Adaptive trust and reputation system as a security service in group communications

Group communications has been facilitating many emerging applications which require packet delivery from one or more sender(s) to multiple receivers. Owing to the multicasting and broadcasting nature, group communications are susceptible to various kinds of attacks. Though a number of proposals have been reported to secure group communications, provisioning security in group communications remains a critical and challenging issue. This work first presents a survey on recent advances in security requirements and services in group communications in wireless and wired networks, and discusses challenges in designing secure group communications in these networks. Effective security services to secure group communications are then proposed. This dissertation also introduces the taxonomy of security services, which can be applied to secure group communications, and evaluates existing secure group communications schemes. This dissertation work analyzes a number of vulnerabilities against trust and reputation systems, and proposes a threat model to predict attack behaviors. This work also considers scenarios in which multiple attacking agents actively and collaboratively attack the whole network as well as a specific individual node. The behaviors may be related to both performance issues and security issues. Finally, this work extensively examines and substantiates the security of the proposed trust and reputation system. This work next discusses the proposed trust and reputation system for an anonymous network, referred to as the Adaptive Trust-based Anonymous Network (ATAN). The distributed and decentralized network management in ATAN does not require a central authority so that ATAN alleviates the problem of a single point of failure. In ATAN, the trust and reputation system aims to enhance anonymity by establishing a trust and reputation relationship between the source and the forwarding members. The trust and reputation relationship of any two nodes is adaptive to new information learned by these two nodes or recommended from other trust nodes. Therefore, packets are anonymously routed from the \u27trusted\u27 source to the destination through \u27trusted\u27 intermediate nodes, thereby improving anonymity of communications. In the performance analysis, the ratio of the ATAN header and data payload is around 0.1, which is relatively small. This dissertation offers analysis on security services on group communications. It illustrates that these security services are needed to incorporate with each other such that group communications can be secure. Furthermore, the adaptive trust and reputation system is proposed to integrate the concept of trust and reputation into communications. Although deploying the trust and reputation system incurs some overheads in terms of storage spaces, bandwidth and computation cycles, it shows a very promising performance that enhance users\u27 confidence in using group communications, and concludes that the trust and reputation system should be deployed as another layer of security services to protect group communications against malicious adversaries and attacks

Low-cost group rekeying for unattended wireless sensor networks

Wireless sensor networks (WSNs) are made up of large groups of nodes that perform distributed monitoring services. Since sensor measurements are often sensitive data acquired in hostile environments, securing WSN becomes mandatory. However, WSNs consists of low-end devices and frequently preclude the presence of a centralized security manager. Therefore, achieving security is even more challenging. State-of-the-art proposals rely on: (1) attended and centralized security systems; or (2) establishing initial keys without taking into account how to efficiently manage rekeying. In this paper we present a scalable group key management proposal for unattended WSNs that is designed to reduce the rekeying cost when the group membership changes.Peer ReviewedPostprint (published version

