• KSII Transactions on Internet and Information Systems (TIIS)
• /
• v.5 no.2
• /
• pp.428-439
• /
• 2011

The main challenge in building efficient broadcast systems is to encrypt messages with short ciphertexts. In this paper, we present a new construction based on the identity. Our construction contains the desirable features, such as constant size ciphertexts and private keys, short public keys and not fixing the total number of possible users in the setup. In addition, the proposed scheme achieves the full security which is stronger than the selective-identity security. Furthermore we show that the proof of security does not rely on the random oracles. To the best our knowledge, it is the first efficient scheme that is full security and achieves constant size ciphertexts and private keys which solve the trade-off between the ciphertext size and the private key size.

• KSII Transactions on Internet and Information Systems (TIIS)
• /
• v.11 no.8
• /
• pp.4025-4042
• /
• 2017

Session initiation protocol (SIP) is a kind of powerful and common protocols applied for the voice over internet protocol. The security and efficiency are two urgent requirements and admired properties of SIP. Recently, Hamed et al. proposed an efficient authentication and key agreement scheme for SIP. However, we demonstrate that Hamed et al.'s scheme is vulnerable to de-synchronization attack and cannot provide anonymity for users. Furthermore, we propose an improved and efficient authentication and key agreement scheme by using elliptic curve cryptosystem. Besides, we prove that the proposed scheme is provably secure by using secure formal proof based on Burrows-Abadi-Needham logic. The comparison with the relevant schemes shows that our proposed scheme has lower computation costs and can provide stronger security.

• Journal of the Korea Institute of Information Security & Cryptology
• /
• v.18 no.6A
• /
• pp.179-183
• /
• 2008

Recently, an efficient password-authenticated key exchange protocol based on RSA has been proposed by Park et al. with formal security proof. In this letter, we analyze their protocol, and show that it is not secure against an active adversary who performs a dictionary attack. Moreover, we analyze the performance of the proposed attack and show that the attack is a threatening attack against the protocol.

• KSII Transactions on Internet and Information Systems (TIIS)
• /
• v.8 no.11
• /
• pp.4226-4241
• /
• 2014

Cloud storage provides an easy, cost-effective and reliable way of data management for users without the burden of local data storage and maintenance. Whereas, this new paradigm poses many challenges on integrity and privacy of users' data, since users losing grip on their data after outsourcing the data to the cloud server. In order to address these problems, recently, Worku et al. have proposed an efficient privacy-preserving public auditing scheme for cloud storage. However, in this paper, we point out the security flaw existing in the scheme. An adversary, who is on-line and active, is capable of modifying the outsourced data arbitrarily and avoiding the detection by exploiting the security flaw. To fix this security flaw, we further propose a secure and efficient privacy-preserving public auditing scheme, which makes up the security flaw of Worku et al.'s scheme while retaining all the features. Finally, we give a formal security proof and the performance analysis, they show the proposed scheme has much more advantages over the Worku et al.'s scheme.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
• /
• v.8 no.2
• /
• pp.140-146
• /
• 2015

We have studied an efficient threshold level for desired target detection in radar system in the paper. A desired target searching detection method detects desired target according to changing for false alarm probability. This time, false alarm probability is close relation to threshold level. Low threshold level can improve detection for desired target, but detect noise signal. Therefor, This method is not good one. In this paper, we propose efficient threshold level method in order to estimation for desired target. Through simulation, we are analysis and performance to compare general method with proposal method. We show that proposed method is more good proof than general method.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.14 no.11
• /
• pp.5885-5889
• /
• 2013

In general, the network survivability means that The user do not know the network faults and the recovery of those. For this, we use the dual(multi) routes between each two nodes. It is important that the each dual routes have efficient costs(or minimum). Even if one route is the minimum cost in case of no fault, another route of dual may be very large cost in case of fault case. Therefore we need the dual routes of each two nodes having the efficient(or minimum) costs. In this paper we find the network design method for the dual routes of each two node having the efficient costs. Although the design method is very simple and heuristic and it may be not useful for some networks, we will use it in various network environment.. Because this design method can be used very easy. A sample design will proof this usefulness.

• The Journal of the Acoustical Society of Korea
• /
• v.23 no.2
• /
• pp.187-191
• /
• 2004

This paper describes an efficient algorithm to generate compact and complete prompts lists for connected spoken words speech corpus. In building a connected spoken digit recognizer, we have to acquire speech data in various contexts. However, in many speech databases the lists are made by using random generators. We provide an efficient algorithm that can generate compact and complete lists of digits in various contexts. This paper includes the proof of optimality and completeness of the algorithm.

• Smart Structures and Systems
• /
• v.9 no.1
• /
• pp.1-20
• /
• 2012

In bridge engineering, maintenance strategies and thus budgetary demands are highly influenced by construction type and quality of design. Nowadays bridge owners and planners tend to include life-cycle cost analyses in their decision processes regarding the overall design trying to optimize structural reliability and durability within financial constraints. Smart permanent and short term monitoring can reduce the associated risk of new design concepts by observing the performance of structural components during prescribed time periods. The objectives of this paper are the discussion and analysis of influence line or influence field approaches in terms of (a) an efficient incorporation of monitoring information in the structural performance assessment, (b) an efficient characterization of performance indicators for the assessment of structures, (c) the ability of optimizing the positions of sensors of a monitoring system, and (d) the ability of checking the robustness of the monitoring systems applied to a structure. The proposed influence line- model correction approach has been applied to an integrative monitoring system that has been installed for the performance assessment of an existing three-span jointless bridge.

• The Journal of the Institute of Internet, Broadcasting and Communication
• /
• v.14 no.1
• /
• pp.245-251
• /
• 2014

Mix network plays a key role in electronic voting to preserve anonymity and lots of mixnet schemes have been proposed so far. However, they requires complex and costly zero-knowledge proofs to provide their correct mixing operations. In 2010, Seb$\acute{e}$ et al. proposed an efficient and lightweight mixnet scheme based on a cryptographic secure hash function instead of zero-knowledge proofs. In this paper, we present a more efficient and faster mixnet scheme than Seb$\acute{e}$ et al.'s scheme under the same assumption. Also, our scheme is secure.

• KSII Transactions on Internet and Information Systems (TIIS)
• /
• v.10 no.5
• /
• pp.2407-2426
• /
• 2016

A group signature scheme allows any member to sign on behalf of a group. It is applied to practical distributed security communication environments, such as privacy-preserving, data mining. In particular, the excellent features of group signatures, including membership joining and revocation, anonymity, traceability, non-frameability and controllable linkability, make group signature scheme more attractive. Among these features, non-frameability can guarantee that a member's signature cannot be forged by any other (including issuer), and controllable linkability supports to confirm whether or not two group signatures are created by the same signer while preserving anonymity. Until now, only Hwang et al.'s group schemes (proposed in 2013 and 2015) can support all of these features. In this paper, we present a new dynamic group signature scheme which can achieve all of the above excellent features. Compared with their schemes, our scheme has the following advantages. Firstly, our scheme achieves more efficient membership revocation, signing and verifying. The cost of update key in our scheme is two-thirds of them. Secondly, the tracing algorithm is simpler, since the signer can be determined without the judging step. Furthermore, in our scheme, the size of group public key and member's private key are shorter. Lastly, we also prove security features of our scheme, such as anonymity, traceability, non-frameability, under a random oracle model.