This diploma thesis deals with wireless doorbell realisation. The doorbell is battery-powered and supports half duplex voice transferring. The general aim is to design system circuitry, PCB and to create microcontroller firmware.

With the rapid development of IoT, more and more cyber security threats occur in people’s lives. In addition, many IoT devices are closely related to lives and have a large number of users, such as smart home. Therefore, it is more worthy for the adversaries to launch attacks. This report provides a security analysis of a specific IoT device —- Xiaomi smart video doorbell, which is a popular choice of the smart home. The smart video doorbell, which is usually set outside the front door, is invented to guarantee and enhance the safety of users’ homes. It has the functionalities of smart motion detection, real-time video and it will send notifications to the user’s mobile application if somebody presses the ring button or stays in front of it. This thesis performs a security analysis of this smart video doorbell system via threat modeling and penetration testing. The results show that the target system is not secure enough and have vulnerabilities which can be exploited, such as data exposure, weak password encryption, lack of logging and so on. Improvements can be made although there is no critical or urgent vulnerability of the target system. / Med den snabba utvecklingen av IoT uppstår fler och fler hot mot cybersäkerhet i människors liv. Dessutom är många IoT -enheter nära besläktade med liv och har ett stort antal användare, till exempel smarta hem. Därför är det mer värt för motståndarna att starta attacker. Denna rapport ger en säkerhetsanalys av en specifik IoT-enhet —- Xiaomi smart video dörrklocka, som är ett populärt val av det smarta hemmet. Den smarta videodörrklockan, som vanligtvis ställs utanför ytterdörren, uppfanns för att garantera och öka säkerheten för användarnas hem. Den har funktioner för smart rörelsedetektering, video i realtid och den skickar meddelanden till användarens mobilapp om någon trycker på ringknappen eller stannar framför den. Denna avhandling utför en säkerhetsanalys av detta smarta videodörrklocksystem via hotmodellering och penetrationstest. Resultaten visar att målsystemet inte är tillräckligt säkert och har sårbarheter som kan utnyttjas, såsom dataexponering, svag lösenordskryptering, brist på loggning och så vidare. Förbättringar kan göras även om det inte finns någon kritisk eller brådskande sårbarhet för målsystemet.

Internet of Things (IoT) devices have entered the home, offices, and other parts of everyday life at an alarming rate in recent years. A large company in the IoT space is Ring. They mostly make smart home security devices, with the mission of making neighborhoods safer, and their flagship product is the Ring doorbell. However, an important question is: Does connecting such a device to your home network introduce new threats? In this thesis, the security of the Ring doorbell and applications in its ecosystem are evaluated and presented. A structured approach is taken for the evaluation by constructing a threat model, evaluating threats, and further pursuing selected threats by penetration testing. One minor vulnerability was discovered but the overall conclusion was that this product followed best practices when it comes to securing IoT devices, reducing attack surfaces, and enforcing user security policies. The conclusion of this thesis is that adding a Ring doorbell to your home network does not introduce a new threat. / Sakernas internet (IoT) enheter har kommit in i hemmet, kontoret och andra delar av vardagen i en alarmerande takt under de senaste åren. Ett stort företag inom IoT området är Ring. De tillverkar mestadels smarta hem säkerhetsenheter, med uppdraget att göra stadsdelar säkrare, och deras flaggskeppsprodukt är Ring-dörrklockan. Men införs nya hot om du ansluter en sådan enhet till ditt hemnätverk? I detta examensarbete utvärderas och presenteras säkerheten för Ring dörrklockan och applikationer i dess ekosystem. Ett strukturerat tillvägagångssätt används för utvärderingen genom att konstruera en hotmodell, utvärdera hot och fortsätta vidare utvalda hot genom penetrationstester. En mindre sårbarhet men den övergripande slutsatesen var att den här produkten följde bästa praxis när det gäller att säkra IoT enheter, minska attackytor och upprätthålla användarsäkerhetspolicyer. Slutsatsen av denna avhandling är att om du lägger till en Ring-dörrklocka i ditt hemnätverk inte introducerar ett nytt säkerhetshot.

The aim of this thesis was to learn and summarize basic information about IoT systems, which protocols are used and introduction of Google Home system. The first part of the thesis describes the individual parts of the system --- microcontrollers, sensors, light elements and possible systems for backend. In the implementation part of the thesis was designed a solution for smart home controling using Google Home technology. Based on data from the weather station, the system controls and adjusts the intensity of outdoor lighting and controls the blinds. Furthermore, a control module for gate and garage door control is implemented. The system also takes care of vacuum cleaning in the house using iRobot Roomba vacuum cleaners with custom Wi-Fi module. The final part of the thesis summarizes the achieved results.

Rex Stout maintained his popular readership despite the often controversial and radical political content expressed in his detective fiction. His political ideals often made him many enemies. Stances such as his ardent opposition to censorship, racism, Nazism, Germany, Fascism, Communism, McCarthyism, and the unfettered FBI were potentially offensive to colleagues and readers from various political backgrounds. Yet Stout attempted to present radical messages via the content of his detective fiction with subtlety. As a literary traditionalist, he resisted using his fiction as a platform for an often extreme political agenda. Where political messages are apparent in his work, Stout employs various techniques to mute potentially offensive messages. First, his hugely successful bantering Archie Goodwin-Nero Wolfe detective duo—a combination of both the lippy American and the tidy, sanitary British detective schools—fosters exploration, contradiction, and conflict between political viewpoints. Archie often rejects or criticizes Wolfe's extreme political viewpoints. Second, Stout utilizes the contradictions between values that occur when the form of detective fiction counters his radical political messages. This suggests that the form of detective fiction (in this case the conventional patterns and attitudes reinforced by the genre) is as important as the content (in this case the muted political message or the lack of overt politics) in reinforcing or shaping political, economic, moral, and social viewpoints. An analysis of the novels The Black Mountain (1954) and The Doorbell Rang (1965) and the novellas "Not Quite Dead Enough" and "Booby Trap" (1944) from Stout's Nero Wolfe series demonstrates his use of detective fiction for both the expression of political viewpoints and the muting of those political messages.