What's an SSL certificate?

Just imagine you post a letter in a transparent envelope. Everybody keeping the letter in her or his hands could see the data. Valuable data could get lost or be modified this way.

An SSL certificate constitutes a private communication channel which enables encryption of data during their transmission. Encryption randomizes the data and establishes in essence an "envelope" protecting the data.

An SSL certificate consists of a public and a private key. The public key is used for the encryption of the data, the private for the decoding. If a Web browser accesses a protected domain, the server (the Web site) and the client (the Web browser) are authenticated by means of a "Secure Sockets Layer" handshake.

Encryption takes place by means of an unambiguous session key and the secure data transmission can start. 128-Bit SSL certificates offer every visitor of a Web site the strongest possible SSL encryption given his settings.

How "authentication" works

Imagine you receive an envelope without return address but with a form where to enter your bank details. Each SSL certificate is established for a particular server in a particular domain for a verified company.

During the "SSL handshake" the browser requests an authentication information from the server.
By clicking on the closed padlock in the browser window or by means of certain seals of confidence, the visitor of the Web site can view the authenticated name of the organization. In the case of high-security browsers, the name of the authenticated organization is highlighted and the address bar turns green as soon as an Extended Validation SSL certificate has been discovered. If the information sets don't match or if the certificate is no longer valid, the browser displays an error message or a warning.