Imperial College London

ProfessorWilliamKnottenbelt

Faculty of EngineeringDepartment of Computing

Professor of Applied Quantitative Analysis
 
 
 
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Contact

 

+44 (0)20 7594 8331w.knottenbelt Website

 
 
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Location

 

E363ACE ExtensionSouth Kensington Campus

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Summary

 

Publications

Publication Type
Year
to

180 results found

Koutsouri A, Poli F, Alfieri E, Petch M, Distaso W, Knottenbelt Wet al., Balancing Cryptoassets and Gold: A Weighted-Risk-Contribution Index for the Alternative Asset Space, 1st International Conference on Mathematical Research for Blockchain Economy

CONFERENCE PAPER

Seakhoa-King S, Alvarez NT, Balaji P, Knottenbelt WJet al., 2019, Revenue-driven scheduling in drone delivery networks with time-sensitive service level agreements, Pages: 183-186

© 2019 Association for Computing Machinery. Drones are widely anticipated to be used for commercial service deliveries, with potential to contribute to economic growth, estimated at £42 billion in the UK alone by the year 2030. Alongside air traffic control algorithms, drone-based courier services will have to make intelligent decisions about how to deploy their limited resources in order to increase profits. This paper presents a new scheduling algorithm for optimising the revenue of a drone courier service provider in these highly utilised time-sensitive service delivery systems. The first input to the algorithm is a monotonically decreasing value over time function which describes the service level agreement between the service provider and its customers. The second is the anticipated drone flight-time duration distribution. Our results show that the newly-developed scheduling algorithm, Least Lost Value, inspired by concepts for real-time computational workload processing, is able to successfully route drones to extract increased revenue to the service provider in comparison with two widely-used scheduling algorithms: First Come First Served and Shortest Job First, in terms of realised revenue.

CONFERENCE PAPER

Werner SM, Zamyatin A, Pritz PJ, Knottenbelt WJet al., 2019, Uncle traps: Harvesting rewards in a queue-based ethereum mining pool, Pages: 127-134

© 2019 Association for Computing Machinery. Mining pools in Proof-of-Work cryptocurrencies allow miners to pool their computational resources as a means of reducing payout variance. In Ethereum, uncle blocks are valid Proof-of-Work solutions which do not become the head of the blockchain, yet yield rewards if later referenced by main chain blocks. Mining pool operators are faced with the non-trivial task of fairly distributing rewards for both block types among pool participants. Inspired by empirical observations, we formally reconstruct a Sybil attack exploiting the uncle block distribution policy in a queue-based mining pool. To ensure fairness of the queue-based payout scheme, we propose a mitigation. We examine the effectiveness of the attack strategy under the current and the proposed policy via a discrete-event simulation. Our findings show that the observed attack can indeed be obviated by altering the current reward scheme.

CONFERENCE PAPER

Zamyatin A, Harz D, Lind J, Panayiotou P, Gervais A, Knottenbelt Wet al., XCLAIM: decentralized, interoperable, cryptocurrency-backed assets, 40th IEEE Symposium on Security and Privacy (IEEE S&P 2019), Publisher: IEEE

Building trustless cross-blockchain trading protocols is challenging. Centralized exchanges thus remain the preferred route to execute transfers across blockchains. However, these services require trust and therefore undermine the very nature of the blockchains on which they operate. To overcome this,several decentralized exchanges have recently emerged which offer support for atomic cross-chain swaps (ACCS). ACCS enable the trustless exchange of cryptocurrencies across blockchains,and are the only known mechanism to do so. However, ACCS suffer significant limitations; they are slow, inefficient and costly,meaning that they are rarely used in practice.We present XCLAIM: the first generic framework for achieving trustless and efficient cross-chain exchanges using cryptocurrency-backed assets(CBAs). XCLAIM offers protocols for issuing,transferring, swapping and redeeming CBAs securely in anon-interactive manner on existing blockchains. We instanti-ate XCLAIM between Bitcoin and Ethereum and evaluate our implementation; it costs less than USD 0.50 to issue an arbi-trary amount of Bitcoin-backed tokens on Ethereum. We show XCLAIMis not only faster, but also significantly cheaper than atomic cross-chain swaps. Finally, XCLAIMis compatible with the majority of existing blockchains without modification, and enables several novel cryptocurrency applications, such as cross-chain payment channels and efficient multi-party swaps

