• Honam Mathematical Journal
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• v.44 no.2
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• pp.296-309
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• 2022

In this paper, we establish the Fricke Group Γ_F (N) which is a new special group of Non-Euclidean Crystallograhic (NEC) group. We obtain this group whose congruence subgroup Γ₀(N) is expanded with Fricke reflection $F(z)={\frac{1}{N{\bar{z}}}}$. Then, we research and calculate the structure of signature and fundamental domain of this group. And then, we calculate the number of boundary components in the signature for this group. Finally, we find the 2, 3, ∞ valued link periods of these boundary components with the H. Jaffee technique.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.11 no.11
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• pp.5625-5641
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• 2017

Certificateless public key cryptography resolves the certificate management problem in traditional public key cryptography and the key escrow problem in identity-based cryptography. In recent years, some good results have been achieved in speeding up the computation of bilinear pairing. However, the computation cost of the pairing is much higher than that of the scalar multiplication over the elliptic curve group. Therefore, it is still significant to design cryptosystem without pairing operations. A multi-signer universal designated multi-verifier signature scheme allows a set of signers to cooperatively generate a public verifiable signature, the signature holder then can propose a new signature such that only the designated set of verifiers can verify it. Multi-signer universal designated multi-verifier signatures are suitable in many different practical applications such as electronic tenders, electronic voting and electronic auctions. In this paper, we propose a certificateless multi-signer universal designated multi-verifier signature scheme and prove the security in the random oracle model. Our scheme does not use pairing operation. To the best of our knowledge, our scheme is the first certificateless multi-signer universal designated multi-verifier signature scheme.

• Bulletin of the Korean Chemical Society
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• v.32 no.4
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• pp.1183-1186
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• 2011

The unique Br signature was utilized for C-terminal amino acid sequencing of model peptides. C-terminal carboxyl group was selectively derivatized in peptides, containing side chain carboxyl group, using 1-ethyl-3-[3-dimethylaminopropyl]carbodiimide hydrochloride (EDC) and Br was introduced using 4-bromophenylhydrazine hydrochloride (BPH) in a one pot reaction. Matrix-assisted laser desorption/ionization (MALDI) time-of-flight (TOF) tandem mass spectra were obtained carrying the Br signature in the y-series ions. The Br signature facilitated C-terminal sequencing and discrimination of C-terminal carboxyl groups in the free acid and amide forms.

• Journal of KIISE:Computer Systems and Theory
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• v.31 no.8
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• pp.465-472
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• 2004

Proxy signatures is a signature scheme that an original signer delegates one's signature capability to a proxy signer, and then the proxy signer creates a signature on behalf of the original signer. Delegation of authority is a common practice in the real world, in particular, it happens naturally in hierarchical groups such as company, bank and army, etc. In this paper, we propose a new dynamic multi-proxy signature scheme allowing repetitive delegations in a hierarchical group. We adopt multi-proxy signatures to enhance the security of proxy signature. In multi-proxy signatures, plural proxy signers can generate a valid proxy signature collectively on behalf of one original signer. In our scheme, the proxy group is not fixed but constructed dynamically according to some situations. Delegations are processed from higher level to lower level in the hierarchy using delegation tickets. When the original signer wants to delegate one's signature authority, the original signer generates a delegation ticket based on secret sharing and Diffie-Hellman problems. The delegation ticket is shared among proxy signers and then all the proxy signers can generate a valid proxy signature collectively by reconstructing the original signer's delegation ticket. If a certain proxy signer can not attend the proxy signature generating protocol, the proxy signer can also delegate repetitively his partial signature authority to the lower level participants, and then the proxies are constructed dynamically.

