• The KIPS Transactions:PartC
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• v.18C no.4
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• pp.227-236
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• 2011

IPTV(Internet Protocol Television) is one of the typical businesses which are the convergence of Broadcast and Communication. It provides broadcasting service using IP networks. Recently, IPTV service is developed to Mobile IPTV or Open IPTV. Especially, Open IPTV uses open platform so not only service providers but also general users can provide contents to other users. Open IPTV system has many content providers, so existing security solution of IPTV cannot be adopted. In this paper, we suggest user authentication and key distribution mechanism on Open IPTV. Our proposed mechanism is based on Kerberos, so it can support distribution environment such as Open IPTV. We demonstrate that proposed mechanism can guarantee secure transmission of contents and reduce the delay of user authentication on Open IPTV system compared to other authentication mechanisms. We also compare our proposal and other mechanisms in various aspects, and analyze efficiency and safety of proposed mechanism. As a result, we insist that this mechanism satisfies the security requirements for IPTV.

• Geomechanics and Engineering
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• v.23 no.2
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• pp.151-163
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• 2020

Grouting method is an effective way of reinforcing cracked rock masses and plugging water gushing. Current grouting diffusion models are generally developed for horizontal cracks, which is contradictory to the fact that the crack generally occurs in rock masses with irregular spatial distribution characteristics in real underground environments. To solve this problem, this study selected a cement-sodium silicate slurry (C-S slurry) generally used in engineering as a fast-curing grouting material and regarded the C-S slurry as a Bingham fluid with time-varying viscosity for analysis. Based on the theory of fluid mechanics, and by simultaneously considering the deadweight of slurry and characteristics of non-uniform spatial distribution of viscosity of fast-curing grouts, a theoretical model of slurry diffusion in an oblique crack in rock masses at constant grouting rate was established. Moreover, the viscosity and pressure distribution equations in the slurry diffusion zone were deduced, thus quantifying the relationship between grouting pressure, grouting time, and slurry diffusion distance. On this basis, by using a 3-d finite element program in multi-field coupled software Comsol, the numerical simulation results were compared with theoretical calculation values, further verifying the effectiveness of the theoretical model. In addition, through the analysis of two engineering case studies, the theoretical calculations and measured slurry diffusion radius were compared, to evaluate the application effects of the model in engineering practice. Finally, by using the established theoretical model, the influence of cracking in rock masses on the diffusion characteristics of slurry was analysed. The results demonstrate that the inclination angle of the crack in rock masses and azimuth angle of slurry diffusion affect slurry diffusion characteristics. More attention should be paid to the actual grouting process. The results can provide references for determining grouting parameters of fast-curing grouts in engineering practice.

• Geomechanics and Engineering
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• v.19 no.5
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• pp.421-434
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• 2019

It is of great significance to study the mechanical properties and failure mechanism of the defected rock for geological engineering. The defected sandstone modeling with power-law distribution of pre-cracks was built in this paper by Particle Flow Code software. Then the mechanical properties of sandstone and the corresponding failure process were meticulously analyzed by changing the power-law index (PLI) and the number of pre-cracks (NPC). The results show that (1) With the increase of the PLI, the proportion of prefabricated long cracks gradually decreases. (2) When the NPC is the same, the uniaxial compressive strength (UCS) of sandstone increases with the PLI; while when the PLI is the same, the UCS decreases with the NPC. (3) The damage model of rock strength is established based on the Mori-Tanaka method, which can be used to better describe the strength evolution of damaged rock. (4) The failure mode of the specimen is closely related to the total length of the pre-crack. As the total length of the pre-crack increases, the failure intensity of the specimen gradually becomes weaker. In addition, for the specimens with the total pre-crack length between 0.2-0.55 m, significant lateral expansion occurred during their failure process. (5) For the specimens with smaller PLI in the pre-peak loading process, the concentration of the force field inside is more serious than that of the specimens with larger PLI.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.8 no.3
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• pp.1144-1156
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• 2014

In Internet, IP multicast has been used successfully to provide an efficient, best-effort delivery service for group communication applications. However, applications such as multiparty private conference, distribution of stock market information, pay per view and other subscriber services may require secure multicast to protect integrity and confidentiality of the group traffic, and validate message authenticity. Providing secure multicast for group communication is problematic without a robust group key management. In this paper, we propose a group key management scheme based on the secret sharing technology to require each member by itself to generate the group key when receiving a rekeying message multicast by the group key distributor. The proposed scheme enforces mutual authentication between a member and the group key distributor while executing the rekeying process, and provides forward secrecy and backward secrecy properties, and resists replay attack, impersonating attack, group key disclosing attack and malicious insider attack.

