sessioonivõtme

A sessioonivõti, or session key, is a temporary cryptographic key used in a communication session. It is typically generated for a specific period of time and is used to encrypt and decrypt data exchanged between two parties during that session. The primary purpose of a session key is to provide confidentiality and integrity for the data being transmitted.

Session keys are distinct from long-term or master keys, which are used for establishing the initial security context. Instead of using a permanent key for every communication, a session key is generated dynamically and then securely exchanged between the communicating parties. This approach enhances security because even if a session key is compromised, it only affects the data transmitted during that particular session, leaving the long-term keys intact.

The process of generating and using a session key often involves a key exchange protocol. Common protocols like Diffie-Hellman or those used in Transport Layer Security (TLS) are employed to establish a shared secret between the client and server without transmitting the key itself over the network. Once established, this shared secret is used to derive the session key.

The lifespan of a session key is limited. It is typically discarded once the communication session ends, or after a predetermined timeout period. This ephemeral nature is a core security feature, minimizing the window of opportunity for attackers to exploit a compromised key. The use of session keys is fundamental to secure online communication, including web browsing, online banking, and secure messaging.