• The Journal of the Korea Contents Association
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• v.9 no.4
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• pp.95-102
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• 2009

Recently, remote user authentication scheme protecting user anonymity using smart card has been researched with interest increasing on user privacy. Although authentication scheme providing user anonymity using smart card had been proposed by Das et al, Chien et al. pointed out Das et al. scheme fail to provide user anonymity and proposed new scheme to overcome the problem. A remote system Kim et al. proposed a scheme which is traceable about malicious user with protecting user anonymity. In this paper, we point out that Kim et a1. scheme fail to provide user anonymity and propose a scheme for some problems Kim et al. scheme has. And then we analysis our scheme on cryptophic security and efficiency with Kim scheme.

• Journal of the Korea Society of Computer and Information
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• v.18 no.2
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• pp.87-94
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• 2013

In this paper, we analyse the weaknesses of authentication scheme preserving user anonymity proposed by Khan et al in 2011 and we propose a new authentication schemes preserving user anonymity that improved these weaknesses. Khan et al's authentication scheme is vulnerable to insider attack and doesn't provide user anonymity to the server. Also, this scheme is still a weakness of wrong password input by mistake in spite of proposing the password change phase. In this paper, we will show that Khan et al's scheme is vulnerable to the stolen smart card attack and the strong server/user masquerade attack. The proposed authentication scheme propose the improved user anonymity, which can provide more secure privacy to user by improving these weaknesses.

• Journal of Information Processing Systems
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• v.7 no.1
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• pp.121-136
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• 2011

With the rapid growth of GPS-enable Smartphones, the interest on using Location Based Services (LBSs) has increased significantly. The evolution in the functionalities provided by those smartphones has enabled them to accurately pinpoint the location of a user. Because location information is what all LBSs depend on to process user's request, it should be properly protected from attackers or malicious service providers (SP). Additionally, maintaining user's privacy and confidentiality are imperative challenges to be overcome. A possible solution for these challenges is to provide user anonymity, which means to ensure that a user initiating a request to the SP should be indistinguishable from a group of people by any adversary who had access to the request. Most of the proposals that maintain user's anonymity are based on location obfuscation. It mainly focuses on adjusting the resolution of the user's location information. In this paper, we present a new protocol that is focused on using cryptographic techniques to provide anonymity for LBSs users in the smartphone environment. This protocol makes use of a trusted third party called the Anonymity Server (AS) that ensures anonymous communication between the user and the service provider.

• Journal of the Korea Society of Computer and Information
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• v.17 no.11
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• pp.83-91
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• 2012

Authentication schemes preserving user anonymity have first been proposed by Das et al, and most of user anonymity schemes provide user anonymity against outside attacks in the communication channel. In this paper, according to the increasing of personal information exposure incidents by server attack, we propose a new authentication scheme that provides user anonymity against server as well as one against outside attacks in the communication channel. Furthermore, the proposed authentication scheme provides traceability that remote server should be able to trace the malicious user and it also solves the problem of increasing computational load of remote server by solving weakness of wrong password input by mistake.

• Journal of Korea Society of Digital Industry and Information Management
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• v.6 no.1
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• pp.115-129
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• 2010

As the fixed mobile communication tools using the internet are developed, the off-line services are serviced through on-line on the internet. our society is divided into the real world and the cyber world. In the cyber world, the authentication to the user is absolutely required. The authentication is divided into the real-name authentication and the anonymous authentication by the kind of the internet service provider. There are some ISPs needed the real-name authentication and there are others ISPs needed the anonymity authentication. The research about the anonymity authentication is steadily established to these days. In this paper, we analyze the problem about blind signature, group signature, ring signature, and traceable signature. And we propose a method of anonymity authentication using the public certificate. In the proposal, the anonymity certificate have the new structure and management. Certificate Authority issues several anonymity certificates to a user through the real-name authentication. Several anonymity certificates give non-linked and non-traceability to the attacker.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.10 no.3
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• pp.1289-1310
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• 2016

Dynamic ID-based authentication solves the ID-theft problem by changing the ID in each session instead of using a fixed ID while performing authenticated key exchanges between communicating parties. User anonymity is expected to be maintained and the exchanged key kept secret even if one of the long-term keys is compromised in the future. However, in the conventional dynamic ID-based authentication scheme, if the server's long-term key is compromised, user anonymity can be broken or the identities of the users can be traced. In addition, these schemes are vulnerable to replay attacks, in which any adversary who captures the authentication message can retransmit it, and eventually cause the legitimate user to be denied service. This paper proposes a novel dynamic ID-based authentication scheme that preserves forward anonymity as well as forward secrecy and obviates replay attacks.

• 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 Journal of Society for e-Business Studies
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• v.18 no.2
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• pp.81-93
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• 2013

Remote user authentication is a method, in which remote server verifies the legitimacy of a user over an common communication channel. Currently, smart card based remote user authentication schemes have been widely adopted due to their low computational cost and convenient portability for the mutual authentication. 2009 years, Wang et al.'s proposed a dynamic ID-based remote user authentication schemes using smart cards. They presented that their scheme preserves anonymity of user, has the feature of storing password chosen by the server, and protected from several attacks. However, in this paper, I point out that Wang et al.'s scheme has practical vulnerability. I found that their scheme does not provide anonymity of a user during authentication. In addition, the user does not have the right to choose a password. And his scheme is vulnerable to limited replay attacks. In particular, the parameter y to be delivered to the user is ambiguous. To overcome these security faults, I propose an enhanced authentication scheme, which covers all the identified weakness of Wang et al.'s scheme and an efficient user authentication scheme that preserve perfect anonymity to both the outsider and remote server.

• Journal of the Korea Society of Computer and Information
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• v.15 no.12
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• pp.109-116
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• 2010

Due to the increasing interest and demands of user privacy, remote user authentication schemes using smart card has been researched in active. Recently, a lot of suggestion have been made in order to provide user's anonymity and trace a malicious user. In 2008, Kim et al. proposed a traceable anonymity authentication scheme. In 2009, Choi et al. pointed out that Kim's protocol was insecure against outsider attacker and proposed an improved scheme. But Kim's and Choi's schemes fail to provide the user's anonymity or compute some values in the protocol. In this paper, we analyse those problems and suggest two improved schemes to resolve those problems.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.17 no.2
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• pp.139-144
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• 2007

Due to the increasing use of Internet and spread of ubiquitous environment the security of private information became an important issue. For this reason, many suggestions have been made in order to protect the privacy of users. In the study of authentication system using a smart card which is one of the methods for protecting private information, the main idea is to offer user anonymity. In 2004, Das et al. suggested an authentication system that guarantees anonymity by using a dynamic ID for the first time. However, this scheme couldn't guarantee complete anonymity as the identity of the user became revealed at log-in phase. In 2005, Chien at al. suggested a authentication system that guarantees anonymity, but this was only safe to the outsider(attacker). In this paper, we propose a scheme that enables the mutual authentication between the user and the sewer by using a smart card. For the protection of the user privacy, we suggest an efficient user authentication system that guarantees perfect anonymity to both the outsider and remote server.