SSL Best Practices

Status
This guide is out of date and incomplete. Please see Transport Layer Protection Cheat Sheet for information on TLS/SSL configuration and best practice.

What is SSL
SSL is the abbreviation of Secured Socket Layer. It is a protocol enabling to settle a secured communication between two hosts. The origin host is viewed as an SSL client and the destination host as an SSL server.

SSL has also been normalised as the TLS (Transport Layer Security) protocol.

SSL is used on top of a transport layer protocol like TCP or UDP, and underneath an application layer protocol like HTTP or FTP in order to secure it.

SSL enables :
 * authentication of the destination host for the origin host or mutual authentication of both the origin and the destination hosts
 * data confidentiality through encryption
 * data integrity checking through hashing.

SSL relies on two types of encryption :
 * public key encryption in the initiation phase, where authentication takes place
 * secret key encryption when a session has been established and data is sent between two peers which trust each other.

SSL only secures the communication between two endpoints : in the origin and destination points, data is in clear text, unless it is encrypted by another means, at the application level.