Secure Sockets Layer (SSL) is a cryptographic protocol that provides secure communication over the internet. It ensures the confidentiality, integrity, and authenticity of data transmitted between a client (such as a web browser) and a server.

SSL uses a combination of asymmetric and symmetric encryption algorithms to establish a secure connection. Here’s how it works:

1. Handshake: The client initiates a connection to the server and requests a secure connection. The server responds by sending its digital certificate, which contains its public key.

2. Certificate Verification: The client verifies the authenticity of the server’s certificate. It checks if the certificate is issued by a trusted Certificate Authority (CA) and if it has not expired or been revoked.

3. Key Exchange: The client generates a random symmetric session key and encrypts it using the server’s public key. The encrypted session key is sent to the server.

4. Encryption: Once the session key is exchanged, both the client and server use it to encrypt and decrypt data transmitted between them. This ensures that the data remains confidential and cannot be intercepted or tampered with by unauthorized parties.

SSL has been widely used to secure sensitive information transmitted over the internet, such as credit card details, login credentials, and personal information. However, SSL has been deprecated in favor of its successor, Transport Layer Security (TLS), which is an updated and more secure version of the protocol. TLS is often referred to as SSL/TLS, as it encompasses both protocols