Message Forwarding and Scheduling in Delay Tolerant Networks

Delay-tolerant networking (DTN) has recently received considerable attention from the research community. This type of networks is characterized by frequent disconnections due to propagation phenomena, node mobility, and power outages. Thus, the complete path between the source and the destination may never have existed. This context requires the design of new communication paradigms and techniques that will make communication possible in these environments. To achieve message delivery, researchers have proposed the use of store-carry-and-forward protocols, whereby a node may store the message and carry it until an appropriate forwarding opportunity arises. Many flooding-routing schemes have been proposed for DTNs in order to increase the probability of message delivery. However, these schemes suffer from excessive energy consumption, severe contention that significantly degrades their performance, especially if we account for the fact that each node could be a hand-held and battery-powered device with stringent buffer size limitation. With such buffer limitations at the DTN nodes, message drop/loss could happen due to buffer overflow. In order to address the problem and improve the performance of DTNs, this thesis focuses on two main design objectives; first, the design and evaluation of new multi-copy routing schemes; second, the design and evaluation of new scheduling and dropping policies to reduce message drop/loss due to buffer overflow. To fulfill the first objective, a protocol called Self Adaptive Routing Protocol (SARP) is introduced. It is a multi-copy scheme designed to suit resource-sufficient DTNs. Based on SARP, two multi-copy routing schemes are further developed to suit resource-limited DTNs, in which compensating the traffic demand become a challenge: i) the Self Adaptive Utility-based Routing Protocol (SAURP), ii) and the Adaptive Reinforcement based Routing Protocol (ARBRP). The introduced protocols form a new framework of DTNs aiming to significantly reduce the resource requirements of flooding-based routing schemes. Each introduced scheme has its own way of exploring the possibility of taking mobile nodes as message carriers in order to increase the delivery ratio of the messages. In SAURP, the best carrier for a message characterized by jointly considering the inter-contact time that is obtained using a novel contact model and the network status, such as including wireless link condition and nodal buffer availability. In ARBRP, the routing problem is solved by manipulating a collaborative reinforcement learning technique, where a group of nodes can cooperate with each other to make a forwarding decision for the stored messages based on a cost function at each contact with another node. ARBRP is characterized by not only considering the contact time statistics, but also looks into the feedback on user behavior and network conditions, such as congestion and buffer occupancy sampled during each previous contact with any other node. The thesis argues and proves that the nodal movement and the predicted collocation with the message recipient can serve as meaningful information to achieve an intelligent message forwarding decision at each node. Therefore, the introduced protocols can achieve high efficiency via an adaptive and intelligent routing mechanism according to network conditions. To fulfill the second objective, we further enhanced the performance of DTN routing by introducing message scheduling and dropping policies such that the delivery ratio is increased and/or the delivery delay is reduced. This thesis investigates new buffer management and scheduling policies to improve the performance of flooding and utility-based forwarding routing in DTNs, such that the forwarding/dropping decision can be made at a node during each contact for either optimal message delivery ratio or message delivery delay. To examine their effectiveness, the introduced protocols and the buffer management and scheduling policies have been implemented and compared to a number of existing counterpart approaches. A near-realistic mobility model is used for testing. A number of scenarios are used to evaluate the performance of the introduced techniques in terms of delivery delay, ratio, and the number of transmissions performed

Efficient Security Protocols for Fast Handovers in Wireless Mesh Networks

Wireless mesh networks (WMNs) are gaining popularity as a flexible and inexpensive replacement for Ethernet-based infrastructures. As the use of mobile devices such as smart phones and tablets is becoming ubiquitous, mobile clients should be guaranteed uninterrupted connectivity and services as they move from one access point to another within a WMN or between networks. To that end, we propose a novel security framework that consists of a new architecture, trust models, and protocols to offer mobile clients seamless and fast handovers in WMNs. The framework provides a dynamic, flexible, resource-efficient, and secure platform for intra-network and inter-network handovers in order to support real-time mobile applications in WMNs. In particular, we propose solutions to the following problems: authentication, key management, and group key management. We propose (1) a suite of certificate-based authentication protocols that minimize the authentication delay during handovers from one access point to another within a network (intra-network authentication). (2) a suite of key distribution and authentication protocols that minimize the authentication delay during handovers from one network to another (inter-network authentication). (3) a new implementation of group key management at the data link layer in order to reduce the group key update latency from linear time (as currently done in IEEE 802.11 standards) to logarithmic time. This contributes towards minimizing the latency of the handover process for mobile members in a multicast or broadcast group

