• Journal of the Korea Institute of Information Security & Cryptology
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• v.24 no.1
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• pp.51-58
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• 2014

A LFSR is commonly used for various stream cryptography applications to generate random numbers. A Leap-ahead LFSR was presented to generate a multi-bits random number per cycle. It only requires a single LFSR and it has an advantages in hardware complexity. However, it suffers from the significant reduction of maximum period of the generated random numbers. This paper presents the new segmented Leap-ahead LFSR to solve this problem. It consists of two segmented LFSRs. We prove the efficiency of the proposed segmented architecture using the precise mathematical analysis. We also demonstrate the proposed comparison results with other counterparts using Xinilx Vertex5 FPGA. The proposed architecture can increase 2.5 times of the maximum period of generated random numbers compared to the typical Leap-ahead architecture.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.33 no.6
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• pp.2465-2471
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• 2013

This paper develops a travel time prediction algorithm that can be used for real-time application. The algorithm searches for the most similar pattern in historical travel time database as soon as a series of real-time data become available. Artificial neural network approach is then taken to forecast travel time in the near future. To examine the performance of this algorithm, travel time data from Gyungbu Highway were obtained and the algorithm is applied. The evaluation shows that the algorithm could predict travel time within 4% error range if comparable patterns are available in the historical travel time database. This paper documents the detailed algorithm and validation procedure, thereby furnishing a key to generating future travel time information.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.26 no.1
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• pp.49-67
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• 2016

SP 800-90B of NIST(USA) and AIS.31 of BSI(Germany) are representative statistical tests for TRNGs. In this paper, we concentrate on AIS.31 which is under the ongoing international standardization process. We examine the probabilistic meaning of each statistic of the test in AIS.31 and investigate its probability distribution. By changing significance level and the length of sample bits, we obtain formalized accept region of the test. Furthermore we propose the accept regions for some iterative tests, that are not mentioned in AIS.31, and provide some simulations.

• Journal of Korea Multimedia Society
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• v.10 no.5
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• pp.623-630
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• 2007

With the development in IT technology and with growing demands of users, a ubiquitous environment is being made. Because of individuals identification is important in ubiquitous environment, RFID, a technology used frequently. RFID, a technology that radio frequency identification, reader send signer, then tag provide user information. RFID has various strengths, such as high recognition rates, quick recognition speed, but Eavesdropping is possible and problem that user information is revealed happens. To solve this, study is proceeded with activity, but, because of low-cost passive tag is limited operation capability, usually used hash function and random number. Also updates value that is used to present session and uses in next session. Therefore, this scheme protects user privacy using random number. And this sheme can offer synchronization by creating variable value without updating value.

• Journal of KIISE:Computing Practices and Letters
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• v.12 no.6
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• pp.367-378
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• 2006

A mobile phone has became as a payment tool in e-commerce and on-line banking areas. This trend of a payment system using various types of mobile devices is rapidly growing, especially in the Internet transaction and small-money payment. Hence, there will be a need to define its standard for secure and safe payment technology. In this thesis, we consider the service types of the current mobile payments and the authentication method, investigate the disadvantages, problems and their solutions for smart and secure payment. Also, we propose a novel authentication method which is easily adopted without modification and addition of the existed mobile hardware platform. Also, we present a simple implementation as a demonstration version. Based on virtual machine (VM) approach, the proposed model is to use a pseudo-random number which is confirmed by the VM in a user's mobile phone and then is sent to the authentication site. This is more secure and safe rather than use of a random number received by the previous SMS. For this payment operation, a user should register the serial number at the first step after downloading the VM software, by which can prevent the illegal payment use by a mobile copy-phone. Compared with the previous SMS approach, the proposed method can reduce the amount of packet size to 30% as well as the time. Therefore, the VM-based method is superior to the previous approaches in the viewpoint of security, packet size and transaction time.

