• KSII Transactions on Internet and Information Systems (TIIS)
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• v.7 no.1
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• pp.119-131
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• 2013

With the explosive growth of computer networks, many remote service providing servers and multi-server network architecture are provided and it is extremely inconvenient for users to remember numerous different identities and passwords. Therefore, it is important to provide a mechanism for a remote user to use single identity and password to access multi-server network architecture without repetitive registration and various multi-server authentication schemes have been proposed in recent years. Recently, Tsaur et al. proposed an efficient and secure smart card based user authentication and key agreement scheme for multi-server environments. They claimed that their scheme satisfies all of the requirements needed for achieving secure password authentication in multi-server environments and gives the formal proof on the execution of the proposed authenticated key agreement scheme. However, we find that Tsaur et al.'s scheme is still vulnerable to impersonation attack and many logged-in users' attack. We propose an extended scheme that not only removes the aforementioned weaknesses on their scheme but also achieves user anonymity for hiding login user's real identity. Compared with other previous related schemes, our proposed scheme keeps the efficiency and security and is more suitable for the practical applications.

• International Journal of Contents
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• v.7 no.4
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• pp.35-43
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• 2011

USN is a technology to detect human external environment. It is an important factor in buildinga ubiquitous computing environment. In this thesis, an authentication method was proposed to allow the sensor nodes, which have weak computing operation capability, to safely communicate with each other in USN and guarantee the anonymity of users for their privacy. In the proposed authentication method that takes into account the characteristics of sensor network, sensor nodes based on a symmetric key algorithm do not transfer keys directly, instead, they mix the random numbers received from AS to generate keys necessary for communications, having a master key and a pseudo-random number generator.In addition, in this thesis, TA was adopted to minimize the leakage of users' information, and a scheme through which virtual IDs received from AS are delivered to sensor nodes was applied to improve anonymity.

• Spatial Information Research
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• v.20 no.4
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• pp.83-92
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• 2012

Location-based services (LBS) are increasingly popular due to the improvement of geo-positioning capabilities and wireless communication technology. However, in order to enjoy LBS services, a user requesting a query must send his/her exact location to the LBS provider. Therefore, it is a key challenge to preserve user's privacy while providing LBS. To solve this problem, the existing method employs a 2PASS cloaking framework that not only hides the actual user location but also reduces bandwidth consumption. However, 2PASS does not fully guarantee the actual user privacy because it does not take the real user distribution into account. Hence, in this paper, we propose a nearest neighbor query processing algorithm that supports K-anonymity property based on the weighted adjacency graph(WAG). Our algorithm not only preserves the location of a user by guaranteeing k-anonymity in a query region, but also improves a bandwidth usage by reducing unnecessary search for a query result. We demonstrate from experimental results that our algorithm outperforms the existing one in terms of query processing time and bandwidth usage.

• The KIPS Transactions:PartC
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• v.18C no.4
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• pp.207-212
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• 2011

Vehicular Ad Hoc Network(VANET) is a communication technology between vehicles and vehicles(V2V) or vehicles and infrastructures(V2I) for offering a number of practical applications. Considering the importance of communicated information through VANET, data authentication, confidentiality and integrity are fundamental security elements. Recently, to enhance a security of VANET in various circumstances, message authentication is widely researched by many laboratories. Among of them, Zhang. et. al. is an efficient method to authenticate the message with condition of anonymity in dense space. In the scheme, to obtain the vehicular ID with condition of anonymity, the k-anonymity is used. However it has a disadvantage, which conducts hash operations in case of determining the vehicular ID. In the paper, we present a location based algorithm using received signal strength for the location based authentication and encryption technique as well, and to enhance the accuracy of algorithm we apply a location determination technique over the 3-dimensional space.

• The Journal of the Korea institute of electronic communication sciences
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• v.12 no.5
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• pp.805-816
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• 2017

Tor is a popular, low-latency open network that offers online anonymity to users by concealing their information from anyone conducting traffic analysis. At the same time, a number of conventional passive and active attacking schemes have been proposed to compromise the anonymity provided by the Tor network. In addition to attacks on the network through traffic analysis, interacting with an unsecured application can reveal a Tor user's IP address. Specific traffic from such applications bypasses Tor proxy settings in the user's machine and forms connections outside the Tor network. This paper presents such applications and shows how they can be used to deanonymize Tor users. Extensive test studies performed in the paper show that applications such as Flash and BitTorrent can reveal the IP addresses of Tor users.

• Journal of Korea Multimedia Society
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• v.9 no.10
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• pp.1314-1321
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• 2006

GSM(Global System for Mobile Communications) is a Pan-European digital cellular mobile system supporting widespread roaming and personal communication services in a worldwide wireless communication network. In suite of providing security capability, however, there are some problems like user authentication in GSM. In this paper, we propose the enhanced authentication mechanism to verify strongly each network entity to so]ye user authentication problem and support anonymity for user privacy.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.9 no.2
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• pp.73-82
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• 1999

In an open network computing environment a host cannot to identity its users correctly to network services. In order to prevent this thing we present the design of a authentication scheme 솟 using the notion of rth -residuosity problem and discrete logarithm problem which is proposed by S. J. Park et al. The proposed scheme described here is efficient method for mutual authentication without leakage of users identity in mobile communication system that ensure user anonymity and untraceability.

• Journal of the Korea Society of Computer and Information
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• v.11 no.1 s.39
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• pp.177-184
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• 2006

The sensors in a ubiquitous network are limited because of the low power and ultra light weight, so many studies have revolved around the sensor. This study improves the process of the registration and authorization and suggests a way to minimize discloser of privacy by using an alias. We introduce RA(Relay Agent) for the restrict function of sensor node, and improve anonymity for private information of each sensor node by assigning alias from SM(Service Manager) in procedure of registration and authentication. The privacy of sensor node is secure in procedure of registration, authentication, and communication between nodes. We could improve the level of security with the only partial increment of computation power of RA and SM without an increase in the amount of sensor nodes.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.26 no.3
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• pp.667-678
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• 2016

Due to a development of the cable/wireless network infra, the traffic as big as unable to compare with the past is being served through the internet, the traffic is increasing every year following the change of the network paradigm such as the object internet, especially the traffic of about 1.6 zettabyte is expected to be distributed through the network in 2018. As the network traffic increases, the performance of the security infra is developing together to deal with the bulk terabyte traffic in the security equipment, and is generating hundreds of thousands of security events every day such as hacking attempt and the malignant code. Efficiently analyzing and responding to an event on the attack attempt detected by various kinds of security equipment of company is one of very important assignments for providing a stable internet service. This study attempts to overcome the limit of study such as the detection of Tor network traffic using the existing low-latency by classifying the anonymous network by means of the suggested algorithm about the event detected in the security infra.

• Journal of Korea Society of Digital Industry and Information Management
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• v.6 no.3
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• pp.69-77
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• 2010

Authentication and key establishment are fundamental procedures to establish secure communications over public insecure network. A password-based scheme is common method to provide authentication. In 2008, Khan proposed an efficient password-based authentication scheme using smart cards to solve the problems inherent in Wu-Chieu's authentication scheme. As for security, Khan claimed that his scheme is secure and provides mutual authentication between legal users and a remote server. In this paper, we demonstrate Khan's scheme to be vulnerable to various attacks, i. e., password guessing attack, insider attack, reflection attack and forgery attack. Our study shows that Khan's scheme does not provide mutual authentication and is insecure for practical applications. This paper proposes an improved scheme to overcome these problems and to preserve user anonymity that is an issue in e-commerce applications.