TLS
also: SSL, Secure Sockets Layer, HTTPS
Transport Layer Security (TLS) is a cryptographic protocol that encrypts data transmitted over networks, ensuring secure communication between clients and servers. It's the modern successor to SSL and is widely used for HTTPS, email, and other sensitive data transfers.
TLS operates at the transport layer of the OSI model, establishing an encrypted tunnel before any application data is sent. It uses a combination of asymmetric encryption (for key exchange) and symmetric encryption (for data transfer) to protect confidentiality and authenticity.
When you visit a website with https://, TLS is negotiating behind the scenes. The client and server perform a handshake, exchange certificates to verify identity, and agree on encryption algorithms. For example, accessing https://example.com uses TLS to encrypt your login credentials and browsing activity from eavesdropping.
Common TLS versions in use today are 1.2 and 1.3, with older versions (1.0, 1.1) deprecated due to vulnerabilities. Linux systems use tools like OpenSSL to implement TLS, and you can check your system's TLS configuration with commands like openssl version or examine server certificates with openssl s_client.