• Journal of Internet Computing and Services
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• v.3 no.5
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• pp.87-94
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• 2002

This paper proposes a group key management protocol for a secure of all the multcast user in PIM-SM multicast group communication. Each subgroup manager gives a secure key to it's own transmitter and the transmitter compress the data with it's own secure key from the subgroup manager, Before the transmitter send the data to receiver, the transmitter prepares to encrypt a user's service by sending a encryption key to the receiver though the secure channel. after checking the user's validity through the secure channel, As the transmitter sending a data after then, the architecture is designed that the receiver will decode the received data with the transmitter's group key, Therefore, transmission time is shortened because there is no need to data translation by the group key on data sending and the data transmition is possible without new key distribution at path change to shortest path of the router characteristic.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.7 no.11
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• pp.2874-2892
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• 2013

Since security plays an important role in several ZigBee applications, such as Smart Energy and medical sensor applications, ZigBee Specification includes various security mechanisms to protect ZigBee frames and infrastructure. Among them, the Join and Leave operations of ZigBee are investigated in this paper. The current Join-Leave operation is protected by the network key (a kind of group key). We claim it is not adequate to employ the network key for such purpose, and propose a new Join-Leave operation protected by the application link key (a kind of pairwise key), which is based on a more efficient key management scheme than that of ZigBee. Hence, the original Join operation consists of a total of 12 command frames, while the new Join operation consists of only 6 command frames. In particular, the security of the proposed Join-Leave operation is equivalent to or better than that of the original Join-Leave operation. The new Join-Leave operation is extensively analyzed in terms of security and efficiency, and compared with the original Join-Leave operation of ZigBee.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.25 no.4
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• pp.759-766
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• 2015

This paper proposes a location-based key management scheme in wireless sensor networks, and among the existing location-based key management techniques, we focused on the LDK (Location Dependent Key management). In order to improve the problems occurred by communication interference, we introduced the key revision process and the method of key establishment using grid information. According to the simulation of this scheme, it increased connectivity while decreased compromise ratio than those of the previous LDK, futhermore, we confirmed that a hexagon distribution of AN reduces the network cost.

• Convergence Security Journal
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• v.2 no.2
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• pp.19-27
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• 2002

This paper proposes a group key management protocol for a secure of all the multicast user in PIM-SM multicast group communication. Each subgroup manager gives a secure key to it's own transmitter and the transmitter compress the data with it's own secure key from the subgroup manager. Before the transmitter send the data to receiver, the transmitter prepares to encrypt a user's service by sending a encryption key to the receiver though the secure channel, after checking the user's validity through the secure channel. As the transmitter sending a data after then, the architecture is designed that the receiver will decode the received data with the transmitter's group key. Therefore, transmission time is shortened because there is no need to data translation by the group key on data sending and the data transmition is possible without new key distribution at path change to shortest path of the router characteristic.

• The Journal of Asian Finance, Economics and Business
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• v.5 no.4
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• pp.57-65
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• 2018

With the paramount importance of key account management in business-to-business relationship, today companies are using this approach as a strategic weapon in their selling efforts targeted at the most important customers to solve their complex requirements with special treatment that eventually ensures both parties' financial and nonfinancial objectives. The aim of this paper is to investigate the level of key account management performance among the export-oriented readymade garments companies in Bangladesh with regards to company's experience in business, size of the company and key account serving capacity of the company. Using a questionnaire, data from 112 readymade garments companies in Bangladesh were collected and analyzed using descriptive analysis and ANOVA to test the level of key account management performance. Results show that the level of key account management performance by the garments companies did not vary by the company's experience in business and size of the company respectively. In contrast, the level of key account management performance was found to be different concerning high, medium, and low customer service capacity. Apparently, companies with big number of customers show better performance than companies with small number of customer. Implications for this study are discussed along with suggestions for future research avenues.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.10 no.7
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• pp.3414-3434
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• 2016

Classical key generation is complicated to update and key distribution generally requires fixed infrastructures. In order to eliminate these restrictions researchers have focused much attention on physical-layer (PHY-layer) based key generation methods. In this paper, we present a PHY-layer fingerprints based fuzzy key generation scheme, which works to prevent primary user emulation (PUE) attacks and spectrum sensing data falsification (SSDF) attacks, with multi-node collaborative defense strategies. We also propose two algorithms, the EA algorithm and the TA algorithm, to defend against eavesdropping attacks and tampering attacks in mobile cognitive radio networks (CRNs). We give security analyses of these algorithms in both the spatial and temporal domains, and prove the upper bound of the entropy loss in theory. We present a simulation result based on a MIMO-OFDM communication system which shows that the channel response characteristics received by legitimates tend to be consistent and phase characteristics are much more robust for key generation in mobile CRNs. In addition, NIST statistical tests show that the generated key in our proposed approach is secure and reliable.