Skip to Main content Skip to Navigation

Construction of multi-user cryptosystems

Abstract : This thesis considers a number of challenging aspects in multi-user cryptosystems such as traitor tracing, broadcast encryption, trace & revoke, and functional encryption. While a broadcast encryption scheme ensures the confidentiality of digital content against unauthorized users in the system, traitor tracing is an important tool to prevent authorized users from sharing decryption keys outside because if so, the tracer, with the help of the traitor tracing algorithm, will identify which user has disclosed information. In the first part, we focus on privacy in broadcast encryption schemes. We propose an anonymous broadcast encryption scheme in the bounded model (AnoBEB) whose security is based on the k-LWE assumption, which is a variant of the learning with errors (LWE) assumption. Our construction enjoys optimal efficiency (as efficient as LWE encryption) in the case where the number of users is bounded. In the second part, we integrate the proposed AnoBEB system with a robust identifiable parent property code (IPP) into a traceable scheme. Moreover, we achieve a very strong functionality scheme, also covering revocation and thus yielding the first trace & revoke scheme from a traceability code. Our construction becomes the most efficient trace & revoke scheme for standard black-box tracing in the bounded collusion model. The third part deals with traitor tracing algorithms for functional encryption. We introduce a new primitive, which is called {em traceable functional encryption}. We then formalize the notion of security and provide a concrete construction for {em traceable inner product functional encryption} (traceable IPFE). The proposed construction relies on pairings. It enjoys a high efficiency and achieves black-box confirmation. Finally, we recall the notion of {em revocable functional encryption}. We provide several pairing-based constructions for inner product functional encryption with short ciphertexts or decryption keys. We will then extend this notion to the {em fine-grained revocable functional encryption} and propose a candidate construction for fine-grained revocable inner product functional encryption.
Document type :
Complete list of metadata
Contributor : Abes Star :  Contact
Submitted on : Monday, May 31, 2021 - 6:16:08 PM
Last modification on : Tuesday, June 1, 2021 - 3:21:46 AM


Version validated by the jury (STAR)


  • HAL Id : tel-03243821, version 1



Xuan Thanh Do. Construction of multi-user cryptosystems. Cryptography and Security [cs.CR]. Université de Limoges; Đại học Quốc gia Thành phố Hồ Chí Minh (Thành phố Hồ Chí Minh), 2021. English. ⟨NNT : 2021LIMO0020⟩. ⟨tel-03243821⟩



Record views


Files downloads