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Proxy encryption delegates workload to a proxy server, reducing user-side computation and communication. 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security assumption are used?",{"text":72,"@type":64},"The scheme is built using lattice-based cryptography and its security is based on the D-RLWE assumption.","https://schema.org",{"og:url":32,"og:type":75,"og:title":10,"og:site_name":45,"og:description":12},"article",{"robots":77,"canonical":32},"index,follow",{"doc_id":79,"site_id":7},203828,1788564181,{"code":4,"msg":82,"data":83},"success",[84,88,92,96,101,106,110,114,119,122,126],{"id":22,"doc_module":4,"doc_module_name":25,"category_name":85,"show_sort_weight":86,"slug":87},"Story & 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Kai-Him Lam, Ming-Feng Tsai, Wei-Cheng Hung, and Chun-I  \nFan†  \nNational Sun Yat-sen University, Kaohsiung, Taiwan  \n{zhuanges, parktasi, [will900329](will900329}@gmail.com)[}](will900329}@gmail.com)[@gmail.com](will900329}@gmail.com) , [s93681147@yahoo.com.hk](s93681147@yahoo.com.hk) ,  \n[cifan@mail.cse.nsysu.edu.tw](cifan@mail.cse.nsysu.edu.tw)  \nAbstract  \nThe rapid advancement of science and technology has led to the emergence of quantum computers, posing a significant threat to traditional encryption schemes. As a result, thereis a pressing need to develop encryption methods that can withstand quantum attacks. This thesis proposes an IBE scheme with a time-invalidation mechanism to revoke expired ciphertext. What sets this scheme apart is its support for multi-keyword search, AND/OR operations and proxy encryption to delegate encryption workload to a proxy server, reducing the computing load on the user side. This IBE scheme eliminates the need for certificates, reducing computation and transmission costs. The proposed scheme’s security is based on the D-RLWE assumption. We also validate the proposed scheme through implementation.  \n1 Introduction  \nThe rise of cloud computing has heightened concerns regarding the privacy and security of sensitive data stored in third-party environments. While cloud services offer scalability and flexibility in data management, they also introduce risks such as unauthorized access, data breaches, and privacy violations. Traditional encryption techniques are inadequate for handling the complex access control demands inherent in collaborative data sharing. As a result, more advanced cryptographic solutions are required.  \nFunctional encryption addresses this need by enabling fine-grained access control, allowing users to decrypt only specific data elements based on predefined privileges. This is particularly valuable in collaborative scenarios, such as cloud environments, where multiple users require access to different subsets of encrypted data. Functional encryption thereby enhances data confidentiality and minimizes unnecessary exposure.  \nTo simplify key management, Shamir introduced identity-based encryption (IBE) in 1984 [10], allowing encryption keys to be derived directly from user identities. This approach eliminates the need for certificates and streamlines key distribution. Later, Blaze et al. proposed proxy re-encryption (PRE) [4], which addresses the inefficiencies of traditional encryption in data sharing. PRE enables ciphertexts to be re-encrypted for a new recipient without decrypting the original content, reducing the risk of data leakage and improving efficiency. Building upon this, Green and Ateniese introduced identity-based proxy re-encryption (IB-PRE) [6], combining the benefits of IBE and PRE to further enhance secure data sharing.  \n∗ Proceedings of the 9th International Conference on Mobile Internet Security (MobiSec’25), Article No. 22, December 16-18, 2025, Sapporo, Japan. © The copyright of this paper remains with the author(s) .  \n†Corresponding author  \nMulti-Keyword Searchable Identity-Based Proxy Re-Encryption  \nwith Validity Period Control from Lattices Zhuang et al.  \nSearchable encryption (SE) addresses the challenge of querying encrypted data without requiring decryption. Traditional methods often necessitate downloading and decrypting entire datasets for local search, leading to high communication and computation overhead. Song, Wagner, and Perrig introduced the first SE scheme [11] to perform keyword searches over encrypted data securely. Subsequently, Boneh et al. proposed a public-key SE scheme [5], allowing a cloud server (CS) to search ciphertexts using trapdoors without learning the plaintext or the search query.  \nData validity control further strengthens SE by enforcing temporal access policies. By restricting access to a pr","cbCaiiwBwQ48QfmW","https://ap.wps.com/l/cbCaiiwBwQ48QfmW","pdf",797717,"English","# Abstract\n# 1 Introduction\n## Functional encryption and access control\n## Identity-based encryption and proxy re-encryption\n# Multi-Keyword Searchable Identity-Based Proxy Re-Encryption\n## Searchable encryption and trapdoors\n## Data validity control\n## Lattice-based cryptography background\n# 1.1 Contributions","[{\"question\":\"What problem does the thesis address in cloud-based data sharing?\",\"answer\":\"It addresses privacy and security risks in third-party environments and the need for advanced cryptographic mechanisms to support fine-grained access control in collaborative scenarios.\"},{\"question\":\"How does the proposed scheme handle time-based access restrictions?\",\"answer\":\"It embeds a validity period into ciphertexts using a time-invalidation mechanism, so expired ciphertext becomes inaccessible or is automatically invalidated.\"},{\"question\":\"What cryptographic foundations and security assumption are used?\",\"answer\":\"The scheme is built using lattice-based cryptography and its security is based on the D-RLWE assumption.\"}]","Multi-Keyword Searchable Identity-Based Proxy Re-Encryption with Validity Period Control from Lattices - Thesis Abstract | PDF"]