• Journal of the Korea Institute of Information Security & Cryptology
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• v.22 no.3
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• pp.505-514
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• 2012

Because people usually establish their online social network based on their offline relationship, the social networks (i.e., the graph of friendship relationships) are often used to share contents. Mobile devices let it easier in these days, but it also increases the privacy risk such as access control of shared data and relationship exposure to untrusted server. To control the access on encrypted data and protect relationship from the server, M. Atallah et al. proposed a hop-based scheme in 2009. Their scheme assumed a distributed environment such as p2p, and each user in it shares encrypted data on their social network. On the other hand, it is very inefficient to keep their relationship private, so we propose an improved scheme. In this paper, among encrypted contents and relationships, some authenticated users can only access the data in distributed way. For this, we adopt 'circular-secure symmetric encryption' first. Proposed scheme guarantees the improved security and efficiency compared to the previous work.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.30 no.5
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• pp.881-893
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• 2020

CFI(Control Flow Integrity) is a mitigation mechanism that protects programs by verifying control flows. IFCC(Indirect Function Call Checks) and SCS(Shadow Call Stack), CFI supported by LLVM Clang compiler, were introduced to protect applications in Android. IFCC protects function calls and SCS protects function returns. In this paper, we propose attacks to bypass CFI on the application environment with IFCC and SCS. Even if IFCC and SCS were applied to user applications, it was confirmed that there were many code segments not protected by IFCC and SCS in the application memory. We execute code in CFI unprotected segments to construct 1) bypassing IFCC to call a protected function, 2) modulating return address via SCS bypass. We identify code segments not protected by IFCC and SCS in Android10 QP1A. 191005.007.A3. We also implement proof-of-concept exploits to demonstrate that modulation of control flow is possible in an environment where IFCC and SCS are applied.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.22 no.5
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• pp.1069-1078
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• 2012

It is known that memory has been frequently a target threatening the computer system's security while attacks on the system utilizing the memory's weakness are actually increasing. Accordingly, various memory protection mechanisms have been studied on OS while new attack techniques bypassing the protection systems have been developed. Especially, buffer overflow attacks have been developed as attacks of Return to Library or Return-Oriented Programing and recently, a technique bypassing the countermeasure against Return-Oriented Programming proposed. Therefore, this paper is intended to suggest a detection mechanism at binary level by analyzing the procedure and features of Jump-Oriented Programming. In addition, we have implemented the proposed detection mechanism and experimented it may efficiently detect Jump-Oriented Programming attack.

• Review of KIISC
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• v.27 no.4
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• pp.22-26
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• 2017

온라인 게임은 가장 성공적인 인터넷 서비스 중 하나로서 빠른 속도로 성장해 왔다. 그러나 게임을 대상으로 하는 다양한 공격들이 있었고 그로 인해 많은 정상 사용자들 및 게임서비스 회사에 피해가 발생함에 따라, 온라인 게임 서비스를 보호하기 위한 다양한 기법들이 연구되어 왔다. 실제로 대규모 이용자들이 접속하는 PC 게임들의 경우, 게임 클라이언트단, 네트워크 단, 서버 단 각 구간별로 다양한 보안 기법들이 개발되어 적용되어 왔다. 이 중, 게임 클라이언트는 사용자 및 해커 쪽에서 손쉽게 접근이 가능하기 때문에 공격에 쉽게 노출되어 있어 신뢰하기 어려운 구간이었다. 더불어, 게임 클라이언트 단에 강력한 보안을 적용할 경우 성능저하가 발생하기 때문에 상용 게임보안 솔루션에 의해 프로세스 및 메모리 보호를 받는 등 역공학 방지 기법 및 난독화 기법 정도만을 최소한으로 적용하고, 그 외에는 대부분의 탐지 및 차단 기법들을 네트워크 단 및 서버 단에 적용하는 것이 일반화 되어 있다. 하지만, 최근 하드웨어의 지원을 받아 클라이언트 단의 성능저하를 최소화 하면서도, 게임 클라이언트를 TEE (Trusted Execution Environment)에서 안전하게 실행할 수 있는 기술들이 등장하면서, 게임 클라이언트 단의 보안기술이 다시 주목받고 있다. 본 논문에서는 메모리 변조 공격 및 게임프로세스에 인젝션 공격을 하는 게임해킹 기법들에 대응하기 위하여 Intel에서 발표한 새로운 하드웨어 보안 기술인 Intel SGX(Software Guard Extensions)를 적용하는 방안에 대해 소개한다. Intel SGX를 적용하여 게임프로그램의 프로세스를 보호할 경우 코드와 데이터의 무결성 및 기밀성을 보장하며 실행시킬 수 있기 때문에, 온라인게임보안 발전에 상당히 기여할 수 있을 것으로 기대된다.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.21 no.3
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• pp.75-88
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• 2011

