• The Transactions of The Korean Institute of Electrical Engineers
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• v.65 no.12
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• pp.2240-2250
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• 2016

MIFARE Classic is the most popular contactless smart card, which is primarily used in the management of access control and public transport payment systems. It has several security features such as the proprietary stream cipher Crypto 1, a challenge-response mutual authentication protocol, and a random number generator. Unfortunately, multiple studies have reported structural flaws in its security features. Furthermore, various attack methods that target genuine MIFARE Classic cards or readers have been proposed to crack the card. From a practical perspective, these attacks can be partitioned according to the attacker's ability. However, this measure is insufficient to determine the optimal attack flow due to the refined random number generator. Most card-only attack methods assume a predicted or fixed random number, whereas several commercial cards use unpredictable and unfixable random numbers. In this paper, we propose optimal MIFARE Classic attack procedures with regards to the type of random number generator, as well as an adversary's ability. In addition, we show actual attack results from our portable experimental setup, which is comprised of a commercially developed attack device, a smartphone, and our own application retrieving secret data and sector key.

• Proceedings of the Korea Information Processing Society Conference
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• 2002.11b
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• pp.1067-1070
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• 2002

EAP(Extensible Authentication Protocol)[3]은 다양한 인증 방법을 제공하기 위한 표준 인증 메커니즘이다. EAP는 PPP[16], 802.1x[17] 등에서 사용되며, 실제 인증 능력을 가지는 TLS[2] 등과 같은 인증 프로토콜과 결합하여 사용된다. TLS(Transport Layer Security)는 두 peer 간에 전송계층에서 상호 인증, 무결성, 기밀성을 제공하기 위해 개발되었다. TLS 는 상호 인증을 위하여 공개키 기반 인증서를 사용한다. 그러나, 인증서를 사용하는 것은 대부분의 사용자들이 ID, password 기반의 응용에 익숙하다는 것을 생각하면 일반적인 인증 방법이 아님을 알 수 있다. 따라서, EAP-TLS와 같은 인증 방법 역시 그런 면에서 PPP 혹은 802.1x에서 사용하기에 부적합하다고 볼 수 있다. 본 논문에서는 패스워드 기반 인증 및 키교환 프레임웍을 TLS 에 적용하고 이를 다시 EAP 와 결합한다. 패스워드 기반 EAP-TLS 는 인증서에 관련된 복잡한 연산을 수행하지 않으면서도 안전성에 있어 수학적 증명을 가지며, PPP 혹은 802.1x 서비스를 받고자 하는 사용자가 인증서를 가질 필요가 없는 장점을 가지게 된다.

• ETRI Journal
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• v.35 no.4
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• pp.655-665
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• 2013

Hybrid digital multimedia broadcasting (DMB) is a next-generation mobile TV system that combines broadcasting and wireless communication networks and can provide various high-quality multimedia services. However, if a system adheres to the current standard of transmitting the DMB content in the form of MPEG2-TS through wireless networks, it results in a burden on the network due to low transmission efficiency. The reasons for the low transmission efficiency are as follows. First, due to its constant bitrate characteristic, DMB MPEG2-TS includes a considerable amount of needless information, such as NULL packets and stuffing bytes. Second, due to the inflexibility of the Real-time Transport Protocol (RTP) standard, one cannot fully utilize the maximum transmission unit of the network when converting MPEG2-TS to RTP stream for transmission. This paper proposes a new transmission scheme that resolves these problems. Experiment results show that the proposed scheme improves data bitrate transmission efficiency by 8% to 36%, compared to the standard scheme, in the streaming of various real-DMB contents.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.42 no.12
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• pp.25-30
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• 2005

We propose and design a fully conversed Ethernet and TDM transport system to guarantee qualify of service for Ethernet packet. Developed convergence system can support not only L2 VPN service and premium multimedia service based on MPLS protocol but also TDM leased line service, simultaneously. Developed convergence system has the advantage of providing high reliability that realizes high-quality and real time communications due to assign QoS profile and guarantee bandwidth per channel consist of VCGs without affect adjacent channels. Evaluation for proposed system was successfully performed within the ling network.

• The Transactions of the Korea Information Processing Society
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• v.6 no.9
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• pp.2512-2523
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• 1999

In this paper, we present the design and implementation results of RTP(Real-time Transport Protocol) which is introduced to provide end-to-end delivery service for multimedia data with real-time characteristics and to provide QoS(quality of service) monitoring services. Conventional RTP communication modules have some problems such as poor reusability and inefficiency. Reusability problem stems from the inherent characteristics of RTP that is framework is deliberately not complete, and so, RTP should have been designed and implemented in application-imbedded from. The RTP communication module, proposed in this paper, is designed and implemented in application-independent from in order to be used in all kinds of high level applications independent of their architectures and functions.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.05a
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• pp.40-44
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• 2002

