June list
If you feel a paper should belong to another category, or that we missed a relevant paper just let us know. Participation is most welcome!
Categories:
- Attacks and defenses
- Blockchain-general
- Blockchain-noncrypto uses
- Ethereum
- Financial
- Internet of Things (IoT)
- Machine learning
- Other cryptocurrencies
- Proof of Work (PoW) alternatives
- Smart contracts
Attacks and defenses
A Novel DDoS Attack Detection Method Using Optimized Generalized Multiple Kernel Learning
Authors: Jieren Cheng, Junqi Li, Xiangyan Tang, S. Victor Sheng, Chen Zhang, Mengyang Li
Abstract: Distributed Denial of Service (DDoS) attack has become one of the most destructive network attacks which can pose a mortal threat to Internet security. Existing detection methods can not effectively detect early attacks.In this paper, we propose a detection method of DDoS attacks based on generalized multiple kernel learning (GMKL) combining with the constructed parameter R. The super-fusion feature value (SFV) and comprehensive degree of feature (CDF) are defined to describe the characteristic of attack flow and normal flow. A method for calculating R based on SFV and CDF is proposed to select the combination of kernel function and regularization paradigm. A DDoS attack detection classifier is generated by using the trained GMKL model with R parameter. The experimental results show that kernel function and regularization parameter selection method based on R parameter reduce the randomness of parameter selection and the error of model detection, and the proposed method can effectively detect DDoS attacks in complex environments with higher detection rate and lower error rate.
Probing the Mystery of Cryptocurrency Theft: An Investigation into Methods for Cryptocurrency Tainting Analysis
Authors: Tin Tironsakkul, Manuel Maarek, Andrea Eross, Mike Just
Abstract: Since the first theft of the Mt.Gox exchange service in 2011, Bitcoin has seen major thefts in subsequent years. For most thefts, the perpetrators remain uncaught and unknown. Although every transaction is recorded and transparent in the blockchain, thieves can hide behind pseudonymity and use transaction obscuring techniques to disguise their transaction trail. First, this paper investigates methods for transaction tracking with tainting analysis techniques. Second, we propose new methods applied to a specific theft case. Last, we propose a metrics-based evaluation framework to compare these strategies with the goal of improving transaction tracking accuracy.
Competing (Semi)-Selfish Miners in Bitcoin
Authors: J. Francisco Marmolejo-Cossío, Eric Brigham, Benjamin Sela, Jonathan Katz
Abstract: The Bitcoin protocol prescribes certain behavior by the miners who are responsible for maintaining and extending the underlying blockchain; in particular, miners who successfully solve a puzzle, and hence can extend the chain by a block, are supposed to release that block immediately. Eyal and Sirer showed, however, that a selfish miner is incentivized to deviate from the protocol and withhold its blocks under certain conditions. The analysis by Eyal and Sirer, as well as in followup work, considers a\emph{single} deviating miner (who may control a large fraction of the hashing power in the network) interacting with a remaining pool of honest miners. Here,we extend this analysis to the case where there are \emph{multiple}(non-colluding) selfish miners. We find that with multiple strategic miners,specific deviations from honest mining by multiple strategic agents canoutperform honest mining, even if individually miners would not be incentivised to be dishonest. This previous point effectively renders the Bitcoin protocol to be less secure than previously thought.
Blockchain-general
Blockchain Technology Overview
Authors: Dylan Yaga, Peter Mell, Nik Roby, Karen Scarfone
Abstract: Blockchains are tamper evident and tamper resistant digital ledgers implemented in a distributed fashion (i.e., without a central repository) and usually without a central authority (i.e., a bank, company, or government). At their basic level, they enable a community of users to record transactions in a shared ledger within that community, such that under normal operation of the blockchain network no transaction can be changed once published. This document provides a high-level technical overview of blockchain technology. The purpose is to help readers understand how blockchain technology works.
