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Security Fundamentals & Crypto · Intermediate

Elliptic Curve Diffie-Hellman (ECDH)

Diffie-Hellman key agreement performed with elliptic curve groups, providing equal security with smaller keys.

Definition

ECDH uses elliptic curve point multiplication instead of modular exponentiation. Its ephemeral form (ECDHE) is the default key exchange in TLS 1.3 and modern VPNs, providing forward secrecy. Common curves include P-256, P-384, and X25519.

Example

A TLS 1.3 handshake using X25519 performs ECDHE to derive session keys.

Exam tip

ECDHE = ephemeral elliptic curve DH = forward secrecy.

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