# Improvements of the xAAL Home Automation System
## 5 The xAAL Communication Protocol
### Security Considerations
#### 5.6.2 Cloud Communication  
Within the home automation context, users are at home, and services are rendered at home by the home. One may wonder where to locate and execute the service: at home or in the clouds. xAAL, and many others, propose to locate home automation services at home. This is a first step to address security and privacy issues. However, nowadays, consumers accept cloud solutions. This implies trusting the involved companies, to give them control of our home, to give them a view of our activities at home, to believe in their ethics today and in the future. Accepting this is a cost for the consumer. The counterpart is the promise to get a simple-to-use service. Mobile Clients to Cloud Servers  
The first promise is simplicity. Generally,'smart devices' wording has to be read as 'devices having Internet access and connected to servers of the company in the clouds'. The consumer buys and installs home automation devices (smart plugs, smart outlets, smart lamps, etc.). Those devices may embed a WiFi network interface, or may be connected via a dedicated radio protocol to a hub/gateway/box also present at home, which has a WiFi network interface and sometimes an ethernet one. There is a persistent connection between devices at home and external computers of the company: usually devices forward sensor measures and events in real time, and can be remotely controlled from those external computers. From its side, the consumer uses a mobile application (a dedicated one or a web page), which is also connected to those external computers of the company. By this means, the user is informed of events at home and can send commands to its devices. Companies usually propose such services for free, or free for the first years. This process conforms, nowadays, to the usual design of mobile applications: user applications are _clients_ of _cloud servers_, servers that are retrieved thanks to a well-known DNS name (Domain Name System, the means to translate names into Internet addresses). This process is transparent to the user. In addition, the user has the same level of service whenever he or she is at home near devices, or outside. Controlling the house from outside by any member of the family is often presented as an advantage despite there is no clear demands from consumers. Mobile applications are rarely designed to reach local servers. Indeed, few end-user services assume that there are servers of anything at home; everything is supposed to be in the clouds. One of the exceptions is for _multimedia drives_, which allows users to store at home photos, videos and music. Note that such services are now also competed by cloud services. These multimedia drives are based on protocols such as DLNA that offers discovering features: user applications can retrieve these drives on the local network and play the contents. xAAL also has a discovering feature by itself, which may be used by an xAAL mobile application. Or else, if the xAAL user interface/control point is a Web service in a box on the home network, it can register its well-known name to the local mDNS server thanks to the Home Networking Control Protocol (HNCP, RFC 7788 [36]). This provides a generic discovering mechanism for local services. The well-known name of such an xAAL box can then be retrieved locally by mobile applications, as usual, but at home. Interoperability in the Clouds  
Another promise is the interoperability in the clouds. Indeed, many home automation vendors propose to interconnect their solution with popular voice assistants (Google Home, Amazon Alexa, Apple Siri). These devices called 'voice assistants','smart speakers', 'connected speakers', but rarely 'connected microphones', are cloud services by themselves: the speech recognition (more or less automatic [37]) is mostly performed by external computers, not at home by the device itself. Thanks to programming API, but also to commercial agreements between companies, cloud computers of voice assistants are connected with cloud computers of home automation vendors.