SoK of Used Cryptography in Blockchain
Authors: Mayank Raikwar, Danilo Gligoroski, Katina Kralevska
Abstract: The underlying fundaments of blockchain are cryptography and cryptographic concepts that provide reliable and secure decentralized solutions. Although many recent papers study the use-cases of blockchain in different industrial areas, such as finance, health care, legal relations, IoT, information security, and consensus building systems, only few studies scrutinize the cryptographic concepts used in blockchain. To the best of our knowledge, there is no Systematization of Knowledge (SoK) that gives a complete picture of the existing cryptographic concepts which have been deployed or have the potential to be deployed in blockchain. In this paper, we thoroughly review and systematize all cryptographic concepts which are already used in blockchain. Additionally, we give a list of cryptographic concepts which have not yet been applied but have big potentials to improve the current blockchain solutions. We also include possible instantiations (references) of these cryptographic concepts in the blockchain domain. Last but not least, we explicitly postulate 18 challenging problems that cryptographers interested in blockchain can work on.
PREStO: A Systematic Framework for Blockchain Consensus Protocols
Authors: Stefanos Leonardos, Daniel Reijsbergen, Georgios Piliouras
Abstract: The rapid evolution of the blockchain community has brought together stakeholders from fundamentally different backgrounds: cryptographers, protocol designers, software developers, startup entrepreneurs, corporate executives and investors, academics of various disciplines, and end users. The result is a diverse ecosystem, presently exemplified by the development of a wide range of different blockchain protocols. This raises questions for policy and decision makers: How do different protocols compare? What are their trade-offs? Existing efforts to survey the area reveal a fragmented terminology, and the lack of a unified framework to make the different desirable properties of blockchain protocols explicit. In this paper, we work towards bridging this gap. We evaluate protocols within a five-dimensional design space with the following axes. Optimality: does the protocol achieve its main goals? Stability: are the incentives of its participating agents well-aligned? Efficiency: is its output maximal relative to its use of resources? Robustness: can it cope when its operational assumptions are invalid or perturbed? Persistence: can it recover from catastrophic events? Based on the relevant literature, we organize the properties of existing protocols in subcategories of increasing granularity.The result is a dynamic scheme — termed the PREStO framework. Its scope is to aid the communication between stakeholders of different backgrounds, including managers and investors, and to identify research challenges and opportunities for blockchain protocols in a systematic way. We illustrate this via use cases and make a first step to understand the blockchain ecosystem through a more comprehensive lens.
Arcula: A Secure Hierarchical Deterministic Wallet for Multi-asset Blockchains
Authors: Adriano Luzio Di, Danilo Francati, Giuseppe Ateniese
Abstract: This work presents Arcula, a new design for hierarchical deterministic wallets that significantly improves the state of the art. Arcula is built on top of provably secure cryptographic primitives. It generates all its cryptographic secrets from a user-provided seed and enables the derivation of new signing public keys without requiring any secret information. Unlike other wallets, it achieves all these properties while being secure against privilege escalation. We prove that an attacker compromising an arbitrary number of users within an Arcula wallet cannot escalate his privileges and compromise users higher in the access hierarchy. Our design works out-of-the-box with any blockchain that enables the verification of signatures on arbitrary messages.We evaluate its usage in a real-world scenario on the Bitcoin Cash network.
A Security Case Study for Blockchain Games
Authors: Tian Min, Wei Cai
Abstract: Blockchain gaming is an emerging entertainment paradigm. However, blockchain games are still suffering from security issues, due to the immature blockchain technologies and its unsophisticated developers. In this work, we analyzed the blockchain game architecture and reveal the possible penetration methods of cracking. We scanned more than 600 commercial blockchain games to summarize a security overview from the perspective of the web server and smart contract,respectively. We also conducted three case studies for blockchain games to show detailed vulnerability detection.
Transwarp Conduit: Interoperable Blockchain Application Framework
Authors: Shidokht Hejazi-Sepehr, Ross Kitsis, Ali Sharif
Abstract: Transwarp-Conduit (TWC) is a protocol for message transfers between two smart-contract enabled blockchains. Furthermore, we specify an application framework (leveraging the TWC protocol) that enables developers to define arbitrarily complex cross-blockchain applications, simply by deploying framework-compliant smart contracts and hosting a TWC node (daemon process).The TWC protocol is implementable without additional effort on part of the base blockchain protocol.
