2 Smart home devices
2.1 Smart TVs

Smart TVs differ from standard TVs in several features. In addition to ability to receive TV broadcasting like any other TV set they are able to make Internet accessible for users thanks to their technical equipment the other TV sets don’t have [7].

They run a complete operating system with a graphical user interface (Fig. 3) which enables users to access web space where they can browse web pages via web browser with the same effect like via standard personal computer. It means that TV viewers can watch multimedia content from Internet without a need to watch standard (linear) broadcasting. Of course the web browsing is not very comfortable via a remote control and therefore smart TVs offer a functionality to connect various wireless devices. Currently, there are several possibilities how to control smart TVs (Fig. 4) and they include:

- standard button based remote control, in some cases enhanced by a touchpad or QWERTY keyboard,
- wireless QWERTY keyboard and mouse (application control),
- voice (commands) recognition (e.g. via a microphone in remote control),
- gesture recognition (via connected/integrated webcam),
- smartphone control.

Very important ability the smart TVs provide is an ability to play multimedia content (pictures, audio and video files) because they support most common formats of these media.

Each TV set is equipped by at least one USB interface in some case even by a memory card reader. User can just plug in an USB stick or hard drive or memory card with multimedia content and watch it on big screen. In case a TV set doesn’t support some media format or resolution it is possible to connect e.g. laptop to a TV set via HDMI port. TV sets that are DLNA (Digital Living Network Alliance) certified are able to play multimedia content from other DLNA devices (PCs, tablets, smartphones, media servers, etc.).

Fig. 3 Example of smart TV set

Smart TVs usually contain at least one integrated digital tuner for reception of terrestrial broadcasting (in HD resolution). They are often equipped by other tuners for satellite or cable television. Since they receive a digital television signal they can provide users with recording function so users can record broadcasting on external USB sticks or hard disk drives. Recording function only works from integrated television tuners not from external sources (e.g. HDMI ports).

Fig. 4 Examples of various remote controls for smart TV sets

As we already mentioned these TV sets run some operating system so they are a bit similar to standard PCs. Currently, there is a lot of smart TV producers. Smart TVs can be based on proprietary (closed) or open (source) platform. The most widely known platforms are: Android TV by Google (Philips, Sharp, Sony), Firefox OS (Panasonic), Roku TV (JVC, LG, Sharp, Hitachi) and Tizen OS (Samsung). In addition to web browsing, as was mentioned above, users can run various applications on the smart TV set. Some of them are already preinstalled other applications can be downloaded by users and installed. All of these applications are web based applications. Smart TV applications cover:

- simple Internet browser,
- social networks,
- video online services (YouTube, Vimeo),
- news applications,
- simple games,
- videoconferences (Skype),
- paid video and audio streaming services (Netflix, Spotify, …).

As can be partially seen in Fig. 5, the smart TVs support Ethernet, Wi-Fi, USB and Bluetooth technologies for communications, memory card reader, coax cable (for antenna) and HDMI (eventually older video signal standards) ports, digital audio input and slot for a CI/CI+ module (for smart/subscription cards).

Fig. 5 Rear side of a smart TV

During evolution of smart TVs an important security aspect has appeared. For example in 2013 at Black Hat conference SeungJin Lee showed how is possible to develop an efficient eavesdropping device from smart TV set and cameras and microphones connected to it [8].