• Journal of the Chungcheong Mathematical Society
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• v.20 no.4
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• pp.355-366
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• 2007

In this paper, we propose a new blind group identification protocol and a hidden group signature protocol as its application. These protocols involve many provers and one verifier such that (1) the statement of all the provers are proved simultaneously, (2) and also all the provers using computationally limited devices (e.g. smart cards) have no need of computing the bilinear pairings, (3) but only the verifier uses the bilinear pairings. A. Saxena et al. proposed a two-round blind (group) identification protocol in 2005 using the bilinear pairings. But it reveals weakness in the active-intruder attack, and all the provers as well as the verifier must have devices computing bilinear pairings. Comparing their results, our protocol is secure from the active-intruder attack and has more fit for smart cards. In particular, it is secure under only the assumption of the hardness of the Discrete-Logarithm Problem in bilinear groups.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.14 no.1
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• pp.299-322
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• 2020

Vehicular ad hoc networks (VANETs) enable wireless communication between vehicles and roadside infrastructure to provide a safer and more efficient driving environment. However, due to VANETs wireless nature, vehicles are exposed to several security attacks when they join the network. In order to protect VANETs against misbehaviours, one of the vital security requirements is to revoke the misbehaved vehicles from the network. Some existing revocation protocols have been proposed to enhance security in VANETs. However, most of the protocols do not efficiently address revocation issues associated with group signature-based schemes. In this paper, we address the problem by constructing a revocation protocol particularly for group signatures in VANETs. We show that this protocol can be securely and efficiently solve the issue of revocation in group signature schemes. The theoretical analysis and simulation results demonstrate our work is secure against adversaries and achieves performance efficiency and scalability.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.13 no.2
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• pp.1003-1019
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• 2019

Threshold ring signature scheme enables any t entities from N ring members to spontaneously generate a publicly verifiable t-out-of-N signature anonymously. The verifier is convinced that the signature is indeed generated by at least t users from the claimed group, but he cannot tell them apart. Threshold ring signatures are significant for ad-hoc groups such as mobile ad-hoc networks. Based on the lattice-based ring signature proposed by Melchor et al. at AFRICRYPT'13, this work presents a lattice-based threshold ring signature scheme, employing the technique of message block sharing proposed by Choi and Kim. Besides, in order to avoid the system parameter setup problems, we proposed a message processing technique called "pad-then-permute", to pre-process the message before blocking the message, thus making the threshold ring signature scheme more flexible. Our threshold ring signature scheme has several advantages: inherits the quantum immunity from the lattice structure; has considerably short signature and almost no signature size increase with the threshold value; provable to be correct, efficient, indistinguishable source hiding, and unforgeable.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.14 no.11
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• pp.4573-4594
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• 2020

Announcement protocol in Internet of Vehicles (IoV) is an intelligent application to enhance public safety, alleviate traffic jams and improve transportation quality. It requires communication between vehicles, roadside units and pedestrian to disseminate safety-related messages. However, as vehicles connected to internet, it makes them accessible globally to a potential adversary. Safety-related application requires a message to be reliable, however it may intrude the privacy of a vehicle. Contrarily, if some misbehaviour emerges, the malicious vehicles must be able to traceable and revoke from the network. This is a contradiction between privacy and accountability since the privacy of a user should be preserved. For a secure communication among intelligent entities, we propose a novel announcement protocol in IoV using group signature. To the best of our knowledge, our work is the first comprehensive construction of an announcement protocol in IoV that deploys group signature. We show that our protocol efficiently solves these conflicting security requirements of message reliability, privacy and accountability using 5G communication channel. The performance analysis and simulation results signify our work achieves performance efficiency in IoV communication.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.14 no.1
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• pp.3-13
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• 2004

E-Commerce is suddenly spreading in a daily life. A rights trading system is a system that circulates digital-tickets such as plane tickets, software license, coupon. There are two main approaches so far account-based and smart-card based systems. The NTT Proposed FlexToken, a new smart card based copy prevention scheme for digital rights. They Proposed using pseudonymous self certified keys of Petersen and Horster in order to ensure anonymity of users. However. Petersen and Holster's scheme should register a pseudonymous key pair at TTP (One-time) every time so that users create the signature which is satisfied with unlinkability property In this paper, we propose a new anonymous rights trading system using group signature. This paper has a meaning having applied to digital rights trading system an efficient smart card based group signature.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.15 no.3
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• pp.109-114
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• 2005

On the research for constructing secure group-oriented proxy signature schemes, there are several proposals of threshold proxy signature schemes which combine the notions of proxy signature with threshold signature. Recently, Hsu and Wu proposed a threshold proxy signature scheme which uses a self-certified public key based on discrete logarithm problem. In this paper, we show that this scheme is vulnerable to original signer's forgery attack. So our attack provides the evidence that this scheme does not satisfy nonrepudiation property.