Messages need to transmit to the neighbors securely in wireless sensor network, because a sensor node is deployed in hostile area. Thus it is necessary to support secure communication. One of the most important communication part is secure multicast. Especially, group rekeying is a big problem for multicast key management. So, group rekeying must be proceed securely when secrete information is exposed by attacker. Many group rekeying schemes have been studied for ad hoc networks. However, these schemes are Ill1desirable in WSNs. In this paper, we proposed a novel group rekeying scheme in WSNs that it has very powerful security.

• Proceedings of the Korea Institutes of Information Security and Cryptology Conference
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• 2006.06a
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• pp.551-554
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• 2006

보안 침해사고시 수집된 디지털 증거를 법적 증거로써 제출하기 위해 신뢰성이 확보되어야한다. 이를 위한 디지털 증거 무결성 보증 기법들중 MDC를 사용한 디지털 증거 무결성 보증 기법은 MDC값을 공격자가 위조 변조 할 수 있다는 단점이 있다. 또 PKI를 이용한 공증 방식은 기존의 증거 수집 시스템을 수정해야 하는 단점과 새로 시스템을 도입하기 위한 비용이 많이 드는 단점이 있다. 따라서 본 논문에서 제안하는 디지털 증거 보호 기법은 Diffie-Hellman(DH) 키 교환 알고리즘을 이용하여 생성된 비밀키와 디지털 증거 수집 대상 시스템(Collecotion System-CS)의 하드웨어 정보($HW_{CS}$)로 디지털 증거(D), 디지털 증거에 대한 해쉬값(H(D))과 타임스탬프(Time)를 암호화해서 디지털 증거에 대한 기밀성, 인증 및 무결성을 보증하는 기법을 제안하였다.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.13 no.2
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• pp.63-68
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• 2003

Signcryption has been proposed to provide authentication md confidentiality of a message efficiently. In the existing schemes, any recipient can unsigncrypt the signcrypted message alone. In this paper, we propose a (t,n)-threshold signcryption scheme in which at least t recipients must participate in an unsigncryption process.

• Proceedings of the Korea Institutes of Information Security and Cryptology Conference
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• 2001.11a
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• pp.202-205
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• 2001

RSA에 기반한 은닉서명 기법은 Chaum이 처음 제안하였고, Fan-Chen-Yeh가 여기에 랜덤화 특성을 추가한 은닉서명 기법을 제안하였다. 본 논문에서는 Fan-Chen-Yeh가 제안한 은닉서명 기법보다 서명 요청자의 계산량을 95% 이상 줄이는 RSA 알고리즘에 기반한 은닉서명 기법을 제안한다.

• Review of KIISC
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• v.1 no.3
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• pp.109-115
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• 1991

• Journal of KIISE:Computing Practices and Letters
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• v.16 no.11
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• pp.1071-1075
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• 2010

Because a sensor node in wireless sensor networks(WSNs) has limited resources, such as battery capacity and memory, data aggregation techniques have been studied to manage the limited resources efficiently. Because sensor network uses wireless communication, a data can be disclosed by attacker. Thus, the study on data protection schemes for data aggregation is essential in WSNs. But the existing data aggregation methods require both a large number of computation and communication, in case of network construction and data aggregation processing. To solve the problem, we propose a data protection scheme based on Hilbert-curve for data aggregation. Our scheme can minimizes communications among neighboring sensor nodes by using tree-based routing. Moreover, it can protect the data from attacker by doing encryption through a Hilbert-curve technique based on a private seed, Finally, we show that our scheme outperforms the existing methods in terms of message transmission and average sensor node lifetime.