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Abstract Decentralised systems have been proved to be quite effective to allow for trusted and accountable data sharing, without the need to resort to a centralised party that collects all the information. While complete decentralisation provides important advantages in terms of data sovereignty, absence of bottlenecks and reliability, it also adds some issues concerned with efficient data lookup and the possibility to implement complex queries without reintroducing centralised components. In this paper, we describe a system that copes with these issues, thanks to a multi‐layer lookup scheme based on Distributed Hash Tables that allows for multiple keyword‐based searches. The service of peer nodes participating in this discovery service is controlled and rewarded for their contribution. Moreover, the governance of this process is completely automated through the use of smart contracts, thus building a Decentralised Autonomous Organization (DAO). Finally, we present a use case where road hazards are collected in order to test the goodness of our system for geodata retrieval. Then, we show results from a performance evaluation that confirm the viability of the proposal.

We present a solution for accountability in Cloud infrastructures based on blockchain. We show that, through smart contracts, it is possible to create an unforgeable log that can be used for auditing and automatic Service Level Agreement (SLA) verification. As a practical case study, we consider Cloud storage services and define interaction protocols for registering the outcome of each file operation in the blockchain. We developed a prototype implementation that runs on the GoQuorum, Hyperledger Besu, and Polygon blockchains, using different consensus protocols. Using a dedicated testbed, we discuss the performance of our implementation in terms of latencies, error rates and gas usage. Results demonstrate the viability of our approach over permissioned blockchains, with better performance for the Polygon and GoQuorum Raft decentralized systems. Our implementation enables interoperability, given that it is supported by the Ethereum Virtual Machine which currently is underlying several blockchain platforms.

Data are becoming the cornerstone of many businesses and entire systems infrastructure. Intelligent Transportation Systems (ITS) are no different. The ability of intelligent vehicles and devices to acquire and share environmental measurements in the form of data is leading to the creation of smart services for the benefit of individuals. In this paper, we present a system architecture to promote the development of ITS using distributed ledgers and related technologies. Thanks to these, it becomes possible to create, store and share data generated by users through the sensors on their devices or vehicles, while on the move. We propose an architecture based on Distributed Ledger Technologies (DLTs) to offer features such as immutability, traceability and verifiability of data. IOTA, a promising DLT for IoT, is used together with Decentralized File Storages (DFSes) to store and certify data (and their related metadata) coming from vehicles or by the users' devices themselves (smartphones). Ethereum is then exploited as the smart contract platform that coordinates the data sharing through access control mechanisms. Privacy guarantees are provided by the usage of distributed key management systems and Zero Knowledge Proof. We provide experimental results of a testbed based on real traces, in order to understand if DLT and DFS technologies are ready to support complex services, such as those that pertain to ITS. Results clearly show that, while the viability of the proposal cannot be rejected, further work is needed on the responsiveness of DLT infrastructures.

Addressing the need for cost-efficient and environmentally friendly electrode materials for large-scale applications of bioelectrochemical systems, this study implemented the principles of circular economy to produce biochar- and hydroxyapatite/biochar-based conductive cathodes to be employed in clean and green technologies for wastewater treatment. Silverskin, the byproduct of coffee roasting responsible for generating significant waste worldwide, was subjected to a pyrolysis process to produce conductive biochar, then characterized in terms of physico-chemical properties. Biochar-based inks were formulated and employed to produce microporous layers on carbon cloth, finally used as cathodic materials in microbial fuel cells systems. The presence of hydroxyapatite in biochar-based composites was also evaluated with the goal of combining the remediation activity of biochar towards dissolved organic compounds, with that of hydroxyapatite towards inorganic ionic pollutants (such as Cd(II) and Zn(II)). Despite underperforming compared to other more technological and optimized materials, waste-derived biochar and its composite with hydroxyapatite were demonstrated to open novel frontiers in design and architecture of “multi-pollutants targeted” smarter bioelectrochemical systems, where not only microcurrent production, but a broader range of wastewater treatment can be addressed.