A Construction for Providing Reusability to Mobile Phone-Based e-Tickets

Nowadays, the use of electronic tickets in public transport is a reality. Several mobile phone-based e-ticket systems have been proposed so far. Even so, very few of them include reusability in the sense that a single e-ticket allows to make several journeys. Although the identity of users is usually hidden behind a pseudonym, the existing proposals providing reusability allow the system to link all the journeys made with a given e-ticket. In this paper we present a privacy-preserving construction allowing to endow a mobile phone-based e-ticket system with reusability. The privacy of users is proven to be preserved even assuming an internal attacker with full access to all the information managed by the system servers. All the sensitive interactions of a user with the system keep anonymous and unlinkable. Further, as a result of an inspection, the system is only able to determine whether the inspected user is allowed to make the current journey.