ABSTRACT In general, attackers carry out scanning or probing against a certain network when they start to attack their victims. Because of this, darknet is very useful to observe the scanning activities of attackers who want to find their victims that have security vulnerabilities in operating systems, applications, services, and so on. Thus, by observing and analyzing darknet traffic, it is able to obtain an insight into malicious activities that are happening on the Internet and to identify potential attackers who sent attack packets to the darknet. However, darknet has a fatal limitation that most of the darknet traffic has no payload data. This means that we cannot collect the real attack codes from the original darknet traffic. To cope with this problem, we propose a security monitoring and response model to analyze cyber threats trend and to trace potential attackers based on darknet traffic. We have evaluated the proposed model using one /24 darknet IP addresses and TMS alerts that were obtained from TMS. The experimental results provided the statistical information of all the incoming darknet traffic so that we could obtain the global cyber threats trend. Furthermore, the experimental results demonstrated that we could obtain malicious attack patterns and attack codes that were not detected by TMS. Copyright © 2013 John Wiley & Sons, Ltd.

ABSTRACT Voice over internet protocol (VoIP) provided voice service using Internet. It receives footlights when it escapes an initial curiosity. Interest to VoIP increased, because it can transfer existing phone service and deliver voice data through Internet technology. Communication service providers introduce Next Generation Network and Broadband convergence Network with VoIP as an added service to the consumer. In addition, session initiation protocol (SIP) service can be applied even outside the Internet phone service. However, it is needed to ensure secrecy of VoIP call in a special situation. It is relatively difficult to eavesdrop in the commonly used Public Switched Telephone Network (PSTN) as it is connected with 1:1 circuit. In this paper, we propose a new model of Internet telephone for eavesdrop prevention enabling VoIP (using SIP protocol) to use the virtual private network (VPN) protocol and establish the probability of practical use comparing it with Internet telephone. Copyright © 2010 John Wiley & Sons, Ltd.

In this paper we propose a new discrete differential error metric for surface simplification. Many surface simplification algorithms have been developed in order to produce rapidly high quality approximations of polygonal models, and the quadric error metric based on the distance error is the most popular and successful error metric so far Even though such distance based error metrics give visually pleasing results with a reasonably fast speed, it is hard to measure an accurate geometric error on a highly curved and thin region since the error measured by the distance metric on such a region is usually small and causes a loss of visually important features. To overcome such a drawback, we define a new error metric based on the theory of local differential geometry in such a way that the first and the second order discrete differentials approximated locally on a discrete polygonal surface are integrated into the usual distance error metric. The benefits of our error metric are preservation of sharp feature regions after a drastic simplification, small geometric errors, and fast computation comparable to the existing methods.