• The Journal of Information Technology
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• v.4 no.4
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• pp.25-35
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• 2001

This paper presents a digital signature scheme for document image which directly embeds a signature onto the document. The time to take in signature is reduced by spreading of signature. Non-repudiation in origin, the 3rd condition of digital signature is realized by proposed digital signature scheme. The transmitter embeds the signature secretly and transfers it and the receiver makes a check of any forgery on the signature and the document, This scheme is compatible with the ITU-T.4(CCITT G3 or G4 facsimile standards).

• Journal of Digital Contents Society
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• v.5 no.1
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• pp.1-6
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• 2004

Electronic cash is used as a payment tool for contents purchase in mobile electronic commerce environment. In order to protect customer`s privacy, we use blind signature. Blind signature has an anonymity property since it does not allow connection between customer`s ID and customer`s message. In this paper, we propose an blind signature scheme using elliptic curve algorithm based on Cap Diffie-Hellman Problem. Proposed scheme efficiently improved against existing blind signature scheme by reducing communication and computation time of the process.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.22 no.8
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• pp.1814-1822
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• 1997

In this paper, we present a new digital signature for copyright protection of digital images. The proposed algorithm is designed to be more robust to both the compression (quantization) errors and the illegal signature attack by a third party. More specifically, to maximize the watermaking effect, we embed the watermark by randomly adding or subtracking a fixed number instead of executing the XORs. Also, to improve the reliability of the watermark detection, we extact the watermark only on some image blocks, which are less sensitive to the compression error. Futhermore, the unrecovered compression errors are further detected by the Hypothesis testing. The illegal signalture attack of a third party is also protected by using some probabilistic decisions of the MSE between the orignal image and the signed image. Experimental results show that the peroposed algorithm is more robust to the quantization errors and illegal signature attack by a third party.

• Journal of Digital Contents Society
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• v.19 no.1
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• pp.205-212
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• 2018

In this paper, we propose a method for more accurate fake discrimination using time information in CNN-based signature recognition. To easily use the time information and not to be influenced by the speed of signature writing, we acquire the signature as a movie and divide the total time of the signature into equal numbers of equally spaced intervals to obtain each image and synthesize them to create signature data. In order to compare the method using the proposed signature image and the method using only the last signature image, various signature recognition methods based on CNN have been experimented in this paper. As a result of experiment with 25 signature data, we found that the method using time information improves performance in fake discrimination compared to the existing method at all experiments.

• Journal of the Korea Society of Computer and Information
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• v.18 no.6
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• pp.47-54
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• 2013

In this paper, we proposed an efficient digital authentication service system for the vehicle data collected from digital tachograph. In domestic, There is no method available to verify that information has not been forged and reliable information for collected vehicle data. The proposed method in this paper can prove transmitted vehicle data that have not been forged using the signature value. The signature value of digital authentication is produced with the digital signature generation key after obtaining the hash value of vehicle data. It is achieved through checking the stored hash value and the hash value match that is obtained with the digital signature verification key from the digital signature value. We confirmed the proposed system can ensure reliability of vehicle data through the system implementation and experiment.

• 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 the Korea Institute of Information and Communication Engineering
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• v.13 no.11
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• pp.2459-2464
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• 2009

In sensor network there are no nodes or servers that are exclusively responsible for packet forwarding and routing. Instead, sensor nodes participating in network communications perform these activities. Thus, they are vulnerable to the alteration and forgery of message in the process of packet forwarding and routing. To solve this problem, a security to ensure authentication and integrity of routing and forwarding messages should be required. To do this, we propose the hash chain-based digital signature model where it takes less time to compute in generating and verifying the digital signature model, unlike he public key-based digital signature model, and verify if this model is proper by comparing computation times between tow models.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2008.10a
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• pp.699-702
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• 2008

인터넷 이용이 활성화되면서 각종 웹 서버에서의 개인정보 과다 수집 및 노출이 큰 이슈가 되고 있다. 인터넷이 우리 생활에 주는 편리함을 그대로 누리면서 개인정보를 보호할 수 있는 방안으로 익명인증 기술이 있을 수 있다. 익명인증은 익명성을 제공하는 디지털서명을 이용한 인증 방법이다. 익명성을 제공하는 디지털서명 방법은 전자화폐와 전자투표 시스템 등의 응용을 위해서 주로 연구되어 왔으나, 최근에는 인터넷 환경에서 개인정보 보호를 위한 익명인증 방법의 하나로써 연구되고 있다. 본 논문에서는 익명성을 제공하는 전자서명 방법 중 그룹서명 방식에 관하여 소개하고, 그룹서명을 이용한 익명인증 시스템의 구조를 제안하고자 한다.

• 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.

• Journal of Korea Multimedia Society
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• v.1 no.1
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• pp.56-65
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• 1998

The multignature system is a digital contract system which can process multi-party contracts electronically. In this paper, we analyzed various insecure elements involved in general multisignature contract systems and suggest requirements needed for making such systems secure. Based on our analysis, we propose a new secure multisignature method and apply it to the conventional electronic digital contract systems along with several other existing multisignature methods. The applicability and the effectiveness of the newly developed method are demonstrated by comparing how well the suggested security requirements are satisfied by each method.