Parking Tickets for Privacy-Preserving Pay-by-Phone Parking

This document is a postprint version of the paper presented at the 18th Workshop on Privacy in the Electronic Society (WPES’19), November 11, 2019, London (United Kingdom).Traditionally, the payment required for parking in regulated areas has been made through parking meters. In the last years, several applications which allow to perform these payments using a mobile device have appeared. In this paper we propose a privacy-preserving pay-by-phone parking system o ering the same privacy as the traditional paper- based method even assuming an internal attacker with full access to all the information managed by the system servers. Drivers'privacy is preserved without requiring them to trust any party. Furthermore, the system can tolerate that the mobile devices of drivers fall out of coverage while their cars are parked

A Digital Cash Paradigm with Valued and No-Valued e-Coins

Digital cash is a form of money that is stored digitally. Its main advantage when compared to traditional credit or debit cards is the possibility of carrying out anonymous transactions. Diverse digital cash paradigms have been proposed during the last decades, providing different approaches to avoid the double-spending fraud, or features like divisibility or transferability. This paper presents a new digital cash paradigm that includes the so-called no-valued e-coins, which are e-coins that can be generated free of charge by customers. A vendor receiving a payment cannot distinguish whether the received e-coin is valued or not, but the customer will receive the requested digital item only in the former case. A straightforward application of bogus transactions involving no-valued e-coins is the masking of consumption patterns. This new paradigm has also proven its validity in the scope of privacy-preserving pay-by-phone parking systems, and we believe it can become a very versatile building block in the design of privacy-preserving protocols in other areas of research. This paper provides a formal description of the new paradigm, including the features required for each of its components together with a formal analysis of its security.This research was funded by the Spanish Ministry of Science, Innovation and Universities grant number MTM2017-83271-R

An Elliptic Curve Based Homomorphic Remote Voting System

A remote voting system allows participants to cast their ballots through the Internet. Remote voting systems based on the use of homomorphic public key cryptography have proven to be a good option for carrying out simple elections with a reduced amount of candidates. In this paper, we present a new system that makes use of the additive homomorphic capabilities of the Elliptic Curve ElGamal (EC-ElGamal) cryptosystem. All the stages of the system are described together with an experimental analysis section which provides an assessment on the type of election our system would be suitable for.Research of the authors was supported in part by grants MTM2010-21580-C02-01 (Spanish Ministerio de Ciencia e Innovación), 2014SGR-1666 (Generalitat de Catalunya) and IPT-2012-0603-430000 (Spanish Ministerio de Economía y Competitividad)