A method carried out by a first system for establishing a secure bidirectional communication path between the first system and a second system for an exchange of one or more messages is described. A first key pair having a first public key and a first private key is generated, and a second key pair having a second public key and a second private key is generated. The second public key is generated based upon a shared secret known to the first system and the second system. The second public key and the first public key are sent to the second system. A third public key and a fourth public key generated by the second system are received, wherein the fourth public key is generated based upon the shared secret. A master key is calculated based upon the first private key, the second private key, the third public key and the fourth public key, wherein the master key is configured to be used in encryption of one or more messages.