• Journal of the Korea Society of Computer and Information
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• v.23 no.2
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• pp.53-61
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• 2018

In this paper, the author proposes an efficient group key agreement scheme in a mobile environment where group members frequently join and leave. This protocol consists of basic protocols and general ones and is expected to be suitable for communications between a mobile device with limited computing capability and a key distributing center (or base station) with sufficient computing capability. Compared with other schemes, the performance of the proposed protocol is a bit more efficient in the aspects of the overall cost for both communication and computation where the computational efficiency of the scheme is achieved by using exclusive or operations and a one-way hash function. Also, in the aspect of security, it guarantees both forward and backward secrecy based on the computational Diffie-Hellman (CDH) assumption so that secure group communication can be made possible. Furthermore, the author proves its security against a passive adversary in the random oracle model.

• Journal of Broadcast Engineering
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• v.13 no.1
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• pp.79-85
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• 2008

An authenticated group key agreement protocol allows a group of parties communicating over an insecure network to share a common secret key. In this paper, we show that Zhou et al.'s ID-based authenticated group key agreement schemes do not provide forward secrecy.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.23 no.1
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• pp.3-10
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• 2013

Several identity-based and authenticated key agreement protocols have been proposed. It remains at issue to design secure identity based and authenticated key agreement protocols. In this paper, we propose a one round authenticated group key agreement protocol which uses one more key pair as well as the public key and private key of typical IBE(Identity-Based Encryption) system. The proposed protocol modified Shi et al.'s protocol and He et al.'s protocol. The public and private keys and the signature process of our protocol are simpler than them of their protocols. Our protocol is secure and more efficient than their protocols in communication and computation costs.

• The Journal of Society for e-Business Studies
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• v.7 no.1
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• pp.167-186
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• 2002

The encryption of a file on a PC before saving can maintain security of the file. However, if the key for the encrypted file is lost or damaged, the encrypted file can not be decrypted, resulting in serious economical loss to the user or the user group. In order to minimize the economical loss a secure and reliable key recovery technology is required. Presented in this paper is the development and evaluation of PKRS (PC based Key Recovery System) which supports encryption and decryption of file and recovery of the encrypted file in emergency. The encapsulating method, which attaches key recovery information to encrypted file, is applied to the PKRS. In addition, the PKRS is developed and evaluated according to the requirements of Requirements for Key Recovery Products proposed by NIST and requirements of Common Criteria 2.0 to prove the safety and reliability of the information security system. This system is applicable to a PC and can be further extended to internet or intranet environment information system where in encryption and recovery of file is possible.

• Journal of Communications and Networks
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• v.17 no.5
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• pp.453-462
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• 2015

Body area networks (BANs) have emerged as an enabling technique for e-healthcare systems, which can be used to continuously and remotely monitor patients' health. In BANs, the data of a patient's vital body functions and movements can be collected by small wearable or implantable sensors and sent using shortrange wireless communication techniques. Due to the shared wireless medium between the sensors in BANs, it may be possible to have malicious attacks on e-healthcare systems. The security and privacy issues of BANs are becoming more and more important. To provide secure and correct association of a group of sensors with a patient and satisfy the requirements of data confidentiality and integrity in BANs, we propose a novel enhanced secure sensor association and key management protocol based on elliptic curve cryptography and hash chains. The authentication procedure and group key generation are very simple and efficient. Therefore, our protocol can be easily implemented in the power and resource constrained sensor nodes in BANs. From a comparison of results, furthermore, we can conclude that the proposed protocol dramatically reduces the computation and communication cost for the authentication and key derivation compared with previous protocols. We believe that our protocol is attractive in the application of BANs.

• The KIPS Transactions:PartC
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• v.10C no.6
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• pp.809-814
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• 2003

The multicast transmitting the real-time data to groups may easily have many attacks from abnormal attacks because it has many links as compared to the unicast. The existing group key management architectures for preventing these problems are designed for protocols suitable for a large scale. Thus these architectures applied to a small scale routing protocols may have many overheads with key distribution and a constant core tree. Therefore this paper proposes a groups key management protocol for a secure multicast in PIM-SM multicast group communication. The proposed method divide multicast groups with RO(Rendezvous-Point), and subgroup key managers are established in each RP and can be transmitted groups keys between senders and receivers, so the security cannel is set up for secure data transfer, And this does not have needs of the data translation for group keys and the new key distribution for path change. As a result of this, the data transmission time can be reduced.

