• Journal of information and communication convergence engineering
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• v.10 no.1
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• pp.53-60
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• 2012

Attribute-based encryption (ABE) is an encryption scheme in which the user is able to decrypt a ciphertext with associated attributes. However, the scheme does not offer the capability of decryption to others when the user is offline. For this reason, the attribute-based proxy re-encryption (ABPRE) scheme was proposed, which combines traditional proxy re-encryption with ABE, so a user is able to empower designated users to decrypt the re-encrypted ciphertext with the associated attributes of designated users. However, previous ABPRE schemes demands a number of pairing operations that imply huge computational overhead. To reduce the number of pairing operations, we reduce the pairing operations with exponent operations. This paper provides a novel approach to an ABPRE scheme with constant pairing operation latency.

• Proceedings of the Korea Information Processing Society Conference
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• 2002.04b
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• pp.947-950
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• 2002

인터넷이 급속히 발달하면서 초기에 제공되던 정보제공의 방법으로는 사용자 신원에 대한 인증으로는 부족하게 되었다. 이에 대해 PKI(Public-Key Infrastructure)에서 인증서를 기반으로 사용자의 신원을 제공하는 보안방법이 대두되었다. 하지만 시스템에 따라 각 사용자에게 다른 서비스를 제공하고 이용해야 할 경우가 발생하게 되는데, 이 경우 각 사용자의 권한이나 임무 등의 사용자 속성을 관리할 필요가 있다. 이때 기존에 사용된 PKI의 확장 영역을 이용하지 않고, 새롭게 사용자 속성을 위한 인증서를 사용하게 되는데 이것을 PMI라고 한다. 본 논문에서는 PMI(Privilege Management Infrastructure)를 이용한 효율적이고 검증 가능한 권한위임 프로토콜에 대하여 제안한다.

• Journal of Broadcast Engineering
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• v.13 no.1
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• pp.53-61
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• 2008

Public Key Broadcast Encryption (PKBE) allows a sender to distribute a message to a changing set of users over an insecure channel. PKBE schemes should be able to dynamically exclude (i.e., revoke) a certain subset of users from decrypting a ciphertext, so that only remaining users can decrypt the ciphertext. Another important requirement is for the scheme to be forward-secrecy. A forward-secure PKBE (fs-PKBE) enables each user to update his private key periodically. This updated private key prevents an adversary from obtain the private key for certain past period, which property is particularly needed for pay-TV systems. In this paper, we present a fs-PKBE scheme where both ciphertexts and private keys are of $O(\sqrt{n})$ size. Our PKBE construction is based on Boneh-Boyen-Goh's hierarchical identity-based encryption scheme. To provide the forward-secrecy with our PKBE scheme, we again use the delegation mechanism for lower level identities, introduced in the BBG scheme. We prove chosen ciphertext security of the proposed scheme under the Bilinear Diffie-Hellman Exponent assumption without random oracles.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.7 no.5
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• pp.1343-1356
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• 2013

Cloud computing has emerged as perhaps the hottest development in information technology at present. This new computing technology requires that the users ensure that their infrastructure is safety and that their data and applications are protected. In addition, the customer must ensure that the provider has taken the proper security measures to protect their information. In order to achieve fine-grained and flexible access control for cloud computing, a new construction of hierarchical attribute-based encryption(HABE) with Ciphertext-Policy is proposed in this paper. The proposed scheme inherits flexibility and delegation of hierarchical identity-based cryptography, and achieves scalability due to the hierarchical structure. The new scheme has constant size ciphertexts since it consists of two group elements. In addition, the security of the new construction is achieved in the standard model which avoids the potential defects in the existing works. Under the decision bilinear Diffie-Hellman exponent assumption, the proposed scheme is provable security against Chosen-plaintext Attack(CPA). Furthermore, we also show the proposed scheme can be transferred to a CCA(Chosen-ciphertext Attack) secure scheme.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.31 no.1C
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• pp.93-101
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• 2006

Proxy signature schemes based on delegation of warrant are frequently studied in these days. Proxy signature schemes that used in these days have some problems about the security. Especially, it is difficult to prevent misuse of certification and private key. In this thesis, we propose the more stronger security structure by turning the point from original signer with proxy signer to original signer with verifier, and the proposed protocol is more stronger than previous scheme and can be applied to various PKI based application.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.11 no.5
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• pp.2762-2777
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• 2017

