DIFFIE-HELLMAN key exchange allows two parties to

1. DIFFIE-HELLMAN (DH): a cryptographic protocol where Alice and Bob each pick a private value, exchange public values, and independently compute the same shared secret. 2. AN EAVESDROPPER who sees the public exchange CANNOT compute the shared secret (relies on the discrete log problem). 3. MODERN versions: Elliptic-Curve DH (ECDH), Curve25519 — much faster than classical DH at similar security level. 4. USED IN: TLS 1.3 handshake (FORWARD SECRECY), Signal, WireGuard, SSH key exchange. 5. Other options misunderstand the purpose. _Source: Boneh & Shoup, §10.4 (Diffie-Hellman key exchange)._