Diffie–Hellman key exchange
In Transport Layer Security (TLS), cipher suites based on Diffie–Hellman key exchange (DHE-RSA, DHE-DSA) and elliptic curve Diffie–Hellman key exchange (ECDHE-RSA, ECDHE-ECDSA) are available. In theory, TLS can choose appropriate ciphers since SSLv3, but in everyday practice many implementations have refused to offer forward secrecy or only provide it with very low encryption grade. TLS 1.3 leaves ephemeral Diffie–Hellman (finite field and elliptic curve variants) as the only remaining key exchange mechanism, in order to ensure forward secrecy.