Attribute-based encryption of LSSS access structure with expressive dynamic attributes based on consortium blockchain

Attribute-based encryption (ABE) allows users to encrypt and decrypt data based on attributes. It realizes fine-grained access control and can effectively solve the one-to-many encryption and decryption problem in open cloud application. Linear secret sharing scheme (LSSS) is the common access structure with a matrix on the attributes in ABE schemes, which may depict AND, OR, threshold operations, etc. However, LSSS access structure does not depict the complex and dynamic access policy of attributes, such as the complicated relationship of different attributes and the generation of dynamic attributes. It severely restricts the expansion of the practical application of ABE. Besides, there exists another problem; attribute authority (AA) in traditional ABE has a concentration of power and easily suffers from single-point failure or privacy leakage for being attacked or corrupted. Blockchain is a decentralized, tamper-free, traceable, and multi-party distributed database technology. Consortium blockchain (CB) is a partially centralized blockchain, whose openness is between the public blockchain and the private blockchain. In this paper, an ABE scheme on LSSS access structure with expressive dynamic attributes (EDA) based on CB (LSSS-EDA-ABE-CB) was proposed to resolve the above issues. EDA can construct the comprehensive attribute calculation expressions by conducting various operations, such as arithmetic operations, relational operations, and string operations. In virtue of the application of EDA, the proposed scheme can reconstruct new composite attributes to realize the dynamic adjustment of attributes. A partitioning method of EDA avoids one attribute appearing in two different EDA expressions. The CB technology enhanced the authority and trustworthiness of AA by openly recording AA’s attribute key distributions in CB transactions. The scheme in the paper was proven CPA-secure under the decision q-PBDHE assumption in standard model in the CB application environment. The scheme provides a more general data access policy and maintains the fine-grained character of ABE simultaneously. Finally, the security and performance analysis shows that the proposed scheme is secure and highly efficient.