2,537 research outputs found
Genet: A Quickly Scalable Fat-Tree Overlay for Personal Volunteer Computing using WebRTC
WebRTC enables browsers to exchange data directly but the number of possible
concurrent connections to a single source is limited. We overcome the
limitation by organizing participants in a fat-tree overlay: when the maximum
number of connections of a tree node is reached, the new participants connect
to the node's children. Our design quickly scales when a large number of
participants join in a short amount of time, by relying on a novel scheme that
only requires local information to route connection messages: the destination
is derived from the hash value of the combined identifiers of the message's
source and of the node that is holding the message. The scheme provides
deterministic routing of a sequence of connection messages from a single source
and probabilistic balancing of newer connections among the leaves. We show that
this design puts at least 83% of nodes at the same depth as a deterministic
algorithm, can connect a thousand browser windows in 21-55 seconds in a local
network, and can be deployed for volunteer computing to tap into 320 cores in
less than 30 seconds on a local network to increase the total throughput on the
Collatz application by two orders of magnitude compared to a single core
Flexi-WVSNP-DASH: A Wireless Video Sensor Network Platform for the Internet of Things
abstract: Video capture, storage, and distribution in wireless video sensor networks
(WVSNs) critically depends on the resources of the nodes forming the sensor
networks. In the era of big data, Internet of Things (IoT), and distributed
demand and solutions, there is a need for multi-dimensional data to be part of
the Sensor Network data that is easily accessible and consumable by humanity as
well as machinery. Images and video are expected to become as ubiquitous as is
the scalar data in traditional sensor networks. The inception of video-streaming
over the Internet, heralded a relentless research for effective ways of
distributing video in a scalable and cost effective way. There has been novel
implementation attempts across several network layers. Due to the inherent
complications of backward compatibility and need for standardization across
network layers, there has been a refocused attention to address most of the
video distribution over the application layer. As a result, a few video
streaming solutions over the Hypertext Transfer Protocol (HTTP) have been
proposed. Most notable are Apple’s HTTP Live Streaming (HLS) and the Motion
Picture Experts Groups Dynamic Adaptive Streaming over HTTP (MPEG-DASH). These
frameworks, do not address the typical and future WVSN use cases. A highly
flexible Wireless Video Sensor Network Platform and compatible DASH (WVSNP-DASH)
are introduced. The platform's goal is to usher video as a data element that
can be integrated into traditional and non-Internet networks. A low cost,
scalable node is built from the ground up to be fully compatible with the
Internet of Things Machine to Machine (M2M) concept, as well as the ability to
be easily re-targeted to new applications in a short time. Flexi-WVSNP design
includes a multi-radio node, a middle-ware for sensor operation and
communication, a cross platform client facing data retriever/player framework,
scalable security as well as a cohesive but decoupled hardware and software
design.Dissertation/ThesisDoctoral Dissertation Electrical Engineering 201
Keeping Authorities "Honest or Bust" with Decentralized Witness Cosigning
The secret keys of critical network authorities - such as time, name,
certificate, and software update services - represent high-value targets for
hackers, criminals, and spy agencies wishing to use these keys secretly to
compromise other hosts. To protect authorities and their clients proactively
from undetected exploits and misuse, we introduce CoSi, a scalable witness
cosigning protocol ensuring that every authoritative statement is validated and
publicly logged by a diverse group of witnesses before any client will accept
it. A statement S collectively signed by W witnesses assures clients that S has
been seen, and not immediately found erroneous, by those W observers. Even if S
is compromised in a fashion not readily detectable by the witnesses, CoSi still
guarantees S's exposure to public scrutiny, forcing secrecy-minded attackers to
risk that the compromise will soon be detected by one of the W witnesses.
