As　embedded　integrated　electronic　systems　(EIESs)　become　more　pervasive　(including　in　mission-critical　applications),　the　need　to　ensure　the　security　of　data　exchange　in　such　a　system　against　various　malicious　activities　becomes　more　pronounced.　However,　designing　secure　and　efficient　solutions,　such　as　authentication　protocols,　for　the　many　different　embedded　systems　with　varying　internal　communication　modes　remains　challenging.　Therefore,　in　this　paper,　we　propose　a　lightweight　authenticated　key-exchange　(AKE)　protocol　for　EIESs　based　on　half-duplex　and　＇command/response＇　bus.　Specifically,　the　proposed　protocol　is　designed　to　operate　on　resource-constrained　devices,　as　well　as　having　minimal　number　of　interactions.　We　then　prove　the　security　of　the　proposed　protocol　and　present　the　security　parameter　selection　strategy　for　protocol　implementation　based　on　the　empirical　evaluations.　Moreover,　efficiency　analysis　also　shows　that　the　protocol　can　be　effectively　deployed　in　the　EIESs　environment.　©　2004-2012　IEEE.