Article Beyond Bitcoin: A Critical Look at Blockchain-Based Systems Diego Romano and Giovanni Schmid * Istituto di Calcolo e Reti ad Alte Prestazioni, I 80131 Naples, Italy;
[email protected] * Correspondence:
[email protected]; Tel.:+39-08-1613-9529 Received: 7 July 2017; Accepted: 16 August 2017; Published: 1 September 2017 Abstract: After more than eight years since the launch of Bitcoin, the decentralized transaction ledger functionality implemented through the blockchain technology is being used not only for cryptocurrencies, but to register, confirm and transfer any kind of contract and property. In this work, we analyze the most relevant functionalities and known issues of this technology, with the intent of pointing out the possible behaviours that are not as efficient and reliable as they should be when thinking with a broader outlook. Keywords: cryptocurrency; blockchain technology; smart contract 1. Introduction The existence of digital currencies is strictly related to the broad diffusion of Internet and on-line markets. A digital currency is similar to electronic money but even if it can be used to buy services or physical goods like traditional money, it is not equivalent or linked to any fiat currency. The idea of using a digital currency became realistic when some important developments in cryptography settled multiple fundamental security challenges in money transfers, e.g., the necessary trust in the transaction. Several digital currencies have been implemented in the last 20 years, but only starting in 2008 did the project for a currency decentralized in every respect become a reality. In fact previous implementations (e.g., [1–4]) employed a point of control over the money supply, which in some cases exposed the whole system to attacks for taking control over it.