• ETRI Journal
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• v.29 no.5
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• pp.655-666
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• 2007

There are nodes and edges in a topological map. Node data has been used as a main source of information for the localization of mobile robots. In contrast, edge data is regarded as a minor source of information, and it has been used in an intuitive and heuristic way. However, edge data also can be used as a good source of information and provide a way to use edge data efficiently. For that purpose, we define a data format which describes the shape of an edge. This format is called local generalized Voronoi graph's angle (LGA). However, the LGA is constituted of too many samples; therefore, real time localization cannot be performed. To reduce the number of samples, we propose a compression method which utilizes wavelet transformation. This method abstracts the LGA by key factors using far fewer samples than the LGA. Experiments show that the LGA accurately describes the shape of the edges and that the key factors preserve most information of the LGA while reducing the number of samples.

• The Transactions of the Korea Information Processing Society
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• v.4 no.10
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• pp.2501-2511
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• 1997

This paper presents an authentication model for security on satellite command & control communications. The proposed authentication scheme is based on the modified Shamir's signature scheme using a satellite ID(Identity) and the model uses time stamp for protection of command replay attack from unauthorized center. The message authentication with command counter that includes an available key and the algorithm is for loading and execution of commands in the model. Two-way scheme for key change and confirmation between satellite control center and satellite is also proposed.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.9 no.5
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• pp.958-964
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• 2005

WLAN user authentication is mostly based on user password resulting in vulnerability to the notorious 'offline dictionary attack'. As a way around this problem. EAP-TTLS and PEAP protocols are increasing finding their way into WLANs, which are a sort of combination of password protocols and the TLS public-key protocol. This leads to the use of the public-key certificate of the WLAM authentication server, and naturally the concern arises about its revocation status. It seems, however, that any proper soulution has not been provided to address this concern. We propose a very efficent and proper solution to check the certificate revocation status.

• Journal of Microbiology and Biotechnology
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• v.22 no.7
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• pp.967-974
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• 2012

Cultivation of Spirulina platensis using ammonium salts or wastewater containing ammonium as alternative nitrogen sources is considered as a commercial way to reduce the production cost. In this research, by analyzing the relationship between biomass production and ammonium-N consumption in the fed-batch culture of Spirulina platensis using ammonium bicarbonate as a nitrogen nutrient source, an online adaptive control strategy based on optical density (OD) measurements for controlling ammonium feeding was presented. The ammonium concentration was successfully controlled between the cell growth inhibitory and limiting concentrations using this OD-based feedback feeding method. As a result, the maximum biomass concentration (2.98 g/l), productivity (0.237 g/l d), nitrogen-to-cell conversion factor (7.32 gX/gN), and contents of protein (64.1%) and chlorophyll (13.4mg/g) obtained by using the OD-based feedback feeding method were higher than those using the constant and variable feeding methods. The OD-based feedback feeding method could be recognized as an applicable way to control ammonium feeding and a benefit for Spirulina platensis cultivations.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.16 no.7
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• pp.575-597
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• 1991

As an elegant solution of the key management scheme for a conventional cryptosystem. Diffie and Hellman introduced a public key distrbution system, whose security depends on the intractabliity of discrete loganthm problem over a finite field, and since then a lot of vartants of DH KDSS have been proposed. In this paper, we present the systematic approach to analyzing the security of a generalized DH KDS and designing an efficient and secure scheme. We classify vanous attacking methods and point out a possible way to avoid these attacks through the examples of successful attacking methods and point out a possible way to avoid these attacks through the examples of successful attack against those systems proposed so far or designed for this purpose. As security analysis tools, we present the redueiblity test, the information theoretic approach, and the protocol analysis technique, which we apply to variations of DH scheme to examine their security under all possble attacks.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.16 no.2
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• pp.121-127
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• 2006

Recently, Chang et at.$^[9]$ proposed a new password-based key agreement protocol and a password change protocol to improve the efficiency in the password-based authenticated key agreement protocol proposed by Yeh et at.$^[8]$. However, Wang et al.$^[10]$ showed that their protected password change protocol is not secure under the denial of service attack and the dictionary attack This paper proposes an improved password change protocol to solve this problems in the Chang et al's protocol. In the proposed protocol, the format of communication messages is modified not to have any clue for the guessing of the password and verifying of the guessed password. The proposed protocol supports the advantages in the previous password-based protocols and solves the problems in them effectively.

