Secure Sockets Layer (SSL) is a protocol that is used to establish a secure, encrypted connection between two computer systems. It is often used to secure communication over the internet, such as when transmitting sensitive data such as credit card numbers or login credentials.
SSL works by using a combination of public key encryption and symmetric key encryption to secure the connection. When a client system (such as a web browser) wants to establish a secure connection with a server, the server sends a copy of its SSL certificate to the client. The certificate contains the server's public key, as well as information about the server's identity.
The client system verifies the certificate by checking it against a list of trusted certificate authorities (CAs). If the certificate is valid, the client system creates a random symmetric key and encrypts it using the server's public key. The encrypted key is then sent back to the server.
The server decrypts the key using its private key and uses the symmetric key to encrypt all further communication between the client and the server. This ensures that the communication is secure and cannot be intercepted by a third party.
SSL is an important security feature for many online activities, such as online banking, shopping, and transmitting sensitive information over the internet. It is often indicated by a padlock icon in the address bar of a web browser or by the use of the "https" prefix in the website's URL.