• Proceedings of the Korea Institutes of Information Security and Cryptology Conference
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• 1994.11a
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• pp.183-192
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• 1994

본 논문에서는 복호키를 모르는 해독자의 입장에서 주파수 영역 비화 및 시간 영역 비화(의사 난수 치환 방법, 유니폼 치환 방법, 의사난수-유니폼 치환 방법)되어진 미지의 신호를 수신한 후 비록 영역을 판단하는 알고리즘과 원 신호를 검출하는 알고리즘을 제안하였다. 그리고 원신호 검출 소요 시간을 측정한 후 사용하고자하는 스크램블링 방식에서 적절한 키를 선택하는 방법을 제시하였다. 각 비화 영역 신호의 세기와 3.6KHz 고역 통과 필터링 후의 신호의 세기를 비교ㆍ분석한 후 비화 영역을 판단하였으며, 퓨리에 변환 후의 신호의 특성과 영교차점(zero-crossin )을 비교ㆍ분석한 후 원 신호를 검출하는 알고리즘을 구현하였다. 그리고 각 영역 비화 신호에 대한 원 신호의 검출 시간을 비교하므로써 7일 동안 보호가 필요한 정보를 비화시키는데 필요한 비화 단위인 블럭의 크기(즉, 키의 크기)를 제안하였다.

• Proceedings of the Korean Information Science Society Conference
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• 2004.10a
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• pp.430-432
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• 2004

무선 센서 네트워크는 특정 관심 대상이나 환경으로부터 데이터를 수집하여 사용자에게 전달해 줌으로써 결정수단이나 연구를 목적으로 이용되어 지기 때문에 효과적인 보안이 요구되어 진다. 기존의 존재하는 많은 네트워크 보안은 센서 노드의 특성상 센서 네트워크에 적용될 수 없다 본 논문은 이런 센서 네트워크의 특성을 감안하여 대칭 키(symmetric key)를 기반으로 한 키(key) 관리 프로토콜을 제안한다. 제안 프로토콜은 키의 직접적인 이동 없이 마스터 키(Master Key), 의사 난수 생성기(Pseudo Random Number Generator:PRNG), 난수(Random Number:RN)의 조합을 통해 임의의 키를 생성함으로써 보안성을 강화함과 동시에, 다양한 통신 모델에서 사용되어지는 키들을 생성하고, 또한 통신 모델의 따라 프로토콜 축소와 확장이 가능하며, 다양한 네트워크 모델에 안도록 변형이 용이하게 설계되었다. 그리고 센서 노드의 에너지 소비를 감안하여 프로토콜 수행에 필요한 통신회수를 최소화하였다.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.18 no.3
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• pp.3-8
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• 2008

Ephemeral data are easily revealed if state specific information is stored in insecure memory or a random number generator is corrupted. In this letter, we show that Nam et al.'s group key agreement scheme, which is an improvement of Bresson et al.'s scheme, is not secure against session-state reveal attacks. We then propose an improvement to fix the security flaw.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.17 no.5
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• pp.3-14
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• 2007

In this paper, we observe that secure tweakable permutation families in the sense of strong pseudorandom permutation (SPRP) can be transformed to secure permutation families in the sense of SPRP against related-key attacks (SPRP-RKA). This fact allows us to construct a secure SPRP-RKA which is the most efficient to date. We also observe that secure function families of a certain form in the sense of a pseudorandom function (PRF) can be transformed to secure permutation families in the sense of PRP-RKA. We can exploit it to get various secure constructions against related-key attacks from known MAC algorithms. Furthermore, we define other security notions for related-key attacks, namely indistinguishability and non-malleability, and look into the relations between the security notions fur related-key attacks. We show that secure tweakable permutation families in the sense of indistinguishability (resp. non-malleability) can be transformed to secure permutation families in the sense of indistinguishability (resp. non-malleability) against related-key attacks.

• Proceedings of the Korea Information Processing Society Conference
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• 2006.05a
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• pp.1011-1014
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• 2006

RFID(Radio Frequency Identification), 즉, 무선 주파수 인식 기술은 주파수를 이용하여 개별 상품을 식별하는 방식을 일컫는다. 바코드나 스마트카드에 비하여 우수한 특성에 의해 다양한 응용이 가능하여, 향후 유비쿼터스 환경을 구축하는 데 핵심적 역할을 할 것으로 보인다. 그러나 이러한 환경을 제대로 갖추기 위해서는 보안 기술이 필수적이다. 작고 가벼움을 필수조건으로 하는 RFID에서는 기존의 보안 기술을 그대로 적용하기 어렵기 때문에 보다 가볍고 안전한 RFID 보호 프로토콜이 요구된다. 본 논문에서는 태그와 리더가 각각 난수를 생성함으로써 기존의 인증 프로토콜보다 적은 연산만으로도 서로를 안전하게 인증하는 기법을 제시한다.