CrowdBC: A blockchain-based decentralized framework for crowdsourcing

Crowdsourcing systems which utilize the human intelligence to solve complex tasks have gained considerable interest and adoption in recent years. However, the majority of existing crowdsourcing systems rely on central servers, which are subject to the weaknesses of traditional trust-based model, such as single point of failure. They are also vulnerable to distributed denial of service (DDoS) and Sybil attacks due to malicious users involvement. In addition, high service fees from the crowdsourcing platform may hinder the development of crowdsourcing. How to address these potential issues has both research and substantial value. In this paper, we conceptualize a blockchain-based decentralized framework for crowdsourcing named CrowdBC, in which a requester’s task can be solved by a crowd of workers without relying on any third trusted institution, users’ privacy can be guaranteed and only low transaction fees are required. In particular, we introduce the architecture of our proposed framework, based on which we give a concrete scheme. We further implement a software prototype on Ethereum public test network with real-world dataset. Experiment results show the feasibility, usability and scalability of our proposed crowdsourcing system

Decentralized Dispute Resolution: Using Blockchain Technology and Smart Contracts in Arbitration

Can blockchain technology and smart contracts be used in the context of alternative dispute resolution, particularly arbitration, turning traditional procedures on their head? This article discusses various possible applications of blockchain technology and smart contracts in ADR. In particular, it addresses the possibility of fully automated execution of arbitral awards using a smart contract through so-called escrow mechanisms. Subsequently, it presents two promising approaches of so-called Decentralized Dispute Resolution (DDR), including Expert-Pooling and Crowdarbitration. DDR generally involves decisions made jointly by multiple or even all participants in a network (usually a blockchain network), rather than by just one or two intermediaries, and is managed by a smart contract. In the first approach, jurors join together to form so-called expert pools and offer their services without the parties knowing the pool members. Crowdarbitration is based on game-theoretic approaches, namely the “Schelling Point Principle” and crowdjustice. In both approaches, arbitral awards are typically enforced by an escrow mechanism. The final section comments on and evaluates each of these approaches, in particular their advantages and disadvantages, as well as their potential scope and limitations

Dragoon: Private Decentralized HITs Made Practical

With the rapid popularity of blockchain, decentralized human intelligence tasks (HITs) are proposed to crowdsource human knowledge without relying on vulnerable third-party platforms. However, the inherent limits of blockchain cause decentralized HITs to face a few "new" challenges. For example, the confidentiality of solicited data turns out to be the sine qua non, though it was an arguably dispensable property in the centralized setting. To ensure the "new" requirement of data privacy, existing decentralized HITs use generic zero-knowledge proof frameworks (e.g. SNARK), but scarcely perform well in practice, due to the inherently expensive cost of generality. We present a practical decentralized protocol for HITs, which also achieves the fairness between requesters and workers. At the core of our contributions, we avoid the powerful yet highly-costly generic zk-proof tools and propose a special-purpose scheme to prove the quality of encrypted data. By various non-trivial statement reformations, proving the quality of encrypted data is reduced to efficient verifiable decryption, thus making decentralized HITs practical. Along the way, we rigorously define the ideal functionality of decentralized HITs and then prove the security due to the ideal-real paradigm. We further instantiate our protocol to implement a system called Dragoon, an instance of which is deployed atop Ethereum to facilitate an image annotation task used by ImageNet. Our evaluations demonstrate its practicality: the on-chain handling cost of Dragoon is even less than the handling fee of Amazon's Mechanical Turk for the same ImageNet HIT.Comment: small differences from a version accepted to appear in ICDCS 2020 (to fix a minor bug

Enabling the Internet of Mobile Crowdsourcing Health Things: A Mobile Fog Computing, Blockchain and IoT Based Continuous Glucose Monitoring System for Diabetes Mellitus Research and Care

