• Korean Journal of Materials Research
• /
• v.23 no.9
• /
• pp.510-516
• /
• 2013

Fly ash is one of the aluminosilicate sources used for the synthesis of geopolymers. The particle size distribution of fly ash and the content of unburned carbon residue are known to affect the compressive strength of geopolymers. In this study, the effects of particle size and unburned carbon content of fly ash on the compressive strength of geopolymers have been studied over a compositional range in geopolymer gels. Unburned carbon was effectively separated in the $-46{\mu}m$ fraction using an air classifier and the fixed carbon content declined from 3.04 wt% to 0.06 wt%. The mean particle size ($d_{50}$) decreased from $22.17{\mu}m$ to $10.79{\mu}m$. Size separation of fly ash by air classification resulted in reduced particle size and carbon residue content with a collateral increase in reactivity with alkali activators. Geopolymers produced from carbon-free ash, which was separated by air classification, developed up to 50 % higher compressive strength compared to geopolymers synthesized from raw ash. It was presumed that porous carbon particles hinder geopolymerization by trapping vitreous spheres in the pores of carbon particles and allowing them to remain intact in spite of alkaline attack. The microstructure of the geopolymers did not vary considerably with compressive strength, but the highest connectivity of the geopolymer gel network was achieved when the Si/Al ratio of the geopolymer gel was 5.0.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.12 no.3
• /
• pp.1350-1355
• /
• 2011

It is very important issues to protect many system resources using authorized client authentication in distributed client server systems. So it is not enough to prevent unauthorized opponents from attacking our systems that client authentication is performed using only the client's identifier and password. In this paper, we propose a secure authentication database modeling with two authentication keys such as a client authentication key and a server authentication key. The proposed authentication model can be used making high quality of computer security using two authentication keys during transaction processing. The two authentication keys are created by client and server, and are used in every request transaction without user's extra input. Using the proposed authentication keys, we can detect intrusion during authorized client's transaction processing because we can know intrusion immediately through comparing stored authentication keys in client server systems when hackers attack our network or computer systems.

• Journal of the Korea Convergence Society
• /
• v.6 no.4
• /
• pp.225-234
• /
• 2015

With the growing number of people that use web services, the perception of the importance of securing web applications is also increasing. There are many different types of attacks that target web applications. In the rapidly-changing knowledge and information society, which came into being with the advancements made in information and communication technology, there is currently an urgent need for building web sites for the purposes of developing one's creativity and character. In this paper, attack schemes that use SQL injections and XSS and target educational digital curation systems which provide educational contents with the aim of developing of one's creativity and character are analyze, in terms of how the attacks are carried out and their vulnerabilities. Furthermore, it suggests ways of dealing appropriately with these web-based attacks that use SQL injections and XSS.

• Journal of Advanced Navigation Technology
• /
• v.17 no.1
• /
• pp.24-32
• /
• 2013

Authentication is one of the necessary elements in the network environment. Many researches have detected security vulnerabilities to the existing authentication mechanisms and suggested secure mutual authentication protocols by resolving these vulnerabilities. The representative ones of them are SPMA(Strong Pass Mutual Authentication) and I-SPMA(Improved Strong Password Mutual Authentication). However, these protocols cause a critical problem when the shared secret information is de-synchronized between the server and the client. This paper proposes a revised protocol to resolve the de-synchronization problem. Based on a security assessment on the proposed protocol, we consider the proposed protocol is safer than the previous ones and possible to effectively make a user authentication system mre secure.

• Journal of the Korea Institute of Information Security & Cryptology
• /
• v.26 no.2
• /
• pp.377-386
• /
• 2016

As the number of malware has been increased, it is necessary to analyze malware rapidly against cyber attack. Additionally, Dynamic malware analysis has been widely studied to overcome the limitation of static analysis such as packing and obfuscation, but still has a problem of exploring multiple execution path. Previous works for exploring multiple execution path have several problems that it requires much time to analyze and resource for preparing analysis environment. In this paper, we proposed efficient exploring approach for multiple execution path in a single analysis environment by pipelining processes and showed the improvement of speed by 29% in 2-core and 70% in 4-core through experiment.