Access Control for Electronic Health Records with Hybrid Blockchain-Edge Architecture
Authors: Hao Guo, Wanxin Li, Mark Nejad, Chien-Chung Shen
Abstract: The global Electronic Health Record (EHR) market is growing dramatically and expected to reach $39.7 billions by 2022. To safe-guard security and privacy of EHR, access control is an essential mechanism for managing EHR data. This paper proposes a hybrid architecture to facilitate access control of EHR data by using both blockchain and edge node. Within the architecture, a blockchain-based controller manages identity and access control policies and serves as a tamper-proof log of access events. In addition, off-chain edge nodes store the EHR data and apply policies specified in Abbreviated Language For Authorization (ALFA) to enforce attribute-based access control on EHR data in collaboration with the blockchain-based access control logs. We evaluate the proposed hybrid architecture by utilizing Hyperledger Composer Fabric blockchain to measure the performance of executing smart contracts and ACL policies in terms of transaction processing time and response time against unauthorized data retrieval.
Mind the Gap: Trade-Offs between Distributed Ledger Technology Characteristics
Authors: Niclas Kannengießer, Sebastian Lins, Tobias Dehling, Ali Sunyaev
Abstract: While design decisions determine the quality and viability of applications in general, in Distributed Ledger Technology (DLT), the decision for a suitable DLT design (e.g., Ethereum, IOTA) is of particular relevance because the retroactive change of the underlying DLT design is currently very hard and often even impossible. Extant research has revealed several trade-offs between DLT characteristics (e.g., availability vs. consistency). Such trade-offs inhibit a one-size-fits-all DLT design that suites the requirements of all applications on DLT. For an appropriate assessment of the suitability of DLT designs for a particular application on DLT, researchers and developers require a systematic and holistic overview of the functioning of different DLT designs,including their configuration of DLT characteristics as well as dependencies and resulting trade-offs between DLT characteristics. In this work, we present a comprehensive set of 49 DLT characteristics synthesized from the literature on DLT, which have been found relevant to consider when developing viable applications on DLT. Furthermore, we conducted an in-depth analysis of dependencies and resulting trade-offs between DLT characteristics. Finally, we consolidated the identified 26 trade-offs into 6 archetypes and explain implications for applications on DLT.
Blockchain-noncrypto uses
B-Ride: Ride Sharing with Privacy-preservation, Trust and Fair Payment atop Public Blockchain
Authors: Mohamed Baza, Noureddine Lasla, Mohamed Mahmoud, Mohamed Abdallah
Abstract: Ride-sharing is a service that enables drivers to share their trips with other riders, contributing to appealing benefits of shared travel costs. However, the majority of existing platforms rely on a central third party, which make them subject to a single point of failure and privacy disclosure issues. Moreover, they are vulnerable to DDoS and Sybil attacks due to malicious users involvement. Besides, high fees should be paid to the service provider. In this paper, we propose a decentralized ride-sharing service based on public Blockchain, named B-Ride. Both riders and drivers can find rides match while preserving their trip data, including pick-up/drop-off location, and departure/arrival date. However, under the anonymity of the public blockchain, a malicious user may submit multiple ride requests or offers, while not committing to any of them, to discover better offer or to make the system unreliable. B-Ride solves this problem by introducing a time-locked deposit protocol for a ride-sharing by leveraging smart contract and zero-knowledge set membership proof. In a nutshell, both a driver and a rider have to show their commitment by sending a deposit to the blockchain. Later, a driver has to prove to the blockchain on the agreed departure time that he has arrived at the pick-up location. To preserve rider/driver location privacy by hiding the exact pick-up location, the proof is done using zero-knowledge set membership protocol. Moreover, to ensure a fair payment, a pay-as-you-drive methodology is introduced based on the elapsed distance of the driver and the rider. Also, we introduce a reputation-based trust model to rate drivers based on their past trips to allow riders to select them based on their history on the system. Finally, we implement B-Ride in a test net of Ethereum. The experiment results show the applicability of our protocol atop the existing real-world blockchain.
Towards a Blockchain based digital identity verification, record attestation and record sharing system
Authors: Mehmet Aydar, Serkan Ayvaz
Abstract: In this study, we investigated the utilization of Blockchain technology in identity systems. We reviewed the drawbacks and weaknesses of traditional identity systems, and discussed the potential benefits of employing Blockchain technology for a more efficient identity system. As a result, we proposed a Blockchain based digital identity verification, record attestation and record sharing system. When compared to traditional identity systems, it makes identity verification and identity based record sharing more efficient and secure, while respecting privacy of identity owners. By exploiting the trust fabric of Blockchain, a Blockchain based identity system eliminates the middle man and wait lines for authentication, authorization, and attestation. It allows individuals to decide what parts of their identity they want to share and with whom they want to share it.
