• KSII Transactions on Internet and Information Systems (TIIS)
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• v.6 no.8
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• pp.1982-1997
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• 2012

Authenticated multiple key agreement protocols not only allow participants to agree the multiple session keys within one run of the protocol but also ensure the authenticity of the other party. In 2011, Dehkordi et al. proposed an identity-based authenticated multiple key agreement protocol. In this paper, we demonstrate that Dehkordi et al.'s protocol is vulnerable to impersonation attacks. Furthermore, we have found that their protocol cannot provide perfect forward security or mutual security. Then we propose an identity-based authenticated multiple key agreement protocol which removes the weaknesses of the Dehkordi et al.'s protocol. Compared with the multiple key agreement protocols in the literature, the proposed protocol is more efficient and holds stronger security.

• Journal of Communications and Networks
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• v.14 no.1
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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.

• Journal of Internet Computing and Services
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• v.7 no.3
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• pp.133-142
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• 2006

The purpose of the multiple key agreement protocol is to get efficiency in computational and communicational aspects compared to multiple executions of single key agreement protocol. However ID based tripartite multiple key agreement protocols have been proposed, it is reported that they can not resist unknown key-share attack or impersonation attack. How to design a secure and efficient ID-based authenticated tripartite multiple key agreement scheme to prevent all kinds of attacks remains an open problem. This paper proposes a multiple key agreement scheme combing the existing single key agreement protocol with a key derivation function. The proposed scheme can not only increase computational efficiency compared to the existing multiple key agreement protocol, but can ensure security of the proposed schemes by using a security proofed single key agreement protocol and key derivation function.

• The KIPS Transactions:PartC
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• v.12C no.1 s.97
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• pp.29-36
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• 2005

A key agreement protocol is the most important part to establish a secure cryptographic system and the effort to standardize the key agreement protocols is in rapid progress. Several efficient and secure key agreement protocols have been proposed so far since Diffie-Hellman proposed a public key agreement system in 1976. But, since Diffie-Hellman based key agreement protocols need a lot of computation to establish the session key, they are not suitable for wireless Internet environment. In this paper, we propose the efficient key agreement protocol using Proxy server. The Proposed Protocol gives the security equivalent to that the Diffie-Hellman based Protocol and the computation work of mobile user can be decreased using proxy server.

• Journal of Communications and Networks
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• v.14 no.6
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• pp.682-691
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• 2012

Key agreement protocol is a fundamental protocol in cryptography whereby two or more participants can agree on a common conference key in order to communicate securely among themselves. In this situation, the participants can securely send and receive messages with each other. An adversary not having access to the conference key will not be able to decrypt the messages. In this paper, we propose a novel identity-based authenticated multi user key agreement protocol employing a symmetric balanced incomplete block design. Our protocol is built on elliptic curve cryptography and takes advantage of a kind of bilinear map called Weil pairing. The protocol presented can provide an identification (ID)-based authentication service and resist different key attacks. Furthermore, our protocol is efficient and needs only two rounds for generating a common conference key. It is worth noting that the communication cost for generating a conference key in our protocol is only O($\sqrt{n}$) and the computation cost is only O($nm^2$), where $n$ implies the number of participants and m denotes the extension degree of the finite field $F_{p^m}$. In addition, in order to resist the different key attack from malicious participants, our protocol can be further extended to provide the fault tolerant property.

• IEIE Transactions on Smart Processing and Computing
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• v.2 no.5
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• pp.297-301
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• 2013

Key agreement protocols allow multi-parties exchanging public information to create a common secret key that is known only to those entities over an insecure network. Since Joux first published the pairing-based one round tripartite key agreement protocol, many authenticated protocols have been proposed. Unfortunately, many of them have been broken while others have been shown to be deficient in some desirable security attributes. In 2004, Cheng et al. presented two protocols aimed at strengthening Shim's certificate-based and Zhang et al.'s tripartite identity-based protocols. This paper reports that 1) In Cheng et al.'s identity-based protocol, an adversary can extract long-term private keys of all the parties involved; and 2) Cheng et al.'s certification-based protocol is weak against key integrity attacks. This paper suggests possible remedies for the security flaws in both protocols and then presents a modified Cheng et al.'s identity-based, one-round tripartite protocol that is more secure than the original protocol.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.6 no.12
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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.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.15 no.4
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• pp.11-27
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• 2005

To date, most identity-based key agreement protocols are based on a single PKG (Private Key Generator) environment. In 2002, Chen and Kudla proposed an identity-based key agreement protocol for a multiple PKG environment, where each PKG shares identical system parameters but possesses distinct master key. However, it is more realistic to assume that each PKG uses different system parameters including the PKG's master key. In this paper, we propose a new two party key agreement protocol between users belonging to different PKGs that do not share system parameters. We also extend this protocol to two types of tripartite key agreement protocols. We show that our two party protocol requires minimal amount of pairing computation for a multiple PKG environment and our tripartite protocol is more efficient than existing protocols. We also show that the proposed key agreement protocols satisfy every security requirements of key agreement protocol.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.6 no.12
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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.

• Journal of Internet Computing and Services
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• v.4 no.6
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• pp.95-102
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• 2003

The Diffle-Hellman Key Exchange scheme can produce a common session key between the two communicators, but its problem is that it makes a man-in-the middle attack possible. To solve problems like these, several protocols have been put forward, and the Simple Authenticated Key Agreement (SAKA) Protocol is among them. This protocol has been suggested by Seo-Sweeney, Tseng, and Ku-Wang, respectively, In this paper, we will put forward a new protocol that has been improved from all the original protocols mentioned above, but is still safe and quick to use, While the existing protocol divides the common session key production stage and the verification stage, the protocol suggested in this paper takes care of both of those stages simultaneously, therefore improving the processing performance.