Browsing by Subject "Networks"

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  • Leskinen, Juno (Helsingin yliopisto, 2022)
    The continuously evolving cyber threat landscape has become a major concern because sophisticated attacks against systems connected to the Internet have become frequent. The concern is on particular threats that are known as Advanced Persistent Threats (APT). The thesis aims to introduce what APTs are and illustrate other topics under the scope, such as tools and methods attackers can use. Attack models will also be explained, providing example models proposed in the literature. The thesis also introduces which kind of operational objectives attacks can have, and for each objective, one example attack is given that characterizes the objective. In addition, the thesis also uncovers various countermeasures, including most essential security solutions, complemented with more advanced methods. The last countermeasure that the thesis introduces is attribution analysis.
  • Porkka, Otto (Helsingin yliopisto, 2022)
    Blockchain technologies and cryptocurrencies have gained massive popularity in the past few years. Smart contracts extend the utility of these distributed ledgers to distributed state machines, where anyone can store and run code and then mutually agree on the next state. This opens up a whole new world of possibilities, but also many new security challenges. In this thesis we give an up-to-date survey on smart contract security issues. First we give a brief introduction to blockchains and smart contracts and explain the most common attack types and some mitigations against them. Then we sum up and analyse our findings. We find out that many of the attacks could be avoided or at least severely mitigated if the coders followed good coding practices and used design patterns that are proven to be good. Another finding is that changing the underlying blockchain technology to counter the issues is usually not the best way, as it is hard and troublesome to do and might restrict the usability of contracts too much. Lastly, we find out that many new automated tools for security are being developed and used, which indicates movement towards more conventional coding where automated tools like scanners and analysers are being used to cover a large set of security issues.
  • Colliander, Camilla (Helsingin yliopisto, 2022)
    Software development speed has significantly increased in recent years with methodologies like Agile and DevOps that use automation, among other technics, to enable continuous delivery of new features and software updates to the market. This increased speed has given rise to concerns over guaranteeing security at such a pace. To improve security in today’s fast-paced software development, DevSecOps was created as an extension of DevOps. This thesis focuses on the experiences and challenges of organizations and teams striving to implement DevSecOps. We first view our concepts through existing literature. Then, we conduct an online survey of 37 professionals from both security and development backgrounds. The results present the participants’ overall sentiments towards DevSecOps and the challenges they struggle with. We also investigate what kind of solutions have been tried to mitigate these issues and if these solutions have indeed worked.
  • Song, Xingchang (Helsingin yliopisto, 2022)
    Quantum networking is developing fast as an emerging research field. Distributing entangled qubits between any two locations in a quantum network is one of the goals of quantum networking, in which repeaters can be used to extend the length of entanglement. Although researchers focus extensively on problems inside one quantum network, further study on communication between quantum networks is necessary because the next possible evolution of quantum networking is the communication between two or more autonomous quantum networks. In this thesis, we adapted a time slotted model from the literature to study the inter quantum network routing problem. Quantum routing problem can be split into path selection and request scheduling. We focus on the latter considering the previous one received considerable interest in the literature. Five request scheduling policies are proposed to study the impact of preference for certain request types on entanglement generation rate. Experiments also demonstrate other factors should be considered in context of entanglement rate in communication between quantum networks, e.g., the number and distribution of requests and inter-network distance.
  • Rikandi, Eva; Mäntylä, Teemu; Lindgren, Maija; Kieseppä, Tuula; Suvisaari, Jaana; Raij, Tuukka T. (2022)
    Background: Psychotic disorders have been suggested to derive from dysfunctional integration of signaling between brain regions. Earlier studies have found several changes in functional network synchronization as well as altered network topology in patients with psychotic disorders. However, studies have used mainly resting-state that makes it more difficult to link functional alterations to any specific stimulus or experience. We set out to examine functional connectivity as well as graph (topological) measures and their association to symptoms in first-episode psychosis patients during movie viewing. Our goal was to understand whole-brain functional dynamics of complex naturalistic information processing in psychosis and changes in brain functional organization related to symptoms. Methods: 71 first-episode psychosis patients and 57 control subjects watched scenes from the movie Alice in Wonderland during 3 T fMRI. We compared functional connectivity and graph measures indicating integration, segregation and centrality between groups, and examined the association between topology and symptom scores in the patient group. Results: We identified a subnetwork with predominantly decreased links of functional connectivity in firstepisode psychosis patients. The subnetwork was mainly comprised of nodes of and links between the cinguloopercular, sensorimotor and default-mode networks. In topological measures, we observed between-group differences in properties of centrality. Conclusions: Functional brain networks are affected during naturalistic information processing already in the early stages of psychosis, concentrated in salience- and cognitive control-related hubs and subnetworks. Understanding these aberrant dynamics could add to better targeted cognitive and behavioral interventions in the early stages of psychotic disorders.
