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ZyConChain: A scalable blockchain for general applications

Nasrin Sohrabi, Zahir Tari
2020 IEEE Access  
Blockchain's popularity has seen a historic rise over the last decade. However, existing blockchain systems have a major issue with scalability, which has become one of the main obstacles in technology's adoption in mainstream. There have been several attempts to address this limitation by identifying Blockchain's scalability/performance bottlenecks (e.g. those mainly related to consensus algorithms), and thus proposed different solutions (e.g., new consensus protocols) to address such
more » ... ns. Other works applied sharding to tackle the issue. All solutions however have mainly focused on Cryptocurrency applications, and thus addressing the scalability of blockchain systems for general applications remains a concern. This work proposes a scalable blockchain protocol for general applications (i.e., not restricted to Cryptocurrencies). To improve the two major factors affecting transaction scalability, namely throughput and latency, we needed to modify both the blockchain structure as well as the block generation process. ZyConChain, the proposed Blockchain system, introduces three types of blocks that form three separate chains: parentBlock, sideBlock and state block. These blocks are generated based on different consensus algorithms, as each algorithm has specific properties that make it suitable for each type of block. To improve the overall performance, ZyConChain generates sideBlocks (that carry transactions) at a high rate and keep them in a pool. To generate parentBlock, miners, instead of packing transactions into a block as they do in conventional blockchains, pack sideBlocks into a parentBlock. SideBlocks are generated based on an adapted Zyzzyva consensus protocol, with O(log n) complexity. This has reduced the final consensus complexity per transaction, in comparison to previous work. To enable the protocol to scale out with the increase in the number of nodes, ZyConChain applied sharding technique. Parallel state chains have also been introduced to address cross-shard transactions.
doi:10.1109/access.2020.3020319 fatcat:nviss7ht4rahtffo37z6ygowhm

A Case for Peering of Content Delivery Networks [article]

Rajkumar Buyya, Al-Mukaddim Khan Pathan, James Broberg, Zahir Tari
2006 arXiv   pre-print
The proliferation of Content Delivery Networks (CDN) reveals that existing content networks are owned and operated by individual companies. As a consequence, closed delivery networks are evolved which do not cooperate with other CDNs and in practice, islands of CDNs are formed. Moreover, the logical separation between contents and services in this context results in two content networking domains. But present trends in content networks and content networking capabilities give rise to the
more » ... t in interconnecting content networks. Finding ways for distinct content networks to coordinate and cooperate with other content networks is necessary for better overall service. In addition to that, meeting the QoS requirements of users according to the negotiated Service Level Agreements between the user and the content network is a burning issue in this perspective. In this article, we present an open, scalable and Service-Oriented Architecture based system to assist the creation of open Content and Service Delivery Networks (CSDN) that scale and support sharing of resources with other CSDNs.
arXiv:cs/0609027v1 fatcat:x35fngvb2zdipgktyvuvl4ia7q

Supporting User Mobility through Cache Relocation

Kwong Yuen Lai, Zahir Tari, Peter Bertok
2005 Mobile Information Systems  
Traffic and access delay can be reduced in a mobile network by caching data objects at network nodes near the clients. Traditional caching techniques, however, are unsuitable in this environment because they do not account for the changing location of the users. To deal with this problem, cache relocation techniques can be applied to dynamically relocate data objects so they remain close to the moving clients. Existing relocation techniques rely heavily on path prediction. Unfortunately, the
more » ... ccuracy of path prediction can lead to high relocation overhead and poor response time. This paper presents an analytical study of the effects of client mobility on network cache performance. Two new cache relocation techniques are proposed to deal with the issue of poor path prediction and reduce the overhead of existing cache relocation schemes. The first technique, 2PR, compensates for poor path prediction by temporarily moving data objects to a common parent node prior to a handover. Objects are moved to the correct destination once the client's new location has been confirmed. The second technique, ROLP, reduces the traffic overhead associated with cache relocation by ensuring duplicate objects are not relocated and relocation of objects are performed only from the nearest node to the destination. Test results show that 2PR reduces the query delay experienced by mobile clients by 60 to 83% after handovers, while ROLP reduces the overhead of cache relocation by between 33 to 65% compared to existing schemes.
doi:10.1155/2005/513531 fatcat:e7u276scifdkjhzkgvricqrgje