[Abstract] Diabetes patients suffer from abnormal blood glucose levels, which can cause diverse health disorders that affect their kidneys, heart and vision. Due to these conditions, diabetes patients have traditionally checked blood glucose levels through Self-Monitoring of Blood Glucose (SMBG) techniques, like pricking their fingers multiple times per day. Such techniques involve a number of drawbacks that can be solved by using a device called Continuous Glucose Monitor (CGM), which can measure blood glucose levels continuously throughout the day without having to prick the patient when carrying out every measurement. This article details the design and implementation of a system that enhances commercial CGMs by adding Internet of Things (IoT) capabilities to them that allow for monitoring patients remotely and, thus, warning them about potentially dangerous situations. The proposed system makes use of smartphones to collect blood glucose values from CGMs and then sends them either to a remote cloud or to distributed fog computing nodes. Moreover, in order to exchange reliable, trustworthy and cybersecure data with medical scientists, doctors and caretakers, the system includes the deployment of a decentralized storage system that receives, processes and stores the collected data. Furthermore, in order to motivate users to add new data to the system, an incentive system based on a digital cryptocurrency named GlucoCoin was devised. Such a system makes use of a blockchain that is able to execute smart contracts in order to automate CGM sensor purchases or to reward the users that contribute to the system by providing their own data. Thanks to all the previously mentioned technologies, the proposed system enables patient data crowdsourcing and the development of novel mobile health (mHealth) applications for diagnosing, monitoring, studying and taking public health actions that can help to advance in the control of the disease and raise global awareness on the increasing prevalence of diabetes.Xunta de Galicia; ED431G/01Xunta de Galicia; ED431C 2016-045Agencia Estatal de Investigación de España; TEC2016-75067-C4-1-

Video marketplace as a new approach to Crowd Journalism using a blockchain-based infrastructure

Atualmente, as plataformas de social media (Facebook, Instagram, Youtube, etc.) dominam o mundo da conectividade social e continuarão a fazê-lo nas próximas gerações. Na sua grande maioria, as redes sociais são plataformas centralizadas regidas e controladas por uma única organização proprietária, o que vem colocar questões críticas de confiança e controle sobre o conteúdo criado e divulgado. Presencia-se também uma grande evolução dos smartphones e dispositivos móveis no que toca à qualidade de criação e visualização de conteúdo multimédia (áudio, vídeo, etc.). Isto faz com que cada vez mais conteúdo de qualidade seja criado a cada instante por pessoas comuns, aumentando a aceitação do crowd journalism por parte da comunidade jornalística internacional. O propósito desta dissertação é a concepção e o desenvolvimento de um Marketplace de conteúdo multimédia tendo como suporte uma rede social descentralizada. Esta plataforma Web permite armazenar vídeos que são transmitidos em direto, visualizá-los, avaliá-los e realizar as transações entre os detentores dos mesmos e possíveis compradores. Todas as operações do sistema são registadas de forma descentralizada e utilizando tecnologia blockchain através de smart contracts, tendo sempre em conta a usabilidade dos componentes desenvolvidos, a experiência de utilização do sistema e os desafios inerentes dado o enquadramento no contexto da rede social descentralizada. O impacto esperado é que esta plataforma, ou a abordagem conceptual tomada, permita oferecer uma solução para os problemas atuais de confiança e de propriedade de conteúdo provenientes das redes sociais centralizadas clássicas, podendo eventualmente revolucionar a forma como se partilha conteúdo socialmente e se explora comercialmente o mesmo.From the start of the 21st century, the social media networks have reached a ruling level of usage and significance on social connectivity and will certainly continue to be the main form of social interaction in the next generations. Most of these social networks are centralized platforms ruled by a single organization owner, raising critical trust and ownership concerns over the content created and shared. Furthermore, there has been a significant growth of the technologies evolving smartphones and its components and functionality, giving to ordinary people the power of creating good-quality content using only their smartphones. This phenomenon contributed to the rise of crowd-streaming and crowd-journalism and its acceptance by the journalistic community all around the world. This work intends to conceive and develop a marketplace of multimedia content based on a decentralized social media network. The web platform is responsible for saving the live-made videos, allowing its visualization, rating and transactions between its owners and potential buyers. All the system mechanism uses smart contracts in a blockchain environment. This work also focuses on understanding how is the usability affected by the decentralized approach and what are the methods, precautions and strategies needed to improve the system's user experience. Regarding this work, the expected impact lies in recognizing the potential benefits of the decentralized approach over the centralized world of social networking as well as effectively propose and implement user interface and experience strategies to support this revolution

