Ana I. González-Tablas

An optimistic fair exchange protocol based on signature policies

The growth of the e-commerce has allowed companies and individuals to sell and purchase almost any kind of product and service through the Internet. However, during the purchase transaction there is a moment during which the seller has sensitive information from the buyer, typically his/her credit card information, while the buyer has nothing from the seller. This situation clearly places the buyer at disadvantage and is, together with fear of fraud, one of the reasons of the lack of confidence in e-commerce. For resolving this situation a new fair exchange protocol based on signature policies is presented. A signature policy is a set of rules to create and validate electronic signatures, under which an electronic signature can be determined to be valid in a particular transaction context. Due to the signature policy-based design, the proposed protocol allows the buyer to decide if trust or not in the rules that will manage the transaction, increasing the users confidence in e-commerce. Security, fairness and timeliness characteristics of the protocol are evaluated. Implementation guidelines are also provided taking into consideration latest security standards.

Security Models in Vehicular Ad-hoc Networks: A Survey

ABSTRACT The security and privacy issues of vehicular ad-hoc networks (VANETs) must be addressed before they are implemented. For this purpose, several academic and industrial proposals have been developed. Given that several of them are intended to co-exist, it is necessary that they consider compatible security models. This study presents a survey of the underlying security models of 41 recent proposals. Four key aspects in VANET security are studied, namely trust on vehicles, trust on infrastructure entities, existence of trusted third parties and attacker features. Based on the survey analysis, a basic mechanism to compare VANET security models is also proposed, thus highlighting their similarities and differences.

Survey on location authentication protocols and spatial-temporal attestation services

A survey on location authentication protocols and spatial-temporal attestation services is presented. Several protocols and services with these objectives have been proposed during the last decade, but still there is a lack of understanding of the security properties they should provide and which security mechanisms are appropriate. We first define the goals and threat model of location authentication protocols, next they are described and analyzed against this model. Also, spatial-temporal attestation services are described and classified depending on their goal and kind of issued evidence.

A taxonomy and survey of attacks on digital signatures

Non-repudiation is a desired property of current electronic transactions, by which a further repudiation of the commitments made by any involved party is prevented. Digital signatures are recognized by current standards and legislation as non-repudiation evidence that can be used to protect the parties involved in a transaction against the others false denial about the occurrence of a certain event. However, the reliability of a digital signature should determine its capability to be used as valid evidence. The inevitability of vulnerabilities in technology and the non-negligible probability of an occurrence of security threats would make non-repudiation of evidence difficult to achieve. We consider that it is of the utmost importance to develop appropriate tools and methods to assist in designing and implementing secure systems in a way that reliable digital signatures can be produced. In this paper, a comprehensive taxonomy of attacks on digital signatures is presented, covering both the signature generation and verification phases. The taxonomy will enable a rigorous and systematic analysis of the causes that may subvert the signature reliability, allowing the identification of countermeasures of general applicability. In addition, an intensive survey of attacks classified under our taxonomy is given.

Privacy-preserving and accountable on-the-road prosecution of invalid vehicular mandatory authorizations

Nowadays, improving road safety is one of the major challenges in developed countries and, to this regard, attaining more effectiveness in the enforcement of road safety policies has become a key target. In particular, enforcing the requirements related to the technical and administrative mandatory documentation of on-the-road motor vehicles is one of the critical issues. The use of modern technologies in the context of Intelligent Transportation Systems (ITS) could enable the design of a more convenient, frequent and effective enforcement system compared to the traditional human patrol controls. In this article we propose a novel system for the on-the-fly verification of mandatory technical and administrative documentation of motor vehicles. Vehicles not complying with the required regulations will be identified and sanctioned whereas those vehicles, observant of the mandatory regulations, will maintain anonymity and non-traceability of their whereabouts. The proposed system is based on the use of anonymous credentials which will be loaded onto the vehicle to automatically and on-the-fly prove holdership of required credentials without requiring the vehicle to stop beside the road. We also implement a prototype of the credential system and analyze the feasibility of our solution in terms of computational cost and time to perform such telematic controls.