Une Technique de Validation de Protocoles basée sur une Exploration avec Retour arrière des Automates Complexes

Farah Zoubeyr, Abdelkamel Tari, Zahir Tari
2009 Conférence Internationale sur l'Informatique et ses Applications  
L'analyse d'accessibilité est généralement l'approche utilisée pour la validation des protocoles. Le problème posé par l'application de cette technique est celui de l'explosion combinatoire. Dans cet article, nous proposons une nouvelle technique de validation de protocoles appelée Reverse Leaping Reachability Analysis (RLRA). Au lieu de parcourir tout l'espace des états de protocole, notre approche explore seulement un ensemble réduit de cet espace afin de détecter les erreurs de type
more » ... age. Les résultats d'expérimentation ont montré que notre technique permet de réduire la taille du graphe d'accessibilité de protocole est donc réduire le problème de l'explosion combinatoire. Mots-clé: validation de protocoles, automate à états complexes, interblocage
dblp:conf/ciia/ZoubeyrTT09 fatcat:xlt2zjtpmrb5vg4ezoplw5xd2q

Editorial: Sustainable Information Security and Forensic Computing

Paul D. Yoo, Zahir Tari
2021 IEEE Transactions on Sustainable Computing  
Zahir Tari is with the School of Science, Royal Melbourne Institute of Technology, Melbourne 3001, Australia. E-mail:  ...  Zahir Tari (Senior Member, IEEE) received the bachelor's degree in mathematics from the University of Algiers, USTHB, Algeria, in 1984, the MSc degree in operational research from the University of Grenoble  ... 
doi:10.1109/tsusc.2020.3039652 fatcat:zcdse2ngkrhdjg4m4qajg5loti

Social Media Identity Deception Detection: A Survey [article]

Ahmed Alharbi, Hai Dong, Xun Yi, Zahir Tari, Ibrahim Khalil
2021 arXiv   pre-print
Social media have been growing rapidly and become essential elements of many people's lives. Meanwhile, social media have also come to be a popular source for identity deception. Many social media identity deception cases have arisen over the past few years. Recent studies have been conducted to prevent and detect identity deception. This survey analyses various identity deception attacks, which can be categorized into fake profile, identity theft and identity cloning. This survey provides a
more » ... ailed review of social media identity deception detection techniques. It also identifies primary research challenges and issues in the existing detection techniques. This article is expected to benefit both researchers and social media providers.
arXiv:2103.04673v1 fatcat:zf6xcn3pafcgfbxmoewc3yhhpi

MetaCDN: Harnessing Storage Clouds for High Performance Content Delivery [chapter]

James Broberg, Zahir Tari
2008 Lecture Notes in Computer Science  
Content delivery networks (CDNs) such as Akamai and Mirror Image place web server clusters in numerous geographical locations to improve the responsiveness and locality of the content it hosts for end-users. However, their services are priced out of reach for all but the largest enterprise customers. An alternative approach to content delivery could be achieved by leveraging existing infrastructure provided by 'Storage Cloud' providers, who offer internet accessible data storage and delivery at
more » ... a fraction of the cost. In this paper, we introduce MetaCDN, a system that exploits 'Storage Cloud' resources, creating an integrated overlay network that provides a low cost, high performance CDN for content creators. MetaCDN removes the complexity of dealing with multiple storage providers, by intelligently matching and placing users' content onto one or many storage providers based on their quality of service, coverage and budget preferences. MetaCDN makes it trivial for content creators and consumers to harness the performance and coverage of numerous 'Storage Clouds' by providing a single unified namespace that makes it easy to integrate into origin websites, and is transparent for end-users. We then demonstrate the utility of this new approach to content delivery by showing that the participating 'Storage Clouds' used by MetaCDN provide high performance (in terms of throughput and response time) and reliable content delivery for content consumers, whilst the MetaCDN system itself introduces minimal overhead compared to using these 'Storage Clouds' directly. Crown
doi:10.1007/978-3-540-89652-4_67 fatcat:y2ror46ln5g2hlc4st2vztqpgq

A High-Level Functional Matching for Semantic Web Services [chapter]

