Multi-server environments are that the user registers the single registration server and since the user uses the service to authenticate on multi-server. For this, many user authentication schemes have been proposed for multi-server environments. In 2013, Li, et al., proposed dynamic ID based remote user authentication scheme for multi-server environments. Unfortunately, their scheme is vulnera...

This paper deals with multi-component machine repair model having provision of warm standby units and repair facility consisting of two heterogeneous servers (primary and secondary) to provide repair to the failed units. The failure of operating and standby units may occur individually or due to some common cause. The primary server may fail partially following full failure whereas secondary se...