A UE, a device and a Direct Communication Element. The UE is configured to establish a UE shared key with a Bootstrapping Server Function (BSF) using a Generic Bootstrapping Architecture (GBA) procedure, to discover the device through a discovery procedure after establishing the UE shared key, and to derive a direct communication key from at least the UE shared key. The device is configured to receive a transaction identifier associated with the UE shared key from the UE, to send the transaction identifier to the Direct Communication Element, and to receive the direct communication key from the Direct Communication Element. The Direct Communication Element is configured to receive the transaction identifier from the device, to obtain a shared session key from the BSF; to derive the direct communication key, and to send the direct communication key to the device.