Islam Elgedawy, Zahir Tari, James A. Thom
2005 Lecture Notes in Computer Science  
Existing service matching techniques such as keyword-based and ontology-based, do not guarantee the correctness of the matching results (i.e. do not guarantee fulfilling user goals). This paper deals with this problem by capturing the high-level functional aspects (namely goals, contexts, and expected external behaviors) for both web services and users in a machine-processable format, then matching these aspects using the proposed functional substitutability matching scheme (FSMS). Based on
more » ... , this paper describes a direct matching technique in which a user request is examined against one service description at a time, such that web services match users requests when they have substitutable goals, contexts and expected external behaviors. The substitutability semantics between the elements of application domains are captured via the proposed substitutability graphs, which are used during the matching process to mediate between users requests and web services descriptions. Simulation results show that the proposed matching approach succeeds in retrieving only the correct answers, while keywordbased and ontology-based retrieval techniques could not eliminate the appearance of false negatives and false positives.
doi:10.1007/11596141_10 fatcat:jlp5ao2f45bn3jjqdw76z4kd5i

Security, Privacy and Interoperability in Heterogeneous Systems [chapter]

Jian Zhong, Peter Bertok, Zahir Tari
2010 IFIP Advances in Information and Communication Technology  
Partners in VOs can share large amount of data. Sharing of individual data items is straightforward, but sharing components of complex data structures stored in heterogeneous systems is often a challenge. Sharing is typically governed by rules and policies that need to be translated into access right / privilege control and data granularity control. Simultaneous control of privileges and data granularity across different organizations is a difficult task, and most traditional approaches, such
more » ... le-based access control can become prohibitively complex in such scenarios. We propose a scheme for concurrent control of subject privileges and object granularity. It includes participants, duties and operations, and generates security labels that describe security features. To facilitate interoperability between heterogeneous systems, the labels also carry information about the data model, including dynamic hierarchy description. The model supports subject activity control over objects with variable data access granularity. It encompasses the advantages of existing role based and label based control. First, an abstract subject privilege control model is built, and the mathematical relationships between privileges in the label system are defined. Second, an abstract object dynamic granularity model is produced and the mathematical relationship between granularity levels is established. At last, a pair-wise privacy label system is provided as an integrated information protection mechanism, where relationships between subject activities and privileges are described for actual access control. A formal verification of the proposed method has also been performed.
doi:10.1007/978-3-642-15961-9_84 fatcat:qgoirb62a5hadpmhuqxpdw2uzy

Matching independent global constraints for composite web services

Nalaka Gooneratne, Zahir Tari
2008 Proceeding of the 17th international conference on World Wide Web - WWW '08  
Service discovery employs matching techniques to select services by comparing their descriptions against user constraints. Semantic-based matching approaches achieve higher recall than syntactic-based ones (as they employ ontological reasoning mechanisms to match syntactically heterogeneous descriptions). However, semantic-based approaches still have problems (e.g. lack of scalability as an exhaustive search is often performed to located services conforming to constraints). This paper proposes
more » ... wo approaches that deal with the problem of scalability/performance for composite service location. First, services are indexed based on the values they assign to their restricted attributes (the attributes restricted by a given constraint). Then, services that assign "conforming values" to those attributes are combined to form composite services. The first proposed approach extends a local optimisation technique to perform the latter, since identifying such values is NP-hard. However, this approach returns false negatives since the local optimisation technique does not consider all the values. Hence, a second approach that derives conforming values using domain rules is defined. The used rules are returned with each composite service so that a user can understand the context in which it is retrieved. Results obtained from the experiments that varied the number of available services demonstrate that the performance of the local optimisation-based approach is 76% better than existing semantic-based approaches and recall is 98% higher than syntactic-based approaches.
doi:10.1145/1367497.1367601 dblp:conf/www/GooneratneT08 fatcat:yjwk66nmrjaypeip73euzeb7q4

A Scalable and Robust QoS Architecture for WiFi P2P Networks [chapter]

