The Internet has plenty of images that are transformations (e.g., resize, blur) of confidential original images. Several scenarios (e.g., selling images over the Internet, fighting disinformation, detecting deep fakes) would highly benefit from systems allowing to verify that an image is the result of a transformation applied to a confidential authentic image. In this paper, we focus on systems for proving and verifying the correctness of transformations of authentic images guaranteeing: 1) confidentiality (i.e., the original image remains private), 2) efficient proof generation (i.e., the proof certifying the correctness of the transformation can be computed with a common laptop) even for high-resolution images, 3) authenticity (i.e., only the advertised transformations have been applied) and 4) fast detection of fraud proofs.. Our contribution consists of new definitions modelling confidentiality and adaptive adversaries, techniques to speed up the prover of a ZK-snark, an efficient construction relying on ad-hoc signatures and hashes, and a less efficient construction that works according to signatures and hashes included in the C2PA specifications. Experimental results confirm the viability of our approach, allowing to compute an authentic transformation of a high-resolution image on a common computer. Prior results instead either require expensive computing resources or provide unsatisfying confidentiality.

The Interested Party Information (IPI) system uniquely identifies the rights holders worldwide, making it possible to know for each subject and at any time which rights are protected, by whom and for which territories. Currently, this service is provided in a centralized way but in 2021, the Italian Society of Authors and Editors (SIAE) deployed a blockchain-based solution to completely decentralize this database to (a) provide greater guarantees to the rights holders as well as end users and (b) make a first tangible step in the path towards an all in-chain solution decentralizing a relevant component of the current architecture. This solution relied on early versions of Algorand smart contracts, delegating some off-chain verification to trusted third parties in many practical scenarios. Moreover, the Algorand technology has developed new tools, allowing us to design new techniques to reduce some of the trust assumptions of the original solution and enhance its efficiency at the same time. In this paper, we present the evolution of the solutions we designed to issue new on-chain non-conflicting rights representations, namely representations that are consistent with those already available on-chain. Our solution relies on smart contracts that have been implemented to run our experiments to prove (a) the feasibility of the proposed approach, (b) the scalability of the proposed solutions, and (c) the sustainability in terms of costs.

Ethereum's founder Buterin raised the challenge of solving the blockchain Trilemma towards a decentralized computer that could together achieve high degrees of security, scalability, and decentralization. Later on, Algorand claimed to have resolved Buterin's blockchain Trilemma and is nowadays increasingly adopted by designers of decentralized computations. Motivated by the need of selecting a blockchain to run some decentralized computations, we observe the limitations of using the Trilemma as benchmark, and we propose as alternative a Quadrilemma that takes into account also computational effectiveness, namely the capability of running non-trivial decentralized computations at affordable costs. For concreteness, motivated by the current trends of using blockchains for the management of non-fungible tokens (NFTs) related to highly desired items (i.e., NFTs for art), we consider the use case of decentralized auctions in various scenarios that mainly differ on the desired degree of confidentiality. Our contribution gives the following insights. Except very limited cases where also Bitcoin can be taken into account (i.e., when latency is not a big deal and only notarization is required), Algorand can often be the right choice as long as decentralized computations consist of basic operations only. Instead, Ethereum is advisable when more sophisticated computations are required, in particular when ad-hoc cryptographic tasks are essential, and one can afford the involved costs and latency. Focusing on those three blockchains, the state of affairs about resolving the blockchain Quadrilemma is somewhat unsatisfying. Even in natural cases where computations and storage requirements for a smart contract are low (e.g., public-key encryption), none of those decentralized computers achieves simultaneously low cost and fast transaction confirmations.

Adopting modern emerging technologies of smart metering based on IoT that extend existing water distribution systems is of paramount importance for improving the operational efficiency of the water supply system in the cities and rural communities. Real-world data collected by smart water meters allows the analysis of consumption of water. In this work, data collected over a period of 28 months is analyzed on weekly, daily and hourly basis to identify usage patterns in relation to the restrictions imposed by the local authorities as a response to the COVID-19 emergency taking place during 2020 and 2021. The evaluation of water consumption before, during and after the lockdown periods highlights the impact of human actions. A novel data-driven method is presented to profile buildings that can help identify similarities and highlight differences across water usage patterns.

In many applications, identity management (IdM) is used to associate a subject public key with an endpoint at which the subject can be contacted (telephone number, email, etc.). In decentralized applications based on blockchains, it is desirable for the IdM to be decentralized as well. In certain applications, it is paramount to be certain that an endpoint actually belong to a specific subject. Currently, when this is needed, endpoints are either verified by who needs it, which is impractical in blockchain-based applications, or by a centralized authority, which contrasts with the spirit of the blockchain.In this paper, we show two layer-two blockchain-based protocols to prove the association between a subject and an endpoint in a decentralized manner. Our protocols are compatible with a wide variety of endpoints and contribute to fill the gap of the current self sovereign IdM approaches with respect to decentralization. We analyze the security of our proposals and evaluate performances and costs against the common approaches.