The aim of this thesis is to study and describe the theme of Public Key Infrastructure (PKI). Within the scope of minute PKI characterization there is a gradual depiction of particular structural elements, which are above all represented by cryptographic operations (asymetric and symetric cryptography, hash function and digital signature); then, there are also individual PKI subjects that are dealt with, like eg. certification authority, certificates, security protocols, secure heap etc. Last but not least there are a few complete Public Key Infrastructure implementation solutions described (OpenSSL, Microsft CA). The practical part of the thesis, a lab exercise, gives potential students the knowledge of installing OpenSSL system based certification authority. The next task educate students how to secure web server with certificate signed with own CA and also how to secure web server users‘ access control through certificates signed by the previously installed CA.

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Vehicular ad hoc networks (VANETs) are a subclass of mobile ad hoc networks (MANETs) in which the mobile nodes are vehicles; these vehicles are autonomous systems connected by wireless communication on a peer-to-peer basis. They are self-organized, self-configured and self-controlled infrastructure-less networks. This kind of network has the advantage of being able to be set-up and deployed anywhere and anytime because it has no infrastructure set-up and no central administration. Distributing information between these vehicles over long ranges in such networks, however, is a very challenging task, since sharing information always has a risk attached to it especially when the information is confidential. The disclosure of such information to anyone else other than the intended parties could be extremely damaging, particularly in military applications where controlling the dissemination of messages is essential. This thesis therefore provides a review of the issue of security in VANET and MANET; it also surveys existing solutions for dissemination control. It highlights a particular area not adequately addressed until now: controlling information flow in VANETs. This thesis contributes a policy-based framework to control the dissemination of messages communicated between nodes in order to ensure that message remains confidential not only during transmission, but also after it has been communicated to another peer, and to keep the message contents private to an originator-defined subset of nodes in the VANET. This thesis presents a novel framework to control data dissemination in vehicle ad hoc networks in which policies are attached to messages as they are sent between peers. This is done by automatically attaching policies along with messages to specify how the information can be used by the receiver, so as to prevent disclosure of the messages other than consistent with the requirements of the originator. These requirements are represented as a set of policy rules that explicitly instructs recipients how the information contained in messages can be disseminated to other nodes in order to avoid unintended disclosure. This thesis describes the data dissemination policy language used in this work; and further describes the policy rules in order to be a suitable and understandable language for the framework to ensure the confidentiality requirement of the originator. This thesis also contributes a policy conflict resolution that allows the originator to be asked for up-to-date policies and preferences. The framework was evaluated using the Network Simulator (NS-2) to provide and check whether the privacy and confidentiality of the originators’ messages were met. A policy-based agent protocol and a new packet structure were implemented in this work to manage and enforce the policies attached to packets at every node in the VANET. Some case studies are presented in this thesis to show how data dissemination can be controlled based on the policy of the originator. The results of these case studies show the feasibility of our research to control the data dissemination between nodes in VANETs. NS-2 is also used to test the performance of the proposed policy-based agent protocol and demonstrate its effectiveness using various network performance metrics (average delay and overhead).

Darbe nagrinėjama atributinės informacijos sertifikavimo šiuo metu naudojamuose elektroniniuse parašuose problema. Trumpai apžvelgiami elektroninio parašo principai ir supažindinama su viešųjų raktų infrastruktūra, nurodant galimybes jai išplėsti, iškilus poreikiui užtikrinti aukštesnį saugumo lygį keičiantis papildoma (atributine) informacija. Nagrinėjami įvairūs atributinės informacijos sertifikavimo metodai, viešųjų raktų infrastruktūroje įvedant atributų sertifikato ir atributų sertifikavimo centro sąvokas. Pateikiamas tinkamiausio metodo pritaikymo pavyzdys, modeliuojant elektroninio parašo naudojimo situaciją, artimą dabartinei situacijai Lietuvoje. Sprendimo pritaikymas demonstruojamas apibrėžiant patobulintos elektroninio parašo infrastruktūros prototipą. / This paper analyses issues of attribute certification in currently used electronic signatures. Fundamentals of electronic signatures and public key infrastructure are briefly described, focusing on possibilities of achieving higher security level in communication when attribute information is important. Various suggestions for attribute certification are analysed, introducing atribute certificates and atribute authorities. Different certification methods are compared and evaluated, applying the most suitable one in the public key infrastructure usage model, that is constructed by simplifying the current situation of electronic signatures. The solution is represented by describing the prototype of improved electronic signature infrastructure.

This thesis deals with the introduction to the security mechanism.The procedure explains the basic concepts, principles of cryptography and security of modern protocols and basic principles that are used for information transmission network. The work also describes the most common types of attacks targeting the eavesdropping of communication. The result is a design of the eavesdropping and the implementation of an attack on the secure communication of the SSL protocol..The attacker uses a false certificate and attacks based on poisoning the ARP and DNS tables for this purpose. The thesis discusses the principles of the SSL protocol and methodology of attacks on the ARP and DNS tables.