Because clients can verify collective signatures efficiently without
communication, CoSi protects clients' privacy, and offers the first
transparency mechanism effective against persistent man-in-the-middle attackers
who control a victim's Internet access, the authority's secret key, and several
witnesses' secret keys. CoSi builds on existing cryptographic multisignature
methods, scaling them to support thousands of witnesses via signature
aggregation over efficient communication trees. A working prototype
demonstrates CoSi in the context of timestamping and logging authorities,
enabling groups of over 8,000 distributed witnesses to cosign authoritative
statements in under two seconds.Comment: 20 pages, 7 figure
CYCLOSA: Decentralizing Private Web Search Through SGX-Based Browser Extensions
By regularly querying Web search engines, users (unconsciously) disclose
large amounts of their personal data as part of their search queries, among
which some might reveal sensitive information (e.g. health issues, sexual,
political or religious preferences). Several solutions exist to allow users
querying search engines while improving privacy protection. However, these
solutions suffer from a number of limitations: some are subject to user
re-identification attacks, while others lack scalability or are unable to
provide accurate results. This paper presents CYCLOSA, a secure, scalable and
accurate private Web search solution. CYCLOSA improves security by relying on
trusted execution environments (TEEs) as provided by Intel SGX. Further,
CYCLOSA proposes a novel adaptive privacy protection solution that reduces the
risk of user re- identification. CYCLOSA sends fake queries to the search
engine and dynamically adapts their count according to the sensitivity of the
user query. In addition, CYCLOSA meets scalability as it is fully
decentralized, spreading the load for distributing fake queries among other
nodes. Finally, CYCLOSA achieves accuracy of Web search as it handles the real
query and the fake queries separately, in contrast to other existing solutions
that mix fake and real query results
Towards practicalization of blockchain-based decentralized applications
Blockchain can be defined as an immutable ledger for recording transactions, maintained in a distributed network of mutually untrusting peers. Blockchain technology has been widely applied to various fields beyond its initial usage of cryptocurrency. However, blockchain itself is insufficient to meet all the desired security or efficiency requirements for diversified application scenarios. This dissertation focuses on two core functionalities that blockchain provides, i.e., robust storage and reliable computation. Three concrete application scenarios including Internet of Things (IoT), cybersecurity management (CSM), and peer-to-peer (P2P) content delivery network (CDN) are utilized to elaborate the general design principles for these two main functionalities. Among them, the IoT and CSM applications involve the design of blockchain-based robust storage and management while the P2P CDN requires reliable computation. Such general design principles derived from disparate application scenarios have the potential to realize practicalization of many other blockchain-enabled decentralized applications.
In the IoT application, blockchain-based decentralized data management is capable of handling faulty nodes, as designed in the cybersecurity application. But an important issue lies in the interaction between external network and blockchain network, i.e., external clients must rely on a relay node to communicate with the full nodes in the blockchain. Compromization of such relay nodes may result in a security breach and even a blockage of IoT sensors from the network. Therefore, a censorship-resistant blockchain-based decentralized IoT management system is proposed. Experimental results from proof-of-concept implementation and deployment in a real distributed environment show the feasibility and effectiveness in achieving censorship resistance.
The CSM application incorporates blockchain to provide robust storage of historical cybersecurity data so that with a certain level of cyber intelligence, a defender can determine if a network has been compromised and to what extent. The CSM functions can be categorized into three classes: Network-centric (N-CSM), Tools-centric (T-CSM) and Application-centric (A-CSM). The cyber intelligence identifies new attackers, victims, or defense capabilities. Moreover, a decentralized storage network (DSN) is integrated to reduce on-chain storage costs without undermining its robustness. Experiments with the prototype implementation and real-world cyber datasets show that the blockchain-based CSM solution is effective and efficient.
The P2P CDN application explores and utilizes the functionality of reliable computation that blockchain empowers. Particularly, P2P CDN is promising to provide benefits including cost-saving and scalable peak-demand handling compared with centralized CDNs. However, reliable P2P delivery requires proper enforcement of delivery fairness. Unfortunately, most existing studies on delivery fairness are based on non-cooperative game-theoretic assumptions that are arguably unrealistic in the ad-hoc P2P setting. To address this issue, an expressive security requirement for desired fair P2P content delivery is defined and two efficient approaches based on blockchain for P2P downloading and P2P streaming are proposed. The proposed system guarantees the fairness for each party even when all others collude to arbitrarily misbehave and achieves asymptotically optimal on-chain costs and optimal delivery communication
Distributed D3: A web-based distributed data visualisation framework for Big Data
