• 한국정보과학회논문지:컴퓨팅의 실제 및 레터
• /
• 제9권1호
• /
• pp.86-94
• /
• 2003

배달 증명 전자 메일(certified e-mail)은 수신자가 메일을 받았을 때 그리고 그 때만 송신자가 0영수증을 받는 시스템이다. 최근에 발표된 낙관적(optimistic) 기법에서는 이전 방법과는 달리 메일이 언제든지 수신자에게 전달될 수 있는 상태가 되면 수신 영수증이 발행된다. 따라서, 송신자는 수신 영수증을 확보하였음에도 불구하고 수신자가 실제로 메일을 받았는지 여부를 알 수 없다. 본 논문에서는 최근에 발표된 낙관적 기법의 문제점을 지적한 후, 수신 의무 시간 개념을 도입하여 기존 프로토콜을 보완한 내용을 제시한다. 수정된 프로토콜에서는 영수증의 의미를 수신 약속으로 변경시켜 위에서 언급한 문제점을 해결했다. 제시된 기법은 대부분의 낙관적 기법에 적용 가능하며 프로토콜 수행에 필요한 메시지 수를 더 이상 늘리지 않아 기존 기법에 비해 추가되는 부담이 거의 없다.

• 한국통신학회논문지
• /
• 제28권5B호
• /
• pp.457-465
• /
• 2003

본 논문은 이더넷 PON 환경에서 다양한 MAC 프로토콜들의 성능을 분석함으로써 효율적인 MAC 프로토콜 구조를 제시한다. 이를 위하여 고정 길이를 갖는 프레임 기반의 MAC 프로토콜로서 사용자의 요구에 관계없이 동등한 대역을 할당하는 정적 TDMA(Static TDMA)와 사용자의 요구 대역 정보를 기반으로 대역을 동적으로 할당하는 동적 TDMA(Dynamic TDMA), 그리고 폴링을 사용하여 각각의 ONU에게 상향 채널 전송 기회를 부여하므로써 가변적인 주기(cycle)를 운용하는 인터리브드 폴링(Interleaved Polling)을 고려하였다. 각 프로토콜이 갖는 구조를 분석하여 이용 가능한 데이터 전송률을 비교하고 또한, OPNET 기반의 시뮬레이션을 수행하여 다양한 트래픽 환경에 대한 각 프로토콜의 성능을 채널 이용률과 큐잉 지연 관점에서 비교하고 분석하였다.

• 디지털산업정보학회논문지
• /
• 제5권4호
• /
• pp.139-150
• /
• 2009

Authentication and key exchange are fundamental for establishing secure communication channels over public insecure networks. Password-based protocols for authenticated key exchange are designed to work even when user authentication is done via the use of passwords drawn from a small known set of values. There have been many protocols proposed over the years for password authenticated key exchange in the three-party scenario, in which two clients attempt to establish a secret key interacting with one same authentication server. However, little has been done for password authenticated key exchange in the more general and realistic four-party setting, where two clients trying to establish a secret key are registered with different authentication servers. In fact, the recent protocol by Yeh and Sun seems to be the only password authenticated key exchange protocol in the four-party setting. But, the Yeh-Sun protocol adopts the so called "hybrid model", in which each client needs not only to remember a password shared with the server but also to store and manage the server's public key. In some sense, this hybrid approach obviates the reason for considering password authenticated protocols in the first place; it is difficult for humans to securely manage long cryptographic keys. In this work, we introduce a key agreement protocol and a key distribution protocol, respectively, that requires each client only to remember a password shared with its authentication server.

• 한국과학교육학회지
• /
• 제10권1호
• /
• pp.57-64
• /
• 1990

In this study, novices' protocols were investigated on the basis of Mayer's analysis of mathematical problem solving. These protocols were obtained by Jae-Sool Kwon and Seong-Wang Lee(1988) by means of thinking aloud while 20 sophomore students in a department of physics education were solving physics problems on Newton's low of motion. The results of investiqation are as follows; (1) We proposed an effective method in analyzing protocols on physics porblem solving (2) We could find the defective types of knowledge of individuals who got an incorrect solution, through analyzing the cause of failure individually (3) The fact that many students considered first the frictional force as muntiplying the coefficient of friction by perpendicular force rather than as resistance of motion, was found And students' misconception on the coefficient of friction was found. (4) If such analyses of test items and protocols are used in physics education, they will be very useful for finding the faults of problem-solving process, and for setting and scoring subjective problems in physics

• Journal of Information Processing Systems
• /
• 제8권1호
• /
• pp.175-190
• /
• 2012

Shuffling is an effective method to build a publicly verifiable mix network to implement verifiable anonymous channels that can be used for important cryptographic applications like electronic voting and electronic cash. One shuffling scheme by Groth is claimed to be secure and efficient. However, its soundness has not been formally proven. An attack against the soundness of this shuffling scheme is presented in this paper. Such an attack compromises the soundness of the mix network based on it. Two new shuffling protocols are designed on the basis of Groth's shuffling and batch verification techniques. The first new protocol is not completely sound, but is formally analyzed in regards to soundness, so it can be applied to build a mix network with formally proven soundness. The second new protocol is completely sound, so is more convenient to apply. Formal analysis in this paper guarantees that both new shuffling protocols can be employed to build mix networks with formally provable soundness. Both protocols prevent the attack against soundness in Groth's scheme. Both new shuffling protocols are very efficient as batch-verification-based efficiency-improving mechanisms have been adopted. The second protocol is even simpler and more elegant than the first one as it is based on a novel batch cryptographic technique.