Secure Architectures Implementing Trusted Coalitions for Blockchained Distributed Learning (TCLearn)
Authors: Sebastien Lugan, Paul Desbordes, Ramos Xavier Luis Tormo, Axel Legay, Benoit Macq
Abstract: Distributed learning across a coalition of organizations allows the members of the coalition to train and share a model without sharing the data used to optimize this model. In this paper, we propose new secure architectures that guarantee preservation of data privacy, trustworthy sequence of iterative learning and equitable sharing of the learned model among each member of the coalition by using adequate encryption and blockchain mechanisms. We exemplify its deployment in the case of the distributed optimization of a deep learning convolutional neural network trained on medical images.
A Blockchain-based Framework for Detecting Malicious Mobile Applications in App Stores
Authors: Sajad Homayoun, Ali Dehghantanha, M. Reza Parizi, Raymond Kim-Kwang Choo
Abstract: The dramatic growth in smartphone malware shows that malicious program developers are shifting from traditional PC systems to smartphone devices.Therefore, security researchers are also moving towards proposing novel antimalware methods to provide adequate protection. This paper proposes a Blockchain-Based Malware Detection Framework (B2MDF) for detecting malicious mobile applications in mobile applications marketplaces (app stores). The framework consists of two internal and external private blockchains forming a dual private blockchain as well as a consortium blockchain for the final decision. The internal private blockchain stores feature blocks extracted by both static and dynamic feature extractors, while the external blockchain stores detection results as blocks for current versions of applications. B2MDFalso shares feature blocks with third parties, and this helps antimalware vendors to provide more accurate solutions.
Integrating Privacy Enhancing Techniques into Blockchains Using Sidechains
Authors: M. Reza Parizi, Sajad Homayoun, Abbas Yazdinejad, Ali Dehghantanha, Raymond Kim-Kwang Choo
Abstract: Blockchains are turning into decentralized computing platforms and are getting worldwide recognition for their unique advantages. There is an emerging trend beyond payments that blockchains could enable a new breed of decentralized applications, and serve as the foundation for Internet's security infrastructure. The immutable nature of the blockchain makes it a winner on security and transparency; it is nearly inconceivable for ledgers to be altered in a way not instantly clear to every single user involved. However, most blockchains fall short in privacy aspects, particularly in data protection.Garlic Routing and Onion Routing are two of major Privacy Enhancing Techniques(PETs) which are popular for anonymization and security. Garlic Routing is a methodology using by I2P Anonymous Network to hide the identity of sender and receiver of data packets by bundling multiple messages into a layered encryption structure. The Onion Routing attempts to provide low latency Internet-based connections that resist traffic analysis, deanonymization attack, eavesdropping, and other attacks both by outsiders (e.g. Internet routers) and insiders (Onion Routing servers themselves). As there are a few controversies over the rate of resistance of these two techniques to privacy attacks, we propose a PET-Enabled Sidechain (PETES) as a new privacy enhancing technique by integrating Garlic Routing and Onion Routing into a Garlic OnionRouting (GOR) framework suitable to the structure of blockchains. The preliminary proposed GOR aims to improve the privacy of transactions in blockchains via PETES structure.
Secure Software-Defined Networking Based on Blockchain
Authors: Weng Jiasi, Weng Jian, Liu Jia-Nan, Zhang Yue
Abstract: Software-Defined Networking (SDN) separates the network control plane and data plane, which provides a network-wide view with centralized control (in the control plane) and programmable network configuration for data plane injected by SDN applications (in the application plane). With these features, a number of drawbacks of the traditional network architectures such as static configuration, non-scalability and low efficiency can be effectively avoided.However, SDN also brings with it some new security challenges, such as single-point failure of the control plane, malicious flows from applications,exposed network-wide resources and a vulnerable channel between the control plane and the data plane. In this paper, we design a monolithic security mechanism for SDN based on Blockchain. Our mechanism decentralizes the control plane to overcome single-point failure while maintaining a network-wide view.The mechanism also guarantees the authenticity, traceability, and accountability of application flows, and hence secures the programmable configuration. Moreover, the mechanism provides a fine-grained access control of network-wide resources and a secure controller-switch channel to further protect resources and communication in SDN.
