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

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제6권12호
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• pp.3338-3351
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• 2012

There is an intuitive connection between signcryption and key agreement. Such a connector may lead to a novel way to construct authenticated and efficient group key agreement protocols. In this paper, we present a primary approach for constructing an authenticated group key agreement protocol from signcryption. This approach introduces desired properties to group key agreement. What this means is that the signcryption gives assurance to a sender that the key is available only to the recipient, and assurance to the recipient that the key indeed comes from the sender. Following the generic construction, we instantiate a distributed two-round group key agreement protocol based on signcryption scheme given by Dent [8]. We also show that this concrete protocol is secure in the outsider unforgeability notion and the outsider confidentiality notion assuming hardness of the Gap Diffie-Hellman problem.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제6권12호
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• pp.3352-3365
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• 2012

Group key agreement (GKA) is a cryptographic primitive allowing two or more users to negotiate a shared session key over public networks. Wu et al. recently introduced the concept of asymmetric GKA that allows a group of users to negotiate a common public key, while each user only needs to hold his/her respective private key. However, Wu et al.'s protocol can not resist active attacks, such as fabrication. To solve this problem, Zhang et al. proposed an authenticated asymmetric GKA protocol, where each user is authenticated during the negotiation process, so it can resist active attacks. Whereas, Zhang et al.'s protocol needs a partially trusted certificate authority to issue certificates, which brings a heavy certificate management burden. To eliminate such cost, Zhang et al. constructed another protocol in identity-based setting. Unfortunately, it suffers from the so-called key escrow problem. In this paper, we propose the certificateless authenticated asymmetric group key agreement protocol which does not have certificate management burden and key escrow problem. Besides, our protocol achieves known-key security, unknown key-share security, key-compromise impersonation security, and key control security. Our simulation based on the pairing-based cryptography (PBC) library shows that this protocol is efficient and practical.

• 한국지능시스템학회:학술대회논문집
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• 한국퍼지및지능시스템학회 2003년도 ISIS 2003
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• pp.256-259
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• 2003

This paper presents mutual authentication scheme between user and network on mobile communications using public key scheme based on counter, and simultaneously shows key agreement between user and user using random number for secure communications. This is also a range of possible solutions to authentication and key agreement problem-authentication and key agreement protocol based on nonce and count, and secure end-to-end protocol based on the function Y=f(.)$\^$1/, C$\^$i/ is count of user I, and f(.) is one way function.

• 정보보호학회논문지
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• 제13권3호
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• pp.101-110
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• 2003

안전하고 안정적인 그룹 통신은 최근 그룹 및 그룹 구성원간의 협조가 필요한 응용 분야가 발전하면서 점차 그 필요성이 대두되고 있다. 이중 가장 중요한 문제는 그룹 내의 키 관리 문제이다. 센터에 의존하는 키 관리 방식의 경우 대용량의 멀티캐스트 그룹에 어울리는 반면 구성원간의 협조에 의하여 이루어지는 그룹(즉, 센터가 없는 그룹)의 경우 분산 키 관리 방식(즉 그룹 키 합의 방식)이 필요하다. 기존의 그룹 키 합의 방식의 경우 계산량을 효율적으로 하는 데만 그 연구가 치중되어 있는 실정이다. 단 한가지 예외는 STR 프로토콜로 이 방식의 경우 Diffie-Hellman protocol을 키 트리에 응용하되 키 트리가 한쪽으로 치우친 구조를 가지고 있어 통신량을 최적화하고 있다. 하지만 계산량에 있어서 그룹 멤버의 변경 시 현재 그룹 멤버의 수에 비례한 계산량을 필요로 한다. 본 논문에서는 STR 키 관리 방식에 pairing을 응용하여 계산량에 있어서 효율성을 제공하는 동시에 통신량을 유지할 수 있는 새로운 방식을 제시한다.