• Journal of Communications and Networks
• /
• 제14권1호
• /
• pp.104-110
• /
• 2012

Group key agreement protocols allow a group of users, communicating over a public network, to establish a shared secret key to achieve a cryptographic goal. Protocols based on certificateless public key cryptography (CL-PKC) are preferred since CL-PKC does not need certificates to guarantee the authenticity of public keys and does not suffer from key escrow of identity-based cryptography. Most previous certificateless group key agreement protocols deploy signature schemes to achieve authentication and do not have constant rounds. No security model has been presented for group key agreement protocols based on CL-PKC. This paper presents a security model for a certificateless group key agreement protocol and proposes a constant-round group key agreement protocol based on CL-PKC. The proposed protocol does not involve any signature scheme, which increases the efficiency of the protocol. It is formally proven that the proposed protocol provides strong AKE-security and tolerates up to $n$-2 malicious insiders for weak MA-security. The protocol also resists key control attack under a weak corruption model.

• 정보처리학회논문지:컴퓨터 및 통신 시스템
• /
• 제1권3호
• /
• pp.119-124
• /
• 2012

스마트 유틸리티 네트워크는 기존의 AMR, 스마트 그리드, 스마트 워터 그리드 등의 다양한 에너지 관련 서비스를 통합할 수 있는 에너지망 인프라로서 기존 사용자 중심의 통신망으로부터 기기 중심의 통신망으로의 새로운 패러다임 전환을 가능케 하고 있다. 이러한 스마트 유틸리티 네트워크는 관련 응용분야의 제약 조건과 요구사항에 있어 센서 네트워크와 많은 유사성을 가진다. 그리하여, 스마트 유틸리티 네트워크를 위한 새로운 네트워크 프로토콜을 개발하기 위해서는 기존의 관련 연구에 대한 철저한 분석이 선행되어야 한다. 따라서 본 논문에서는 스마트 유틸리티 네트워크의 서비스 요구사항과 설계 고려사항을 분석하고 기존의 저 전력 프로토콜과 데이터 수집기법 그리고 In-network 저장기법에 대한 분석을 통해 스마트 유틸리티 네트워크를 위한 새로운 네트워크 프로토콜의 설계 가이드라인을 제시한다.

• 정보처리학회논문지C
• /
• 제9C권6호
• /
• pp.799-808
• /
• 2002

인터넷과 같은 첨단의 정보 전송 시스템이 발달함에 따라 네트워크 상에서 전송되는 메시지에 대한 기밀성을 제공하기 위해서 암호 시스템의 사용이 증가하고 있으며 그 중요성은 더욱 강조되고 있다. 안전한 암호 시스템을 구현하는 데 있어서 키 분배 프로토콜은 가장 필수적인 요소이며, 지금까지 여러 키 분배 프로토콜들이 표준으로 제안되었으나 이에 대한 엄밀한 안전성 증명은 아직까지 부족한 실정이다. 따라서 본 논문에서는 ANSI X9.42의 Diffie-Hellman형 표준 키 분배 프로토콜의 특징을 자세히 분석하고 이를 기반으로 여러 능동적 공격자 모델에 대한 프로토콜의 안전성을 증명하고자 한다

• 한국군사과학기술학회지
• /
• 제2권2호
• /
• pp.117-130
• /
• 1999

In this paper, the performance of data communication function of military radio equipment P-999K is analyzed based on the standard CSMA/CA protocol which is DFWMAC standard protocol done by IEEE802.11 work group. Basic three standard protocols, i.e. Basic CSMA/CA, Stop & Wait ARQ and 4-Way Handshake CSMA/CA protocols are analyzed and compared with each other under the hidden terminal environment. The computer simulation is also done by using SIMSCRIPT II.5 which is popular software tool for an independent processing. The results show that p-persistent(with p=0.3) CSMA scheme is superior to non-persistent CSMA scheme with non-hidden terminal condition, but the performances of both schemes are almost same with hidden terminal situation. And the results of computer simulations are also showed that Basic CSMA/CA protocol is superior to the other protocols when the ratio of hidden terminals is below 10 % of total user population, however, with the above 20% hidden terminals environment and the higher offered traffic conditions the 4-Way Handshake CSMA/CA protocol shows the most superior performance.

• KSII Transactions on Internet and Information Systems (TIIS)
• /
• 제5권9호
• /
• pp.1684-1697
• /
• 2011

We show that two protocols for RFID mutual authentication in pervasive computing environments, recently proposed by Kang et al, are vulnerable to several attacks. First, we show these protocols do not preserve the privacy of users' location. Once a tag is authenticated successfully, we show several scenarios where legitimate or illegitimate readers can trace the location of that tag without any further information about the tag's identifier or initial private key. Second, since the communication between readers and the database takes place over an insecure communication channel and in the plaintext form, we show scenarios where a compromised tag can gain access to confidential information that the tag is not supposed get access to. Finally, we show that these protocols are also vulnerable to the replay and denial-of-service attacks. While some of these attacks are due to simple flaws and can be easily fixed, others are more fundamental and are due to relaxing widely accepted assumptions in the literature. We examine this issue, apply countermeasures, and re-evaluate the protocols overhead after taking these countermeasures into account and compare them to other work in the literature.