Sécurité dans les réseaux mobiles de nouvelle génération

RÉSUMÉ Les réseaux de nouvelle génération visent à converger les réseaux fixes et mobiles hétérogènes afin d’offrir tous les services à travers un réseau coeur tout IP. Faisant parti du réseau d’accès mobile, un des principaux objectifs du réseau 4G est de permettre une relève ininterrompue entre les réseaux cellulaires et WIFI pour ainsi favoriser l’apprivoisement de services vidéo mobiles exigeant des critères de qualité de service très stricts à moindres coûts. Cependant, l’uniformisation du trafic au niveau de la couche réseau favorise sa centralisation à travers un réseau coeur IP partagé par tous les opérateurs, la rendant ainsi comme une cible vulnérable de choix pour les pirates informatiques. La conception de solutions sécuritaires dans un environnement où les entités ne se connaissent pas à priori s’annonce comme une tâche très ardue. La thèse se penche sur quatre problématiques importantes dans les réseaux de nouvelle génération dont chacune est traitée dans un article distinct. Les deux premiers articles touchent à la sécurité dans un contexte décentralisé, à savoir les réseaux mobiles ad hoc (MANETs), alors que les deux derniers proposent des mécanismes innovateurs pour sécuriser des solutions visant à réduire la consommation de bande passante et d’énergie, en conformité avec le virage vert informatique promu par les opérateurs réseautiques. Plus précisément, le troisième article traite de la sécurisation des flots multicast dans un environnement à haut taux de perte de paquet et le dernier propose une solution d’optimisation de route sécuritaire pour mobile IPv6 (MIPv6) utilisant une version améliorée de l’algorithme de genération d’adresses cryptographiques (CGA) et les extensions de sécurité du système de nom de domaine (DNSSEC). Les systèmes de détection d’intrusion (IDS) pour les MANETs basés sur la réputation des noeuds classifient les participants du réseau selon leur degré de confiance. Cependant, ils partagent tous une vulnérabilité commune : l’impossibilité de détecter et de réagir aux attaques complices. Le premier article propose un IDS qui intègre efficacement le risque de collusion entre deux ou plusieurs noeuds malveillants dans le calcul de la fiabilité d’un chemin. L’algorithme propos´e ne se limite pas qu’au nombre et à la réputation des noeuds intermédiaires formant un chemin, mais intègre également d’autres informations pertinentes sur les voisins des noeuds intermédiaires d’un chemin pouvant superviser le message original et celui retransmis. Le IDS proposé détecte efficacement les noeuds malicieux et complices dans le but de les isoler rapidement du réseau. Les simulations lancées dans divers environnements MANETs contenant une proportion variable d’attaquants complices montrent bien l’efficacité du IDS proposée en offrant un gain en débit considérable comparativement aux solutions existantes. À l’instar de prévenir les comportements égoïstes des noeuds par la menace d’être privés de certaines fonctions, voire même isolés du réseau, due à une baisse de réputation, le second article opte pour un incitatif non-punitif en la monnaie virtuelle plus communément appelée nuglets. Plus précisément, l’article présente un cadre de travail issu de la théorie des jeux basé sur la compétition de Bertrand pour inciter les noeuds intermédiaires à retransmettre les messages selon les requis de QoS demandés par la source. Pour qu’un noeud source envoie ou accède à un flot sensible à la QoS comme par exemple les applications en temps réel, il débute par envoyer un contrat qui spécifie les critères de QoS, sa durée et son prix de réserve. Sur réception du contrat, les noeuds intermédiaires formant une route entre la source et la destination partagent les informations sur eux-mêmes et celles recueillies sur les noeuds voisins, anciens et courants pour estimer la probabilité de bris de contrat ainsi que le nombre de compétiteurs actifs. Ces deux paramètres sont cruciaux dans le processus de fixation des prix. Une fois les réponses de route recueillies, la source choisit la route la moins chère. Le cadre de travail multijoueur proposé, basé sur la compétition de Bertrand avec des firmes asymétriques et ayant accès à de l’information imparfaite, possède un équilibre de Nash en stratégies mixtes dans lequel le profit des firmes est positif et baisse non seulement avec le nombre de compétiteurs, mais aussi avec l’impression d’une précision accrue que les compétiteurs ont sur le coût de production du joueur. Les résultats montrent que l’incertitude sur les coûts augmente le taux de la marge brute et la fluctuation des prix tout en diminuant les chances d’honorer le contrat. Dans un autre ordre d’idée, l’intérêt sans cesse grandissant des opérateurs à converger les réseaux fixes et mobiles dans le but d’offrir une relève sans interruption favorise l’utilisation des applications vidéo mobiles qui surchargeront rapidement leurs réseaux. Dans un contexte du virage vert qui prend de plus en plus d’ampleur dans le domaine des télécommunications, la transmission des flots en multidiffusion (multicast) devient essentiel dans le but de réduire la consommation