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Traceable multi-authority ciphertext-policy attribute-based encryption (CP-ABE) is a practical encryption method that can achieve user traceability and fine-grained access control simultaneously. However, existing traceable multi-authority CP-ABE schemes have two main limitations that prevent them from practical applications. First, these schemes only support small universe: the attributes must be fixed at system setup and the attribute space is restricted to polynomial size. Second, the schemes are either less expressive (the access policy is limited to "AND gates with wildcard") or inefficient (the system is constructed in composite order bilinear groups). To address these limitations, we present a traceable large universe multi-authority CP-ABE scheme, and further prove that it is statically secure in the random oracle model. Compared with existing traceable multi-authority CP-ABE schemes, the proposed scheme has four advantages. First, the attributes are not fixed at setup and the attribute universe is not bounded to polynomial size. Second, the ciphertext polices can be expressed as any monotone access structures. Third, the proposed scheme is constructed in prime order groups, which makes this scheme more efficient than those in composite order bilinear groups. Finally, the proposed scheme requires neither a central authority nor an identity table for tracing.

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Hidden policy ciphertext-policy attribute-based encryption with keyword search against keyword guessing attack SCIENCE CHINA Information Sciences 60, 052105 (2017); Ciphertext-policy attribute-based proxy re-encryption via constrained PRFs SCIENCE CHINA Information Sciences 64, 169301 (2021); Efficient large-universe multi-authority ciphertext-policy attribute-based encryption with white-box traceability SCIENCE CHINA Information Sciences 61, 032102 (2018); Accountable authority key policy attribute-based encryption SCIENCE CHINA Information Sciences 55, 1631 (2012); Adaptively secure multi-authority attribute-based encryption with verifiable outsourced decryption SCIENCE CHINA Information Sciences 59, 099105 (2016);. RESEARCH PAPER. SCIENCE CHINA Information Sciences

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In order to realize attribute‐based data sharing in cloud computing, multi‐authority attribute‐based encryption (MA‐ABE) is extremely attractive. However, most of the existing MA‐ABE schemes cannot support a fully large attribute universe and are not suitable for resource‐constrained mobile data owners in that the computation cost in secret key generation and encryption is extremely heavy. To tackle the earlier challenges, we propose an online/offline MA‐ABE scheme, which realizes both the online/offline secret key generation and the online/offline encryption while supporting a fully large attribute universe. In the offline phase, one global‐identity authority and multiple attribute authorities do the majority of the work to issue attribute secret keys before knowing users' global identity and attributes. The data owner can perform most of the encryption computation tasks before knowing the actual message and access structure. Furthermore, the online phase can rapidly assemble the final decryption key and ciphertexts when related specifications become known. Particularly, global‐identity authority and attribute authorities need not to cooperate in the whole process. Our online/offline MA‐ABE scheme allows the access policies encoded in linear secret sharing schemes. The formal selective security proof and extensive performance analysis indicate that our scheme is very suitable for data sharing in mobile cloud computing. Copyright © 2016 John Wiley & Sons, Ltd.

With the rapid development of big data and Internet of things (IOT), the number of networking devices and data volume are increasing dramatically. Fog computing, which extends cloud computing to the edge of the network can effectively solve the bottleneck problems of data transmission and data storage. However, security and privacy challenges are also arising in the fog-cloud computing environment. Ciphertext-policy attribute-based encryption (CP-ABE) can be adopted to realize data access control in fog-cloud computing systems. In this paper, we propose a verifiable outsourced multi-authority access control scheme, named VO-MAACS. In our construction, most encryption and decryption computations are outsourced to fog devices and the computation results can be verified by using our verification method. Meanwhile, to address the revocation issue, we design an efficient user and attribute revocation method for it. Finally, analysis and simulation results show that our scheme is both secure and highly efficient.