Invoice Financing of Supply Chains with Blockchain technology and Artificial Intelligence
Authors: Sandra Johnson, Peter Robinson, Kishore Atreya, Claudio Lisco
Abstract: Supply chains lend themselves to blockchain technology, but certain challenges remain, especially around invoice financing. For example, the further a supplier is removed from the final consumer product, the more difficult it is to get their invoices financed. Moreover, for competitive reasons, retailers and manufacturers do not want to disclose their supply chains. However, upstream suppliers need to prove that they are part of a`stable' supply chain to get their invoices financed, which presents the upstream suppliers with huge, and often unsurmountable, obstacles to get the necessary finance to fulfil the next order, or to expand their business. Using a fictitious supply chain use case, which is based on a real world use case, we demonstrate how these challenges have the potential to be solved by combining more advanced and specialised blockchain technologies with other technologies such as Artificial Intelligence. We describe how atomic crosschain functionality can be utilised across private blockchains to retrieve the information required for an invoice financier to make informed decisions under uncertainty, and consider the effect this decision has on the overall stability of the supply chain.
A Blockchain-Based Architecture for Traffic Signal Control Systems
Authors: Wanxin Li, Mark Nejad, Rui Zhang
Abstract: Ever-growing incorporation of connected vehicle (CV) technologies into intelligent traffic signal control systems brings about significant data security issues in the connected vehicular networks. This paper presents a novel decentralized and secure by design architecture for connected vehicle data security, which is based on the emerging blockchain paradigm. In a simulation study, we applied this architecture to defend the Intelligent Traffic Signal System (I-SIG), a USDOT approved CV pilot program, against congestion attacks. The results show the performance of the proposed architecture for the traffic signal control system.
TrustChain: Trust Management in Blockchain and IoT supported Supply Chains
Authors: Sidra Malik, Volkan Dedeoglu, S. Salil Kanhere, Raja Jurdak
Abstract: Traceability and integrity are major challenges for the increasingly complex supply chains of today’s world. Although blockchain technology has the potential to address these challenges through providing a tamper-proof audit trail of supply chain events and data associated with a product life-cycle, it does not solve the trust problem associated with the data itself. Reputation systems are an effective approach to solve this trust problem. However, current reputation systems are not suited to the blockchain based supply chain applications as they are based on limited observations, they lack granularity and automation, and their overhead has not been explored. In this work, we propose TrustChain, as a three-layered trust management framework which uses a consortium blockchain to track interactions among supply chain participants and to dynamically assign trust and reputation scores based on these interactions.The novelty of TrustChain stems from: (a) the reputation model that evaluates the quality of commodities, and the trustworthiness of entities based on multiple observations of supply chain events, (b) its support for reputation scores that separate between a supply chain participant and products, enabling the assignment of product-specific reputations for the same participant, (c)the use of smart contracts for transparent, efficient, secure, and automated calculation of reputation scores, and (d) its minimal overhead in terms of latency and throughput when compared to a simple blockchain based supply chain model.
Ethereum
The merits of using Ethereum MainNet as a Coordination Blockchain for Ethereum Private Sidechains
Authors: Peter Robinson
Abstract: A Coordination Blockchain is a blockchain with the task of coordinating activities of multiple private blockchains. This paper discusses the pros and cons of using Ethereum MainNet, the public Ethereum blockchain, as a Coordination Blockchain. The requirements Ethereum MainNet needs to fulfil to perform this role are discussed within the context of Ethereum Private Sidechains, a private blockchain technology which allows many blockchains to be operated in parallel, and allows atomic crosschain transactions to execute across blockchains. Ethereum MainNet is a permissionless network which aims to offer strong authenticity, integrity, and non-repudiation properties, that incentivises good behaviour using crypto economics. This paper demonstrates that Ethereum MainNet does deliver these properties. It then provides a comprehensive review of the features of Ethereum Private Sidechains, with a focus on the potential usage of Coordination Blockchains for these features.Finally, the merits of using Ethereum MainNet as a Coordination Blockchain are assessed. For Ethereum Private Sidechains, we found that Ethereum MainNet is best suited to storing long term static data that needs to be widely available,such as the Ethereum Registration Authority information. However, due to Ethereum MainNet’s probabilistic finality, it is not well suited to information that needs to be available and acted upon immediately, such as the Sidechain Public Keys and Atomic Crosschain Transaction state information that need to be accessible prior to the first atomic crosschain transaction being issued on a sidechain. Although this paper examined the use of Ethereum MainNet as a Coordination Blockchain within reference to Ethereum Private Sidechains, the discussions and observations of the typical tasks a Coordination blockchain maybe expected to perform are applicable more widely to any multi-blockchain system.