• International Journal of Internet, Broadcasting and Communication
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• v.13 no.2
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• pp.60-66
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• 2021

Blockchain is a technology that enables trust-based consensus and verification based on a decentralized network. Distributed ID (DID) is based on a decentralized structure, and users have the right to manage their own ID. Recently, interest in self-sovereign identity authentication is increasing. In this paper, as a method for transparent and safe sovereignty management of data, among data pseudonymization techniques for blockchain use, various methods for data encryption processing are examined. The public key technique (homomorphic encryption) has high flexibility and security because different algorithms are applied to the entire sentence for encryption and decryption. As a result, the computational efficiency decreases. The hash function method (MD5) can maintain flexibility and is higher than the security-related two-way encryption method, but there is a threat of collision. Zero-knowledge proof is based on public key encryption based on a mutual proof method, and complex formulas are applied to processes such as personal identification, key distribution, and digital signature. It requires consensus and verification process, so the operation efficiency is lowered to the level of O (log_eN) ~ O(N²). In this paper, data encryption processing for blockchain DID, based on zero-knowledge proof, was proposed and a one-way encryption method considering data use range and frequency of use was proposed. Based on the content presented in the thesis, it is possible to process corrected zero-knowledge proof and to process data efficiently.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.7 no.4
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• pp.878-894
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• 2013

Secure multimedia multicast applications involve group communications where group membership requires secured dynamic key generation and updating operations. Such operations usually consume high computation time and therefore designing a key distribution protocol with reduced computation time is necessary for multicast applications. In this paper, we propose a new key distribution protocol that focuses on two aspects. The first one aims at the reduction of computation complexity by performing lesser numbers of multiplication operations using a ternary-tree approach during key updating. Moreover, it aims to optimize the number of multiplication operations by using the existing Karatsuba divide and conquer approach for fast multiplication. The second aspect aims at reducing the amount of information communicated to the group members during the update operations in the key content. The proposed algorithm has been evaluated based on computation and communication complexity and a comparative performance analysis of various key distribution protocols is provided. Moreover, it has been observed that the proposed algorithm reduces the computation and communication time significantly.

• The Journal of the Korea Contents Association
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• v.9 no.1
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• pp.115-122
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• 2009

In this paper, we proposed scheme that we use a difference of timestamp in time in Ubiquitous environments as we use the Diffie-Hellman method that OTP was applied to when it deliver a key between nodes, and can detect a malicious node at these papers. Existing methods attempted the malicious node detection in the ways that used correct synchronization or directed antenna in time. We propose an intermediate malicious node detection way at these papers without an directed antenna addition or the Trusted Third Party (TTP) as we apply the OTP which used timestamp to a Diffie-Hellman method, and we verify safety regarding this. A way to propose at these papers is easily the way how application is possible in Ubiquitous environment.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.8 no.12
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• pp.4432-4450
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• 2014

It is widely observed that in practical wireless cooperative communication systems, different links may experience different fading characteristics. In this paper, we investigate into the outage probability and channel capacity of two-way amplify-and-forward (TWAF) relaying systems operating over a mixed asymmetric Rician and Rayleigh fading scenario, with different amplification policies (AP) adopted at the relay, respectively. As TWAF relay network carries concurrent traffics towards two opposite directions, both end-to-end and overall performance metrics were considered. In detail, both uniform exact expressions and simplified asymptotic expressions for the end-to-end outage probability (OP) were presented, based on which the system overall OP was studied under the condition of the two source nodes having non-identical traffic requirements. Furthermore, exact expressions for tight lower bounds as well as high SNR approximations of channel capacity of the considered scenario were presented. For both OP and channel capacity, with different APs, effective power allocation (PA) schemes under different constraints were given to optimize the system performance. Extensive simulations were carried out to verify the analytical results and to demonstrate the impact of channel asymmetry on the system performance.