BITCOIN is a novel decentralized cryptocurrency system which has recently received great attention from wider audience. An interesting and unique feature of this that the complete list all transactions occurred its inception publicly available. This enables investigation funds movements to uncover properties economy. In paper we present set analyses user graph, i.e. graph obtained by an heuristic clustering transactions. Our consider up-to-date blockchain, as in December 2015, after...

Recent years have witnessed, especially in Europe, a shift aimed at bringing users back the center of digital systems. This has driven innovation towards affirmation decentralized systems, line with Self Sovereign Identity paradigm. User control over consumption and disclosure their data is key topic such drive. In this paper we show how it possible to apply increasingly popular concept traditionally centralized opaque process: Access Control To aim expand XACML standard for Attribute Based...

This paper presents a new design approach for Access Control services leveraging smart contracts provided by blockchain technology. The key idea of our proposal is to codify policies as executable on blockchain. transforms the policy evaluation process into completely distributed contract executions. In fully based also Attribute Managers required are managed blockchain, i.e., they implemented well. To study feasibility we present working reference implementation using XACML and Solidity...

The availability of the entire Bitcoin transaction history, stored in its public blockchain, offers interesting opportunities for analysing graph to obtain insight on users behaviour. This paper presents an analysis graph, obtained by clustering highlight connectivity structure and economical meaning different components. In fact, bow tie structure, already observed web, is augmented, Bitocoin with information about entities involved. We study components individually, infer their macroscopic...

The recent interest for decentralised systems and decentralisation of the control over users' data brings a shift in way identities their information are managed. Self Sovereign Identity (SSI) has been proposed as next generation paradigm identity management. Research on SSI is getting more traction, focusing mainly management identifiers providing standard to express verify credentials. Instead, this paper focuses understanding role trust it provides new insight into relationships existing...

Set accumulators are cryptographic primitives used to represent arbitrarily large sets of elements with a single constant-size value and efficiently verify whether belongs that set. Accumulators support the generation membership proofs, meaning they can certify presence given among In this paper we present an overview theoretical concepts underlying set accumulators, compare most popular constructions from complexity perspective, survey number their applications related blockchain...

Abstract The increasing adoption of tokens on the Ethereum blockchain has given rise to many distinct economic communities whose activity history is publicly accessible. In this paper we study fungible and non-fungible tokens, regulated, respectively, by ERC-20 ERC-721 standards. particular, focus token transfers consider top 100 largest ecosystems number transfers, modeling them as networks where nodes correspond participants edges represent transfers. We analyze their main topological...

Abstract In the Bitcoin protocol, dust refers to small amounts of currency that are lower than fee required spend them in a transaction. Although “economically irrational”, is commonly used for achieving unconventional side effects, rather exchanging value. For instance, might be linked on-chain services or malicious activity, such as attacks attempting break users’ pseudonymity. To study this phenomenon, paper presents an depth analysis transactions involving dust, showing how created and...

Cryptocurrencies are notorious for their exchange rate high volatility, and often tools of wild speculation rather than decentralised value exchange. This is especially true Bitcoin, still, nowadays, the most popular cryptocurrency. paper presents an analysis to detect influence a set topological properties Bitcoin Users Graph on Bitcoin's rate. <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1</sup> 1. In rest this we will use terms "Bitcoin...

New applications such as remote surgery and connected cars, which are being touted use cases for 5G beyond, mission-critical. As such, communications infrastructure needs to support enforce stringent guaranteed levels of service before can take off. However, from an operator's perspective, it be difficult provide uniformly high over long durations or large regions. network conditions change time, when a mobile end point goes regions with poor coverage, may the operator previously agreed upon...