A trust-driven privacy architecture for vehicular ad-hoc networks

Vehicular Ad-Hoc NETworks (VANETs) are an emerging technology which aims to improve road safety by preventing and reducing traffic accidents. While VANETs offer a great variety of promising applications, such as, safety-related and infotainment applications, they remain a number of security and privacy related research challenges that must be addressed. A common approach to security issues widely adopted in VANETs is the use of Public Key Infrastructures (PKI) and digital certificates in order to enable authentication, authorization and confidentiality. These approaches usually rely on a large set of regional Certification Authorities (CAs). Despite the advantages of PKI-based approaches, there are two main problems that arise, i) the secure interoperability among the different and usually unknown- issuing CAs, and ii) the sole use of PKI in a VANET environment cannot prevent privacy related attacks, such as, linking a vehicle with an identifier, tracking vehicles ¿big brother scenario" and user profiling. Additionally, since vehicles in VANETs will be able to store great amounts of information including private information, unauthorized access to such information should be carefully considered. This thesis addresses authentication and interoperability issues in vehicular communications, considering an inter-regional scenario where mutual authentication between nodes is needed. To provide interoperability between vehicles and services among different domains, an Inter-domain Authentication System (AS) is proposed. The AS supplies vehicles with a trusted set of authentication credentials by implementing a near real-time certificate status service. The proposed AS also implements a mechanism to quantitatively evaluate the trust level of a CA, in order to decide on-the-y if an interoperability relationship can be created. This research work also contributes with a Privacy Enhancing Model (PEM) to deal with important privacy issues in VANETs. The PEM consists of two PKI-based privacy protocols: i) the Attribute-Based Privacy (ABP) protocol, and ii) the Anonymous Information Retrieval (AIR) protocol. The ABP introduces Attribute-Based Credentials (ABC) to provide conditional anonymity and minimal information disclosure, which overcome with the privacy issues related to linkability (linking a vehicle with an identifier) and vehicle tracking (big brother scenario). The AIR protocol addresses user profiling when querying Service Providers (SPs), by relying in a user collaboration privacy protocol based on query forgery and permutation; and assuming that neither participant nodes nor SPs could be completely trusted. Finally, the Trust Validation Model (TVM) is proposed. The TVM supports decision making by evaluating entities trust based on context information, in order to provide i) access control to driver and vehicle's private information, and ii) public information trust validation

