TLS

TLS is the acronym for Transport Layer Security.

Transport Layer Security

A cryptographic protocol designed to provide secure communication over the internet. It is the successor to the Secure Sockets Layer (SSL) protocol. TLS provides three essential security properties:

Confidentiality: The data exchanged between the client and server is encrypted, preventing unauthorized parties from reading it.
Integrity: TLS uses message authentication codes to detect if the data has been altered in transit.
Authentication: The server’s identity is verified through its TLS certificate, ensuring the client communicates with the intended server.

How TLS Works

Handshake: When a client (e.g., a web browser) connects to a server (e.g., a website), it initiates a handshake process. The client sends a message to the server, specifying the version of TLS it supports and a list of cryptographic algorithms it can use.
Server Certificate: The server responds with its TLS certificate containing its public key and other identifying information. This certificate is typically issued by a trusted third-party Certificate Authority (CA) that verifies the server’s identity.
Certificate Verification: The client verifies the server’s certificate by checking if a trusted CA issues it and if the certificate’s hostname matches the server’s hostname. This step ensures that the client is communicating with the intended server and not an imposter.
Key Exchange: If the certificate is valid, the client generates a random session key, encrypts it using the server’s public key (obtained from the certificate), and sends it to the server. Only the server can decrypt this message using its private key, ensuring the session key remains secure.
Secure Communication: With the session key established, the client and server can now communicate securely. They use the session key to encrypt and decrypt all the data exchanged between them, preventing eavesdropping and tampering.
End of Session: When the communication is complete, the session is terminated, and the session key is discarded.

TLS is commonly used to secure websites (HTTPS), email communications (SMTPS, IMAPS), and other applications requiring secure internet data transmission. While SSL is still widely referred to, it is an older protocol and has been largely replaced by TLS in modern secure communication.