Crowdsourcing atop blockchains

Traditional crowdsourcing systems, such as Amazon\u27s Mechanical Turk (MTurk), though once acquiring great economic successes, have to fully rely on third-party platforms to serve between the requesters and the workers for basic utilities. These third-parties have to be fully trusted to assist payments, resolve disputes, protect data privacy, manage user authentications, maintain service online, etc. Nevertheless, tremendous real-world incidents indicate how elusive it is to completely trust these platforms in reality, and the reduction of such over-reliance becomes desirable. In contrast to the arguably vulnerable centralized approaches, a public blockchain is a distributed and transparent global consensus computer that is highly robust. The blockchain is usually managed and replicated by a large-scale peer-to-peer network collectively, thus being much more robust to be fully trusted for correctness and availability. It, therefore, becomes enticing to build novel crowdsourcing applications atop blockchains to reduce the over-trust on third-party platforms. However, this new fascinating technology also brings about new challenges, which were never that severe in the conventional centralized setting. The most serious issue is that the blockchain is usually maintained in the public Internet environment with a broader attack surface open to anyone. This not only causes serious privacy and security issues, but also allows the adversaries to exploit the attack surface to hamper more basic utilities. Worse still, most existing blockchains support only light on-chain computations, and the smart contract executed atop the decentralized consensus computer must be simple, which incurs serious feasibility problems. In reality, the privacy/security issue and the feasibility problem even restrain each other and create serious tensions to hinder the broader adoption of blockchain. The dissertation goes through the non-trivial challenges to realize secure yet still practical decentralization (for urgent crowdsourcing use-cases), and lay down the foundation for this line of research. In sum, it makes the next major contributions. First, it identifies the needed security requirements in decentralized knowledge crowdsourcing (e.g., data privacy), and initiates the research of private decentralized crowdsourcing. In particular, the confidentiality of solicited data is indispensable to prevent free-riders from pirating the others\u27 submissions, thus ensuring the quality of solicited knowledge. To this end, a generic private decentralized crowdsourcing framework is dedicatedly designed, analyzed, and implemented. Furthermore, this dissertation leverages concretely efficient cryptographic design to reduce the cost of the above generic framework. It focuses on decentralizing the special use-case of Amazon MTurk, and conducts multiple specific-purpose optimizations to remove needless generality to squeeze performance. The implementation atop Ethereum demonstrates a handling cost even lower than MTurk. In addition, it focuses on decentralized crowdsourcing of computing power for specific machine learning tasks. It lets a requester place deposits in the blockchain to recruit some workers for a designated (randomized) programs. If and only if these workers contribute their resources to compute correctly, they would earn well-deserved payments. For these goals, a simple yet still useful incentive mechanism is developed atop the blockchain to deter rational workers from cheating. Finally, the research initiates the first systematic study on crowdsourcing blockchains\u27 full nodes to assist superlight clients (e.g., mobile phones and IoT devices) to read the blockchain\u27s records. This dissertation presents a novel generic solution through the powerful lens of game-theoretic treatments, which solves the long-standing open problem of designing generic superlight clients for all blockchains

Integration of Blockchain and Auction Models: A Survey, Some Applications, and Challenges

In recent years, blockchain has gained widespread attention as an emerging technology for decentralization, transparency, and immutability in advancing online activities over public networks. As an essential market process, auctions have been well studied and applied in many business fields due to their efficiency and contributions to fair trade. Complementary features between blockchain and auction models trigger a great potential for research and innovation. On the one hand, the decentralized nature of blockchain can provide a trustworthy, secure, and cost-effective mechanism to manage the auction process; on the other hand, auction models can be utilized to design incentive and consensus protocols in blockchain architectures. These opportunities have attracted enormous research and innovation activities in both academia and industry; however, there is a lack of an in-depth review of existing solutions and achievements. In this paper, we conduct a comprehensive state-of-the-art survey of these two research topics. We review the existing solutions for integrating blockchain and auction models, with some application-oriented taxonomies generated. Additionally, we highlight some open research challenges and future directions towards integrated blockchain-auction models