A Dynamic Validation Infrastructure for Interoperable Grid Services

Los encargados de recursos Grid pueden autorizar el acceso a sus elementos de cómputo por medio de procedimientos bien establecidos para los clientes, regularmente a través del uso de credenciales criptográficas que en su mayoría tienen un tiempo de vida definido.A pesar que la adopción de Autoridades de Certificación -AC- ha parcialmente resuelto el problema de identificación y autenticación entre entidades y, la tecnología PKI (Infraestructuras de Clave Pública) es bastante madura, no es posible hacer los mismos supuestos cuando existen dominios que no confían entre si. En los últimos años han proliferado las Organizaciones Virtuales -VOs- dentro del Grid, cada una instalando su propia Autoridad de Certificación y dando lugar a un gran número de diferentes dominios de seguridad, que efectivamente no confían entre si. Esto da lugar a un complejo escenario de interoperabilidad en Grid, que requiere mecanismos capaces de determinar si una credencial cliente puede ser confiada en un momento dado. Este proceso (llamado "validacion") ha sido tradicionalmente tratado via Listas de Revocación de Certificados (CRLs). Sin embargo, esta solución es ineficiente tanto para la ACs como para las aplicaciones Grid. En consecuencia son requeridos mecanismos mas eficientes que permitan conocer el estado de un certificado en tiempo real. Entre estas soluciones, el Online Certificate Status Protocol (OCSP) sobresale para los Grids. A pesar de su importancia para la seguridad, OCSP conlleva considerables retos para el Grid y de momento es incapaz para garantizar un grado seguro de interoperabilidad entre las ACs que participan en dicho ambiente.De momento la comunidad Grid ha resuelto el problema de interoperabilidad mediante el uso de "Policy Management Authorities" (PMAs), las cuales representan "Federaciones de Grid-PKIs" cuyas ACs miembros cumplen con niveles mínimos de seguridad. Estos requisitos mínimos forman el llamado "Perfil de Autenticación de la PMA". Actualmente el cumplimiento con el perfil de una cierta PMA se lleva a cabo a través de un proceso bien definido, pero manual, que se realiza una sola ocasión cuando una AC desea ser parte de dicha PMA. Esto se denomina "Proceso de Acreditación".Cualquier cliente invocando una operación de un servicio Grid, activa un proceso de autenticación que valida su certificado digital de acuerdo a un proceso llamado "Path Validation".Cuando las ACs participantes interoperan gracias a acuerdos explícitos de confianza, solamente se require un "Path Validation Básico": verificación criptográfica y chequeo del estado del certificado. Software Grid como el Globus Toolkit, provee mecanismos estáticos para dicho proceso. Esto sin embargo resulta inapropiado para VOs actuales.Asi pues, a pesar de la importancia que un proceso automático y "Extendido" de "Path Validation" tendría para construir relaciones de confianza dinámicamente en Grid-PKIs, a la fecha no existe ningún mecanismo para hacerlo.Esta tesis presenta una arquitectura novedosa para llevar a cabo el proceso "Extendido de Path Validation" en ambientes Grid para ACs que pertenecen a la misma PMA, gracias al uso de una Infraestructura de Validación basada en el Grid-OCSP y, una metodología de evaluación de políticas que compara las Políticas de Certificación de las ACs involucradas para asegurarse que cumplen con un Perfil de Autenticación y, que por lo tanto pueden interoperar entre ellas. La metodología de evaluación de políticas está basada en una propuesta de investigación de la "Universidad de Nápoles, Federico II" y la "Segunda Universidad de Nápoles". Un prototipo de la Infraestructura de Validación ha sido desarrollado durante nuestra investigación, y es ampliamente explicado en esta tesis.Grid Resource owners can authorize access to their computing elements by means of well established Authentication and Authorization processes for End-entities, through the use of cryptographic credentials that in most of the cases have a defined lifetime. Nevertheless, despite the fact that the adoption of Certification Authorities -CAs- has partially solved the problem of identification and authentication between the involved parties, and that Public Key Infrastructure -PKI- technologies are mature enough, we cannot make the same assumptions when untrusted domains are involved. In the last years a lot of Grid Virtual Organizations -VOs- have been proliferating, each one usually installing its own Certificate Authority and thus giving birth to a large set of different and possibly untrusted security domains. This brings a quite complex Grid interoperability scenario requiring mechanisms able to determine whether a particular end-entity's credential can be trusted at a given moment. This process is commonly named validation and traditionally it is performed via Certificate Revocation Lists (CRL). However this solution tends to be cumbersome for both, the CA and the application. In consequence, more efficient mechanisms to allow for the provision of real time certificate status information are required. Among these solutions, the Online Certificate Status Protocol (OCSP) stands out in the Grid community. Despite its importance for security, OCSP not only faces considerable challenges in the computational Grid but also, in its current form, this protocol is unable to guarantee a secure degree of interoperability among all the involved Grid-Certification Authorities. At the state of the art, the Grid community is circumventing the interoperability problem with the "Policy Management Authorities (PMAs)", which represent "Federations of Grid PKIs" whose CA members accomplish minimum levels of security. These minimum requirements comprise the PMA's Authentication Profile. In the case of the existing Grid PMAs, compliance with their respective authentication profile is given through a well-defined, but manual process involving a careful analysis of the applicant PKI's Certification Policy -CP-, performed just once, when a new CA wishes to be part of an existing PMA. This is known as the PMA's accreditation process.Any end-entity invoking a Grid Service's operation from the server, activates an authentication process that validates the end-entity's digital certificate according to the traditional path validation procedure.When involved CAs interoperate thanks to explicit trust agreements, only basic path validation is required: cryptographic verifications and status' checks over the involved certificates. State of the art Grid software like the Globus Toolkit, provides static mechanisms for the basic path validation. This is a cumbersome process in nowadays Virtual Organizations.Therefore, despite the importance that an automated and extended path validation process has got in order to build dynamic trust relationships among Grid PKI's, to date there is no mechanism to automatically obtain this information.This thesis presents a novel architecture for enabling extended path validation in Grid environments for CAs that are part of the same PMA, thanks to the use of a Validation Infrastructure based on a Grid-enabled Online Certificate Status Protocol and, a policy evaluation methodology that compares the involved CAs' Certificate Policies to assert that they fulfil with a particular Authentication Profile and that they can therefore interoperate among them. The policy evaluation technique is based on a formal methodology originally proposed by researchers of the "Università di Napoli, Federico II" and the "Seconda Università di Napoli". A working prototype of the proposed Validation Infrastructure was also developed during our research, and is widely explained along this thesis

