Transport Layer Security (TLS) is a cryptographic protocol used for secure communication over the internet. It is the successor to the Secure Sockets Layer (SSL) protocol and provides secure communication between client-server applications. TLS is commonly used in web browsers, email, instant messaging, and other online applications.
The TLS protocol operates at the Transport Layer of the OSI model, providing end-to-end security for data transport. It is designed to provide authentication, confidentiality, and integrity of data by using encryption and decryption techniques. TLS protocol is used to secure different types of data in motion, such as HTTP, FTP, SMTP, and other internet protocols.
TLS uses a combination of symmetric and asymmetric encryption techniques to ensure secure communication. The symmetric encryption algorithm is used to encrypt data and ensure confidentiality, while the asymmetric encryption algorithm is used to authenticate the server and provide integrity. The server's public key is used to encrypt the session key, which is then used for symmetric encryption during the session.
TLS operates through a series of handshakes between the client and server. During the initial handshake, the client sends a request to the server to establish a TLS connection. The server responds by sending a digital certificate that contains its public key, which the client uses to authenticate the server. The client then generates a session key, encrypts it with the server's public key, and sends it to the server. The server decrypts the session key using its private key and uses it for symmetric encryption during the session.
TLS also provides perfect forward secrecy (PFS), which means that even if a hacker manages to obtain the private key, they cannot decrypt previously recorded traffic. PFS is accomplished by generating a new session key for each session, which is not derived from any previously shared secret.