Financial
Invoice Financing of Supply Chains with Blockchain technology and Artificial Intelligence
Authors: Sandra Johnson, Peter Robinson, Kishore Atreya, Claudio Lisco
Abstract: Supply chains lend themselves to blockchain technology, but certain challenges remain, especially around invoice financing. For example, the further a supplier is removed from the final consumer product, the more difficult it is to get their invoices financed. Moreover, for competitive reasons, retailers and manufacturers do not want to disclose their supply chains. However, upstream suppliers need to prove that they are part of a`stable’ supply chain to get their invoices financed, which presents the upstream suppliers with huge, and often unsurmountable, obstacles to get the necessary finance to fulfil the next order, or to expand their business. Using a fictitious supply chain use case, which is based on a real world use case, we demonstrate how these challenges have the potential to be solved by combining more advanced and specialised blockchain technologies with other technologies such as Artificial Intelligence. We describe how atomic crosschain functionality can be utilised across private blockchains to retrieve the information required for an invoice financier to make informed decisions under uncertainty, and consider the effect this decision has on the overall stability of the supply chain.
The Effects of the Introduction of Bitcoin Futures on the Volatility of Bitcoin Returns
Authors: Wonse Kim, Junseok Lee, Kyungwon Kang
Abstract: This paper investigates the effects of the launch of Bitcoin futures on the intraday volatility of Bitcoin. Based on one-minute price data collected from four cryptocurrency exchanges, we first examine the change in realized volatility after the introduction of Bitcoin futures to investigate their aggregate effects on the intraday volatility of Bitcoin. We then analyze the effects in more detail utilizing the discrete Fourier transform. We show that although the Bitcoin market became more volatile immediately after the introduction of Bitcoin futures, over time it has become more stable than it was before the introduction.
(In)Stability for the Blockchain: Deleveraging Spirals and Stablecoin Attacks
Authors: Ariah Klages-Mundt, Andreea Minca
Abstract: We develop a model of stable assets, including noncustodial stablecoins backed by cryptocurrencies. Such stablecoins are popular methods for bootstrapping price stability within public blockchain settings. We demonstrate fundamental results about dynamics and liquidity in stablecoin markets, demonstrate that these markets face deleveraging spirals that cause illiquidity during crises, and show that these stablecoins have `stable’ and `unstable’ domains. Starting from documented market behaviors, we explain actual stablecoin movements; further our results are robust to a wide range of potential behaviors. In simulations, we show that these systems are susceptible to high tail volatility and failure. Our model builds foundations for stablecoin design. Based on our results, we suggest design improvements that can improve long-term stability and suggest methods for solving pricing problems that arise in existing stablecoins. In addition to the direct risk of instability, our dynamics results suggest a profitable economic attack during extreme events that can induce volatility in the `stable’ asset. This attack additionally suggests ways in which stablecoins can cause perverse incentives for miners, posing risks to blockchain consensus.
Contagion in Bitcoin networks
Authors: Célestin Coquidé, José Lages, L. Dima Shepelyansky
Abstract: We construct the Google matrices of bitcoin transactions for all year quarters during the period of January 11, 2009 till April 10, 2013. During the last quarters the network size contains about 6 million users (nodes) with about 150 million transactions. From PageRank and CheiRank probabilities, analogous to trade import and export, we determine the dimensionless trade balance of each user and model the contagion propagation on the network assuming that a user goes bankrupt if its balance exceeds a certain dimensionless threshold $κ$. We find that the phase transition takes place for $κ0.55$ almost all users remain safe. We find that even on a distance from the critical threshold $κ_c$ the top PageRank and CheiRank users, as a house of cards, rapidly drop to the bankruptcy. We attribute this effect to strong interconnections between these top users which we determine with the reduced Google matrix algorithm. This algorithm allows to establish efficiently the direct and indirect interactions between top PageRank users. We argue that this study models the contagion on real financial networks.
