Various embodiments relate to a key protocol exchange that provide a simple but still secure key exchange protocol. Security of key exchange protocols has many aspects; providing and proving all these properties gets harder with more complex protocols. These security properties may include: perfect forward secrecy; forward deniability; key compromise impersonation resistance; security against unknown key share attack; explicit or implicit authentication; key confirmation; protocol is (session-)key independent; key separation (different keys for encryption and MACing); extendable, e.g. against DOS attacks . . . (e.g. using cookies, . . . ); support of early messages; small communication footprint; and support of for public-key and/or password authentication.