  • Blomgren, Roger Arne (Helsingin yliopisto, 2022)
    The cloud computing paradigm has risen, during the last 20 years, to the task of bringing powerful computational services to the masses. Centralizing the computer hardware to a few large data centers has brought large monetary savings, but at the cost of a greater geographical distance between the server and the client. As a new generation of thin clients have emerged, e.g. smartphones and IoT-devices, the larger latencies induced by these greater distances, can limit the applications that could benefit from using the vast resources available in cloud computing. Not long after the explosive growth of cloud computing, a new paradigm, edge computing has risen. Edge computing aims at bringing the resources generally found in cloud computing closer to the edge where many of the end-users, clients and data producers reside. In this thesis, I will present the edge computing concept as well as the technologies enabling it. Furthermore I will show a few edge computing concepts and architectures, including multi- access edge computing (MEC), Fog computing and intelligent containers (ICON). Finally, I will also present a new edge-orchestrator, the ICON Python Orchestrator (IPO), that enables intelligent containers to migrate closer to the users. The ICON Python orchestrator tests the feasibility of the ICON concept and provides per- formance measurements that can be compared to other contemporary edge computing im- plementations. In this thesis, I will present the IPO architecture design including challenges encountered during the implementation phase and solutions to specific problems. I will also show the testing and validation setup. By using the artificial testing and validation network, client migration speeds were measured using three different cases - redirection, cache hot ICON migration and cache cold ICON migration. While there is room for improvements, the migration speeds measured are on par with other edge computing implementations.
  • Podpecan, Vid; Ramšak, Živa; Gruden, Kristina; Toivonen, Hannu; Lavrac, Nada (2019)
  • Kalinen, Riku (Helsingin yliopisto, 2022)
    In this thesis, we cover blockchain applications in public administration. First we cover components related to blockchain technology. We cover especially issues related to management of digital evidence, electronic voting, and health data. In the beginning we cover hash functions and the general structure of the blockchain. Then we cover the cryptocurrency Bitcoin as an example of the blockchain technology. The management of the digital evidence is covered by evaluating three published studies. Likewise, the applications related to voting are evaluated in the light of three publications. Lastly, the management of health data is covered by evaluating three publications. For each of the three areas, we present an estimation of the applicability of the blockchain technology, in the form presented in the evaluated publications. Additionally, we cover a few other potential blockchain application areas. Finally, we present the general evaluation of blockchain applicability to the public administration and the conclusion.
  • Lindholm, Krista (Helsingin yliopisto, 2022)
    Nowadays a growing number of mobile devices are in use, and the internet connections with mobile devices are increasingly important for the everyday life of the global population. As a result, applications and use cases of different requirements including high throughput, reliability and continuous connection have emerged for mobile device connections. Multipath transport located on the transport layer of the TCP/IP model has been proposed as a solution for providing better throughput, reliability and smooth handovers for mobile devices. Multiple network interfaces are present in current mobile devices, and multipath protocols can utilize them to transfer data through multiple paths inside one connection. Multipath protocols of parallel functionality have been proposed over the years, and relevant protocol versions include multipath extensions for well-known transport layer protocols. The aim of the thesis is to provide an overview of three multipath protocols, MPTCP, CMT-SCTP and MPQUIC and the advantages and limitations they have when used for mobile connectivity through a literature review. First the challenges of multipath transport and requirements specific for mobile device usage are identified, and an overview of the protocols and their features are discussed. Then the protocols are compared in the context of the identified challenges and mobile device use. MPTCP is the only transport layer multipath protocol currently deployed and in use, while CMT-SCTP faces problems with deployability. MPQUIC shows promise for having initially comparable performance and deployability with MPTCP. Transport layer multipath protocols are currently not optimal for interactive applications and have suboptimal performance in heterogeneous network conditions. Conversely, they can provide a boost for throughput with data intensive applications and can be helpful for providing smoother handovers, but at the cost of higher energy consumption.
