• Journal of Korea Multimedia Society
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• v.12 no.6
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• pp.833-841
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• 2009

In this paper we propose a flexible video authentication scheme based on aggregate signature, which provides authenticity of a digital video by means of cryptographic signature to guarantee right of users. In contrast to previous works, the proposed scheme provides flexible usages on content distribution system, and it allows addition of new contents to the signed contents and deletion of some parts of the signed contents. A modification can be done by content owner or others. Although contents are modified by one or more users, our scheme can guarantee each user's right by aggregation of the each user's signatures. Moreover, proposed scheme has half size of Digital Signature Algorithm (DSA) with comparable security.

• The KIPS Transactions:PartC
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• v.12C no.4 s.100
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• pp.489-494
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• 2005

In 2002, Shundong Xia proposed a new ID-based group signature scheme with strong separability. The nature of a strong separability is to divide group manager's role into a membership manager and a revocation manager Jianhong et al showed that the scheme was not coalition-resistant. In this letter, we first propose two new attacks, forgery and link attacks, for Xia-You's scheme. We also propose a new ID-based group signature scheme that Is resistant to coalition, forgery and link attacks

• Journal of the Korean Society for Industrial and Applied Mathematics
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• v.2 no.1
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• pp.15-26
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• 1998

By "secure", we mean that some well-defined computational assumption can be shown to be sufficient for the scheme not to be existentially forgeable, even under an adaptive chosen message attack. Most, if not all, signature schemes used in practice are based on a computational assumption that is certainly necessary for this kind of security, not known to be sufficient. Since the work of Goldwasser, Micali and Rivest[?], many researches have been done for the secure signature schemes. We modify the Cramer-Damg$\dot{a}$rd scheme to implement a practical and secure signature scheme for smart cards.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.6 no.10
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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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• 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 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 Institute of Information Security & Cryptology
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• v.13 no.6
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• pp.149-161
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• 2003

Partially blind signature scheme allows the signer to insert non-removable common information into his blind signature. Blind signatures providing with both users privacy and data authenticity are one of key parts of information systems, such anonymous electronic cash and electronic voting as typical examples. Partially blind signature, with which all expired e-cash but for still-alive can be removed from the banks database, copes well with the problem of unlimited growth of the banks' database in an electronic cash system. In this paper we propose an efficient ID-based partially blind signature scheme using the Weil-pairing on Gap Diffie-Hellman group. The security of our scheme relies on the hardness of Computational Diffie-Hellman Problem. The proposed scheme provides higher efficiency than existing partially blind signature schemes by using three-pass protocol between two participants, the signer and requesters also by reducing the computation load. Thus it can be efficiently used in wireless environment.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.7 no.2
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• pp.55-72
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• 1997

This paper presents a digital signature scheme for facsimile document which directly embeds a signature onto the document. We use multiple reference lines which have been scanned just before and modify each distance of changing pels both on the reference line specified by key and on the coding line with a single bit of the signature data. 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). The total amount of data transmitted and the image quality are about the same to that of the original document, and thus a third party notices that no signature is embedded on the document.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.20 no.5
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• pp.37-48
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• 2010

Designated verifier signatures allow a signer to prove the validity of a signature to a specifically designated verifier. The designated verifier can be convinced but unable to prove the source of the message to a third party. Unlike conventional digital signatures, designated verifier signatures make it possible for a signer to repudiate his/her signature against anyone except the designated verifier. Recently, two designated verifier signature schemes, Zhang et al.'s scheme and Kang et al.'s scheme, have been shown to be insecure by concrete attacks. In this paper, we find the essential reason that the schemes open attacks while those were given with its security proofs, and show that Huang-Chou scheme and Du-Wen scheme have the same problem. Indeed, the security proofs of all the schemes reflect no message attackers only. Next, we show that Huang-Chou scheme is insecure by presenting universal forgery attack. Finally, we show that Du-Wen scheme is, indeed, secure by completing its defective security proof.

• Journal of KIISE:Computer Systems and Theory
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• v.35 no.4
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• pp.172-177
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• 2008

In this paper, we design an authentication protocol based on Fuzzy Signature Vault Scheme using a light signature feature extraction method for user convenience and efficiency of electronic commerce. The signature is used broadly in electronic commerce because it is one of the simple and low-cost biometric items. However, signature has a problem that there are few low-cost and safe protocols. To solve this problem, we design a feature extraction method which is adequate for characters of signature and Fuzzy Vault Scheme. In addition, we design and analyze an efficient authentication protocol with some parameters used in this procedure. The followings are advantages when this protocol is applied to authentication procedure; 1) using convenient and low-cost signatures, 2) being possible to verify users with spending only about second for signature processing and authentication, 3) one time on transmission for sign-in and verification and 4) getting user authentication with secret value at the same time.