• The Journal of the Korea Contents Association
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• v.5 no.1
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• pp.55-63
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• 2005

In undeniable digital signature scheme, the signature can not be verified without the signer's cooperation. The undeniable signature scheme can be used to computerize many applications which can not be done by a conventional digital signature scheme. In this study, we propose the undeniable digital multi-signature scheme which requires many signers and designated verifier The multi-signature can be verified only in cooperation with all signers. The proposed scheme satisfies undeniable property and it is secure against active attacks such as modification and denial of the multi-signature by signers. We also propose copyright protection method of co-authored digital contents as an application of the proposed scheme.

• The Journal of Korean Association of Computer Education
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• v.8 no.4
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• pp.97-105
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• 2005

In this study, the undeniable digital multi-signature scheme based on the discrete logarithms is proposed. The proposed multi-signature scheme satisfies undeniability and is secure against active attacks such as fabrication and denial of multi-signature by signers. It is suitable for electronic election scheme in which several administrators are required. Especially in case of dispute among voters and administrators, the proposed scheme can resolve it due to the undeniable property. It can provide fair electronic election by minimizing the role of voting center, and can enable user-oriented electronic election.

• Proceedings of the Korea Contents Association Conference
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• 2004.05a
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• pp.261-267
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• 2004

In undeniable digital signature scheme, the signature can not be verified without the signer's cooperation. The undeniable signature scheme can be used to computerize many applications which can not be done by a conventional digital signature scheme. In this study, we propose the undeniable digital multi-signature scheme which requires many signers and designated verifier. The multi-signature can be verified only in cooperation with all signers. The proposed scheme satisfies undeniable property and it is secure against active attacks such as modification and denial of the multi-signature by signers. We also discuss practical applications such as joint copyright protection on digital contents.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.8 no.3
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• pp.549-555
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• 2007

A digital signature scheme provides integrity of the document, authentication and non-repudiation of a signer. Usually the key for digital signature is stored in hard disk or removal disk storage. The drawback of this approach is that the signer can let the agent to sign instead of the signer by providing the key information. It can be abused in applications such as electronic election. In this paper, we propose the undeniable biometric digital multi-signature scheme suitable for applications where the signer should not make an agent sign instead of himself/herself. The undeniable multi-signature scheme requires many signers and only the designated user can confirm the authenticity of multi-signature. The proposed scheme satisfies undeniable property and it is secure against active attacks such as modification and denial of the multi-signature by signers. As the key is generated through the signer's fingerprint image, it's also secure against signing by an agent.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.11 no.5
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• pp.1670-1676
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• 2010

It is easy to reproduce and manipulate the digital contents. It's difficult to distinguish the original contents with a pirate one. A digital signature scheme is used to protect the contents author's ownership and to provide secure contents distribution. Generally, the digital contents is completed with many authors' help. It's necessary to apply a cryptographic method for protecting co-authors' rights and interests. In this paper, the biometric based convertible undeniable multi-signature scheme is proposed. In the proposed scheme, keys are generated by using a signer's biometric data. Consigning the private key to another signer is infeasible. Signers must participate in signature generation and verification stages. Our scheme also provides signature conversion protocol in which the undeniable signature is converted to the ordinary one. For applications, we show how the proposed scheme is used to protect co-authors' rights and to distribute the contents securely.

• Journal of Internet of Things and Convergence
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• v.7 no.2
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• pp.7-12
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• 2021

Wisdom Contents are created with experiences and ideas of multiple authors, and consumed in Internet based Social Network Services that are not subjected to regional restrictions. Existing copyright management systems are designed for the protection of professional authors' rights, and effective in domestic area. On the contrary, the blockchain protocol is subjected to the service and the block is added by the consensus of participating nodes. If the data is stored to the blockchain, it cannot be modified or deleted. In this paper, we propose the blockchain based undeniable multi-signature scheme for the protection of multiple authorship on Wizdom Contents. The proposed scheme is consisted of co-authors' common public key generation, multi-signature generation and verification protocols. In the undeniable signature scheme, the signature cannot be verified without help of the signer. The proposed scheme is best suited to the contents purchase protocol. All co-authors cannot deny the fairness of the automated profit distribution through the verification of multiple authorship on Wizdom Contents.

• Journal of Digital Convergence
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• v.10 no.2
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• pp.161-169
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• 2012

It requires a lot of costs and manpower to manage the election system. The electronic voting scheme is needed to make the election system to be economic and fair. Especially, wide spread use of smart phones and wireless networks makes the mobile voting is of major concern. In mobile voting scheme, a smart phone user can vote regardless of the places. In this paper, the mobile voting scheme is proposed where candidates can guarantee fairness of the election system. We analyze mobile voting requirements and create the mobile ID which has legal binding forces and PKI based digital signature keys. In the proposed scheme, a voter's ballot is signed by all candidates using undeniable multi-signature scheme. During the counting stage, the multi-signature on the ballot is not verified without help of all candidates.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.7 no.1
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• pp.166-183
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• 2013

It requires a lot of costs and manpower to manage an election. The electronic voting scheme can make the election system economic and trustful. The widespread use of smart phones causes mobile voting to be a major issue. The smart phone can be used as a mobile voting platform since it can carry out many services in addition to basic telephone service. To make mobile voting practical and trustful, we analyzed two subjects of study. Firstly, the way to make a biometric based mobile ID, which has legal binding forces. In mobile voting, user identification is accomplished on line since the voter should be able to vote wherever they go. The digital ID conducts a similar role to the need for a resident card. The user's identity is bound to the resident card legally. To bind the user's identity to the smart phone, we use USIM. Biometric recognition is also needed to authenticate the user, since the user cannot prove him or her on line face-to-face. The proposed mobile ID can be reissued by means of introducing a random secret value. Secondly, the mobile voting scheme is proposed where candidates can accept election results without doubt. The goal of an election is to select a leader among two or more candidates. Existing electronic voting schemes mainly focus on the study of ballot verification accomplished by voters. These approaches are not safe against collusion attacks where candidates and the election administration center are able to collude to fabricate election results. Therefore, a new type of voting and counting method is needed where candidates can directly take part in voting and counting stages. The biometric based multi-signature scheme is used to make the undeniable multi-signed ballot. The ballot cannot be verified without the help of all candidates. If candidates accept election results without a doubt, the fairness of the election is satisfied.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.10 no.5
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• pp.2427-2445
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• 2016

In contrast to traditional "store-and-forward" routing mechanisms, network coding offers an elegant solution for achieving maximum network throughput. The core idea is that intermediate network nodes linearly combine received data packets so that the destination nodes can decode original files from some authenticated packets. Although network coding has many advantages, especially in wireless sensor network and peer-to-peer network, the encoding mechanism of intermediate nodes also results in some additional security issues. For a powerful adversary who can control arbitrary number of malicious network nodes and can eavesdrop on the entire network, cryptographic signature schemes provide undeniable authentication mechanisms for network nodes. However, with the development of quantum technologies, some existing network coding signature schemes based on some traditional number-theoretic primitives vulnerable to quantum cryptanalysis. In this paper we first present an efficient network coding signature scheme in the standard model using lattice theory, which can be viewed as the most promising tool for designing post-quantum cryptographic protocols. In the security proof, we propose a new method for generating a random lattice and the corresponding trapdoor, which may be used in other cryptographic protocols. Our scheme has many advantages, such as supporting multi-source networks, low computational complexity and low communication overhead.