Follow blockchain research across journals, conferences, and preprint repositories.
1,187 results · page 47 of 50
Yoad Lewenberg, Yonatan Sompolinsky, Aviv Zohar
No abstract is available for this record.
Steve Y. Yang, Jinhyoung Kim
Bit coin, as the foundation for a secure electronic payment system, has drawn broad interests from researchers in recent years. In this paper, we analyze a comprehensive Bit coin transaction dataset and investigate the interrelationship between the flow of Bit coin transactions and its price movement. Using network theory, we examine a few complexity measures of the Bit coin transaction flow networks, and we model the joint dynamic relationship between these complexity measures and Bit coin market variables such as return and volatility. We find that a particular complexity measure of the Bit coin transaction network flow is significantly correlated with the Bit coin market return and volatility. More specifically we document that the residual diversity or freedom of Bit coin network flow scaled by the total system throughput can significantly improve the predictability of Bit coin market return and volatility.
David Vandervort, Dale Gaucas, Robert St. Jacques
No abstract is available for this record.
Matthias Tarasiewicz, Andrew Newman
No abstract is available for this record.
Christian Decker, James Guthrie, Jochen Seidel, Roger Wattenhofer
No abstract is available for this record.
Ryan Farell
No abstract is available for this record.
Lam Pak Nian, David Lee Kuo Chuen
No abstract is available for this record.
Christian Decker, Jochen Seidel, Roger Wattenhofer
The Bitcoin system only provides eventual consistency. For everyday life, the time to confirm a Bitcoin transaction is prohibitively slow. In this paper we propose a new system, built on the Bitcoin blockchain, which enables strong consistency. Our system, PeerCensus, acts as a certification authority, manages peer identities in a peer-to-peer network, and ultimately enhances Bitcoin and similar systems with strong consistency. Our extensive analysis shows that PeerCensus is in a secure state with high probability. We also show how Discoin, a Bitcoin variant that decouples block creation and transaction confirmation, can be built on top of PeerCensus, enabling real-time payments. Unlike Bitcoin, once transactions in Discoin are committed, they stay committed.
Fu Hou, Xinjun Mao, Wei Wu, Lu Liu · 5 authors
The services in open and dynamic Cloud Computing environments are often decentralized, evolving and are cross-organized. Efficient management of the Cloud resources for the improvement of the quality and efficiency of the service provisions is still being a continuous challenge in Cloud domain. To this end, this paper proposes a self-management approach for the cloud services, with an autonomous and context-aware management of the resources by employing a number of service agents in the Cloud environment. Such service agents are responsible for organizing the service management through their local interactions in the system, and further leading to the expected emergence of the service organization. Based on this approach, we present a cloud-oriented services self-management framework with suitable mechanisms for service aggregations and service provisions. And, two supporting algorithms are designed to implement the proposed services self-organization process and also the service provision process. We conduct various experiments on public data sets, and the experimental results prove the efficiency of our system in improving the quality of the Cloud services and also the practical adaptability of our system to the ever changing Cloud environment.
Alex Biryukov, Ivan Pustogarov
Bitcoin is a decentralized P2P digital currency in which coins are generated by a distributed set of miners and transaction are broadcasted via a peer-to-peer network. While Bitcoin provides some level of anonymity (or rather pseudonymity) by encouraging the users to have any number of random-looking Bitcoin addresses, recent research shows that this level of anonymity is rather low. This encourages users to connect to the Bitcoin network through anonymizers like Tor and motivates development of default Tor functionality for popular mobile SPV clients. In this paper we show that combining Tor and Bitcoin creates an attack vector for the deterministic and stealthy man-in-the-middle attacks. A low-resource attacker can gain full control of information flows between all users who chose to use Bitcoin over Tor. In particular the attacker can link together user's transactions regardless of pseudonyms used, control which Bitcoin blocks and transactions are relayed to the user and can \ delay or discard user's transactions and blocks. In collusion with a powerful miner double-spending attacks become possible and a totally virtual Bitcoin reality can be created for such set of users. Moreover, we show how an attacker can fingerprint users and then recognize them and learn their IP address when they decide to connect to the Bitcoin network directly.
