Seansivõti

Seansivõti, often translated as "session key," is a temporary cryptographic key used in secure communication protocols, most notably in Transport Layer Security (TLS) and its predecessor, Secure Sockets Layer (SSL). Its primary purpose is to encrypt the data exchanged during a specific communication session between two parties, such as a web browser and a server.

Unlike long-term symmetric keys or asymmetric key pairs used for initial authentication and key exchange, a session key is generated for a single connection. This means that once the session is terminated, the session key is discarded. This ephemeral nature is a crucial security feature. If a session key were to be compromised, it would only affect the data transmitted during that particular session, limiting the potential damage.

The generation of a session key typically involves a handshake process. During this process, the client and server exchange messages to agree upon encryption algorithms and to securely generate the session key. This often utilizes asymmetric cryptography to establish a shared secret, which is then used to derive the symmetric session key. Because session keys are used for symmetric encryption, they allow for much faster data transmission compared to the computationally intensive asymmetric encryption methods. The combination of initial secure key exchange and subsequent fast symmetric encryption is fundamental to the security and efficiency of modern internet communication.