• Journal of the Korea Society of Computer and Information
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• v.11 no.2 s.40
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• pp.275-283
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• 2006

Writers enroll their outcome to Program Deliberation & Mediation Committee and get the copyright preserved for the protection of IPR. The program registration is conducted through off-line and on-line methods, and especially on-line registration provides program registrants convenience along with the safety of property from external copyright invaders. However, it is a shortcoming that the integrity and confidentiality of the enrolled program cannot be guaranteed in case of internal factors such as system errors, administrator's illegal access and revision. This paper proposes the reliable system, ensuring programs and offering convenience of Digital signature management from the system errors and intruding factors by internal administrator, using the security of confidentiality, integrity and Multi-Signature Scheme for program.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.15 no.8
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• pp.2865-2878
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• 2021

As a current popular technology, the blockchain has a serious issue: the private key cannot be retrieved due to force majeure. Since the outcome of the blockchain-based Bitcoin, there have been many occurrences of the users who lost or forgot their private keys and could not retrieve their token wallets, and it may cause the permanent loss of their corresponding blockchain accounts, resulting in irreparable losses for the users. We propose a recoverable private key scheme for consortium blockchain based on the verifiable secret sharing which can enable the user's private key in the consortium blockchain to be securely recovered through a verifiable secret sharing method. In our secret sharing scheme, users use the biometric keys to encrypt shares, and the preset committer peers in the consortium blockchain act as the participants to store the users' private key shares. Due to the particularity of the biometric key, only the user can complete the correct secret recovery. Our comparisons with the existing mnemonic systems or the multi-signature schemes have shown that our scheme can allow users to recover their private keys without storing the passwords accurately. Hence, our scheme can improve the account security and recoverability of the data-sharing systems across physical and virtual platforms that use blockchain technology.

• Proceedings of the Korean Information Science Society Conference
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• 2004.04b
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• pp.52-54
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• 2004

모바일 환경에서 효과적인 데이터 전송 방법인 브로드 캐스트 기법에서 중요한 문제 중의 하나가 데이터에 대한 인덱스 생성이다. 데이터에 대한 인덱스가 제공되면 클라이언트는 튜닝 타임과 엑세스 타임을 줄일 수 있고, 그와 함께 배터리 소모도 줄일 수 있다 기존에 제시된 인덱스 생성 기법온 대부분 트리 구조를 기반으로 하고 있다. 트리 기반 인덱싱 기법은 튜닝 타임을 최소화하지만, 반면 멀티-어트리뷰트(multi-attribute)에 대한 엑세스나 다양한 종류의 멀티미디어 데이터들 혹은 클러스터링 된 데이터에 대한 인덱스 생성이 어렵다. 이러한 문제를 해결하기 위해 시그너쳐 기반의 인덱싱 기법이 제시되었다. 그러나 기존의 시그너쳐 기반 인덱싱 기법에서는 엑세스 타임이 전체 브로드 캐스트 타임으로 고정되는 문제가 있었다. 본 논문비서는 앞으로 브로드 캐스팅 될 데이터들에 대한 포괄적인 정보를 가지는 시그너쳐 집합을 인덱스로 제공해서 클라이언트의 엑세스 타임을 최소화시키는 시그너쳐 스킴을 제시한다.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.24 no.2
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• pp.95-101
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• 2011

In wireless X networks where all transmitters send the independent messages to all receivers, the theoretical bound on the degrees of freedom (DOF) and interference alignment (IA) scheme for its achievability are given by Cadambe and Jafar [1]. However, IA scheme for wireless X network may be infeasible in practice unless the transmitters have the perfect channel information. In addition, if the transmitter with single antenna uses time-varying channel coefficients as a beamforming vector, the infinite channel extension is required to achieve the theoretical bound on the DOF of wireless X networks with perfect IA scheme. In this paper, we consider K-user MIMO X network where K transmitters and K receivers have M antennas each. While the beamforming vectors have been constructed with multiple channel uses over multiple time slot in the earlier work, we consider the beamforming vectors constructed only by a spatial signature over unit time. Accordingly the channel information at the transmitters can be available instantaneously. Then we propose the perfect IA scheme with no channel extension. Based on our sum-rate analysis and the simulation results, we confirm that our proposed scheme can achieve MK/2 DOF which is quite close to the theoretical bound on the DOF region of wireless X networks.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.29 no.3A
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• pp.248-256
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• 2004

