SilcSKEStatus silc_ske_payload_ke_encode(SilcSKE ske,
                                             SilcSKEKEPayload payload,
                                             SilcBuffer *return_buffer);

    Utility function used to encode Key Exchange Payload from the
    `payload' structure. The encoded buffer is returned into the
    `return_buffer' and the caller must free it.