京都大学 / 0048 / 新制・課程博士 / 博士(工学) / 甲第20373号 / 工博第4310号 / 新制||工||1668(附属図書館) / 京都大学大学院工学研究科電気工学専攻 / (主査)教授 引原 隆士, 教授 土居 伸二, 教授 梅野 健 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DFAM

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The ability to access the Internet while remaining anonymous is a necessity in today's society. Whistleblowers need it to establish contact with journalists, and individuals living under repressive regimes need it to access essential resources. Anonymity also allows malicious actors to evade identification from law enforcement and share ill-intentioned resources. Therefore, digital forensics is an area that needs to stay up to date with these developments. We investigate what artefacts can be discovered by conducting acquisition and analysis of a Windows 11 computer that has used the Tor browser to browse the Dark Web. Our results identify a variety of artefacts acquired from Windows Registry, active memory, storage, and network traffic. Furthermore, we discuss how these can be used in a digital forensic investigation.

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As sensing technology develops, it plays an important role in context-aware systems. Using context information improves the user experience of ubiquitous computing. One use of sensed information is to detect a meeting in progress in an office or a conference room. In our system, sensors gather context information from an office environment and act as a presence user agent to update a presence server with context changes. These context changes can be utilized by context-aware services. The presence messaging uses the SIP for Instant Messaging and Presence Leveraging Extensions (SIMPLE) protocol and the presence information is described in eXtensible Makeup Language (XML) format. In this thesis we present a context-sensing component that recognizes meetings in a typical office environment. A context-aware system is able to use this occupancy information to infer that the room is empty, an individual is alone in the room, or a meeting is taking place in the meeting room. Context-aware services might utilize this environmental information to automatically forward a user's incoming calls to their voice mail server. This and other example applications were developed to show the usefulness of this context information. / Så som sensor tekniken utvecklas, spelar de en viktig roll i kontextmedvetna system. Genom att använda kontextuell information förbättras användarupplevelsen av 'ubiquitous computing'. Ett användningsområde för sensorinsamlad information är att upptäcka ett möte som pågår i ett kontor eller konferenslokal. I vårt system samlar sensorer information från en kontorsmiljö och uppdaterar en närvaroserver med kontextuella förändringar. Dessa förändringar kan sedan utnyttjas av kontextmedvetna tjänster. För att förmedla den närvarostatusen använder närvaroservern SIP och ’Presence Leveraging Extensions’ (SIMPLE) protokoll. Närvaro information levereras i 'eXtensible Makeup Language' (XML) format. I denna avhandling presenterar vi en kontextsensorkomponent som känner av möten i en typisk kontorsmiljö. Ett kontextmedvetet system kan använda denna komponent för att dra slutsatsen att lokalen är tom, en person är ensam i lokalen, eller ett möte äger rum i lokalen. Kontextmedvetna tjänster kan utnyttja denna information för att automatiskt vidarebefordra en användares inkommande samtal till deras röstbrevlåda. Detta och andra exempel, har utvecklats för att visa nyttan av denna kontextuella information.

