• 한국정보과학회논문지:시스템및이론
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• 제29권5호
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• pp.299-306
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• 2002

'부분은닉서명(Partially Blind Signature)'기법은 전자화폐나 전자투표와 같이 사용자의 프라이버시가 중요시되는 응용에서 사용된다. 본 논문에서는 서명 요청자의 계산량을 줄이는 RSA 알고리즘에 기반한 부분은닉서명 기법을 제안한다. 서명 요청자는 메시지를 은닉하여 서명자에게 전송하고 서명자가 생성한 중간 서명으로부터 최종 서명을 생성하는 과정에서 계산을 필요로 한다. 논문에서 제안하고 있는 기법은 서명 요청자가 적은 계산량을 필요로 하는 모듈러 합과 곱 연산만으로 최종 서명을 계산할 수 있게 하므로 서명 요청자의 계산량을 많이 감소시킨다. 따라서, 이동통신 기기나 스마트카드, 전자지갑 같이 계산능력이 떨어지는 장치들에서 사용하기에 적합하다.

• Journal of Communications and Networks
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• 제15권1호
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• pp.1-7
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• 2013

Most of the provably-secure proxy signature schemes rely on the average-case hardness problems such as the integer factorization problems and the discrete logarithm problems. Therefore, those schemes are insecure to quantum analysis algorithms, since there exist quantum algorithms efficiently solving the factorization and logarithm problems. To make secure proxy signature schemes against quantum analysis, some lattice-based proxy signature schemes are suggested. However, none of the suggested lattice-based proxy signature schemes is proxy-protected in the adaptive security model. In the paper, we propose a provably-secure ID-based proxy signature scheme based on the lattice problems. Our scheme is proxy-protected in the adaptive security model.

• 디지털콘텐츠학회 논문지
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• 제19권1호
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• pp.205-212
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• 2018

본 논문에서는 CNN 기반 서명인식에서 시간 정보를 이용하여 위조판별을 보다 정확하게 하는 방법을 제안한다. 시간정보를 쉽게 이용하고 서명 작성속도에 영향을 받지 않기 위해 서명을 동영상으로 획득하고 서명 전체 시간을 동일한 개수의 등 간격으로 나누어 각 이미지를 얻은 후 이를 합성하여 서명 데이터를 만든다. 본 논문에서 제안한 합성 서명이미지를 이용한 방법과 기존에 마지막 서명 이미지만을 이용하는 방법을 비교하기 위하여 CNN 기반의 다양한 서명인식 방법을 실험하였다. 25명의 서명데이터로 실험한 결과 시간 정보를 이용하는 방법이 기존 방법에 비하여 모든 위조판별 실험에서 성능이 향상됨을 보았다.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제11권7호
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• pp.3629-3647
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• 2017

Certificate-based cryptography is a useful public key cryptographic primitive that combines the merits of traditional public key cryptography and identity-based cryptography. It not only solves the key escrow problem inherent in identity-based cryptography, but also simplifies the cumbersome certificate management problem in traditional public key cryptography. So far, four short certificate-based signature schemes have been proposed. However, three of them fail in achieving the existential unforgeability under adaptive chosen-message attacks and the remaining one was not constructed in the normal framework of certificate-based signature. In this paper, we put forward a new short certificate-based signature scheme. The proposed scheme is devised in the normal framework of certificate-based signature and overcomes the security weaknesses in the previous short certificate-based signature schemes. In the random oracle model, we formally prove that it achieves the existential unforgeability against adaptive chosen-message attacks. Performance comparison shows that it is efficient and practical.

• 정보처리학회논문지D
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• 제9D권2호
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• pp.307-312
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• 2002

본 논문에서는 무선 PKI 환경에 적합한 은닉 서명을 제안한다. 제안하는 방식은 [5]에서 제안한 Gap problem을 이용한 시스템으로 이에 대한 예로는 타원곡선 기반의 Weil pairing을 이용한 서명 방식등이 될 수 있다. 특히 Weil pairing을 이용한 서명 방식은 작은 키 크기로 높은 안전성을 제공할 수 있으며, Diffie-Hellman 문제에 기반한 실용적인 은닉 서명으로는 최초의 방식이라고 할 수 있다.