• The KIPS Transactions:PartC
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• v.9C no.4
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• pp.597-604
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• 2002

Changing group key is necessary for the remaining members when a new member joins or a member leaves the group in multicast communications. It is required to guarantee perfect forward and backward confidentiality. Unfortunately, in large groups with frequent membership changes, key changes become the primary bottleneck for scalable group. In this paper, we propose a novel approach for providing efficient group key distribution in large and dynamic groups. Unlike existing secure multicast protocols, our protocol is scalable to large groups because both the frequency and computational overhead of re-keying is determined by the size of a subgroup instead of the size of the whole group, and offers mechanism to prevent the subgroup managers with group access control from having any access to the multicast data that are transfered by sender. It also provides security service for preserving privacy in wireless computing environments.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.12 no.3
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• pp.1315-1329
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• 2018

Ciphertext-policy attribute-based encryption (CP-ABE) associates ciphertext with access policies. Only when the user's attributes satisfy the ciphertext's policy, they can be capable to decrypt the ciphertext. Expressivity and security are the two directions for the research of CP-ABE. Most of the existing schemes only consider monotonic access structures are selectively secure, resulting in lower expressivity and lower security. Therefore, fully secure CP-ABE schemes with non-monotonic access structure are desired. In the existing fully secure non-monotonic access structure CP-ABE schemes, the attributes that are set is bounded and a one-use constraint is required by these projects on attributes, and efficiency will be lost. In this paper, to overcome the flaw referred to above, we propose a new fully secure non-monotonic access structure CP-ABE. Our proposition enforces no constraints on the scale of the attributes that are set and permits attributes' unrestricted utilization. Furthermore, the scheme's public parameters are composed of a constant number of group elements. We further compare the performance of our scheme with former non-monotonic access structure ABE schemes. It is shown that our scheme has relatively lower computation cost and stronger security.

• Journal of KIISE:Information Networking
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• v.31 no.4
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• pp.353-362
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• 2004

Mobile Ad-Hoc network tends to expose scarce computing resources and various security threats because all traffics are carried in air along with no central management authority. To provide secure communication and save communication overhead, a scheme is inevitable to serurely establish session keys. However, most of key establishment methods for Ad-Hoc network focus on the distribution of a group key to all hosts and/or the efficient public key management. In this paper, a secure and efficient scheme is proposed to establish a session key between two Ad-Hoc nodes. The proposed scheme makes use of the secret sharing mechanism and the Diffie-Hellman key exchange method. For secure intra-cluster communication, each member node establishes session keys with its clusterhead, after mutual authentication using the secret shares. For inter-cluster communication, each node establishes session keys with its correspondent node using the public key and Diffie-Hellman key exchange method. The simulation results prove that the proposed scheme is more secure and efficient than that of the Clusterhead Authentication Based Method(1).

• The KIPS Transactions:PartC
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• v.13C no.3 s.106
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• pp.339-344
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• 2006

Secure delivery of multicast data can be achieved with the use of a group key for data encryption in mobile ad hoc network (MANET) applications based on the group communication. However, for the support of dynamic group membership, the group key has to be updated for each member joining/leaving and, consequently, a mechanism distributing an updated group key to members is required. The two major categories of the group key distribution mechanisms proposed for wired networks are the naive and the tree-based approaches. The naive approach is based on unicast, so it is not appropriate for large group communication environment. On the other hand, the tree-based approach is scalable in terms of the group size, but requires the reliable multicast mechanism for the group key distribution. In the sense that the reliable multicast mechanism requires a large amount of computing resources from mobile nodes, the tree-based approach is not desirable for the small-sized MANET environment. Therefore, in this paper, we propose a new key distribution protocol, called the proxy-based key management protocol (PROMPT), which is based on the naive approach in the small-sized MANET environment. PROMPT reduces the message overhead of the naive through the first-hop grouping from a source node and the last-hop grouping from proxy nodes using the characteristics of a wireless channel.