Uniswap is regarded as the leading decentralized exchange (DEX) platform, allowing users to trade (i.e., swap) one asset for another without intermediaries, thanks to blockchain technology. The platform consists of smart contracts holding asset reserves, called liquidity pools, and its widespread adoption constitutes an opportunity for assessing whether the promises of decentralization of DEXes are effectively fulfilled in practice. For this reason, in this paper we propose an analysis of the Uniswap ecosystem, focusing on the implementation of version 3 on the Ethereum blockchain. First, we study liquidity pools and their core operations, aiming to quantify the overall activity levels. Next, we focus on liquidity provision to assess whether users diversify their participation across multiple pools. We then analyze asset swapping activity, identifying the most active pools and the most frequently traded assets. Finally, we perform a complex network analysis of multi-hop swaps, namely trades routed through multiple pools. We represent them as a graph and study its topological properties. Results show that pool creations and activity have grown steadily, but many pools trigger few operations and remain active for at most two weeks. Also, trader activity concentrates in pools involving the Wrapped Ether asset and major stablecoins, while about 60% of liquidity providers hold only a single position, thus participating in only one pool. Finally, network analysis suggested a preferential attachment phenomenon, with a few pools handling most swaps and acting symmetrically as both entry and exit bridges.

This paper considers the application scenario of Intellectual Property (IP) management, a business process yet to fully embrace digitisation and the advantages it brings. We propose to leverage Distributed Ledger Technology (DLT) to digitise license agreements management by providing automated and trustworthy royalty computation, transaction execution, and payment distribution. This can be achieved by employing smart licenses, i.e., bundles of smart contracts implementing the royalty logic of license agreements. To provide scalability, flexibility, and resilience, we propose to deploy smart licenses on a network of networks model, i.e., a set of heterogeneous networks potentially running different DLT protocols and connected by cross-chain information exchange protocols. A novel advantage of the network of networks approach is that it allows for the use of private values for royalty computation, which is impossible in the traditional model. Of course, supporting private DLT networks requires privacy-preserving cross-chain schemes, a still open problem in the literature. This is why we present two alternative privacy-preserving cross-chain schemes for our considered application scenario of license agreements management, one based on Homomorphic Encryption (HE) and the other on Zero-Knowledge (ZK) proofs. Besides discussing their theoretical advantages and drawbacks, we present an experimental evaluation of a prototype implementation of smart licenses based on both schemes.

Decentralized applications, the driving force behind the new Web3 paradigm, require continuous access to blockchain data. Their adoption, however, is hindered by the constantly increasing size of blockchains and the sequential scan nature of their read operations, which introduce a clear inefficiency bottleneck. Also, the growing amount of data recorded on the blockchain makes resource-constrained light nodes dependent on untrusted full nodes for fetching information, with a consequent need for query authentication protocols ensuring result integrity. Motivated by these reasons, in this paper we propose the skip index, an indexing data structure that allows users to quickly retrieve information simultaneously from multiple blocks of a blockchain. Our solution is also designed to be used as an authenticated data structure to guarantee the integrity of query results for light nodes. We discuss the theoretical properties of skip indices, propose efficient algorithms for their construction and querying, and detail their computational complexity. Finally, we assess the effectiveness of our proposal through an experimental evaluation on the Ethereum blockchain. As a reference use case, we focus on the popular CryptoKitties application and simulate a scenario where users seek to retrieve the events generated by the service. Our experimental results suggest that the use of skip indices offers a constant multiplicative speedup, thanks to search times that are at most logarithmic within a chosen search window. This allows to reduce the number of visited blocks by up to two orders of magnitude if compared to the naive sequential approach currently in use. • We propose the skip index, a data structure for efficient blockchain data retrieval. • The skip index provides guarantees about the integrity of query results. • We devise efficient algorithms to construct and query skip indices. • Compared to a sequential scan, skip indices offer a constant multiplicative speedup. • Skip indices experimentally provide a speedup of up to two orders of magnitude.