Saramago, Rodrigo Q., Meling, Hein, Jehl, Leander N.
A certification system is responsible for issuing digital credentials, which attest claims about a subject, e.g., an academic diploma. Such credentials are valuable for individuals and society, and widespread adoption requires a trusted certification system. Trust can be gained by being transparent when issuing and verifying digital credentials. However, there is a fundamental tradeoff between privacy and transparency. For instance, admitting a student to an academic program must preserve the student’s privacy, i.e., the student’s grades must not be revealed to unauthorized parties. At the same time, other applicants may demand transparency to ensure fairness in the admission process. Thus, building a certification system with the right balance between privacy and transparency is challenging. This paper proposes a novel design for a certification system that provides sufficient transparency and preserves privacy through selective disclosure of claims such that authorized parties can verify them. Moreover, unauthorized parties can also verify the correctness of the certification process without compromising privacy. We achieve this using an incremental Merkle tree of cryptographic commitments to users' credentials. The commitments are added to the tree based on verifying zero-knowledge issuance proofs. Users store credentials off-chain and can prove the ownership and authenticity of credentials without revealing their commitments. Further, our approach enables users to prove statements about the credential’s claims in zero-knowledge. Our design offers a cost-efficient solution, reducing the amount of linkable on-chain data by up to 79% per credential compared to prior work, while maintaining transparency.
Andrew Miller, Ari Juels, Elaine Shi, Bryan Parno · 5 authors
Bit coin is widely regarded as the first broadly successful e-cash system. An oft-cited concern, though, is that mining Bit coins wastes computational resources. Indeed, Bit coin's underlying mining mechanism, which we call a scratch-off puzzle (SOP), involves continuously attempting to solve computational puzzles that have no intrinsic utility. We propose a modification to Bit coin that repurposes its mining resources to achieve a more broadly useful goal: distributed storage of archival data. We call our new scheme Perm coin. Unlike Bit coin and its proposed alternatives, Perm coin requires clients to invest not just computational resources, but also storage. Our scheme involves an alternative scratch-off puzzle for Bit coin based on Proofs-of-Retrievability (PORs). Successfully minting money with this SOP requires local, random access to a copy of a file. Given the competition among mining clients in Bit coin, this modified SOP gives rise to highly decentralized file storage, thus reducing the overall waste of Bit coin. Using a model of rational economic agents we show that our modified SOP preserves the essential properties of the original Bit coin puzzle. We also provide parameterizations and calculations based on realistic hardware constraints to demonstrate the practicality of Perm coin as a whole.
Gideon Samid
No abstract is available for this record.
Sebastian Feld, Mirco Schönfeld, Martin Werner
Bitcoin has become increasingly important in recent years. The exchange rate raised from $14 in January 2013 up to $240 in April 2013 and even $900 in early 2014. In this paper, we present novel insights about Bitcoin's peer-to-peer (P2P) network with a special focus on its distribution among distinct autonomous systems. We traversed Bitcoin's P2P network in a protocol-compliant manner and collected information about the network size, the number of clients, and the network distribution among autonomous systems. Our findings lead to conclusions about the resilience of the Bitcoin ecosystem, the unambiguousness of the blockchain in use, and the propagation and verification of transaction blocks.
Huan Meng
Bitcoin is a digital currency which is based on P2P network and open source software. It is avirtual currency without any control by any centralized organization. New Bitcoins are issuedby lots of specified algorithms. The whole Bitcoin network utilizes the distributed database toverify and record all the transactions through the nodes in the P2P network in which thedouble spending is prevented. No person or organization is able to control Bitcoin based on adecentralized P2P network and algorithm. The cryptographic functions of Bitcoin are designedto allow only the real Bitcoin owner to pay and transfer, and ensure the anonymity andmarketability.The purpose of this thesis is to analyze the security architecture and services for the Bitcoin system and describe of all the features and infrastructures of the whole Bitcoin network. A whole establishment demo including wallet client, mining server with GUI and mining client is implemented. Further improvement will be suggested and recommended for the system
KS Krzysztof Okupski
No abstract is available for this record.
