TLSistunto

TLSistunto is a Finnish term that translates to "TLS session" in English. It refers to the stateful security context established between a client and a server using the Transport Layer Security (TLS) protocol. Once a TLS handshake is successfully completed, a session is established, allowing for more efficient subsequent communication.

During a TLS session, the client and server share a set of cryptographic parameters, including encryption algorithms, master secret, and session keys. This shared context enables them to encrypt and decrypt data without needing to perform a full, computationally expensive handshake for every new connection or message. The session parameters are typically valid for a limited period or a certain number of transactions to maintain security.

Session resumption is a key feature of TLS sessions. It allows a client that has previously established a TLS session with a server to resume that session instead of initiating a new handshake. This significantly reduces latency and the computational overhead associated with establishing secure connections, particularly in scenarios with frequent or short-lived connections. There are two main methods for TLS session resumption: session IDs and session tickets.

TLSistunto is a fundamental concept in understanding how TLS optimizes secure communication. By maintaining session state, it balances robust security with the need for efficient data transfer in modern networked applications.