The influx of Big Data has created an ever-growing need for analytic tools targeting towards the acquisition of insights and knowledge from large datasets. Visual perception as a fundamental tool used by humans to retrieve information from the outside world around us has its unique ability to distinguish patterns pre-attentively. Visual analytics via data visualisations is therefore a very powerful tool and has become ever more important in this era. Data-Driven Documents (D3.js) is a versatile and popular web-based data visualisation library that has tended to be the standard toolkit for visualising data in recent years. However, the library is technically inherent and limited in capability by the single thread model of a single browser window in a single machine, and therefore not able to deal with large datasets. The main objective of this thesis is to overcome this limitation and address possible challenges by developing the Distributed D3 framework that employs distributed mechanism to enable the possibility of delivering web-based visualisations for large-scale data, which also allows to effectively utilise the graphical computational resources of the modern visualisation environments. As a result, the first contribution is that the integrated version of Distributed D3 framework has been developed for the Data Observatory. The work proves the concept of Distributed D3 is feasible in reality and also enables developers to collaborate on large-scale data visualisations by using it on the Data Observatory. The second contribution is that the Distributed D3 has been optimised by investigating the potential bottlenecks for large-scale data visualisation applications. The work finds the key performance bottlenecks of the framework and shows an improvement of the overall performance by 35.7% after optimisations, which improves the scalability and usability of Distributed D3 for large-scale data visualisation applications. The third contribution is that the generic version of Distributed D3 framework has been developed for the customised environments. The work improves the usability and flexibility of the framework and makes it ready to be published in the open-source community for further improvements and usages.Open Acces
Survey of Models and Architectures to Ensure Linked Data Access
Mobile Access to the Web of Data is currently a real challenge in developing countries, mainly characterized by limited Internet connectivity and high penetration of mobile devices with the limited resources (such as cache and memory). In this paper, we survey and compare proposed solutions (such as models and architectures) that could contribute to solving this problem of mobile access to the Web of Data with intermittent Internet access. These solutions are discussed in relation to the underlying network architectures and data models considered. We present a conceptual study of peer-to-peer solutions based on gossip protocols dedicated to design the connected overlay networks. In addition, we provide a detailed analysis of client-server and data replication systems generally designed to ensure the local availability of data on the system. We conclude with some recommendations to achieve a connected architecture that provides mobile contributors with local access to the Web of data
U-DiVE: Design and evaluation of a distributed photorealistic virtual reality environment
This dissertation presents a framework that allows low-cost devices to visualize and
interact with photorealistic scenes. To accomplish this task, the framework makes use of
Unity’s high-definition rendering pipeline, which has a proprietary Ray Tracing algorithm,
and Unity’s streaming package, which allows an application to be streamed within its
editor. The framework allows the composition of a realistic scene using a Ray Tracing
algorithm, and a virtual reality camera with barrel shaders, to correct the lens distortion
needed for the use on an inexpensive cardboard. It also includes a method to collect
the mobile device’s spatial orientation through a web browser to control the user’s view,
delivered via WebRTC. The proposed framework can produce low-latency, realistic and
immersive environments to be accessed through low-cost HMDs and mobile devices. To
evaluate the structure, this work includes the verification of the frame rate achieved by the
server and mobile device, which should be higher than 30 FPS for a smooth experience. In
addition, it discusses whether the overall quality of experience is acceptable by evaluating
the delay of image delivery from the server up to the mobile device, in face of user’s
movement. Our tests showed that the framework reaches a mean latency around 177 (ms)
with household Wi-Fi equipment and a maximum latency variation of 77.9 (ms), among
the 8 scenes tested.Esta dissertação apresenta um framework que permite que dispositivos de baixo
custo visualizem e interajam com cenas fotorrealÃsticas. Para realizar essa tarefa, o
framework faz uso do pipeline de renderização de alta definição do Unity, que tem um
algoritmo de rastreamento de raio proprietário, e o pacote de streaming do Unity, que
permite o streaming de um aplicativo em seu editor. O framework permite a composição
de uma cena realista usando um algoritmo de Ray Tracing, e uma câmera de realidade
virtual com shaders de barril, para corrigir a distorção da lente necessária para usar um
cardboard de baixo custo. Inclui também um método para coletar a orientação espacial
do dispositivo móvel por meio de um navegador Web para controlar a visão do usuário,
entregue via WebRTC. O framework proposto pode produzir ambientes de baixa latência,
realistas e imersivos para serem acessados por meio de HMDs e dispositivos móveis de
baixo custo. Para avaliar a estrutura, este trabalho considera a verificação da taxa de
quadros alcançada pelo servidor e pelo dispositivo móvel, que deve ser superior a 30 FPS
para uma experiência fluida. Além disso, discute se a qualidade geral da experiência é
aceitável, ao avaliar o atraso da entrega das imagens desde o servidor até o dispositivo
móvel, em face da movimentação do usuário. Nossos testes mostraram que o framework
atinge uma latência média em torno dos 177 (ms) com equipamentos wi-fi de uso doméstico
e uma variação máxima das latências igual a 77.9 (ms), entre as 8 cenas testadas
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