Sathish Rajasekhar, Ibrahim Khalil, Zahir Tari
2004 Lecture Notes in Computer Science  
Peer-to-Peer (P2P) resource sharing between mobile devices in Wireless Fidelity (WiFi) hot-spots environment is a challenging problem. This would require an infrastructure with automated process for registering new mobile devices, as well as authentication and authorisation of existing devices. Further, issues such as maintenance, and updating the state information, as devices join and leave the P2P network; optimising route selection and protection of the existing mobile devices from malicious
more » ... devices are crucial. To address these issues, we propose a generalised architecture and a dynamic protocol for effective and optimal file transfer between devices. We use quality of service (QoS) capacity-tohop count ratio, routing algorithm, to find an optimal mobile device for a service request. The goal and contribution of this paper is to provide a scalable, robust and reliable architecture incorporating QoS; effective and optimal communication for P2P networks in a cooperative manner.
doi:10.1007/978-3-540-30555-2_9 fatcat:yxnmo7ezxngpnfd2zv2wgjnijy

Optimizing the Transition Waste in Coded Elastic Computing [article]

Hoang Dau and Ryan Gabrys and Yu-Chih Huang and Chen Feng and Quang-Hung Luu and Eidah Alzahrani and Zahir Tari
2019 arXiv   pre-print
Dau, Eidah Alzahrani, and Zahir Tari are with the School of Science, RMIT University. Emails: {sonhoang.dau, eidah.alzahrani, zahir.tari}  ... 
arXiv:1910.00796v1 fatcat:4mvz3kdyyzcgxgz4rjtfka3sd4

A Case for Peering of Content Delivery Networks

Rajkumar Buyya, Al-mukaddim Pathan, James Broberg, Zahir Tari
2006 IEEE Distributed Systems Online  
The proliferation of Content Delivery Networks (CDN) reveals that existing content networks are owned and operated by individual companies. As a consequence, closed delivery networks are evolved which do not cooperate with other CDNs and in practice, islands of CDNs are formed. Moreover, the logical separation between contents and services in this context results in two content networking domains. But present trends in content networks and content networking capabilities give rise to the interest in interconnecting content networks.
doi:10.1109/mdso.2006.57 fatcat:2wtxnoirtrcu7kup5tz7jegfee

Pair-Wise Privilege Control for Cross-Domain Private Data Sharing

Jian Zhong, Peter Bertók, Zahir Tari
2010 Pacific Asia Conference on Information Systems  
Enterprise-scale organizations have large numbers of internal and external users, with different privilege requirements spanning across many resources. The dynamic nature of modern organizations demands that they efficiently and securely provision and deactivate data privileges to reflect rapidly changing user responsibilities. Previous approaches to consolidated user provisioning have focused on constructing and maintaining a formal model of user privileges, in order to predict what role/roles
more » ... should be assigned to any given user, based on user classification and other user attributes. In realworld deployments, formal models have not scaled well, because many users are unique and consequently there is no leverage to be gained by grouping them into roles. This paper proposes a scheme for dual control of user granular privilege and dynamic granular data access. The framework includes a correlated privilege control model and a label-based dynamic access level process. The method supports user activity control over cross-domain objects with variable data access granularity. It encompasses the advantages of existing role based and label based control, while reducing computation complexity and storage requirements. The proposed method has been formally verified and implemented in JAVA.
dblp:conf/pacis/ZhongBT10 fatcat:yqibchzz4bfnvfmcjzlfslsk6u

A Variable Cache Consistency Protocol for Mobile Systems Using Time Locks [chapter]

Abhinav Vora, Zahir Tari, Peter Bertok
2003 Lecture Notes in Computer Science  
By locally caching data, mobile hosts can operate while disconnected from the central server, however, consistency of data becomes more difficult to maintain. In this paper we propose a protocol that makes a distinction between two classes of consistency: weak and strict, and treats them differently. Strict consistency is used for data that needs to be consistent all the time, whereas weak consistency is for cases when stale data can be tolerated in the form of requiring only specific updates.
more » ... onsistency is maintained by using strict read/write and permissive read/write time locks that enable data sharing for a fixed time period and support concurrency control. A Notification Protocol is also proposed, which enables propagating updates to clients and retrieving data from clients in a consistent manner. Performance tests have demonstrated that switching from strict to weak consistency can reduce the number of aborts (due to no access to a lock or conflicting operations) by almost half, even with high read-write sharing.
doi:10.1007/978-3-540-40010-3_14 fatcat:2pt3n43wwjawtk4hiu3yknc6dy
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