In cryptography, a key memorandum of understanding is a protocol in which two or more parties can agree on a key in such a way that both influence the outcome. If properly implemented, it prevents unwanted third parties from imposing an important choice on the parties. Protocols that are useful in practice also do not reveal to any wiretapped party which key has been agreed. TLS 1.3 now has a radically simpler encryption negotiation model and a reduced set of important options (no RSA, no custom DH settings). This means that each connection uses a key agreement based on DH and the parameters supported by the server are probably easy to guess (ECDHE with X25519 or P-256). Because of these limited choices, the client can easily send DH key shares in the first message instead of waiting for the server to confirm the key shares it wants to support. This way, the server can learn the common secret key and send encrypted data a round trip earlier. For example, Chrome`s implementation of TLS 1.3 sends an X25519 key share to the server in the first message. Many key exchange systems allow one party to generate the key and send that key simply to the other party – the other party has no influence on the key. Using a key-agreement protocol avoids some key distribution issues related to these systems.

Authenticated key protocols require the separate setting of a password (which can be smaller than a key) in a way that is both private and integrity. These are designed to withstand man-in-the-middle attacks and other active attacks against the password and established keys. For example, DH-EKE, SPEKE, and SRP are authenticated variations of Diffie-Hellman. Before the client and server can begin exchanging TLS-protected information, they must securely exchange or agree on an encryption key and code to be used in data encryption (see § Code). the methods used for the key exchange/agreement belong to: public and private keys generated with RSA (in the TLS handshake Protocol TLS_RSA called), Diffie-Hellman (TLS_DH), ephemeral Diffie-Hellman (TLS_DHE), Diffie-Hellman elliptic curve (TLS_ECDH), elliptical ephemere Diffie-Hellman curve (TLS_ECDHE), Diffie-Hellman anonymous (TLS_DH_anon), [1] pre-shared key (TLS_PSK)[44] and Secure Password Remote (TLS_SRP). [45] The first publicly known public key MOU[1] meeting the above criteria was the Diffie-Hellman key exchange, in which two parties together expose a random generator in such a way that an earpiece cannot determine in a feasible way what is the resulting value used to make a common key. . . .