Woerner had suggested an asynchronous trellis-coded DS/CDMA system based on a multi-sequence signaling, biorthogonal sequence, which is superior to single sequence signaling, such as M-ary PSK, due to their better cross-correlation properties. This paper analyzes and compares system performance between OPSM, a recently-presented multi-sequence signaling scheme, and biorthogonal sequence signaling. Interuser interference moments of the two schemes are derived and compared which verifies that OPSM, having smaller signature sequences per symbol than biorthogonal signaling, reduces cross-correlation. Numerical results compare the power and spectral efficiency of asynchronous trellis-coded DS/CDMA systems based on multi-sequence signaling.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.25 no.7A
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• pp.943-950
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• 2000

In this paper, an asynchronous multi-rate optical wireless pulse position modulation-code division multiple access (PPM-CDMA) is proposed for an indoor non-directed diffuse channel. As a signature sequence for CDMA, an optical orthogonal code (OOC) is used and an interference cancellation scheme is applied to improve the bit error rate. It is known that the optical PPM-CDMA has advantages due to its power efficiency. Moreover, it provides multi-rate services by varying the modulation level with fixed pulse duration. In the proposed multi-rate PPM-CDMA system with fixed pulse duration, chip rate and sampling time do not change for each transmission rate and this simplifies overall system structure.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.30 no.7C
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• pp.666-674
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• 2005

A hybrid multicarrier CDMA/FDM system with a truncated adaptive transmission scheme is analyzed in forward link based on the feedback information from the mobile station. In the single cell environment, the prop(mea scheme outperforms the adaptive FH/DS system as well as the MC DS/CDMA system when orthogonal signature sequences are used. In the multiple cell environment also, the proposed scheme has better performance characteristics than the adaptive FH/DS system when orthogonal and random codes are used as spreading sequences.

• Proceedings of the Korean Information Science Society Conference
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• 2007.10d
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• pp.556-559
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• 2007

Due to its ease of deployment, low cost, self-configuring and self-healing capabilities, Wireless Mesh Networks (WMNs) have emerged as a key technology to be used in a wide scale applications in personal, local, campus, and metropolitan areas. Security and more specifically privacy is an important issue in this type of multi-hop WMN which has given a little attention in the research community. We focus on privacy compromise of a mesh client in a community mesh network that may lead an attacker to reveal mesh clients identity. his other profiles and gain information about mobility. In this paper. we have presented an authentication mechanism with the aid of blind signature that ensures a mesh client to anonymously authenticate itself with a nearby mesh router and thereby preserve identity privacy We have also presented the security and performance analysis of the proposed scheme.

• Proceedings of the Korean Information Science Society Conference
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• 2000.10c
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• pp.591-593
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• 2000

Mobile Agent System은 최근 각광받기 시작한 새로운 컴퓨팅 기법으로서 서버의 과부하를 줄이고, 네트워크 이벤트의 발생을 줄이면서 필요한 서비스를 사용자에게 지원하기 위한 해결책으로 연구되고 있다. 이동에이전트시스템은 해결해야할 많은 과제들이 있으나 그 중에서 주요한 문제로 인식되고 있는 것이 보안 문제이다. 본 논문은 이동에이전트시스템의 보안 고려사항을 분석하고, 공개키 기반의 암호시스템과 일반향함수를 사용하는 디지털 다중서명 기법을 적용하여 이동에이전트 시스템의 보안구조를 제안한다.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.25 no.3B
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• pp.557-564
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• 2000

This paper presents a watermarking algorithm for embedding visually recognizable pattern (Mark, Logo, Symbol, stamping or signature) into the image. first, the color image(RGB model)is transformed in YCbCr model and then the Y component is transformed into 3-level wavelet transform. Next, the values are assembled with pattern watermark. PN(pseudo noise) code at spread spectrum communication method and mutilevel watermark weights. This values are inserted into discrete wavelet domain. In our scheme, new calculating method is designed to calculate wavelet transform with integer value in considering the quantization error. and we used the color conversion with fixed-point arithmetic to be easy to make the hardware hereafter. Also, we made the new solution using mutilevel threshold to robust to common signal distortions and malicious attack, and to enhance quality of image in considering the human visual system. the experimental results showed that the proposed watermarking algorithm was superior to other similar water marking algorithm. We showed what it was robust to common signal processing and geometric transform such as brightness. contrast, filtering. scaling. JPEG lossy compression and geometric deformation.