This study examined the perception of managers in the Institute of Public Administration (IPA), Riyadh, Saudi Arabia as to the way public relations is practiced within Saudi Arabia based on a comparison with Grunig's four models of public relations. Out of a population of 38 directors and director generals, 30 participated in a personal interview for a 79 percent response rate.A Q-sort analysis revealed two perceptions of public relations performance in the Institute. Perceptions differed based on educational experience, and managerial levels. Top managers with Ph.Ds tended to view performance as related to Grunig's Press Agentry and One-Way Information models. Fewer level employees saw performance related to the Two-Way Asymmetrical and Symmetrical models. The researcher concluded that the more higher educated level managers had a better understanding of the reality of performance of public relations in IPA. Main attitudes from the sorts of the participants showing a significantly and different attitude in how directors generals and directors perceived public relations was being practiced in the IPA. The directors generals and directors strongly held different views concerning the practice of public relations in the IPA. / Department of Journalism

Security and privacy are among the growing concerns of a Vehicular Ad hoc Network (VANET) which requires a high degree of liability from its participants. In this dissertation, We address security, anonymity and privacy challenges of VANETs in the light of the IEEE standards for vehicular communications. VANET provides a variety of road-safety and other applications through wireless devices installed in vehicles and roadside infrastructure. A roadside infrastructure in VANET is generally public, and is prone to several different malicious attacks including node compromise, impersonation, and false message delivery attacks. Therefore, a user of a VANET must verify the integrity of a message that is delivered from a roadside infrastructure. On the other hand, a vehicle-originated message should be anonymous in order to ensure user-privacy in a VANET. However, a vehicle must not be able to take advantage of its anonymity for any misbehavior like sending false messages or malicious updates to other vehicles or a roadside infrastructure. We use proxy signature, identity-based signature, and elliptic curve cryptosystems to provide authentication for infrastructure generated messages, and anonymous authentication for vehicle originated messages. Authentication in a dense traffic condition is a challenge for a receiving entity as it incurs a processing delay at the receiving end. We address this issue with a dynamic approach that selectively verifies received messages based on a message's MAC-layer priority and a sender's information relevance. This approach makes a trade-off between priority and fairness in vehicular message authentication. We develop a network simulator to measure the impact of our authentication schemes over a WAVE protocol stack. Also, we investigate how some of the MAC-layer weaknesses may impair the security of a VANET. Our solutions are lightweight, bandwidth friendly and compatible to the current standards of vehicular communications.

Univ., Diss.--Potsdam, 2004. / Literaturverz. S. 371 - 400.

Univ., Diss.--Leipzig, 2004.

Univ., Diss--Bamberg, 2007.

Universiẗat, Diss.-2005--Heidelberg, 2004. / Literaturverz. S. [261] - 274. Zusammenfassung in engl. Sprache.

Techn. Universiẗat, Diplomarbeit--Ilmenau, 2007. / Parallel als Online-Ausg. erschienen unter der Adresse http://www.db-thueringen.de/servlets/DocumentServlet?id=10122.

Univ., Diss.--Köln, 2005.

Univ., Diss.--Rostock, 2004.

Univ., Diss.--Münster, 2006. / Literaturverz. S. 199 - 206.