SilcSKEStatus silc_ske_initiator_phase_1(SilcSKE ske,
                                             SilcBuffer start_payload);

    Function called after ske_initiator_start fuction. This receives
    the responder's Key Exchange Start payload which includes the
    security properties selected by the responder from our payload
    sent in the silc_ske_initiator_start function. The `start_payload'
    is the received payload and the application must send it as argument.

    After calling this function the application must call immediately,
    or with short timeout, the silc_ske_initiator_phase_2 function.