Internet of Things (IoT)
Mobile Edge Computing, Blockchain and Reputation-based Crowdsourcing IoT Federated Learning: A Secure, Decentralized and Privacy-preserving System
Authors: Yang Zhao, Jun Zhao, Linshan Jiang, Rui Tan, Dusit Niyato
Abstract: Internet-of-Things (IoT) companies strive to get feedback from users to improve their products and services. However, traditional surveys cannot reflect the actual conditions of customers’ due to the limited questions. Besides, survey results are affected by various subjective factors. In contrast, the recorded usages of IoT devices reflect customers’ behaviours more comprehensively and accurately. We design an intelligent system to help IoT device manufacturers to take advantage of customers’ data and build a machine learning model to predict customers’ requirements and possible consumption behaviours with federated learning (FL) technology. The FL consists of two stages: in the first stage, customers train the initial model using the phone and the edge computing server collaboratively. The mobile edge computing server’s high computation power can assist customers’ training locally. Customers first collect data from various IoT devices using phones, and then download and train the initial model with their data. During the training, customers first extract features using their mobiles, and then add the Laplacian noise to the extracted features based on differential privacy, a formal and popular notion to quantify privacy. After achieving the local model, customers sign on their models respectively and send them to the blockchain. We use the blockchain to replace the centralized aggregator which belongs to the third party in FL. In the second stage, miners calculate the averaged model using the collected models sent from customers. By the end of the crowdsourcing job, one of the miners, who is selected as the temporary leader, uploads the model to the blockchain. Besides, to attract more customers to participate in the crowdsourcing FL, we design an incentive mechanism, which awards participants with coins that can be used to purchase other services provided by the company.
U2Fi: A Provisioning Scheme of IoT Devices with Universal Cryptographic Tokens
Authors: Wang Kang
Abstract: Provisioning is the starting point of the whole life-cycle of IoT devices. The traditional provisioning methods of IoT devices are facing several issues, either about user experience or privacy harvesting. Moreover, IoT devices are vulnerable to different levels of attacks due to limited resources and long online duration. In this paper, we proposed U2Fi, a novel provisioning scheme for IoT devices. We provide a solution to make the U2F device that has been trusted by the cloud in the distribution process, via WiFi or its side channel,to provision the new IoT device. Further, subsequent device settings modification, setting update, and owner transfer can also be performed by usinga U2F device that has been trusted to improve security and provide a better user experience. This could provide helpful user friendliness to some valuable new application scenarios in IoT, such as smart hotel. Users could migrate the whole authentication of smart devices into a new site by simply inserting the universal cryptographic token into the secure gateway and authorizing by pressing the user-presence button on the token. Besides, the relevant unbinding process could also be done with a single cryptographic operation signed by the cryptographic token.
Machine learning
Towards Fair and Decentralized Privacy-Preserving Deep Learning with Blockchain
Authors: Lingjuan Lyu, Jiangshan Yu, Karthik Nandakumar, Yitong Li, Xingjun Ma, Jiong Jin
Abstract: In collaborative deep learning, current learning frameworks follow either a centralized architecture or a distributed architecture. Whilst centralized architecture deploys a central server to train a global model over the massiveamount of joint data from all parties, distributed architecture aggregates parameter updates from participating parties’ local model training, via a parameter server. These two server-based architectures present security and robustness vulnerabilities such as single-point-of-failure, single-point-of-breach, privacy leakage, and lack of fairness. To address these problems, we design, implement, and evaluate a purely decentralized privacy-preserving deep learning framework, called DPPDL. DPPDL makes the first investigation on the research problem of fairness in collaborative deep learning, and simultaneously provides fairness and privacy by proposing two novel algorithms: initial benchmarking and privacy-preserving collaborative deep learning. During initial benchmarking, each party trains a local Differentially Private Generative Adversarial Network (DPGAN) and publishes the generated privacy-preserving artificial samples for other parties to label, based on the quality of which to initialize local credibility list for other parties. The local credibility list reflects how much one party contributes to another party, and it is used and updated during collaborative learning to ensure fairness. To protect gradients transaction during privacy-preserving collaborative deep learning, we further put forward a three-layer onion-style encryption scheme. We experimentally demonstrate, on benchmark image datasets, that accuracy, privacy and fairness in collaborative deep learning can be effectively addressed at the same time by our proposed DPPDL framework. Moreover, DPPDL provides a viable solution to detect and isolate the cheating party in the system.