A fuzzy identity based signature (FIBS) scheme allows a signer with identity ${\omega}$ to generate a signature which could be verified under identity ${\omega}^{\prime}$ if and only if ${\omega}$ and ${\omega}^{\prime}$ are within a certain distance of each other as judged by some metric. In this paper, we propose an efficient FIBS scheme from lattice assumption, which can resist quantum-computer attacks. Without using the Bonsai Tree technique, we utilize the lattice basis delegation technique to generate the private key, which has the advantage of keeping the lattice dimension invariant. We also prove that our proposed scheme is existentially unforgeable under an adaptive chosen message and identity attack in the random oracle model. Compared with existing scheme, our proposed scheme is much more efficient, especially in terms of communication overhead. Since our FIBS scheme possesses similar error-tolerance property, it can be well applied in post-quantum communication biometric authentication environments, where biometric identifiers such as fingerprints, voice, iris and gait are used in human identification.

• Journal of the Korea Convergence Society
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• v.7 no.1
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• pp.49-55
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• 2016

In a delegate authentication, a user can lend his/her own authentication data to the third parties to let them be authenticated instead of himself/herself. The user authentication schemes based on the memory of unique data such as password, are vulnerable to this type of attack. Biometric authentication could minimize the risk of delegate authentication since it uses the biometric data unique by each person. Group authentication scheme is used to prove that each group member belongs to the corresponding group. For applications such as an electronic voting or a mobile meeting where the number of group members is changing dynamically, a new group authentication method is needed to reflect the status of group in real time. In this paper, we propose biometric authentication based dynamic group signature scheme. The proposed scheme is composed of biometric key generation, group public key creation, group signature generation, group signature verification and member update protocols. The proposed member update protocol is secure against colluding attacks of existing members and could reflect group status in real time.

• The Journal of the Korea Contents Association
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• v.11 no.1
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• pp.42-49
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• 2011

Proxy signature schemes are configured as proxy signers on behalf of their original signers can be allowed to sign messages. Basic security requirements of proxy signature schemes include the strong unforgeability and the verifiability of delegation. So far, a variety of proxy signature schemes that proved on individual basic security terms but not proved on compounded security terms are proposed. Especially the proposed proxy signature schemes based on RSA problem are proved vulnerable to an attacker with his own private key in terms of the impersonating attack. A unauthorized attacker can generate the proxy signature without the appointee's consent or authorization. In this paper, we propose a proxy signature scheme based on RSA problems and warrants that can be proved the security against the impersonating attack. The proposed proxy signature scheme is analyzed on the safety and compared in terms of efficiency with other proxy signature schemes.

• Journal of Korea Multimedia Society
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• v.15 no.8
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• pp.1048-1058
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• 2012

This paper proposes the DDMPF(Distributed Data Management Protocol using FAT) which prevents data loss and keeps the security of self-organized storages by comprising a client, a storage server, and a verification server in clouding environment. The DDMPF builds a self-organized storage server, solves data loss by decentralizing the partitioned data in it in contrast to the centralized problem and the data loss caused by the storage server problems of existing clouding storages, and improves the efficiency of distributed data management with FAT(File Allocation Table). And, the DDMPF improves the reliability of data by a verification server's verifying the data integrity of a storage server, and strengthens the security in double encryption with a client's private key and the system's master key using EC-DH algorithm. Additionally, the DDMPF limits the number of verification servers and detects the flooding attack by setting the TS(Time Stamp) for a verification request message and the replay attack by using the nonce value generated newly, whenever the verification is requested.

• Convergence Security Journal
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• v.14 no.3_2
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• pp.83-91
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• 2014

International society got a severe shock from terrorism of hostage, abduction and murder that was committed on a target of Israel athlete delegation in Munich Olympics, West Germany by Black September, a Palestine terrorism organization. Korea with 1986 Asian Games and 1988 Olympics ahead was directly and indirectly exposed to threats of North Korea's nation-support terrorism, a military provocation and a local war limited warfare. This study explores the roles of the police at the time of the National Police Headquarters with regard to counter-terrorism, and analyzed academic research trends of Studies of Counter-terrorism published by the same office between 1983 and 1990. Looking into them shows a fact firstly, that the most frequently appearing key words in common were "terrorism," "hostages," "measures," and "international," etc. Secondly, before and after 1988 Olympics, the key word "Olympics" was frequently addressed. Thirdly, looking at the difference by the year, the key word, "policies of defense and borderlands" was frequently addressed between 1983 and 1984, "terrorism against South Korea," and "civil aircraft" frequently addressed in 1985, and "corporate" in 1986. In 1987, the key word "terrorism trends" was addressed, and in 1990, "international terrorism," and "separatism" were used.