\section{Related Work}\label{related}

Wireless sensor and actor networks are a crucial elements of today's effort to support and implement \textit{Industry 4.0} architectures and modern manufacturing processes. Small programmable logic controllers (PLC) and cloud computing are enabler but also drivers of these new manufacturing paradigms\cite{Nigappa:2016eb}. Thus, the networked interconnection of everyday objects, the automation of home appliances and environmental metering and monitoring based on sensor and actor networks controlled by ESP-based chipsets are subject of current research. In \cite{DiNisio:2015fg}, a low-cost  multipurpose wireless sensor network using \textit{ESP8266} PLCs is introduced. The usage of \textit{ESP8266} PLCs in combination with Raspberry PI acting as base station for the sensors is discussed in \cite{Thaker:2016fi}. The article \cite{Kodali:2016hc} presents a home automation solution based on a \textit{MQTT} message queue with \textit{ESP8266}-based sensors and actors. The control of smart bulbs with PLCs is summarized in \cite{Walia:2016bj}. Unfortunately, soft ware update mechanisms are not addressed in these publications. The importance of regular security updates for today's infrastructures is summarized in \cite{beresford2016whack}. An approach of decentralized software updates in Contiki-based IoT environments are introduced in \cite{Ruckebusch:2016vo}. In \cite{Weisbach:2016bs}, a software update solution for devices able to execute a Java Virtual Machine (JVM) is introduced. Both solutions are not applicable for small MCU devices. In \cite{Mansour:2012fu}, a diagnoses and update system for embedded software of electronics control units in vehicles is introduced. Secure firmware updates targeted for the automotive industry is introduced in \cite{Nilsson:2008ik}. Furthermore, a secure The \textit{Over the Air} programming capabilities of the \textit{ESP8266} PLCs are described in \cite{Gore:2016ue}.