de bande passante et la congestion du réseau en rejoignant simultanément plusieurs destinataires. La sécurisation des flots en multidiffusion a été largement étudiée dans la littérature antérieure, cependant aucune des solutions proposées ne tient compte des contraintes imposées par les liaisons sans fil et la mobilité des noeuds, en particulier le haut taux de perte de paquets. La nécessité d’un mécanisme de distribution de clés régénératrices efficace et pouvant supporter un grand bassin d’abonnés pour les réseaux mobiles n’aura jamais été aussi urgent avec l’arrivée de la convergence fixe-mobile dans les réseaux 4G. Le troisième article présente deux algorithmes de clés régénératrices basés sur les chaînes de hachage bidirectionnelles pour le protocole de distribution de clés logical key hierarchy (LKH). Ainsi, un membre ayant perdu jusqu’à un certain nombre de clés de déchiffrement consécutives pourrait lui-même les régénérer sans faire la requête de retransmission au serveur de clés. Les simulations effectuées montrent que les algorithmes proposés offrent des améliorations considérables dans un environnement de réseau mobile à taux de perte de paquet, notamment dans le percentage de messages déchiffrés. Le souci d’efficacité énergétique est également présent pour les opérateurs de réseaux cellulaires. D’ailleurs, près de la moitié des abonnements sur Internet proviennent présentement d’unités mobiles et il est attendu que ce groupe d’utilisateurs deviennent le plus grand bassin d’usagers sur Internet dans la prochaine décennie. Pour supporter cette croissance rapide du nombre d’utilisateurs mobiles, le choix le plus naturel pour les opérateurs serait de remplacer mobile IPv4 par MIPv6. Or, la fonction d’optimisation de route (RO), qui remplace le routage triangulaire inefficace de MIP en permettant au noeud mobile (MN) une communication bidirectionnelle avec le noeud correspondant (CN) sans faire passer les messages à travers l’agent du réseau mère (HA), est déficiente au niveau de la sécurité. L’absence d’informations pré-partagées entre le MN et le CN rend la sécurisation du RO un défi de taille. MIPv6 adopte la routabilité de retour (RR) qui est davantage un mécanisme qui vérifie l’accessibilité du MN sur son adresse du réseau mère (HoA) et du réseau visité (CoA) plutôt qu’une fonction de sécurité. D’autres travaux se sont attaqués aux nombreuses failles de sécurité du RR, mais soit leur conception est fautive, soit leurs suppositions sont irréalistes. Le quatrième article présente une version améliorée de l’algorithme de génération cryptographique d’adresse (ECGA) pour MIPv6 qui intègre une chaîne de hachage arrière et offre de lier plusieurs adresses CGA ensemble. ECGA élimine les attaques de compromis temps-mémoire tout en étant efficace. Ce mécanisme de génération d’adresse fait parti du protocole Secure MIPv6 (SMIPv6) proposé avec un RO sécuritaire et efficace grâce à DNSSEC pour valider les CGAs qui proviennent d’un domaine de confiance et qui permet une authentification forte plutôt que l’invariance de source. Le vérificateur de protocoles cryptographiques dans le modèle formel AVISPA a été utilisé pour montrer qu’aucune faille de sécurité n’est présente tout en limitant au maximum les messages échangés dans le réseau d’accès. ----------ABSTRACT Next generation networks aim at offering all available services through an IP-core network by converging fixed-mobile heterogeneous networks. As part of the mobile access network, one of the main objectives of the 4G network is to provide seamless roaming with wireless local area networks and accommodating quality of service (QoS) specifications for digital video broadcasting systems. Such innovation aims expanding video-based digital services while reducing costs by normalizing the network layer through an all-IP architecture such as Internet. However, centralizing all traffic makes the shared core network a vulnerable target for attackers. Design security solutions in such an environment where entities a priori do not know each other represent a daunting task. This thesis tackles four important security issues in next generation networks each in distinct papers. The first two deal with security in decentralized mobile ad hoc networks (MANETs) while the last two focus on securing solutions aiming at reducing bandwidth and energy consumption, in line with the green shift promoted by network operators. More precisely, the third paper is about protecting multicast flows in a packet-loss environment and the last one proposes a secure route optimization function in mobile IPv6 (MIPv6) using an enhanced version of cryptographically generated address (CGA) and domain name service security extensions (DNSSEC). Most intrusion detection systems (IDS) for MANETs are based on reputation system which classifies nodes according to their degree of trust. However, existing IDS all share the same major weakness: the failure to detect and react on colluding attacks. The first paper proposes an IDS that integrates the colluding risk factor into the computation of the path reliability which considers the number and the reputation of nodes that can compare both the source