This thesis concerns the security of tomorrow’s peer-to-peer real-time communication in heterogeneous networks. Because of the additional delay caused by inband handshake and the poor compatibilities of some transport protocols, it was determined that existing security protocols such as transport layer security (TLS) and datagram transport layer security (DTLS) are not suitable in such a user scenario and a new security protocol should be designed. This new security protocol is called transport encapsulation security payload (TESP). TESP not only has the advantage of low initialization delay, but also fully supports transport protocols including TCP, UDP, stream control transmission protocol (SCTP), and datagram congestion control protocol (DCCP). Also a security analysis of TESP was carried out and no security flaws were found. / Denna uppsats behandlar säkerheten för morgondagens "peer-to-peer" (P2P) realtidskommunikation i heterogena nät. På grund av den adderade fördröjning som orsakas av inbandssignalering och dålig kompabilitet hos många transportprotokoll, så kan man fastställa att existerande säkerhetsprotokoll, såsom "(Datagram) Transport Layer Security" (TLS och DTLS), inte är lämpade för denna typ av kommunikation och att ett nytt säkerhetsprotokoll bör tas fram. "Transport Encapsulation Security Payload" (TESP) är ett sådant protokoll. TESP har inte bara fördelar såsom låg uppstartsfördröjning, utan har också stöd för många transportprotokoll, t.ex. "Transport Control Protocol" (TCP), "User Datagram Protocol" (UDP), "Stream Control Transmission Protocol" (SCTP) och "Datagram Congestion Control Protocol" (DCCP). Även en säkerhetsanalys av TESP har gjorts, där inga säkerhetsproblem har kunnat påvisas.

Multimedia conferences held using services provided by clouds owned by third party companies are becoming increasingly popular. While using such services, end users will want to keep their audio/video data private when they pass through the servers situated in the cloud. Application of SRTP (Secure Real-time Transport Protocol) in such use cases fail to provide the desired privacy because it leads to sharing the master keys for encryption and authentication of the media content with the semi trusted media servers of the cloud. As a solution, modifications of SRTP are proposed in this thesis with the result of redesigning the security mechanisms of RTP header extensions and RTCP packets by separating the cryptographic contexts and keying materials for protecting end-to-end sensitive data. A couple of design choices for key management through DTLS-SRTP for Cloud conferencingare also proposed. Moreover, analysis of existing solutions for modifying SRTP packets for cloud conferences have also been carried out in this project. The solutions are found by studying related protocols, understating the problems and analyzing current solutions if there were any. The proposed solutions show different alternatives to solve a specific problem and their tradeoffs in terms of complexity and compatibility with current standards.

Quantum dots (QDs) are a semiconductor nanostructure in which a small island of one type of semiconductor material is contained within a larger bulk of a different one. These structure are interesting for a wide range of applications, including highly efficient LASERs, high-density novel memory devices, quantum computing and more. In order to understand the nature of QDs, electrical characterisation techniques such as capacitance-voltage (CV) profiling and deep-level transient spectroscopy (DLTS) are used to probe the nature of the carrier capture and emission processes. This is limited, however, by the nature of QD formation which results in a spread of sizes which directly affects the energy structure of the QDs. In this work, I sought to overcome this by using Si substrates patterned with a focused ion beam (FIB) to grow an array of identically-sized Ge dots. Although I was ultimately unsuccessful, I feel this approach has great merit for future applications.In addition, this thesis describes several unusual characteristics observed in InAs QDs in a GaAs bulk (grown by molecular beam epitaxy-MBE). Using conventional and Laplace DLTS, I have been able to isolate a single emission transient. I further show an inverted relation between the emission rate and the temperature under high field (emissions increase at lower temperatures). I attribute this to a rapid capture to and emission from excited states in the QD. In addition, I examine a metastable charging effect that results from the application of a sustained reverse bias and decreases the apparent emission rate from the dots. I believe this to be the result of a GaAs defect with a metastable state which acts as a screen, inhibiting emission from the dots due to an accumulation of charge in the metastable state. These unusual characteristics of QDs require further intensive work to fully understand. In this work I have sought to describe the phenomena fully and to provide hypotheses as to their origin.