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Security Fundamentals & Crypto · Advanced

Curve25519

Elliptic curve designed by Daniel Bernstein for fast, safe Diffie-Hellman key agreement (X25519).

Definition

Curve25519 provides about 128-bit security and was designed to avoid implementation pitfalls of earlier curves. Its key agreement function X25519 is used in TLS 1.3, SSH, Signal, and WireGuard, and its twisted Edwards form underlies Ed25519 signatures. It is defined in RFC 7748.

Example

ssh-keygen -t ed25519 creates an SSH key on the Edwards form of Curve25519.

Exam tip

X25519 = key agreement; Ed25519 = signatures.

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