• 정보보호학회논문지
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• 제15권1호
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• pp.41-55
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• 2005

그룹키 통의 프로토콜은 일련의 그룹을 형성하는 다수의 통신 참여자들이 공개된 통신망을 통해 안전하고 효율적인 방법으로 그룹의 세션키를 설정하기 위한 목적으로 설계된다. 본 논문에서는 유료 방송 시스템과 같은 그룹중심의 응용이나 서비스에 적합한 ID 기반의 2 라운드의 그룹키 동의 프로토콜을 제안하고, 이의 안전성을 CDH 가정과 BDDH 가정에 기반하여 랜덤 오라클 모델에서 증명한다. 제안하는 프로토콜은 Nam이 제안한 3 라운드 그룹키 동의 프로토콜을 기초로 설계된 것으로, 개인식별정보에 기반한 암호 시스템을 사용하여 키 관리 절차를 보다 간단히 하였으며, 새로운 인증 메카니즘을 사용하여 키 전송 메시지들의 길이를 줄이고 결합적 단순성을 제공하였다. 또한 제안하는 프로토콜은 전송되는 메시지들에 대한 인증을 묶음(batch) 기법을 사용하여 검증하도록 설계하여 효율성을 더욱 개선 시 켰다.

• 정보보호학회논문지
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• 제22권6호
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• pp.1253-1263
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• 2012

그룹응용이 늘어감에 따라 효율적인 인증 그룹 키 합의 프로토콜이 많은 관심을 받고 있다. Lee et al.는 삼진트리 구조와 pairing기반의 암호방식을 가진 트리기반의 그룹 키 합의 프로토콜을 제안했다. 그들의 프로토콜은, 모든 멤버들의 세션랜덤 키를 아는 오직 한 명의 그룹 스폰서가 블라인드 키들을 계산한다. 또, 그 스폰서가 그룹을 떠나면, 트리의 모든 정보가 바뀌어져야 한다. 본 논문에서 제안하는 프로토콜은 여러 명의 스폰서를 두었고, 각 멤버의 비밀정보가 그룹스폰서에게 알려지지 않으므로 그룹스폰서가 떠났을 때, 키 갱신이 Lee et al.의 프로토콜보다 훨씬 효율적이다. 그러므로, 제안된 프로토콜은 동적 피어 그룹에 적합하다.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제3권2호
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• pp.178-194
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• 2009

Current group key agreement protocols(often tree-based) involve unnecessary delays because members with low-performance computer systems can join group key computation. These delays are caused by the computations needed to balance a key tree after membership changes. An alternate approach to group key generation that reduces delays is the dynamic prioritizing mechanism of filtering low performance members in group key generation. This paper presents an efficient tree-based group key agreement protocol and the results of its performance evaluation. The proposed approach to filtering of low performance members in group key generation is scalable and it requires less computational overhead than conventional tree-based protocols.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제5권4호
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• pp.822-839
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• 2011

Group key agreement protocols derive a shared secret key for a group of users to ensure data confidentiality or/and integrity among the users in the subsequent communications. In this paper, we inspect two group key agreement schemes which have been proposed by Shi et al. and Zheng et al. in 2005 and 2007 respectively. Although both schemes were claimed to be secure in a heuristic way, we reveal several flaws using the Bellare-Rogaway security model extended to multi-party setting by Bresson et al. These flaws are found to be originated from inappropriate selection of key derivation function, inadvertent exclusion of partners' identities from the protocol specification and insufficient consideration in preserving known temporary information security and key freshness properties. Furthermore, we suggest and discuss proper countermeasures to address such flaws.

• 중소기업융합학회논문지
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• 제4권3호
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• pp.21-25
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• 2014

Group communications are becoming popular in Internet applications such as video conferences, on-line chatting programs, games, and gambling. Secure and efficient group communication is needed for message integration, confidentiality, and system usability. However, the conventional group key agreement protocols are too much focused on minimizing the computational overhead by concentrating on generating the common group key efficiently for secure communication. As a result, the common group key is generated efficiently but a failure in authentication allows adversaries to obtain valuable information during the group communication. After achieving the secure group communication, the secure group communication should generate the group key efficiently and distribute it to group members securely, so the balance of security and system usage must be considered at the same time. Therefore, this research proposes the software architecture model of a secure and efficient group communication that will be imbedded into networking applications.