SSL is short for Secure Sockets Layer and it means that the entire communication between the client (the browser) and the server is encrypted using public/private key technology. Basically one is using one key to encrypt the data and another to decrypt the data. That way only the two participating computers can communicate.

Usng the internet normally all communication based on HTTP (web pages), FTP (file transfer), SMTP and POP (mail) is what is called clear text, unencrypted and readable to anyone monitoring the network traffic.

Everyone running a web site asking the visitor for any kind of information like, log-on details, user information, addresses, payment information etc should no doubt offer the vistior a secure way of transmitting that information and by default use SSL.

The number is referring to the key length. In short, the key is the length of 2 times 2 in a total of 128 or 256 times. (2 x 2 x 2 .... x 2). Using 128 bit that gives a total of about 339 septillion possible keys

To break that kind of encryption one will need enormous amounts of computerized calculation power. Using 129 bit will take twice that time again...

256 bit means that the highest level of encryption supported by the browser and the server will be used and it can be as high as 256 bit.

On the browser end: Nothing since all modern browsers support SSL and TLS (newer version of SSL). Even most smartphones support SSL today.

On the server end: You need access to the server platform so that you can create the certificate request file and later install the actual certificate.

SSL certificates generated by GeoTrust have been tested on the following web server platforms:

Apache + ApacheSSL
Apache + MODSSL
Apache + OpenSSL
Apache + Raven
Apache + SSLeay
Apache 2.x
C2Net Stronghold
Cobalt Series
CPANEL
Ensim
HSPHERE
IBM-HTTP
IBM Domino Go 4.6.2.6+
iPlanet Enterprise Server 4.1
IPSWITCH
Jakarta_Tomcat
Lotus Domino 4.6
Lotus Domino 5.x
Microsoft IIS 4.0
Microsoft IIS 5.0
Microsoft IIS 6.0
Netscape Enterprise Enterprise 3.51
O'Reilly WebSite Professional 2.X
Deerfield (O'Reilly) Website Professional 3.x
Plesk
WebLogic 5.x
WebLogic 6.x
WebLogic 7.x
WebSTAR 4
WebSTAR 5
Zeus Web Server V3

The three market leaders today are Verisign, Thawt and GeoTrust where GeoTrust has a market share of about 25%.

GeoTrust recommend using the QuickSSL Premium certificate if your site is to be accessed using smartphones. Thawte recommend SSL123, which also supports IDN-domains.

Extended Validation is a new standard. To issue an SSL Certificate that complies with the standard, a CA must adopt the extended certificate validation practice and pass a Webtrust audit. The validation process requires the CA to authenticate the certificate applicant’s domain ownership and organizational identity, as well as the individual approver’s employment with the applicant, and authority to obtain the Extended Validation SSL Certificate.

If you use Microsoft® Internet Explorer 7 to go to a Web site secured with an SSL Certificate that meets the Extended Validation Standard, IE7 will cause the URL address bar to turn green. A display next to the green bar will toggle between the organization name listed in the certificate and the Certificate Authority (VeriSign, for example). Firefox and Opera have announced their intention to support Extended Validation SSL in upcoming releases. Older browsers will display Extended Validation SSL Certificates with the same security symbols as existing SSL Certificates.