  • Viholainen, Tuomo (Helsingin yliopisto, 2020)
    The purpose of this thesis is to gain insight into the effects of different transaction and price setting methods and network structures in an intermediation network setting on profit allocation between their agents. The paper will be formulated as a literature review, and while every discussed intermediation model is not covered in detail, the goal is still to provide a clear outline on the topic. The focus is mostly in network models with exogenously determined connections between agents that restrict the trade, although search models, where the trade is restricted by randomizing the encounters between agents, are also discussed. The presented models are divided into three categories based on the restrictions placed on their intermediaries. First, we will look at models where intermediaries are not allowed to trade with each other. Next are models where intermediaries are allowed to trade with each other, causing intermediation chains to form. Lastly, we look at models where intermediaries are not exogenously separated from buyers. We will see that the results of intermediation network models are very sensitive to changes in the models' premises. Two largest contributors to the profit distribution between the agents in the models are the way the bargaining game between trading partners is modelled and how connections between agents in the model are restricted, which is directly tied to the restrictions on the trading partners of the intermediaries. The former on the other hand splits the models roughly into two categories, one utilizing a predetermined surplus split between the trade partners and the other using a strategic bargaining game. A pre-determined surplus split, depending on how even it is, usually favours agents further along the chain. The results of having a strategic bargaining game are largely dependent on positions of the agents in the network, where agents who can exploit competition between other agents can usually extract higher profits. In some models, the ability of intermediaries to make a positive profit is also tied to their necessity for the efficiency of the trade.
  • Godenhjelm, Sebastian; Johanson, Jan-Erik (2018)
    The delivery of public services in collaborative agency networks has given rise to an increasing use of projects in administering policy and service delivery. Projects are assumed to provide mechanisms by which flexibility can be achieved and innovative solutions produced. The aim of the article is to advance the understanding of collaboration between stakeholders and its effect on innovation. It analyses stakeholders' influence on the creation of project innovations in 275 European Union-funded projects by using content analyses and logistic regression analyses. The results show that projects can act as hubs where valuable information is produced but that few projects produce innovations. Project stakeholder network, knowledge dissemination and project influence, as well as sources of advice, play a role in predicting project innovations. The article concludes that the overly optimistic view of collaboration as a remedy for a lack of innovation in the public sector can be questioned. Points for practitioners The results of the article help practitioners to compose public sector development projects that foster innovation. The results suggest that it pays to include representatives of research and education facilities among project staff as their inclusion predicts the possibilities of achieving innovations. The empirical findings provide insight into project innovation and indicate which practices to avoid. It is suggested that when managed correctly, stakeholder inclusion has an effect on public sector project innovation.
  • Kuorikoski, Jaakko; Marchionni, Caterina (2014)
    We examine the diversity of strategies of modelling networks in (micro) economics and (analytical) sociology. Field-specific conceptions of what explaining (with) networks amounts to or systematic preference for certain kinds of explanatory factors are not sufficient to account for differences in modelling methodologies. We argue that network models in both sociology and economics are abstract models of network mechanisms and that differences in their modelling strategies derive to a large extent from field-specific conceptions of the way in which a good model should be a general one. Whereas the economics models aim at unification, the sociological models aim at a set of mechanism schemas that are extrapolatable to the extent that the underlying psychological mechanisms are general. These conceptions of generality induce specific biases in mechanistic explanation and are related to different views of when knowledge from different fields should be seen as relevant. (C) 2014 Elsevier Ltd. All rights reserved.