Applying Information Hiding in VANETs to Covertly Report Misbehaving Vehicles

Vehicular ad hoc networks (VANETs) are a new communication scenario in which vehicles take an active part. Real-time reporting of misbehaving vehicles by surrounding ones is enabled by in-vehicle sensors and VANETs. Thus, sensors allow detecting the misbehavior whereas VANETs allow sending the report to the authority. Nevertheless, these reports should pass unnoticed by the reported driver to avoid his/her potential reprisals. Information hiding techniques could be used to allow vehicles to transmit information covertly. In this work, two mechanisms for vehicle reporting are proposed based on two information hiding techniques—subliminal channels and steganography. The approach is to embed information into beacon messages either in the signature process (subliminal channel) or altering the least significant bits of selected sensorial fields (steganography). Results show that the proposal is computationally feasible for current vehicular devices and that it is possible to configure the system to operate in highways, secondary roads, and urban maps.

SoNeUCONABC, an expressive usage control model for Web-Based Social Networks

Abstract In the era of hyper-connectivity Web-Based Social Networks (WBSNs) are demanding applications. They facilitate the interaction of huge amounts of users and the development of appropriate Access Control Models (ACMs) is an arising necessity. Particularly, the development of WBSNs ACMs with expressive power and capable of managing access control along the whole usage process is the challenge pursued. To contribute on this issue, first, 23 proposals have been analysed and second, SoNeUCON ABC , an expressive usage control model for WBSNs, is proposed. It extends UCON ABC ( Park, 2003 ) including relationships management and it is formally defined, specifying entities and elements involved and an access control policy language. Moreover, policy construction is carefully detailed by using regular expressions and access control enforcement functions are described. Finally, the evaluation shows, theoretically, the significant expressive power of SoNeUCON ABC and, empirically, the feasibility of its implementation by the development of a proof of concept system.

Towards an XML format for time-stamps

XML has become a well-established format for information exchange. Several formats have been defined to secure XML data, such as XML Digital Signatures, XML Encryption and XKMS. In recent work by ETSI on XML digital signatures conforming to European legislation, time-stamps play a key role for qualified digital signatures. Some ASN.1-based formats for time-stamp protocols have been defined within IETF and ISO/IEC. In this paper, we investigate how the wide range of time-stamping protocols in the literature can be embedded into a single XML format; our work is based on existing standardisation efforts. We present our ideas in the form of a concrete XML structure, which can be used as the starting point to develop a mature XML-based time-stamping protocol.

WEVAN - A mechanism for evidence creation and verification in VANETs

There are traffic situations (e.g. incorrect speeding tickets) in which a given vehicles driving behavior at some point in time has to be proved to a third party. Vehicle-mounted sensorial devices are not suitable for this matter since they can be maliciously manipulated. However, surrounding vehicles may give their vision on another ones behavior. Furthermore, these data may be shared with the affected vehicle through VANETs. In this paper, a VANET-enabled data exchange mechanism called WEVAN is presented. The goal of this mechanism is to build and verify evidences based on surrounding vehicles (called witnesses) testimonies. Due to the short-range nature of VANETs, the connectivity to witnesses may be reduced with time - the later their testimonies are requested, the lower the amount of witnesses may be. Simulation results show that if testimonies are ordered 5s later, an average of 38 testimonies may be collected in highway scenarios. Other intervals and road settings are studied as well.

Formal Validation of OFEPSP+ with AVISPA

Formal validation of security protocols is of utmost importance before they gain market or academic acceptance. In particular, the results obtained from the formal validation of the improved Optimistic Fair Exchange Protocol based on Signature Policies (OFEPSP+) are presented. OFEPSP+ ensures that no party gains an unfair advantage over the other during the protocol execution, while substantially reducing the probability of a successful attack on the protocol due to a compromise of the signature creation environment. We have used the Automated Validation of Internet Security Protocols and Applications (AVISPA) and the Security Protocol ANimator for AVISPA (SPAN), two powerful automated reasoning technique tools to formally specify and validate security protocols for the Internet.