SSL (Secure Sockets Layers) is a process that manages the security of transactions made on the Internet. The SSL standard was developed by Netscape, together with Mastercard, Bank of America, MCI and Silicon Graphics. It is based on a public-key encryption process to guarantee that data sent over the Internet remain secure. Its principle involves establishing a secure (encrypted) communication channel between two machines (a client and a server) after an authentication phase.
The SSL system is independent of the protocol used, which means it can secure transactions made on the Web via the HTTP protocol as well as connections via the FTP, POP and IMAP protocols. SSL acts as an additional layer, making it possible to guarantee secure data, that is located between the application layer and the transport layer (TCP protocol for example).
As such, SSL is transparent for the user (this means the user may not know he is using SSL). For example, a user using an Internet browser to connect to an e-commerce website protected by SSL will send encrypted data without having to perform any special operation.
Almost all browsers now support the SSL protocol. Netscape Navigator, for example, displays a locked padlock to indicate a connection to an SSL secure website and an open padlock in the opposite case, whereas Microsoft Internet Explorer displays a padlock only for a connecton to an SSL secure site.
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An SSL secure web server has a URL that starts with https://, where the "s" of course means secure.
Transaction security with SSL 2.0 is based on an exchange of keys between a client and a server. An SSL secure transaction is made according to the following model: