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Security Fundamentals & Crypto · Foundational

Pre-Shared Key (PSK)

Secret shared in advance between parties and used for authentication or key derivation.

Definition

PSKs are used in WPA2-Personal, IPsec site-to-site VPNs, and some TLS deployments. They are simple to deploy but hard to rotate and scale, and a weak PSK can be cracked offline after capturing a handshake. Certificates or SAE are stronger alternatives.

Example

Two firewalls authenticate an IPsec tunnel using a 32-character random pre-shared key.

Exam tip

Weak PSKs are vulnerable to offline dictionary attacks; use long random keys or certificates.

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