message and the retransmitted one. Also, the extended architecture effectively detects malicious and colluding nodes in order to isolate them and protect the network. The simulations launched in various MANETs containing various proportions of malicious and colluding nodes show that the proposed solution offers a considerable throughput gain compared to current solutions. By effectively selecting the most reliable route and by promptly detecting colluding attacks, the number of lost messages is decreased, and therefore, offering more efficient transmissions. Instead of thwarting selfishness in MANETs by threatening nodes to limit their network functions, the second paper opts for a non-punishment incentive by compensating nodes for their service through the use of virtual money, more commonly known as nuglets. The last paper presents a game-theoretic framework based on Bertrand competition to incite relaying nodes in forwarding messages according to QoS requirements. For a source to send or access QoS-sensitive flows, such as real-time applications, it starts by sending a contract specifying the QoS requirements, its duration and a reservation price. Upon receiving a contract submission, intermediary nodes forming a route between the source and the destination share their current and past collected information on themselves and on surrounding nodes to estimate the probability of breaching the contract and the number of active competitors. Both parameters are crucial in setting a price. Once the source gets the responses from various routes, it selects the most cheapest one. This multiplayer winner-takes-all framework based on Bertrand competition with firms having asymmetric costs and access imperfect information has a mixed-strategy equilibrium in which industry profits are positive and decline not only with the number of firms having an estimated cost below the reservation price but also with the perception of a greater accuracy on a player’s cost that competitors have. In fact,results show that cost uncertainty increases firms’ gross margin rate and the prices fluctuation while making the contract honoring much riskier. On another topic, with the growing interest in converging fixed and mobile networks, mobile applications will require more and more resources from both the network and the mobile device. In a social-motivated context of shifting into green technologies, using multicast transmissions is essential because it lowers bandwidth consumption by simultaneously reaching a group of multiple recipients. Securing multicast flows has been extensively studied in the past, but none of the existing solutions were meant to handle the constraints imposed by mobile scenarios, in particular the high packet-loss rate. The need for a low overhead selfhealing rekeying mechanism that is scalable, reliable and suitable for mobile environments has never been more urgent than with the arrival of fixed-mobile convergence in 4G networks. The second paper presents two self-healing recovery schemes based on the dual directional hash chains for the logical key hierarchy rekeying protocol. This enables a member that has missed up to m consecutive key updates to recover the missing decryption keys without asking the group controller key server for retransmission. Conducted simulations show considerable improvements in the ratio of decrypted messages and in the rekey message overhead in high packet loss environments. The concern of energy efficiency is also present for mobile access network operators. In fact, nearly half of all Internet subscribers come from mobile units at the moment and it is expected to be the largest pool of Internet users by the next decade. The most obvious choice for mobile operators to support more users would be to replace Mobile IP for IPv4 with MIPv6. However, the Route Optimization (RO) function, which replaces the inefficient triangle routing by allowing a bidirectional communication between a mobile node (MN) and the corresponding node (CN) without passing through its home agent (HA), is not secure and has a high overhead. The lack of pre-shared information between the MN and the CN makes security in RO a difficult challenge. MIPv6 adopts the return routability (RR) mechanism which is more to verify the MN reachability in both its home address (HoA) and care-of address (CoA) than a security feature. Other works attempted to solve the multiple security issues in RR but either their design are flawed, or rely on unrealistic assumptions. The third paper presents an enhanced cryptographically generated address (ECGA) for MIPv6 that integrates a built-in backward key chain and offers support to bind multiple logically-linked CGAs together. ECGA tackles the time-memory tradeoff attacks while being very efficient. It is part of the proposed secure MIPv6 (SMIPv6) with secure and efficient RO which uses DNSSEC to validate CGAs from trusted domains and provide strong authentication rather than sender invariance. The AVISPA on-the-fly model checker (OFMC) tool has been used to show that the proposed solution has no security flaws while still being lightweight in signalling messages in the radio network