• Current Optics and Photonics
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• 제4권6호
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• pp.483-499
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• 2020

In this paper, a novel analog signature scheme is proposed by modifying an RSA-based digital signature scheme with optical phase-shifting digital holography. The purpose of the proposed method is generating an analog signature to provide data confidentiality and security during the data transfer, compared to the digital signature. The holographic encryption technique applied to a hash value reveals an analog-type of pseudo-random pattern in the analog signature scheme. The public key and secret key needed to verify the analog signature are computed from public key ciphers which are generated by the same holographic encryption. The proposed analog signature scheme contains a kind of double encryption in the process of generating signature and key, which enhances security level more than the digital signature. The results of performance simulations show the feasibility of the highly secure signature scheme, and security analysis shows high robustness against known-message attacks and chosen-message attacks. In addition, the proposed method can apply to one-time signature schemes which can be used to sign only one message and it can also apply to authentication, e-mails, electronic banking and electronic data interchange.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제11권5호
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• pp.2792-2810
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• 2017

Forward-secure signature is a specific type of signature, which can mitigate the damage caused by the signing key exposure. Most of the existing forward-secure (identity-based) signature schemes can update users' secret keys at each time period, achieve the existential unforgeability, and resist against classical computer attacks. In this paper, we first revisit the framework of forward-secure identity-based signatures, and aim at supporting flexible key update at multi time period. Then we propose a post-quantum forward-secure identity-based signature scheme from lattices and use the basis delegation technique to provide flexible key update. Finally, we prove that the proposed scheme is strongly unforgeable under the short integer solution (SIS) hardness assumption in the random oracle model.

• 한국정보과학회논문지:정보통신
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• 제30권6호
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• pp.720-728
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• 2003

은닉서명(blind signature scheme)은 서명문의 내용을 숨기는 서명 방식으로 서명의뢰자의 신원과 서명문을 연결시킬 수 없는 익명성을 가지며 전자화폐나 전자투표 등 주로 행위자의 행동이 노출되어서는 안되는 보안서비스에 중요하게 활용된다. 본 논문에서는 GDH군에서의 ID 기반 은닉서명 방식을 제안한다. 제안한 방식의 안전성은 CDHP의 어려움에 기반을 두며, 효율성은 두 사용자간의 2회 통신만으로 서명을 생성함으로써 기존의 은닉서명 방식을 훨씬 개선하였다. 통신횟수와 계산량이 적으므로 제안한 은닉서명 방식은 무선 PKI 환경에서도 적용할 수 있다.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제6권10호
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• pp.2692-2707
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• 2012

A separable identity-based ring signature scheme has been constructed as a fundamental cryptographic primitive for protecting user privacy. Using the separability property, ring members can be selected from arbitrary domains, thereby, giving a signer a wide range of ways to control privacy. In this paper we propose a generic method to construct efficient identity-based ring signature schemes with various levels of separability. We first describe a method to efficiently construct an identity-based ring signature scheme for a single domain, in which a signer can select ring identities by choosing from identities defined only for the domain. Next, we present a generic method for linking ring signatures constructed for a single domain. Using this method, an identity-based ring signature scheme with a compact structure, supporting multiple arbitrary domains can be designed. We show that our method outperforms the best known schemes in terms of signature size and computational costs, and that the security model based on the separability of identity-based ring signatures, presented in this paper, is highly refined and effective by demonstrating the security of all of the proposed schemes, using a model with random oracles.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제7권12호
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• pp.3261-3273
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• 2013

In the paper, we propose a novel adaptively secure hierarchical identity-based signature scheme from lattices. The size of signatures in our scheme is shortest among the existing hierarchical identity-based signature schemes from lattices. Our scheme is motivated by Gentry et al.'s signature scheme and Agrawal et al.'s hierarchical identity-based encryption scheme.