A guide to SSL and Digital Certificates

Secure Socket Layer (SSL) is a protocol developed by Netscape in 1996 which quickly became the method of choice for securing data transmissions across the Internet.
SSL is an integral part of most Web browsers and Web servers and makes use of the public-and-private key encryption system developed by Rivest, Shamir, and Adleman.

In order to make an SSL connection, the SSL protocol requires that the website's hosting server has a valid SSL digital certificate installed. A digital certificate is an electronic file that uniquely identifies individuals and servers. Think of a digital certificate as a kind of digital passport or credential which authenticates the website or server as being who they say they are, prior to the SSL session being established.

Typically, digital certificates are signed by an independent and trusted third party to ensure their validity. The "signer" of a certificate is known as a Certification Authority (CA), such as VeriSign, Thawte and GeoTrust but there many other providers.