Synoptic analysis techniques for intrusion detection in wireless networks

Current system administrators are missing intrusion alerts hidden by large numbers of false positives. Rather than accumulation more data to identify true alerts, we propose an intrusion detection tool that e?ectively uses select data to provide a picture of ?network health?. Our hypothesis is that by utilizing the data available at both the node and cooperative network levels we can create a synoptic picture of the network providing indications of many intrusions or other network issues. Our major contribution is to provide a revolutionary way to analyze node and network data for patterns, dependence, and e?ects that indicate network issues. We collect node and network data, combine and manipulate it, and tease out information about the state of the network. We present a method based on utilizing the number of packets sent, number of packets received, node reliability, route reliability, and entropy to develop a synoptic picture of the network health in the presence of a sinkhole and a HELLO Flood attacker. This method conserves network throughput and node energy by requiring no additional control messages to be sent between the nodes unless an attacker is suspected. We intend to show that, although the concept of an intrusion detection system is not revolutionary, the method in which we analyze the data for clues about network intrusion and performance is highly innovative

Protocols and Architecture for Privacy-preserving Authentication and Secure Message Dissemination in Vehicular Ad Hoc Networks

The rapid development in the automotive industry and wireless communication technologies have enhanced the popularity of Vehicular ad hoc networks (VANETs). Today, the automobile industry is developing sophisticated sensors that can provide a wide range of assistive features, including accident avoidance, automatic lane tracking, semi-autonomous driving, suggested lane changes, and more. VANETs can provide drivers a safer and more comfortable driving experience, as well as many other useful services by leveraging such technological advancements. Even though this networking technology enables smart and autonomous driving, it also introduces a plethora of attack vectors. However, the main issues to be sorted out and addressed for the widespread deployment/adoption of VANETs are privacy, authenticating users, and the distribution of secure messages. These issues have been addressed in this dissertation, and the contributions of this dissertation are summarized as follows: Secure and privacy-preserving authentication and message dissemination in VANETs: Attackers can compromise the messages disseminated within VANETs by tampering with the message content or sending malicious messages. Therefore, it is crucial to ensure the legitimacy of the vehicles participating in the VANETs as well as the integrity and authenticity of the messages transmitted in VANETs. In VANET communication, the vehicle uses pseudonyms instead of its real identity to protect its privacy. However, the real identity of a vehicle must be revealed when it is determined to be malicious. This dissertation presents a distributed and scalable privacy-preserving authentication and message dissemination scheme in VANET. Low overhead privacy-preserving authentication scheme in VANETs: The traditional pseudonym-based authentication scheme uses Certificate Revocation Lists (CRLs) to store the certificates of revoked and malicious entities in VANETs. However, the size of CRL increases significantly with the increased number of revoked entities. Therefore, the overhead involved in maintaining the revoked certificates is overwhelming in CRL-based solutions. This dissertation presents a lightweight privacy-preserving authentication scheme that reduces the overhead associated with maintaining CRLs in VANETs. Our scheme also provides an efficient look-up operation for CRLs. Efficient management of pseudonyms for privacy-preserving authentication in VANETs: In VANETs, vehicles change pseudonyms frequently to avoid the traceability of attackers. However, if only one vehicle out of 100 vehicles changes its pseudonym, an intruder can easily breach the privacy of the vehicle by linking the old and new pseudonym. This dissertation presents an efficient method for managing pseudonyms of vehicles. In our scheme, vehicles within the same region simultaneously change their pseudonyms to reduce the chance of linking two pseudonyms to the same vehicle