Internet of Things (IoT) is the idea that every device around us is connected and these devices continually collect and communicate data for analysis at a large scale in order to enable better end user experience, resource utilization and device performance. Therefore, data is central to the concept of IoT and the amount being collected is growing at an unprecedented rate. Current networking systems and hardware are not fully equipped to handle influx of data at this scale which is a serious problem because it can lead to erroneous interpretation of the data resulting in low resource utilization and bad end user experience defeating the purpose of IoT. This thesis aims at improving data transportation for IoT. In IoT systems, devices are connected to one or more cloud services over the internet via an access link. The cloud processes the data sent by the devices and sends back appropriate instructions. Hence, the performance of the two ends of the network ie the access networks and datacenter network, directly impacts the performance of IoT. The first portion of the our research targets improvement of the access networks by improving access link (router) design. Among the important design aspects of routers is the size of their output buffer queue. %Selecting an appropriate size of this buffer is crucial because it impacts two key metrics of an IoT system: 1) access link utilization and 2) latency. We have developed a probabilistic model to calculate the size of the output buffer that ensures high link utilization and low latency for packets. We have eliminated limiting assumptions of prior art that do not hold true for IoT. Our results show that for TCP only traffic, buffer size calculated by the state of the art schemes results in at least 60% higher queuing delay compared to our scheme while achieving almost similar access link utilization, loss-rate, and goodput. For UDP only traffic, our scheme achieves at least 91% link utilization with very low queuing delays and aggregate goodput that is approx. 90% of link capacity. Finally, for mixed traffic scenarios our scheme achieves higher link utilization than TCP only and UDP only scenarios as well as low delays, low loss-rates and aggregate goodput that is approx 94% of link capacity. The second portion of the thesis focuses on datacenter networks. Applications that control IoT devices reside here. Performance of these applications is affected by the choice of TCP used for data communication between Virtual Machines (VM). However, cloud users have little to no knowledge about the network between the VMs and hence, lack a systematic method to select a TCP variant. We have focused on characterizing TCP Cubic, Reno, Vegas and DCTCP from the perspective of cloud tenants while treating the network as a black box. We have conducted experiments on the transport layer and the application layer. The observations from our transport layer experiments show TCP Vegas outperforms the other variants in terms of throughput, RTT, and stability. Application layer experiments show that Vegas has the worst response time while all other variants perform similarly. The results also show that different inter-request delay distributions have no effect on the throughput, RTT, or response time. / Master of Science / Internet of Things (IoT) is the idea that every electronic device around us, like watches, thermostats and even refrigerators, is connected to one another and these devices continually collect and communicate data. This data is analyzed at a large scale in order to enable better user experience and improve the utilization and performance of the devices. Therefore, data is central to the concept of IoT and because of the unprecedented increase in the number of connected devices, the amount being collected is growing at an unprecedented rate. Current computer networks over which the data is transported, are not fully equipped to handle influx of data at this scale. This is a serious problem because it can lead to erroneous analysis of the data, resulting in low device utilization and bad user experience, hence, defeating the purpose of IoT. This thesis aims at improving data transportation for IoT by improving different components involved in computer networks. In IoT systems, devices are connected to cloud computing services over the internet through a router. The router acts a gateway to send data to and receive data from the cloud services. The cloud services act as the brain of IoT i.e. they process the data sent by the devices and send back appropriate instructions for the devices to perform. Hence, the performance of the two ends of the network i.e. routers in the access networks and cloud services in datacenter network, directly impacts the performance of IoT. The first portion of our research targets the design of routers. Among the important design aspects of routers is their size of their output buffer queue which holds the data packets to be sent out. We have developed a novel probabilistic model to calculate the size of the output buffer that ensures that the link utilization stays high and the latency of the IoT devices stays low, ensuring good performance. Results show that that our scheme outperforms state-of-the-art schemes for TCP only traffic and shows very favorable results for UDP only and mixed traffic scenarios. The second portion of the thesis focuses on improving application service performance in datacenter networks. Applications that control IoT devices reside in the cloud and their performance is directly affected by the protocol chosen to send data between different machines. However, cloud users have almost no knowledge about the configuration of the network between the machines allotted to them in the cloud. Hence, they lack a systematic method to select a protocol variant that is suitable for their application. We have focused on characterizing different protocols: TCP Cubic, Reno, Vegas and DCTCP from the perspective of cloud tenants while treating the network as a black-box (unknown). We have provided in depth analysis and insights into the throughput and latency behaviors which should help the cloud tenants make a more informed choice of TCP congestion control.

Several trends can be observed in modern microprocessor design. Architectures have become increasingly complex while design time continues to dwindle. As feature sizes shrink, wire resistance and delay increase, limiting architects from scaling designs centered around a single thread of execution. Where previous decades have focused on exploiting instruction-level parallelism, emerging applications such as streaming media and on-line transaction processing have shown greater thread-level parallelism. Finally, the increasing gap between processor and off-chip memory speeds has constrained performance of memory-intensive applications. The Single-Chip Message Passing (SCMP) parallel computer sits at the confluence of these trends. SCMP is a tiled architecture consisting of numerous thread-parallel processor and memory nodes connected through a structured interconnection network. Using an interconnection network removes global, ad-hoc wiring that limits scalability and introduces design complexity. However, routing data through general purpose interconnection networks can come at the cost of dedicated bandwidth, longer latency, increased area, and higher power consumption. Understanding the impact architectural decisions have on cost and performance will aid in the eventual adoption of general purpose interconnects. This thesis covers the design and analysis of the on-chip network and its integration with the SCMP system. The result of these efforts is a framework for analyzing on-chip interconnection networks that considers network performance, circuit area, and power consumption. / Master of Science

This thesis deals with problematics of installing wireless routers into specific locations depending on their heating and ideal signal transmission. The thesis is divided into eight chapters. The beginning of the thesis is theoretical describes the introduction into the problematics, the second part is practical and covers the executed experiment. The theoretical part contains six chapters – heat, signal, wireless router and measured climatic conditions. The practical part describes the executed experiment by thermo-camera which was used to scan wireless routers in IoT Lab in Avast Software company. Based on this experiment, the ideal position for installing the wireless router is then established. The conclusion of the practical part includes an analysis of the results of the questionnaire survey, in which technically skilled people were asked to describe the height of installation of their wireless router or whether did they consider heat and signal propagation while installing their wireless routers.

This thesis deals with theoretical analysis of First Hop Redundancy Protocols. It describes Hot Standby Router Protocol, Virtual Router Redundancy Protocol and Gateway Load Balancing Protocol. It also shows examples of configuration of each protocol on Cisco devices with supported version of the Cisco IOS. Furthermore, this thesis includes design of two of these protocols, Hot Standby Router Protocol and Gateway Load Balancing Protocol, and their implementation in discrete event simulator OMNeT++ and Automated Network Simulation and Analysis library. Finally, the thesis presents results of testing of the implementations in comparison with actual Cisco devices.