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dc.contributorDepartment of Computingen_US
dc.contributor.advisorGao, Shang (COMP)en_US
dc.contributor.advisorXiao, Bin (COMP)en_US
dc.creatorChen, Xue-
dc.identifier.urihttps://theses.lib.polyu.edu.hk/handle/200/13212-
dc.languageEnglishen_US
dc.publisherHong Kong Polytechnic Universityen_US
dc.rightsAll rights reserveden_US
dc.titleRing signature constructions and applications based on discrete logarithm and lattice assumptionsen_US
dcterms.abstractRing signatures, in comparison to most digital signature schemes, have garnered significant attention due to their strong anonymity alongside unforgeability. The compelling attributes of ring signatures have garnered substantial scholarly interest in the field of security and privacy. Consistent with this trend, ring signatures are widely applied across a broad spectrum of privacy-preserving scenarios.en_US
dcterms.abstractTherefore, this thesis is dedicated to the study of ring signature constructions and applications, encompassing Discrete Logarithm (DL)-based and lattice-based ring signatures.en_US
dcterms.abstractDL-based Ring Signature Construction and Applicationen_US
dcterms.abstractCurrently, various Σ-based standard signature schemes serve a wide range of privacy-preserving scenarios. However, these schemes are prone to leakage of the signer’s identity information due to a lack of consideration for user anonymity. To address this issue, the ring signature is considered a desirable alternative, as it allows any ring member to generate a signature on a message without revealing the signer’s identity. But to our best knowledge, in the aforementioned privacy-preserving scheme, replac­ing the original standard signature with existing (non-standardized) ring signatures would result in the inability to maintain the original properties. Thus, proposing a general mechanism to convert a standardized Σ-based signature to a ring signature is far-reaching.en_US
dcterms.abstractThe first contribution of this thesis is that we propose a general construction for con­verting Σ-based signatures into ring signatures. To achieve this, we initially introduce a Σ-based general model, providing a generic transformation to convert existing Σ-based signatures into a Σ-protocol form. Subsequently, we incorporate our redesigned one-out-of-many relation within our general model and proceed to devise a general ring signature leveraging on the Fiat-Shamir heuristic. Furthermore, to enhance the efficiency, we employ the Bulletproofs folding technique, enabling the attainment of the logarithmic size ring signature. To showcase the broad range of uses for our gen­eral construction, we provide four prominent signatures as case studies. Ultimately, we conduct a security analysis and experimental evaluation of our proposed ring sig­nature. The signing and verifying times are 0.38 - 0.83 times and 0.23 - 0.65 times compared to existing ring signatures, respectively. Our general ring signature exhibits the lowest storage overhead compared to others.en_US
dcterms.abstractLattice-based Ring Signature Construction and Applicationen_US
dcterms.abstractRing signatures have been extensively researched for Cloud-assisted Electronic Medi­cal Records (EMRs) sharing, aiming to address the challenge of “medical information silos” while safeguarding the privacy of patients’ personal information and the security of EMRs. However, most existing EMRs sharing systems that utilize ring signatures are vulnerable to quantum attacks, posing a severe challenge. To alleviate this is­sue, some studies have been conducted on lattice-based ring signatures. Nevertheless, there still exist two challenges. Firstly, current schemes fail to verify if multiple EMRs come from the same signer, undermining e-health reliability. Additionally, adversaries can exploit weaknesses in the network security of signers’ secret keys to forge signa­tures. Therefore, it is essential to design a lattice-based ring signature for the EMRs sharing system to tackle the mentioned challenges.en_US
dcterms.abstractThe second contribution is that we propose an efficient lattice-based linkable ring signature (LLRS) for EMRs sharing to ensure patient privacy through anonymity, EMRs security through unforgeability, and checking the linkability for multiple sig­natures. We then present an enhancement scheme, called FS-LLRS, to additionally offer forward security, ensuring the security of previous ring signatures even if the current key leaked. To achieve this, we introduce a binary tree to divide time and leverage the ExtBasis algorithm to update the secret keys periodically. Ultimately, we conduct a rigorous security analysis and compare our primitives with prior arts. In computational cost, the best performance of our LLRS and FS-LLRS schemes are just 0.17 and 0.34 times compared to others, respectively. Our LLRS scheme only incurs 0.08 times the communication overhead of others.en_US
dcterms.extentxiii, 113 pages : color illustrationsen_US
dcterms.isPartOfPolyU Electronic Thesesen_US
dcterms.issued2024en_US
dcterms.educationalLevelM.Phil.en_US
dcterms.educationalLevelAll Masteren_US
dcterms.LCSHDigital signaturesen_US
dcterms.LCSHComputer securityen_US
dcterms.LCSHCryptographyen_US
dcterms.LCSHHong Kong Polytechnic University -- Dissertationsen_US
dcterms.accessRightsopen accessen_US

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