Resumen
Anonymous service delivery has attracted the interest of research and the industry for many decades. To obtain effective solutions, anonymity should be guaranteed against the service provider itself. However, if the full anonymity of users is implemented, no accountability mechanism can be provided. This represents a problem, especially when referring to scenarios in which a user, protected by anonymity, may perform illegally when leveraging the anonymous service. In this paper, we propose a blockchain-based solution to the trade-off between anonymity and accountability. In particular, our solution relies on three independent parties (one of which is the service provider itself) such that only the collaboration of all three actors allows for the disclosure of the real identity of the user. In all other cases, anonymity is guaranteed. To show the feasibility of the proposal, we developed a prototype with user-friendly interfaces that minimize the client-side operations. Our solution is then also effective from the point of view of usability.