These elements work together to establish a secure SSL connection.
Client: The client needs to be an FTP client with SSL capabilities..
Certificate: Certificates are digital identification documents that allow both servers and clients to authenticate each other. Server certificates contain information about your company and the organization that issued the certificate [such as Verisign or Thawte] while client certificates contain information about the user and the organization that signed the certificate. You can choose to either trust or distrust a certificate. In some cases, the client's certificate must be signed by the server's certificate in order to open an SSL connection.
Session Key: The client and the server use the session key to encrypt data. It is created by the client via the server’s public key.
Public Key: The client encrypts a session key with the server’s public key. It does not exist as a file, but is produced when a certificate and private key are created.
Private Key: The server's private key decrypts the client's session. The private key has a .key extension and is part of the public-private key pair.
Certificate Signing Request: A certificate signing request is generated each time a certificate is created. This file is used when you need to have your certificate signed. Once the Certificate Signing Request file is signed, a new certificate is made and can be used to replace the unsigned certificate.