Oscar Esparza

A review of trust modeling in ad hoc networks

Purpose – Mobile ad hoc networks rely on cooperation to perform essential network mechanisms such as routing. Therefore, network performance depends to a great extent on giving participating nodes an incentive for cooperation. The level of trust among nodes is the most frequently used parameter for promoting cooperation in distributed systems. There are different models for representing trust, each of which is suited to a particular context and leads to different procedures for computing and propagating trust. The goal of this study is to analyze the most representative approaches for mobile ad hoc networks. It aims to obtain a qualitative comparison of the modeling approaches, according to the three basic components of a trust model: information gathering, information scoring and ranking, and action execution.Design/methodology/approach – The paper identifies the different tasks required by a trust system and compares the way they are implemented when the system model itself is based on information theor...

Secure brokerage mechanisms for mobile electronic commerce

The possibility of making the Internet accessible via mobile devices has generated an important opportunity for electronic commerce. Nevertheless, some deficiencies deter a massive use of m-commerce applications. Security and easiness of use are unavoidable conditions. The use of brokerage systems constitutes an interesting solution to speed up the information delivery to the users. Moreover, brokers can use mobile agents to efficiently and easily perform the search and retrieval of commercial information in the Internet. Although the mobile agent technology is a very suitable choice for the m-commerce scenario, there are security issues that hinder its use. In particular, an important aspect that must be solved for the m-commerce scenario is the mobile agent protection from manipulation attacks performed by malicious hosts. The first part of this paper describes a mechanism to reach this protection. We describe how to use software watermarking techniques in the mobile agent to detect manipulation attacks, and how the broker can be used to punish the malicious hosts. Once an m-commerce site is selected by the user, an end-to-end secure transaction must be established. The transaction can use several protocols, from a simple secure TLS channel to send a credit card number until a sophisticated payment protocol. In any case, Public Key Certificates (PKCs) are required for these protocols. It must be stressed that certificates management is a heavy process and that clients in the brokerage scenario are usually resource-limited. For this reason, the best option is that clients delegate this task to the broker. Notice that the broker is a Trusted Third Party (TTP) and, in general, it is not resource-limited. Therefore, the broker is appropriate for storing and managing PKCs. The second part of this paper addresses this issue, with a particular emphasis in the certificate status management which is the most complex task of certificate management.

Host revocation authority: a way of protecting mobile agents from malicious hosts

Mobile agents are software entities that consist of code, data and state, and that can migrate autonomously from host to host executing their code. Despite its benefits, security issues restrict the use of code mobility. The approach that is presented here aids to solve the problem of malicious hosts by using a Trusted Third Party, the Host Revocation Authority. The HoRA controls which are the hosts that acted maliciously in the past. The agent sender must consult the HoRA before sending an agent in order to remove from the agents itinerary all the revoked hosts. The HoRA can also revoke a malicious host if the agent sender detects and proves that this malicious host did not act honestly.

Mobile Agent Watermarking and Fingerprinting: Tracing Malicious Hosts

Mobile agents are software entities consisting of code and data that can migrate autonomously from host to host executing their code. Despite its benefits, security issues strongly restrict the use of code mobility. The protection of mobile agents against the attacks of malicious hosts is considered the most difficult security problem to solve in mobile agent systems.

Certificate revocation system implementation based on the Merkle hash tree

Public-key cryptography is widely used to provide Internet security services. The public-key infrastructure (PKI) is the infrastructure that supports the public-key cryptography, and the revocation of certificates implies one of its major costs. The goal of this article is to explain in detail a certificate revocation system based on the Merkle hash tree (MHT) called AD–MHT. AD–MHT uses the data structures proposed by Naor and Nissim in their authenticated dictionary (AD) [20]. This work describes the tools used and the details of the AD–MHT implementation. The authors also address important issues not addressed in the original AD proposal, such as responding to a request, revoking a certificate, deleting an expired certificate, the status checking protocol for communicating the AD–MHT repository with the users, verifying a response, system security, and, finally, performance evaluation.

