1 Preface This book contains the contributions which were selected for publication at the second edition of the Distributed Ledger Technology Workshop (DLT 2019), which has been held in conjunction with ITASEC19 in Pisa, on February 12, 2019. This event follows the First edition of the workshop held in Perugia in 2018, and represents the annual meeting of the Italian DLT group. Distributed Ledger Technology is having an ever growing popularity. Nowa- days, the most popular application of DLT concerns cryptocurrencies (Bitcoin, Litecoin, Monero, etc.), but the DLT features allow them to be applied in many scenarios, both in research and business contexts. In particular, the DLT tech- nology is suitable to be adopted in a large number of application fields, e.g. Internet of Things, cyber-physical Systems, edge computing, and supply-chain management. The DLT workshops are meant as a forum for researchers, developers, and users to discuss issues related to Distributed Ledger Technology and its adoption in research and business scenarios. The primary goal is to foster discussion and cross-fertilisation of ideas among experts in different fields related to DLTs, and thus advance the national and international state-of-the-art. Research, applications, case studies, and experiences concerning DLT are all encouraged. The workshop solicited two kind of contributions: research papers and oral communications. Both contributions entailed an oral presentation at the work- shop, but only the former are reported in this book. In particular, the workshop accepted 6 research papers and 9 oral contributions. We would like to express our thanks to the authors who submitted their pa- pers to our workshop, and to the members of the Technical Program Committee for their valuable work in evaluating the submitted papers. February, 12 2019 Paolo Mori Stefano Bistarelli Massimo Bartoletti 2 Workshop Chairs Paolo Mori Consiglio Nazionale delle Ricerche, Italy Massimo Bartoletti Università degli Studi di Cagliari, Italy Stefano Bistarelli Università degli Studi Perugia, Italy Steering Committee Leonardo Aniello University of Southampton, UK Massimo Bartoletti Università degli Studi di Cagliari, Italy Stefano Bistarelli Università degli Studi Perugia, Italy Maurizio Pizzonia Università degli Studi Roma Tre, Italy Andrea Vitaletti Università degli Studi di Roma “La Sapienza”, Italy Technical Program Committee Leonardo Aniello University of Southampton, UK Andrea Bracciali University of Stirling, UK Francesco Buccafurri Università degli Studi “Mediterranea” di Reggio Calabria, Italy Stelvio Cimato Università degli Studi di Milano, Italy Gabriele D’Angelo Università di Bologna, Italy Andrea De Salve Consiglio Nazionale delle Ricerche, Italy Damiano Di Francesco Maesa University of Cambridge, UK Stefano Ferretti Università di Bologna, Italy Letterio Galletta IMT Scuola Alti Studi Lucca, Italy Alberto Leporati Università degli Studi di Milano, Italy Michele Marchesi Università degli Studi di Cagliari, Italy Remo Pareschi Università degli Studi del Molise, Italy Maurizio Pizzonia Università degli Studi Roma Tre, Italy Laura Ricci Università di Pisa, Italy Giovanni Sartor Università di Bologna, Italy and European University Institute Francesco Tiezzi Università degli Studi di Camerino, Italy Andrea Vitaletti Università degli Studi di Roma “La Sapienza”, Italy Roberto Zunino Università degli Studi di Trento, Italy Organizing Committee Ivan Mercanti IMT Scuola Alti Studi, Lucca Andrea De Salve Consiglio Nazionale delle Ricerche, Italy 3 Workshop Program You can find below the DLT 2019 technical sessions. We point out the 6 papers contained in these proceeding in bold font. All the remaining oral com- munications are not contained therein, and they have been presented at the workshop. Technical Session 1 • Massimo Bartoletti, Roberto Zunino Verifying liquidity of Bitcoincontracts • Chantal Bomprezzi Smart contracts on blockchain: some false myths • Lodovica Marchesi, Michele Marchesi, Roberto Tonelli dApp Implementation using an Agile, yet Systematic Approach • Francesco Buccafurri, Gianluca Lax, Lorenzo Musarella, Anto- nia Russo Ethereum Transactions and Smart Contracts among Secure Iden- tities • Ettore Battaiola, Fabio Massacci, Chan Nam Ngo, Pierantonia Sterlini Blockchain-based Invoice Factoring: from business requirements to commitments • Alessio Meneghetti, Armanda Ottaviano Quintavalle, Massim- iliano Sala, Alessandro Tomasi Two-tier blockchain timestamped notarization with incremental security Technical Session 2 • Matteo Bernardini, Diego Pennino, Maurizio Pizzonia Blockchains Meet Distributed Hash Tables: Decoupling Valida- tion from State Storage (Extended Abstract) • Andrea Morichetta, Andrea Polini, Barbara Re, Francesco Tiezzi Choreographies Enactment Via Smart Contracts • Stefano Bistarelli, Gianmarco Mazzante, Matteo Micheletti, Leonardo Mostarda, Francesco Tiezzi Analysis of Ethereum Smart Contracts and Opcodes • Paolo Mori, Damiano Di Francesco Maesa, Laura Ricci Exploiting Blockchain Technology to Design an Attribute Based Access Control System 4 • Luisa Siniscalchi, Ivan Visconti On Deleting Data from a Blockchain • Alessandra Scafuro, Luisa Siniscalchi, Ivan Visconti Publicly Verifiable Argument Systems Through Generic Blockchains Technical Session 3 • Laura Ricci, Andrea Marino, Damiano Di Francesco Maesa Analysing the structure of the Bitcoin users graph • Claudio Ferretti, Alberto Leporati, Luca Mariot, Luca Nizzar do Transferable Anonymous Payments via TumbleBit in Permis- sioned Blockchains • Roberto Carlini, Federico Carlini, Stefano Dalla Palma, Remo Pareschi Genesy: a Blockchain-based Platform for DNA Sequencing External session • Contracts and Smart Contracts Giovanni Sartor Panel • Adozione della blockchain in azienda: aspetti tecnici e legali Pierangelo Soldavini (moderatore), Massimo Chiriatti, Notaio Michele Manente, Nicola Santoni Tutorial • Blockchain for Public Administrations Massimo Bartoletti, Andrea Vitaletti