• Journal of KIISE:Information Networking
• /
• v.30 no.6
• /
• pp.705-713
• /
• 2003

For group security to protect group data or to charge, group keys should be updated via key update messages when the membership of group changes. If we lose these messages, it is not possible to decrypt the group data and so this is why the recovery of lost keys is very significant. Any message lost during a certain member is logged off can not be recovered in real-time. Saving all messages and resending them by KDC (Key Distribution Center) not only requests large saving spaces, but also causes to transmit and decrypt unnecessary keys. This paper analyzes the problem of the loss of key update messages along with other problems that may arise during member login procedure, and also gives an efficient method for recovering group keys and auxiliary keys. This method provides that group keys and auxiliary keys can be recovered and sent effectively using information stored in key-tree. The group key generation method presented in this paper is simple and enable us to recover any group key without storing. It also eliminates the transmissions and decryptions of useless auxiliary keys.

• Smart Structures and Systems
• /
• v.14 no.6
• /
• pp.1269-1289
• /
• 2014

With the sub-stepping technique, the numerical analysis in real-time dynamic hybrid testing is split into the response analysis and signal generation tasks. Two target computers that operate in real-time may be assigned to implement these two tasks, respectively, for fully extending the simulation scale of the numerical substructure. In this case, the integration time-step of solving the dynamic response of the numerical substructure can be dozens of times bigger than the sampling time-step of the controller. The time delay between the real and desired feedback forces becomes more striking, which challenges the well-developed delay compensation methods in real-time dynamic hybrid testing. This paper focuses on displacement prediction and force correction for delay compensation in the real-time dynamic hybrid testing with a large integration time-step. A new displacement prediction scheme is proposed based on recently-developed explicit integration algorithms and compared with several commonly-used prediction procedures. The evaluation of its prediction accuracy is carried out theoretically, numerically and experimentally. Results indicate that the accuracy and effectiveness of the proposed prediction method are of significance.

• KSII Transactions on Internet and Information Systems (TIIS)
• /
• v.7 no.2
• /
• pp.366-385
• /
• 2013

In this paper, we propose a compressed sensing (CS) based Wyner-Ziv (WZ) codec using motion-aligned auto regressive model (MAAR) based side information (SI) extrapolation to improve the compression performance of low-delay distributed video coding (DVC). In the CS based WZ codec, the WZ frame is divided into small blocks and CS measurements of each block are acquired at the encoder, and a specific CS reconstruction algorithm is proposed to correct errors in the SI using CS measurements at the decoder. In order to generate high quality SI, a MAAR model is introduced to improve the inaccurate motion field in auto regressive (AR) model, and the Tikhonov regularization on MAAR coefficients and overlapped block based interpolation are performed to reduce block effects and errors from over-fitting. Simulation experiments show that our proposed CS based WZ codec associated with MAAR based SI generation achieves better results compared to other SI extrapolation methods.

• Journal of the Korea Computer Industry Society
• /
• v.5 no.9
• /
• pp.891-902
• /
• 2004

Membership changing is deeply associated with scalability problem for group key management. If members of the group join or leave, new group key has to be geneerated and distributed to all remaining members of group. Group key changing is perform for group controller. The following parameters are important evaluating criteria of multicast key management scheme that generate and deliver new keys for rekeying: the number of keys stored by both controller and member, messages to deliver, keys to initially be delivered by controller, blocking capability of collusion attacks, messages to deliver at the batch rekeyng. Batch rekeying can reduce messages to deliver and operation costs of generation for message rather than removing members sequentially in fashion one after another. We propose efficient batch rekeying scheme applicable to Pegueroles scheme using random number and prove to be a efficient group key scheme for enhanced Pegueroles model with batch rekeying capability.

• Journal of Communications and Networks
• /
• v.16 no.2
• /
• pp.162-171
• /
• 2014

Spectrum sensing is a key technical challenge for cognitive radio (CR). It is well known that multicycle cyclostationarity (MC) detection is a powerful method for spectrum sensing. However, a conventional MC detector is difficult to implement because of its high computational complexity. This paper considers reducing computational complexity by simplifying the test statistic of a conventional MC detector. On the basis of this simplification process, an improved MC detector is proposed. Compared with the conventional detector, the proposed detector has low-computational complexity and high-accuracy sensing performance. Subsequently, the sensing performance is further investigated for the cases of Rayleigh, Nakagami-m, Rician, and Rayleigh fading and lognormal shadowing channels. Furthermore, square-law combining (SLC) is introduced to improve the detection capability in fading and shadowing environments. The corresponding closed-form expressions of average detection probability are derived for each case by the moment generation function (MGF) and contour integral approaches. Finally, illustrative and analytical results show the efficiency and reliability of the proposed detector and the improvement in sensing performance by SLC in multipath fading and lognormal shadowing environments.

