Incorporation Of Certification Revocation And Time Concept Into A Trust Model For Information Security System

In large open networks, handling trust and authenticity adequately is an important prerequisite for security policy. Trust issues influence not only the specification of security policies but also the techniques needed to manage and implement security policies for systems. Certification is one of the main components of trust models and is known as a common mechanism for authentic public key distribution. In order to obtain a public key, verifiers need to extract a certificate path from a network of certificates, which is called the public key infrastructure (PKI). There are two classifications of PKI; namely the centralized and decentralized PKIs. In this thesis, attention is paid the decentralized PKIs, such as Maurer’s model. This model is comprised of two parts; the deterministic and probabilistic models. An important limitation in this model is that certification revocation is not considered. Revocation happens in cases, among others, such as the loss of private key. Another limitation of Maurer’s model is that it lacks time consideration, which is important as trust changes over time. In this thesis, a novel trust model is developed, addressing the limitations of other models. Negative values such as revocation of certification have been incorporated, making a complete trust model that includes both positive and negative evidences. Particularly, certification is considered as positive evidence while certification revocation is considered negative. The time concept is then added to the model in order to address the change of trusts status over time. Hence, the complete trust model is able to incorporate certification revocation and time concept into both deterministic and probabilistic parts of a model. Incorporating two new concepts into Maurer’s model increases the generality and expressive power of the model. Novel extension of the trust model enabling it to capture all aspects of public key certification which includes trust, recommendations, confidence values for trust metric and authenticity of public keys, multiple certification paths, certification revocation and the time concept. Experimental results show that after incorporating the new concept, a decrease in confidence value in comparison to Maurer’s model was observed, resulting to a more realistic model

PKI Scalability Issues

This report surveys different PKI technologies such as PKIX and SPKI and the issues of PKI that affect scalability. Much focus is spent on certificate revocation methodologies and status verification systems such as CRLs, Delta-CRLs, CRS, Certificate Revocation Trees, Windowed Certificate Revocation, OCSP, SCVP and DVCS.Comment: 23 pages, 2 figure

PKI Safety Net (PKISN): Addressing the Too-Big-to-Be-Revoked Problem of the TLS Ecosystem

In a public-key infrastructure (PKI), clients must have an efficient and secure way to determine whether a certificate was revoked (by an entity considered as legitimate to do so), while preserving user privacy. A few certification authorities (CAs) are currently responsible for the issuance of the large majority of TLS certificates. These certificates are considered valid only if the certificate of the issuing CA is also valid. The certificates of these important CAs are effectively too big to be revoked, as revoking them would result in massive collateral damage. To solve this problem, we redesign the current revocation system with a novel approach that we call PKI Safety Net (PKISN), which uses publicly accessible logs to store certificates (in the spirit of Certificate Transparency) and revocations. The proposed system extends existing mechanisms, which enables simple deployment. Moreover, we present a complete implementation and evaluation of our scheme.Comment: IEEE EuroS&P 201

A robust self-organized public key management for mobile ad hoc networks

A mobile ad hoc network (MANET) is a self-organized wireless network where mobile nodes can communicate with each other without the use of any existing network infrastructure or centralized administration. Trust establishment and management are essential for any security framework of MANETs. However, traditional solutions to key management through accessing trusted authorities or centralized servers are infeasible for MANETs due to the absence of infrastructure, frequent mobility, and wireless link instability. In this paper, we propose a robust self-organized, public key management for MANETs. The proposed scheme relies on establishing a small number of trust relations between neighboring nodes during the network initialization phase. Experiences gained as a result of successful communications and node mobility through the network enhance the formation of a web of trust between mobile nodes. The proposed scheme allows each user to create its public key and the corresponding private key, to issue certificates to neighboring nodes, and to perform public key authentication through at least two independent certificate chains without relying on any centralized authority. A measure of the communications cost of the key distribution process has been proposed. Simulation results show that the proposed scheme is robust and efficient in the mobility environment of MANET and against malicious node attacks

Data-centric Misbehavior Detection in VANETs

Detecting misbehavior (such as transmissions of false information) in vehicular ad hoc networks (VANETs) is very important problem with wide range of implications including safety related and congestion avoidance applications. We discuss several limitations of existing misbehavior detection schemes (MDS) designed for VANETs. Most MDS are concerned with detection of malicious nodes. In most situations, vehicles would send wrong information because of selfish reasons of their owners, e.g. for gaining access to a particular lane. Because of this (\emph{rational behavior}), it is more important to detect false information than to identify misbehaving nodes. We introduce the concept of data-centric misbehavior detection and propose algorithms which detect false alert messages and misbehaving nodes by observing their actions after sending out the alert messages. With the data-centric MDS, each node can independently decide whether an information received is correct or false. The decision is based on the consistency of recent messages and new alert with reported and estimated vehicle positions. No voting or majority decisions is needed, making our MDS resilient to Sybil attacks. Instead of revoking all the secret credentials of misbehaving nodes, as done in most schemes, we impose fines on misbehaving nodes (administered by the certification authority), discouraging them to act selfishly. This reduces the computation and communication costs involved in revoking all the secret credentials of misbehaving nodes.Comment: 12 page