SSL is a standard mechanism for sending and receiving electronic communications in encrypted form. SSL can be used wherever confidential information is to be sent between machines, such as a network, a company intranet, or the Internet. For brevity, this book generally talks about the Internet.
SSL is heavily reliant on the use of Public Key Infrastructures (PKIs). A PKI is a system of issuing online certificates to people and organizations involved in electronic communications - such as Web sites - to confirm their authenticity and trustworthiness.
SSL is widely used by organizations large and small. For example, if you use online banking, you may notice that the Web addresses - also known as universal resource locators (URL) - of many pages on your bank's Web site have addresses beginning https rather than http. This indicates that messages between that Web page and the Web site are sent via a version of HTTP that uses SSL.
Any two software programs that communicate with one another and have SSL support can send their messages to one another in encrypted form, provided that they also have a trust relationship with a PKI.
SSL can provide the following benefits:
Some of the above benefits are provided by PKIs that are used by SSL.