Other cryptocurrencies
What is Stablecoin?: A Survey on Price Stabilization Mechanisms for Decentralized Payment Systems
Authors: Makiko Mita, Kensuke Ito, Shohei Ohsawa, Hideyuki Tanaka
Abstract: Since the first theoretical concept of blockchains was proposed, over 100 digital currencies have been issued by online platformers as cryptocurrencies and traded by online consumers mainly in emerging countries. From the perspective of online payment systems, several studies have regarded blockchains as decentralized payment systems (DPSs), enabling international payment with lower cost and higher traceability with sophisticated peer-to-peer protocols in contrast to other centralized systems. Despite the advantages, DPSs are not chosen by the owners of online shops due to the high volatility of cryptocurrency prices. Stablecoins are cryptocurrencies with price stabilization mechanisms to match the price of another currency with lower volatility. Our motivation is to gather various price stabilization mechanisms for the purpose of comparing them from the perspective of implementation and enterprise usage. After dividing the methods into four collateral types (fiat, crypto, commodity, and non-collateralized) and two layers (protocol and application), we show that non-collateralized stablecoin on the application layer is the simplest approach for implementation. Moreover, we discuss their connection with traditional economic studies on Hayek money, Seigniorage Share, and Tobin tax. Some current stablecoin projects are also discussed and compared. This is the first survey of stablecoins to the best of our knowledge.
Proof of Work (PoW) alternatives
MaGPoS — A novel decentralized consensus mechanism combining magnetism and proof of stake
Authors: Tommy Mckinnon
Abstract: We describe MaGPoS, a novel consensus mechanism which is well suited to decentralized blockchain based protocols. MaGPoS is based on a combination of the well known physics of nano-scale magnetism, and previous implementations of proof of stake. This system has been studied by hundreds of thousands of scientists worldwide for over a hundred years, giving it an extreme level of reliability that is needed for a consensus mechanism. We start by explaining the physics, and study the properties that make it particularly beneficial for use in a consensus mechanism. We then show how to apply the physical model to a decentralized network of nodes, each with their own copy of a blockchain. After this, we describe some example calculations that a node in the decentralized network would make, and provide pseudo code for implementation. Finally, we discuss the how the model achieves all of the important properties that one expects of a consensus mechanism.
A Secure Consensus Protocol for Sidechains
Authors: Fangyu Gai, Cesar Grajales, Jianyu Niu, Chen Feng
Abstract: Sidechain technology has been envisioned as a promising solution to accelerate today’s public blockchains in terms of scalability and interoperability. By relying on the mainchain for security, different sidechains can formulate their own rules to reach consensus. Although the literature has considered the possibility of using consensus protocols in the sidechain, so far a tailor-made consensus protocol for sidechains with high performance and formal security proof has not been attempted. To fill this gap, we introduce Vulcan, a low overhead, highly efficient, security provable sidechain protocol. Vulcan makes use of smart contracts to ensure that only one block proposed in the sidechain will be enforced on the mainchain in each round, achieving consensus in an efficient manner. We give formal specifications of Vulcan which ensures safety and liveness with $f$ validators (total number of $n\geq 2f+1$) without online requirement of clients. For security analysis, we give formal security definitions and proofs under Universally Composable Security (UCS) model. As a proof of concept, we implement Vulcan and evaluate it in Ethereum testnet.
A Unifying Hybrid Consensus Protocol
Authors: Yulong Wu, Yunfei Zha, Yao Sun
Abstract: We introduce Unity, a new consensus algorithm for public blockchain settings. Unity is an eventual consistency protocol merging the Proof-of-Work (PoW) and Proof-of-Stake (PoS) into a coherent stochastic process. It encompasses hardware and economic security without sacrificing availability, unpredictability and decentralization. Empirical results indicate that the proposed protocol is fair and scalable to an arbitrary number of miners and stakers.
Smart contracts
Cryptocurrency Smart Contracts for Distributed Consensus of Public Randomness
Authors: Peter Mell, John Kelsey, James Shook
Abstract: Most modern electronic devices can produce a random number. However, it is difficult to see how a group of mutually distrusting entities can have confidence in any such hardware-produced stream of random numbers, since the producer could control the output to their gain. In this work, we use public and immutable cryptocurrency smart contracts, along with a set of potentially malicious randomness providers, to produce a trustworthy stream of timestamped public random numbers. Our contract eliminates the ability of a producer to predict or control the generated random numbers, including the stored history of random numbers. We consider and mitigate the threat of collusion between the randomness providers and miners in a second, more complex contract.
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