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Security Fundamentals & Crypto · Foundational

Session Key

A temporary symmetric key used to encrypt a single communication session.

Definition

Session keys limit the amount of data exposed if one key is compromised. They are typically derived through key agreement at the start of a session and destroyed afterward. Ephemeral session keys support perfect forward secrecy.

Example

Each HTTPS connection derives fresh session keys during the TLS handshake.

Exam tip

Session keys are symmetric and short-lived; long-term asymmetric keys authenticate the exchange.

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