Grid Cryptographic Simulation: A Simulator to Evaluate the Scalability of the X.509 Standard in the Smart Grid

PKI may be pushed beyond known limits when scaled to some visions of the smart grid; our research developed a simulation, Grid Cryptographic Simulation (GCS), to evaluate these potential issues, identify cryptographic bottlenecks, and evaluate tradeoffs between performance and security. Ultimately, GCS can be used to identify scalability challenges and suggest improvements to make PKI more efficient, effective, and scalable before it is deployed in the envisioned smart grid

SoK: Delegation and Revocation, the Missing Links in the Web's Chain of Trust

The ability to quickly revoke a compromised key is critical to the security of any public-key infrastructure. Regrettably, most traditional certificate revocation schemes suffer from latency, availability, or privacy problems. These problems are exacerbated by the lack of a native delegation mechanism in TLS, which increasingly leads domain owners to engage in dangerous practices such as sharing their private keys with third parties. We analyze solutions that address the long-standing delegation and revocation shortcomings of the web PKI, with a focus on approaches that directly affect the chain of trust (i.e., the X.509 certification path). For this purpose, we propose a 19-criteria framework for characterizing revocation and delegation schemes. We also show that combining short-lived delegated credentials or proxy certificates with an appropriate revocation system would solve several pressing problems.Comment: IEEE European Symposium on Security and Privacy (EuroS&P) 202

Digital certificates and threshold cryptography

This dissertation discusses the use of secret sharing cryptographic protocols for distributing and sharing of secret documents, in our case PDF documents. We discuss the advantages and uses of such a system in the context of collaborative environments. Description of the cryptographic protocol involved and the necessary Public Key Infrastructure (PKI) shall be presented. We also provide an implementation of this framework as a “proof of concept” and fundament the use of a certificate extension as the basis for threshold cryptography. Details of the shared secret distribution protocol and shared secret recovery protocol shall be given as well as the associated technical implementation details. The actual secret sharing algorithm implemented at this stage is based on an existing well known secret sharing scheme that uses polynomial interpolation over a finite field. Finally we conclude with a practical assessment of our prototype

EMI Security Architecture

This document describes the various architectures of the three middlewares that comprise the EMI software stack. It also outlines the common efforts in the security area that allow interoperability between these middlewares. The assessment of the EMI Security presented in this document was performed internally by members of the Security Area of the EMI project

Challenges for Trusted Computing

This article identifies and discusses some of the key challenges that need to be addressed if the vision of Trusted Computing is to become reality. Topics addressed include issues with setting up and maintaining the PKI required to support the full set of Trusted Computing functionality, the practical use and verification of attestation evidence, and backwards compatibility, usability and compliance issues

Solving identity delegation problem in the e-government environment

At present, many countries allow citizens or entities to interact with the government outside the telematic environment through a legal representative who is granted powers of representation. However, if the interaction takes place through the Internet, only primitive mechanisms of representation are available, and these are mainly based on non-dynamic offline processes that do not enable quick and easy identity delegation. This paper proposes a system of dynamic delegation of identity between two generic entities that can solve the problem of delegated access to the telematic services provided by public authorities. The solution herein is based on the generation of a delegation token created from a proxy certificate that allows the delegating entity to delegate identity to another on the basis of a subset of its attributes as delegator, while also establishing in the delegation token itself restrictions on the services accessible to the delegated entity and the validity period of delegation. Further, the paper presents the mechanisms needed to either revoke a delegation token or to check whether a delegation token has been revoked. Implications for theory and practice and suggestions for future research are discussed