• The KIPS Transactions:PartC
• /
• v.15C no.6
• /
• pp.507-512
• /
• 2008

At a recent, enterprises based on online-service are established because of rapid growth of information network. These enterprises collect personal information and do customer management. If customers use a paid service, company send billing information to customer and customer pay it. Such circulation and management of information is big issue but most companies don't care of information security. Actually, personal information that was managed by largest internal open-market was exposed. For safe customer information management, this paper proposes the method that decrease load of RSA cryptography algorithm that is commonly used for preventing from illegal attack or hacking. The method for decreasing load was designed by Binary NAF Method and it can operates modular Exponentiation rapidly. We implemented modular Exponentiation algorithm using existing Binary Method and Windows Method and compared and evaluated it.

• Journal of Korea Society of Industrial Information Systems
• /
• v.17 no.7
• /
• pp.51-57
• /
• 2012

This paper proposes a group key design based on ECDH(Elliptic Curve Diffie Hellman) which guarantees secure V2V and V2I communication. The group key based on ECDH generates the VGK(Vehicular Group key) which is a group key between vehicles, the GGK(Global Group Key) which is a group key between vehicle groups, and the VRGK(Vehicular and RSU Group key) which is a group key between vehicle and RSUs with ECDH algorithm without an AAA server being used. As the VRGK encrypted with RGK(RSU Group Key) is transferred from the current RSU to the next RSU through a secure channel, a perfect forward secret security is provided. In addition, a Sybil attack is detected by checking whether the vehicular that transferred a message is a member of the group with a group key. And the transmission time of messages and the overhead of a server can be reduced because an unnecessary network traffic doesn't happen by means of the secure communication between groups.

• The Journal of the Korea Contents Association
• /
• v.17 no.3
• /
• pp.231-237
• /
• 2017

Threat intelligences collected from cyber incident sharing system and security events collected from Security Information & Event Management system are analyzed and coped with expanding malicious code rapidly with the advent of big data. Analytical classification of the threat intelligence in cyber incidents requires various features of cyber observable. Therefore it is necessary to improve classification accuracy of the similarity by using multi-profile which is classified as the same features of cyber observables. We propose a multi-profile ensemble model performed similarity analysis on cyber incident of threat intelligence based on both attack types and cyber observables that can enhance the accuracy of the classification. We see a potential improvement of the cyber incident analysis system, which enhance the accuracy of the classification. Implementation of our suggested technique in a computer network offers the ability to classify and detect similar cyber incident of those not detected by other mechanisms.

• Journal of KIISE:Computing Practices and Letters
• /
• v.15 no.12
• /
• pp.998-1002
• /
• 2009

In IPTV multicast architecture, the IGMP(Internet Group Management Protocol) is used for access networks. This protocol supports the functionality of join or leave for a specific multicast channel group. But, malicious attackers can disturb legitimate users being served appropriately. By using spoofed IGMP messages, attackers can hi-jack the premium channel, wasting bandwidth and exhausting the IGMP router's resources. To prevent the message spoofing, we can introduce the packet-level authentication methods. But, it causes the additional processing overhead to an IGMP processing router, so that the router is more susceptible to the flooding attacks. In this paper, we propose the two-level authentication scheme in order to mitigate the IGMP flooding attack.

• IMMUNE NETWORK
• /
• v.4 no.2
• /
• pp.73-80
• /
• 2004

Viruses are obligate intracellular parasites which cause infection by invading and replicating within cells. The immune system has mechanisms which can attack the virus in extracellular and intracellular phase of life cycle, and which involve both non-specific and specific effectors. The survival of viruses depends on the survival of their hosts, and therefore the immune system and viruses have evolved together. Immune responses to viral infection may be variable depending on the site of infection, the mechanism of cell-to-cell spread of virus, physiology of the host, host genetic variation, and environmental condition. Viral infection of cells directly stimulates the production of interferons and they induce antiviral state in the surrounding cells. Complement system is also involved in the elimination of viruses and establishes the first line of defence with other non-specific immunity. During the course of viral infection, antibody is most effective at an early stage, especially before the virus enters its target cells. The virus- specific cytotoxic T lymphocytes are the principal effector cells in clearing established viral infections. But many viruses have resistant mechanism to host immune responses in every step of viral infection to cells. Some viruses have immune evasion mechanism and establish latency or persistency indefinitely. Furthermore antibodies to some viruses can enhance the disease by the second infection. Immune responses to viral infection are very different from those to bacterial infection.