Method, system and computer program for exchanging data between a client computer and a storage device are described, in which the storage device may send a long-term DH-component to an intermediate server. The client computer may send a first short-term DH-component to the storage device through the intermediate server that adds a communication expiration time. The storage device may send a second short-term DH-component to the client computer. The client computer and the storage device may calculate a symmetric key from the long-term component and from both short-term DH-components to exchange data and may delete the short-term DH-components upon reaching the expiration time.