• Journal of Computing Science and Engineering
• /
• v.9 no.3
• /
• pp.142-154
• /
• 2015

Fault localization techniques help locate faults in source codes by exploiting collected test information and have shown promising results. To precisely locate faults, the techniques require a large number of test cases that sufficiently exercise the executable statements together with the label information of each test case as a failure or a success. However, during the process of software development, developers may not have high-coverage test cases to effectively locate faults. With the test case generation techniques, a large number of test cases without expected outputs can be automatically generated. Whereas the execution results for generated test cases need to be inspected by developers, which brings much manual effort and potentially hampers fault-localization effectiveness. To address this problem, this paper presents a method to select a few test cases from a number of test cases without expected outputs for result inspection, and in the meantime selected test cases can still support effective fault localization. The experimental results show that our approach can significantly reduce the number of test cases that need to be inspected by developers and the effectiveness of fault localization techniques is close to that of whole test cases.

• Asian Pacific Journal of Cancer Prevention
• /
• v.14 no.3
• /
• pp.1571-1578
• /
• 2013

Cancer is a leading cause of death worldwide. Recently, the demand for more effective and safer therapeutic agents for the chemoprevention of human cancer has increased. As a white rot fungus, Inonotus obliquus is valued as an edible and medicinal resource. Chemical investigations have shown that I. obliquus produces a diverse range of secondary metabolites, including phenolic compounds, melanins, and lanostane-type triterpenoids. Among these are active components for antioxidant, antitumoral, and antiviral activities and for improving human immunity against infection of pathogenic microbes. Importantly, their anticancer activities have become a hot recently, but with relatively little knowledge of their modes of action. Some compounds extracted from I. obliquus arrest cancer cells in the G0/G1 phase and then induce cell apoptosis or differentiation, whereas some examples directly participate in the cell apoptosis pathway. In other cases, polysaccharides from I. obliquus can indirectly be involved in anticancer processes mainly via stimulating the immune system. Furthermore, the antioxidative ability of I. obliquus extracts can prevent generation of cancer cells. In this review, we highlight recent findings regarding mechanisms underlying the anticancer influence of I. obliquus, to provide a comprehensive landscape view of the actions of this mushroom in preventing cancer.

• Convergence Security Journal
• /
• v.12 no.4
• /
• pp.49-55
• /
• 2012

In this paper, we consider the limit of the previous works for ad-hoc network, then propose a dynamic routing scheme which employs a 2-tier hierarchical structure. We adopt the advantages of proactive and reactive routing scheme for efficient network management. We define this method as NSDR(New Secure Dynamic Routing) scheme. We also propose a trustworthy authentication and key management for the proposed ad-hoc network. We currently study the possibility that ad-hoc networks can provide a service such as key management and authentication for the next generation mobile network.

• Journal of Power Electronics
• /
• v.17 no.5
• /
• pp.1327-1337
• /
• 2017

Photovoltaic (PV) systems are influenced by disproportionate impacts on energy production caused by frequent mismatch cases. The occurrence of multiple maximum power points (MPPs) adds complexity to the tracking process in various PV systems. However, current maximum-power point tracking (MPPT) techniques exhibit limited performance. This paper introduces an enhanced simulated annealing (ESA)-based GMPPT technique against multiple MPP issues in P-V curve with different PV system structures. The proposed technique not only distinguishes global and local MPPs but also performs rapid convergence speed and high tracking accuracy of irradiance changing and restart capability detection. Moreover, the proposed global maximum power tracking algorithm can be applied in the central converter of DMPPT and hybrid PV system to meet various application scenarios. Its effectiveness is verified by simulation and test results.

• Journal of Korea Society of Digital Industry and Information Management
• /
• v.12 no.1
• /
• pp.35-41
• /
• 2016

Internet of Things (IoT) services are widely used in appliances of daily life and industries. IoT services also provide various conveniences to users and are expected to affect value added of all industries and national competitiveness. However, a variety of security threats are increased in IoT environments and lowers reliability of IoT devices and services that make some obstacles for commercialization. The attacks arising in IoT environments are making industrial and normal life accidents unlike existing information leak and monetary damages, and can expand damage scale of leakage of personal information and privacy more than existing them. To solve these problems, we design a session key based access control scheme for secure communications in IoT environments. The proposed scheme reinforces message security by generating session key between device and access control network system. We analyzed the stability of the proposed access scheme in terms of data forgery and corruption, unauthorized access, information disclosure, privacy violations, and denial of service attacks. And we also evaluated the proposed scheme in terms of permission settings, privacy indemnity, data confidentiality and integrity, authentication, and access control.