CONFERENCE PAPER

Wu H, Knottenbelt W, Wolter K, 2019, An efficient application partitioning algorithm in mobile environments, IEEE Transactions on Parallel and Distributed Systems, ISSN: 1045-9219

Application partitioning that splits the executions into local and remote parts, plays a critical role in high-performance mobile offloading systems. Mobile devices can obtain the most benefit from Mobile Cloud Computing (MCC) or Mobile Edge Computing (MEC) through optimal partitioning. Due to unstable resources at the wireless network (network disconnection, bandwidth fluctuation, network latency, etc.) and at the service nodes (different speeds of mobile devices and cloud/edge servers, memory, etc.), static partitioning solutions with fixed bandwidth and speed assumptions are unsuitable for offloading systems. In this paper, we study how to dynamically partition a given application into local and remote parts effectively, while keeping the total cost as small as possible. For general tasks (i.e., arbitrary topological consumption graphs), we propose a Min-Cost Offloading Partitioning (MCOP) algorithm that aims at finding the optimal partitioning plan (determine which portions of the application to run on mobile devices and which portions on cloud/edge servers) under different cost models and mobile environments. Simulation results show that the MCOP algorithm provides a stable method with low time complexity which significantly reduces execution time and energy consumption by optimally distributing tasks between mobile devices and servers, besides it well adapts to mobile environmental changes.

JOURNAL ARTICLE

Zamyatin A, Stifter N, Judmayer A, Schindler P, Weippl E, Knottenbelt WJet al., 2019, A wild velvet fork appears! Inclusive blockchain protocol changes in practice: (Short Paper), Pages: 31-42, ISSN: 0302-9743

© International Financial Cryptography Association 2019. The loosely defined terms hard fork and soft fork have established themselves as descriptors of different classes of upgrade mechanisms for the underlying consensus rules of (proof-of-work) blockchains. Recently, a novel approach termed velvet fork, which expands upon the concept of a soft fork, was outlined in [22]. Specifically, velvet forks intend to avoid the possibility of disagreement by a change of rules through rendering modifications to the protocol backward compatible and inclusive to legacy blocks. We present an overview and definitions of these different upgrade mechanisms and outline their relationships. Hereby, we expose examples where velvet forks or similar constructions are already actively employed in Bitcoin and other cryptocurrencies. Furthermore, we expand upon the concept of velvet forks by proposing possible applications and discuss potentially arising security implications.

CONFERENCE PAPER

Zamyatin A, Harz D, Lind J, Panayiotou P, Arthur G, Knottenbelt Wet al., 2018, XCLAIM: A Framework for Blockchain Interoperability

Building trustless cross-blockchain trading protocols is challenging. Centralized exchanges thus remain the preferred route to executing transfers across blockchains. However, these services require trust and therefore undermine the very nature of the blockchains on which they operate. To overcome this, several decentralized exchanges have recently emerged which offer support for atomic cross-chain swaps (ACCS). ACCS enable the trustless exchange of cryptocurrencies across blockchains, and are the only known mechanism to do so. However, ACCS suffer significant limitations; they are slow, inefficient and costly, meaning that they are rarely used in practice.We present XCLAIM: the first generic framework for achieving trustless and efficient cross-chain exchanges using cryptocurrency-backed assets (CbAs). XCLAIM offers protocols for issuing, transferring, swapping and redeeming CbAs securely in a non-interactive manner on existing blockchains. We instantiate XCLAIM between Bitcoin and Ethereum and evaluate our implementation; it costs less than USD 0.50 to issue an arbitrary amount of Bitcoin-backed tokens on Ethereum. We show XCLAIM is not only faster, but also significantly cheaper than atomic cross-chain swaps. Finally, XCLAIM is compatible with the majority of existing blockchains without modification, and enables several novel cryptocurrency applications, such as cross-chain payment channels and efficient multi-party swaps.

