SSL, you may disable FTP. Enable HTTPS for secure web browser access, including secure WebDAV access. Click Next.
2. Depending on the options selected in step 1, you will be taken to an FTPS and/or HTTPS configuration page. To enable SSL/TLS access on this server, select the appropriate check box:
   1. Enable SSL/TLS access on this server, after which you can also Enable Explicit SSL/TLSand/or Enable Implicit SSL/TLS
   2. Enable HTTPS/SSL browser based interface to Cornerstone MFT
3. Select a certificate using the dropdown menu, click Certificate Management to launch the Certificate Wizard to create a certificate for this server, or use the “…”button to browse to your Certificate Store Folder.
4. When you are finished configuring certificate options, click Next.

For more detailed information, see our FTPS Public Key Certificate Authentication Quick Start Guide

http://www.southrivertech.com/wp-content/uploads/qs_Cornerstone_SSL_PubKeySec.pdf