sesjonsgjenopptak

Sesjonsgjenopptak, or session resumption, is a networking technique that allows a client and server to re-establish a previous communication session without going through the full initial handshake process. This is particularly useful in protocols like TLS (Transport Layer Security), which are commonly used for secure web communication.

When a client initiates a TLS session, it performs a handshake with the server. This handshake involves the exchange of certificates, negotiation of cryptographic algorithms, and establishment of a shared secret key. This process can be computationally intensive and consume bandwidth. If the connection is interrupted or the client needs to reconnect shortly after, performing the full handshake again can be inefficient.

Sesjonsgjenopptak addresses this by allowing the client to present a session identifier to the server. If the server recognizes this identifier and has retained the necessary session state (such as the master secret), it can skip the negotiation steps and immediately resume the secure communication. This significantly speeds up the reconnection process and reduces server load.

There are typically two main mechanisms for sesjonsgjenopptak in TLS: session IDs and session tickets. Session IDs are maintained by the server, while session tickets are encrypted by the server and sent to the client, who then returns them for resumption. The effectiveness of sesjonsgjenopptak depends on factors such as the server's configuration and the lifespan of the session state.