REPORT

Stewart I, Ilie D, Zamyatin A, Werner S, Torshizi MF, Knottenbelt WJet al., 2018, Committing to quantum resistance: a slow defence for Bitcoin against a fast quantum computing attack, ROYAL SOCIETY OPEN SCIENCE, Vol: 5, ISSN: 2054-5703

JOURNAL ARTICLE

Harz D, Knottenbelt WJ, 2018, Towards Safer Smart Contracts: A Survey of Languages and Verification Methods.

WORKING PAPER

Zamyatin A, Stifter N, Schindler P, Weippl ER, Knottenbelt WJet al., 2018, Flux: Revisiting Near Blocks for Proof-of-Work Blockchains., IACR Cryptology ePrint Archive, Vol: 2018, Pages: 415-415

JOURNAL ARTICLE

Zamyatin A, Harz D, Knottenbelt WJ, 2018, Issue, Trade, Redeem: Crossing Systems Bounds with Cryptocurrency-Backed Tokens., IACR Cryptology ePrint Archive, Vol: 2018, Pages: 643-643

JOURNAL ARTICLE

, 2018, Proceedings of the 2018 ACM/SPEC International Conference on Performance Engineering, ICPE 2018, Berlin, Germany, April 09-13, 2018, Publisher: ACM

CONFERENCE PAPER

Zamyatin A, Stifter N, Judmayer A, Schindler P, Weippl ER, Knottenbelt WJet al., 2018, (Short Paper) A Wild Velvet Fork Appears! Inclusive Blockchain Protocol Changes in Practice., Pages: 87-87

CONFERENCE PAPER

, 2018, Companion of the 2018 ACM/SPEC International Conference on Performance Engineering, ICPE 2018, Berlin, Germany, April 09-13, 2018, Publisher: ACM

CONFERENCE PAPER

Pesu T, Kettunen J, Knottenbelt WJ, Wolter Ket al., 2017, Three-way optimisation of response time, subtask dispersion and energy consumption in split-merge systems, Pages: 244-251

© 2017 ACM. This paper investigates various ways in which the triple trade-off metrics between task response time, subtask dispersion and energy can be improved in split-merge queueing systems. Four ideas, namely dynamic subtask dispersion reduction, state-dependent service times, multiple redundant subtask service servers and restarting subtask service, are examined in the paper. It transpires that all four techniques can be used to improve the triple trade-off, while combinations of the techniques are not necessarily beneficial.

CONFERENCE PAPER

Mora SV, Knottenbelt WJ, 2017, Deep Learning for Domain-Specific Action Recognition in Tennis, 30th IEEE/CVF Conference on Computer Vision and Pattern Recognition Workshops (CVPRW), Publisher: IEEE, Pages: 170-178, ISSN: 2160-7508

CONFERENCE PAPER

Zamyatin A, Wolter K, Werner S, Mulligan CEA, Harrison PG, Knottenbelt WJet al., 2017, Swimming with Fishes and Sharks: Beneath the Surface of Queue-based Ethereum Mining Pools, 25th IEEE International Symposium on Modeling, Analysis, and Simulation of Computer and Telecommunication Systems (MASCOTS), Publisher: IEEE COMPUTER SOC, Pages: 99-109, ISSN: 1526-7539

CONFERENCE PAPER

Pesu T, Knottenbelt WJ, 2017, Optimising hidden stochastic PERT networks, Pages: 133-136

Copyright © 2016 EAI. This paper introduces a technique for minimising subtask dispersion in hidden stochastic PERT networks. The technique improves on existing research in two ways. Firstly, it enables subtask dispersion reduction in DAG structures, whereas previous techniques have only been applicable to single-layer split-merge or fork-join systems. Secondly, the exact distributions of subtask processing times do not need to be known, so long as there is some means of generating samples. The technique is further extended to use a metric which trades off subtask dispersion and task response time.