Contributions to the security of cognitive radio networks

The increasing emergence of wireless applications along with the static spectrum allocation followed by regulatory bodies has led to a high inefficiency in spectrum usage, and the lack of spectrum for new services. In this context, Cognitive Radio (CR) technology has been proposed as a possible solution to reuse the spectrum being underutilized by licensed services. CRs are intelligent devices capable of sensing the medium and identifying those portions of the spectrum being unused. Based on their current perception of the environment and on that learned from past experiences, they can optimally tune themselves with regard to parameters such as frequency, coding and modulation, among others. Due to such properties, Cognitive Radio Networks (CRNs) can act as secondary users of the spectrum left unused by their legal owners or primary users, under the requirement of not interfering primary communications. The successful deployment of these networks relies on the proper design of mechanisms in order to efficiently detect spectrum holes, adapt to changing environment conditions and manage the available spectrum. Furthermore, the need for addressing security issues is evidenced by two facts. First, as for any other type of wireless network, the air is used as communications medium and can easily be accessed by attackers. On the other hand, the particular attributes of CRNs offer new opportunities to malicious users, ranging from providing wrong information on the radio environment to disrupting the cognitive mechanisms, which could severely undermine the operation of these networks. In this Ph.D thesis we have approached the challenge of securing Cognitive Radio Networks. Because CR technology is still evolving, to achieve this goal involves not only providing countermeasures for existing attacks but also to identify new potential threats and evaluate their impact on CRNs performance. The main contributions of this thesis can be summarized as follows. First, a critical study on the State of the Art in this area is presented. A qualitative analysis of those threats to CRNs already identified in the literature is provided, and the efficacy of existing countermeasures is discussed. Based on this work, a set of guidelines are designed in order to design a detection system for the main threats to CRNs. Besides, a high level description of the components of this system is provided, being it the second contribution of this thesis. The third contribution is the proposal of a new cross-layer attack to the Transmission Control Protocol (TCP) in CRNs. An analytical model of the impact of this attack on the throughput of TCP connections is derived, and a set of countermeasures in order to detect and mitigate the effect of such attack are proposed. One of the main threats to CRNs is the Primary User Emulation (PUE) attack. This attack prevents CRNs from using available portions of the spectrum and can even lead to a Denial of Service (DoS). In the fourth contribution of this the method is proposed in order to deal with such attack. The method relies on a set of time measures provided by the members of the network and allows estimating the position of an emitter. This estimation is then used to determine the legitimacy of a given transmission and detect PUE attacks. Cooperative methods are prone to be disrupted by malicious nodes reporting false data. This problem is addressed, in the context of cooperative location, in the fifth and last contribution of this thesis. A method based on Least Median Squares (LMS) fitting is proposed in order to detect forged measures and make the location process robust to them. The efficiency and accuracy of the proposed methodologies are demonstrated by means of simulation