Using OCSP to Secure Certificate-Using Transactions in M-commerce

The possibility of making the Internet accessible via mobile telephones has generated an important opportunity for electronic commerce. Nevertheless, some deficiencies deter its mass acceptance in e-commerce applications. In order to speed up the information delivery, the use of brokerage systems constitutes an interesting solution. In this paper we review the problem of certificate validation in m-commerce transactions and we present an architecture where a broker is used as OCSP responder for the certificate validation. A modification over OCSP called \(\mathcal{H}\)-OCSP is also proposed as a way to reduce the computational load and the bandwidth requirements of OCSP which is specially desirable in the wireless environment. The ASN.1 add-on for \(\mathcal{H}\)-OCSP that makes it inter-operable with the standard OCSP is defined and the behaviour of \(\mathcal{H}\)-OCSP compared to standard OCSP is evaluated.

Certificate status validation in mobile ad hoc networks

Certificate validation is much more complex in mobile ad hoc networks than in conventional networks because online access to trusted authorities is not always guaranteed. For this reason, we require new solutions to overcome both the lack of infrastructure and the limited capabilities of several user devices. In this article we study the application of different mechanisms for certificate validation in MANETs and present a cooperative mechanism for certificate validation suitable for MANETs.

COACH: COllaborative certificate stAtus CHecking mechanism for VANETs

Vehicular Ad Hoc Networks (VANETs) require mechanisms to authenticate messages, identify valid vehicles, and remove misbehaving vehicles. A public key infrastructure (PKI) can be used to provide these functionalities using digital certificates. However, if a vehicle is no longer trusted, its certificates have to be revoked and this status information has to be made available to other vehicles as soon as possible. In this paper, we propose a collaborative certificate status checking mechanism called COACH to efficiently distribute certificate revocation information in VANETs. In COACH, we embed a hash tree in each standard Certificate Revocation List (CRL). This dual structure is called extended-CRL. A node possessing an extended-CRL can respond to certificate status requests without having to send the complete CRL. Instead, the node can send a short response (less than 1 kB) that fits in a single UDP message. Obviously, the substructures included in the short responses are authenticated. This means that any node possessing an extended-CRL can produce short responses that can be authenticated (including Road Side Units or intermediate vehicles). We also propose an extension to the COACH mechanism called EvCOACH that is more efficient than COACH in scenarios with relatively low revocation rates per CRL validity period. To build EvCOACH, we embed an additional hash chain in the extended-CRL. Finally, by conducting a detailed performance evaluation, COACH and EvCOACH are proved to be reliable, efficient, and scalable.

Optimal tag suppression for privacy protection in the semantic Web

Leveraging on the principle of data minimization, we propose tag suppression, a privacy-enhancing technique for the semantic Web. In our approach, users tag resources on the Web revealing their personal preferences. However, in order to prevent privacy attackers from profiling users based on their interests, they may wish to refrain from tagging certain resources. Consequently, tag suppression protects user privacy to a certain extent, but at the cost of semantic loss incurred by suppressing tags. In a nutshell, our technique poses a trade-off between privacy and suppression. In this paper, we investigate this trade-off in a mathematically systematic fashion and provide an extensive theoretical analysis. We measure user privacy as the entropy of the users tag distribution after the suppression of some tags. Equipped with a quantitative measure of both privacy and utility, we find a close-form solution to the problem of optimal tag suppression. Experimental results on a real-world tagging application show how our approach may contribute to privacy protection.

RDSR-V. Reliable Dynamic Source Routing for video-streaming over mobile ad hoc networks

Mobile ad hoc networks (MANETs) are infrastructureless networks formed by wireless mobile devices with limited battery life. In MANETs for civilian applications, the network nodes may not belong to a single authority and they may not have a common goal. These MANETs are particularly vulnerable to selfish behavior, as some nodes may prefer saving resources to forward data. There are a few generic reputation-based systems for MANETs which could be used to enforce cooperation among nodes. However, we envision that the system performance can be highly improved by using cross-layer techniques that take into account the specific characteristics of each particular service. In this article, we propose a distributed and easy-to-implement routing mechanism based on reputation for the provision of MPEG-2 video-streaming services over MANETs. The main novelty that we introduce regarding the existent literature is that our proposal is service aware, that is to say, we consider the video-streaming service characteristics to develop a cross-layer design with the routing protocol. In addition, we do not introduce extra signaling overhead to monitor reputation because we use the standard video-streaming end-to-end signaling. Finally, simulation results show that our proposal clearly outperforms both standard Dynamic Source Routing (DSR) and OCEAN (a generic reputation-based mechanism).