CONFERENCE PAPER

Harrison PG, Patel NM, Knottenbelt WJ, 2016, Energy--Performance Trade-Offs via the EP Queue, ACM Transactions on Modeling and Performance Evaluation of Computing Systems, Vol: 1, Pages: 1-31, ISSN: 2376-3639

JOURNAL ARTICLE

McGinn D, Birch D, Akroyd D, Molina-Solana M, Guo Y, Knottenbelt WJet al., 2016, Visualizing Dynamic Bitcoin Transaction Patterns, BIG DATA, Vol: 4, Pages: 109-119, ISSN: 2167-6461

JOURNAL ARTICLE

Tsimashenka I, Knottenbelt WJ, Harrison PG, 2016, Controlling variability in split-merge systems and its impact on performance, ANNALS OF OPERATIONS RESEARCH, Vol: 239, Pages: 569-588, ISSN: 0254-5330

JOURNAL ARTICLE

Haughian G, Osman R, Knottenbelt WJ, 2016, Benchmarking Replication in Cassandra and MongoDB NoSQL Datastores, 27th International Conference on Database and Expert Systems Applications (DEXA), Publisher: SPRINGER INT PUBLISHING AG, Pages: 152-166, ISSN: 0302-9743

CONFERENCE PAPER

Wu H, Knottenbelt WJ, Wolter K, Sun Yet al., 2016, An Optimal Offloading Partitioning Algorithm in Mobile Cloud Computing., Publisher: Springer, Pages: 311-328

CONFERENCE PAPER

Kelly J, Knottenbelt WJ, 2016, Does disaggregated electricity feedback reduce domestic electricity consumption? A systematic review of the literature., CoRR, Vol: abs/1605.00962

JOURNAL ARTICLE

Pesu T, Knottenbelt WJ, 2015, Dynamic Subtask Dispersion Reduction in Heterogeneous Parallel Queueing Systems, ELECTRONIC NOTES IN THEORETICAL COMPUTER SCIENCE, Vol: 318, Pages: 129-142, ISSN: 1571-0661

JOURNAL ARTICLE

Parson O, Fisher G, Hersey A, Batra N, Kelly J, Singh A, Knottenbelt W, Rogers Aet al., 2015, Dataport and NILMTK: A Building Data Set Designed for Non-intrusive Load Monitoring, IEEE Global Conference on Signal and Information Processing (GlobalSIP), Publisher: IEEE, Pages: 210-214

CONFERENCE PAPER

Chen X, Knottenbelt WJ, 2015, A performance tree-based monitoring platform for clouds, Pages: 97-98

Copyright © 2015 ACM. Cloud-based software systems are expected to deliver reli- able performance under dynamic workload while eficiently managing resources. Conventional monitoring frameworks provide limited support for exible and intuitive performance queries. In this paper, we present a prototype monitor- ing and control platform for clouds that is a better fit to the characteristics of cloud computing (e.g. extensible, user- defined, scalable). Service Level Objectives (SLOs) are ex- pressed graphically as Performance Trees, while violated SLOs trigger mitigating control actions.

CONFERENCE PAPER

Chen X, Rupprecht L, Osman R, Pietzuch P, Knottenbelt W, Franciosi Fet al., 2015, CloudScope: Diagnosing and Managing Performance Interference in Multi-Tenant Clouds, 23rd International Symposium on Modeling, Analysis, and Simulation of Computer and Telecommunication Systems (MASCOTS), Publisher: IEEE, Pages: 164-173, ISSN: 1526-7539

CONFERENCE PAPER

Bradley J, Knottenbelt W, Thomas N, 2015, Preface, Electronic Notes in Theoretical Computer Science, Vol: 310, Pages: 1-3, ISSN: 1571-0661

JOURNAL ARTICLE

Kelly J, Knottenbelt WJ, 2015, Neural NILM: Deep Neural Networks Applied to Energy Disaggregation., Publisher: ACM, Pages: 55-64

CONFERENCE PAPER

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