• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2016.06a
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• pp.231-234
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• 2016

본 논문에서는 전송하고자 하는 원영상 대신에 전혀 다른 영상을 전송하여 원영상 정보를 보호하는 스테가노그래피(steganography) 기법을 제안한다. 전송할 영상의 자연스러움을 잃어버리지 않으면서 원영상을 복구할 수 있는 차영상 정보를 LSB(Least Significant Bit)에 담고, 픽셀간의 위치 관계를 무작위로 섞어 줌으로써, 원영상을 보호하는 기법을 제안한다. 본 논문에서는 우선 원영상과 전송할 영상 (cover image)의 차영상을 생성하고, 각 픽셀의 차이값을 큰 범위로 양자화하여 차영상의 데이터 크기를 줄인다. 그리고, 각 픽셀의 차이값을 전송할 영상의 4 픽셀에 걸쳐서 하위 2bit 에 나누어 담는다. 8bit 영상에서 하위 2 bit 를 다루기 때문에, 각 채널 밝기값의 최대 차이값은 3 으로 설정되어 자연스럽게 영상을 생성할 수 있다. 끝으로 신호의 보호를 위하여 차영상의 픽셀과 전송할 영상의 픽셀간의 대응위치를 무작위 순열로 변환하여 외부에서 쉽게 복원할 수 없도록 한다. 이러한 스테가노그래피 제안 기법을 통하여 원영상 대신에 커버 영상을 전송함으로써, 자연스러운 정보전송이 가능하며, 외부의 감시와 복원에 안전한 정보보호 기능이 강화될 수 있다. 여러 영상에 대한 실험을 통한 제안 기법에 의하면, 전송되는 커버 영상이 자연스럽기 때문에 외부에서 정보가 숨겨진 사실을 느끼지 못하며, 송수신 장치에 내장된 무작위 순열을 통하여 외부에서는 원영상 정보를 복구하는 것도 매우 어렵게 되어 있음을 확인하였다. 본 제안 기법은 군사통신이나 중요한 정보를 다루는 기관에서의 정보 전달 및 정보보호 시스템에서 사용될 수 있다.

• Journal of Korea Society of Industrial Information Systems
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• v.17 no.6
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• pp.1-9
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• 2012

Low-cost RFID tags are used in many applications. However, since it has very limited power of computation and storage, it's not easy to make a RFID mutual authentication protocol which can resist from the various security attacks. Quite recently, Tian et al. proposed a new ultralightweight authentication protocol (RAPP) for low-cost RFID tags using the low computation cost operations; XOR, rotation, and permutation operations, which is able to resist from the various security attacks. In this paper, we show that RAPP is vulnerable to the de-synchronization attack and present an improved RAPP which overcomes the vulnerability of RAPP.

• Journal of the Institute of Electronics Engineers of Korea SC
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• v.37 no.3
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• pp.1-8
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• 2000

In this paper, we formulate an optimal control problem to obtain the optimal signal strength and detection threshold for tracking with NN filter, First, we predict the tracking performance of NN filter by using the HYCA method. Based on this method, the predicted tracking performance is represented with respect to signal strength and detection threshold. Using this relation, we find the optimal parameters for following three examples： 1) the sequence of optimal detection threshold which minimizes sum of position estimation error； 2) the sequence of optimal detection threshold which minimizes sum of validation gate volume； and 3) the sequence of optimal signal strength and detection threshold which minimizes sum of signal strength.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.17 no.3
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• pp.35-42
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• 2007

We describe the problem of reducing the key material in the Even-Mansour cipher without security degradation. Even and Mansour proposed a block cipher based on XORing secret key material just prior to and after applying random oracle permutation P such that $C=k_2\bigoplus P(M\bigoplus k_1)$. Recently, Gentry and Ramzan showed that this scheme in the random permutation oracle can be replaced by the four-round Feistel network construction in the random function oracle and also proved that their scheme is super-pseudorandom. In this paper we reduce the key size from 2n to n, which is the optimal key size of Even-Mansour cipher in the random function oracle model and also give almost the same level of security.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.31 no.3C
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• pp.286-292
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• 2006

Both composition and XOR are operations widely used to enhance security of cryptographic schemes. The more number of random permutations we compose (resp. XOR), the more secure random permutation (resp. random function) we get. Combining the two methods, we consider a generalized form of random function: $SUM^s - CMP^c = ({\pi}_{sc} ... {\pi}_{(s-1)c+1}){\oplus}...{\oplus}({\pi}_c...{\pi}_1)$ where ${\pi}_1...{\pi}_{sc}$ are random permutations. Given a fixed number of random permutations, there seems to be a trade-off between composition and XOR for security of $SUM^s - CMP^c$. We analyze this trade-off based on some upper bound of insecurity of $SUM^s - CMP^c$, and investigate what the optimal number of each operation is, in order to lower the upper bound.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.30 no.3
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• pp.325-336
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• 2020

Nonlinear Invariant Attack is an attack that should be considered when constructing lightweight block ciphers with relatively simple key schedule. A shortcut to prove a block cipher's resistance against nonlinear invariant attack is checking the smallest dimension of linear layer-invariant linear subspace which contains all known differences between round keys is equal to the block size. In this paper, we presents the following results. We identify the structure and number of optimal bit-permutations which require only one known difference between round keys for a designer to show that the corresponding block cipher is resistant against nonlinear invariant attack. Moreover, we show that PRESENT-like block ciphers need at least two known differences between round keys by checking all PRESENT-like bit-permutations. Additionally, we verify that the variants of PRESENT-like bit-permutations requiring the only two known differences between round keys do not conflict with the resistance against differential attack by comparing the best differential trails. Finally, through the distribution of the invariant factors of all bit-permutations that maintain BOGI logic with GIFT S-box, GIFT-variant block ciphers require at least 8 known differences between round keys for the resistance.

• Journal of the Korean Society of Marine Environment & Safety
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• v.28 no.5
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• pp.753-763
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• 2022

In coastal and inland bays, where most of Korea's aquaculture is located, massive aquaculture damage occurs every year due to frequent anomalous high water temperatures. The interannual fluctuations of water temperature in July over the past four years (2018-2021) were the second largest since 1990 (after the period of 1994-1997) due to anomalous high temperatures, rainy seasons, and typhoons. Through analysis of heat flux and heat balance in areas of concern for high water temperatures (i.e., Cheonsu Bay, Gamak Bay, Guryongpo), the occurrence of high water temperatures in Cheonsu Bay and Gamak Bay in the summer seasons was confirmed to derive mainly from heat inflow through the sea surface from the air. Based on estimations of the average ocean heat transport rate in July for the four-year period of 2018-2021, Cheonsu Bay and Gamak Bay accounted for 13.5% and 62.3% outflow of the net heat flux, respectively. However, the ocean heat transport rate in Guryongpo Hajeong differed significantly from -174.5% to 132.5% of the net heat flux by year depending on the occurrence of cold water mass.

• 한국상하수도협회지
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• s.23
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• pp.4-9
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• 2008

• 농업기술회보
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• v.45 no.4
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• pp.46-48
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• 2008

• Proceedings of the KSLP Conference
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• 2002.06a
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• pp.218-224
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• 2002