The increase of vehicles stagnations leads to the increasing attention to the way customers pay and a large number of projects on electronic cash system. Transport system is comprised of a number of advanced technologies, including information processing, communications, control, and electronics. Recently many research on a system which provides contact in order to protect driver's vehicle passage have been carried out. And some potential problems from that system are being reviewed by electronic cash system. In this papers, we suggest RF protocol developing technology using the concept of electronic cash. ATM electronic cash developing is consist of component of pre-developed coin throw, integration of component using its, and production of more requirement-satisfactory ITS solution. Result increase 15~40% pre-type vehicles stagnations. Especially, we expect this proposed concept would be well adapted to our national environments.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.7 no.6
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• pp.1200-1205
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• 2006

In this paper, it is presented to the designed and implemented care system fur health diagnosis. The designed handhold care system is implemented by embedded Visual C++4.0 and Pocket PC2003 software development kit (SDK) in an 802.11 wireless network, and we were conducted that the research provide sufficiently the usefulness of the U health system for the collection of care management information. The proposed system is consists of care management module for health diagnosis, personal record module, data transport module, image information management module for clinic. Also, fur emergency status, transmission function of clinic information is implemented by wireless LAN protocol and serial communication.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.2 no.6
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• pp.333-351
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• 2008

Transmission control protocols have to overcome common problems in wireless networks. TCP employing both packet loss discrimination mechanism and available bandwidth estimation algorithm, known as the good existing solution, shows significant performance enhancement in wireless networks. For instance, TCP New Jersey which exhibits high throughput in wireless networks intends to improve TCP performance by using available bandwidth estimation and congestion warning. Even though it achieves 17% and 85% improvements in terms of goodput over TCP Westwood and TCP Reno, respectively, we further improve it by exploring maximized available bandwidth estimation, handling bit-error-rate error recovery, and effective adjustment of sending rate for retransmission timeout. Hence, we propose TCP NJ+, showing that for up to 5% packet loss rate, it outperforms other TCP variants by 19% to 104% in terms of goodput when the network is in bi-directional background traffic.

• Proceedings of the Korean Information Science Society Conference
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• 2003.04d
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• pp.277-279
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• 2003

본 논문에서는 편재 컴퓨팅(ubiquitous and pervasive computing) 환경에 입력 시스템으로 사용하는 센서 네트워크에서 측정한 데이터의 품질 (sampling rate and quantization depth) 을 보증하며 네트워크 트래픽 또는 소모전력과 같은 비용을 최소화하기 위한 방법으로, 휴리스틱 알고리즘에 의한 비주기적 샘플링과 신뢰성 있는 전송규약을 사용하는 비주기적 전송방식을 제안한다. 그리고 제안한 비주기적 전송방식에 핵심기술인 신뢰성 있는 전송 규약의 비용을 최적화하기 위한 방법으로 ACK방식과 NACK방식을 패킷 에러율과 동일한 라우터를 사용하는 이웃 노드의 수와 같은 네트워크 상황에 따라 상보적으로 사용하는 상보적 방식(alternative method)을 제안하고, 전체 통신규약을 설계하며, 해석을 통해 성능을 분석하고, 네트워크 상태에 따라 두 방식의 성능상의 우열이 전환되는 전환점을 유도한다. 제안하는 상보형 신뢰성 있는 전송규약은 전체 센서 네트워크에서 처리되는 패킷의 비트 수를 최소화해, 각 노드의 총 전력 소모의 20-60%를 차지하는 통신모듈의 소비 전력을 줄일 수 있어 전력소모를 크게 개선 할 수 있다. 나아가서 다양한 센서 네트워크에서 설계한 전송규약을 바탕으로 하는 제안하는 비주기적 전송방식을 활용한다면 최적의 비용으로 측정하는 데이터의 품질을 보증할 수 있다.

• Journal of KIISE:Computer Systems and Theory
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• v.26 no.7
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• pp.827-838
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• 1999

멀티미디어 통신에서 통신 성능에 관련된 요구 사항들은 QoS 매개 변수들로서 서술된다. QoS매개 변수들에서 중요한 매개 변수 중의 하나가 전송 신뢰성이다. QoS 매개 변수로서의 신뢰성은 오류 감지, 보고 그리고 정정 기법으로 정의된다. 하지만 기존의 오류 제어 기법들은 멀티미디어 데이타의 통합된 관점을 고려하지 않았다. 그래서 우리는 MEC(multimedia-oriented error control)라고 명명된 오류 제어 기법을 제안하였다. 1 본 논문에서는 MEC기법의 성능을 조사 하였다. 성능평가 결과는 MEC기법이 기존의 오류 제어 기법보다도 낮은 전송지연(lower delay)과 호손율(blocking probability) 을 갖는다는 것을 볼 수 있었다. 결국 제안된 MEC기법은 수송 프로토콜에게 유연성과 높은 성능을 갖도록 해준다.Abstract Communication performance requirements are described as QoS parameters in multimedia communication. One of the important QoS parameters is the reliability of the transfer. As a QoS parameter, the reliability defines error detection, report and correction mechanisms. Conventional error control mechanisms, however, do not consider the integrated viewpoint of multimedia data. So we have proposed the MEC(multimedia-oriented error control). 1 In this paper, we have investigated the performance evaluation of the MEC. The results show that the MEC mechanism provides lower transfer delay and blocking probability than those of the conventional error recovery mechanism. Therefore, the proposed MEC mechanism makes the transport protocol have the flexibility and high performance.