Harald Gjermundrød, Ioanna Dionysiou
No abstract is available for this record.
George M. Giaglis, Kalliopi N. Kypriotaki
No abstract is available for this record.
Malte Möser, Rainer Böhme, Dominic Breuker
No abstract is available for this record.
Joan Antoni Donet Donet, Cristina Pérez‐Solà, Jordi Herrera‐Joancomartí
No abstract is available for this record.
Philip Koshy, Diana Koshy, Patrick McDaniel
No abstract is available for this record.
Paul L. Snyder, Giuseppe Valetto
Describing, understanding, and modeling the emergent behavior of self-organizing software systems remains an open challenge. Such systems can solve problems in computing domains where traditional, centralized models are impractical or problematic, including ubiquitous and pervasive computing, peer-to-peer networks, large-scale grids, and Ultra-Large-Scale Systems. Self-organizing approaches have demonstrated great promise in building adaptive behavior into decentralized systems, enabling cooperative, autonomous self-management and the exploitation of the heterogeneity of system components. My investigation of self-organizing software systems has revolved around Myconet, an unstructured overlay protocol for peer-to-peer networks. Myconet takes inspiration from fungal growth patterns in order to build an efficient self-optimizing superpeer topology that can also rapidly self-heal in response to damage orattacks. Myconet has proven to be flexible, and has been used as a platform for the development of other self-organizing applications in large-scale distributed systems, including load-balancing in distributed service networks (Mycoload), and detection and mitigation of attacks against the overlay (Hormone-Inspired Topology Adaptation Protection [HITAP] and Self-Organized Degree Adaptation Protection [SODAP]). Each extension has given additional insights into the self-organizing dynamics of such systems, but has also shown the limitations of ad hoc approaches to the design and analysis of new applications. These experiences have led me to investigate formal tools and models that may provide the designer of a self-organizing system with early and accurate insight through augmented analytical power. This research selects a small set of synergistic modeling techniques, and builds an integrated approach to modeling for the design and validation of self-organizing software systems. These tools are used to model the core Myconet platform and its currently developed extensions, particularly focusing on the SODAP layer which provides self-protection features to a superpeer-based P2P overlay network. Once established, this modeling approach can be applied to the principled design of further Myconet extensions, as well as other self-organizing systems, thus advancing the understanding of how to model and engineer self-organization in software systems.
Craig Warmke
Many want to know what bitcoin is and how it works. But bitcoin is as complex as it is controversial, and relatively few have the technical background to understand it. In this paper, I offer an accessible on-ramp for understanding bitcoin in the form of a model. My model reveals both what bitcoin is and how it works. More specifically, it reveals that bitcoin is a fictional substance in a massively coauthored story on a network that automates and distributes jobs normally entrusted to centralized publishing institutions. My model therefore falsifies a popular view according to which each bitcoin is a chunk of code.
Christian Decker, Roger Wattenhofer
Bitcoin is a digital currency that unlike traditional currencies does not rely on a centralized authority. Instead Bitcoin relies on a network of volunteers that collectively implement a replicated ledger and verify transactions. In this paper we analyze how Bitcoin uses a multi-hop broadcast to propagate transactions and blocks through the network to update the ledger replicas. We then use the gathered information to verify the conjecture that the propagation delay in the network is the primary cause for blockchain forks. Blockchain forks should be avoided as they are symptomatic for inconsistencies among the replicas in the network. We then show what can be achieved by pushing the current protocol to its limit with unilateral changes to the client's behavior.