The need to secure the transmission of data between computers or between a computer and a server appeared since the first connection was made and has become ever more important as we began to send more and more data over the internet. Thus, the Secure Sockets Layer (SSL) and later on Transport Layer Security (TLS), which are cryptographic protocols, were created. These provide security for the data that is sent over the Internet.
Secure Sockets Layer (SSL) – how does it work?
In the background, your computer and the server negotiate the connection by using a handshaking procedure, during which they agree on various parameters used to establish the connection's security. By design, the data that is sent between the computer and server can only be sent/read by them, through the encryption/decryption keys. As a user, you will recognize the difference between a secure and a nonsecure connection, because websites that use encryption have the corresponding “lock” icon being displayed and, more often than not, there is an extra S added to the address (HTTPS instead of HTTP).
Research project : BEAST (Browser Exploit Against SSL/TLS) vs SSL