What is SSL?
by Ian Rochat (ianr@rnrtech.com)

Secure Sockets Layer (SSL) is a protocol used to help secure communications. This article will not cover the actual details of the protocol.

The basic concept.

SSL is used to transmit data in an encrypted form from one point to another. On public network such as the Internet, there are many points through which data transfers. If you are viewing a web page in Dublin, Ireland from Portland, Oregon, USA the contents of the web page pass through many points in between those two points. Even viewing a web page across town will pass through many points, possibly even passing through another state before reaching your computer system. Any of these points in between could have somebody snooping on data, watching for sensitive information (or more likely running a program that looks for them). This is where SSL comes in. Nobody between the two points of which the connection is made can snoop in on any of the data since it is encrypted.

Now, this is only half of the formula. It will do no good having a secure connection if you are sending sensitive data directly to somebody who shouldn't have it. So if you don't have a way of knowing that the computer you are sending the data to is actually the computer you think it is, then encryption is worthless. That's where a thrid party comes into play called a Certificate Authority (CA). All web browsers that support SSL have a listing of Certificate Authorities which they will consider to be trusted and real. Everytime you access a secure site, your web browser (or whatever software you may be using) will ask one of these Certificate Authorities if the computer that you are trying to access is actually the computer it is claiming to be. If it is not, whatever software you are using will generally warn you that you may making a connection to an imposter.

That is the basic concept of SSL. Since everybody must sign up with a CA, that is where the fees comes in. The CA can tell you how much money they want per year for this service and you must pay if you want a secure connection. There are not too many Certificate Authorities out there. Here is a listing of most common with links to their web pages. If you are considering running a secure site here are a few of the more popular CA's:
VeriSign
Thawte
Equifax Secure

HTTPS

HyperText Transfer Protocol Secure is a SSL implementation of the standard web protocol, allowing secure transfer of web pages and other data across the World Wide Web (WWW).

SSH

Secure SHell is a SSL implementation allowing secure telnet-like access.

S/MIME

Secure Multipurpose Internet Mail Extensions is a SSL implementation of standard mail extensions allowing secure e-mail transfers.

SFTP

Secure File Transfer Protocol is a SSL implementation allowing secure file transfers.