An Attribute-Based Searchable Encryption Scheme for Non-Monotonic Access Structure

Introduction

Recently, cloud computing has become a technology trend. Considering its flexibility, affordability and availability more and more organizations are shifting to cloud paradigm as it also unburdens them from the cumbersome task of data management. Although, cloud computing provides some innovative benefits yet this concept has also raised some privacy concerns as the data stored over third party cloud server cloud be misused. To address such concerns the concept of searchable encryption is introduced which not only provides data security by encrypting data but also facilitate seamless search over encrypted data (Zheng, et. al, 2017; Yu et al., 2018; Premkamal et al., 2020; Olakanmi et al., 2019;).

To develop a searchable encryption scheme using public key cryptographic primitives, there are several options like identity-based encryption (IBE), attribute-based encryption (ABE), homomorphic encryption (HE) and function encryption (FE) etc. In this paper, we have used attribute-based encryption scheme and particularly its ciphertext policy (CP) framework to build a searchable encryption scheme (CP-ABSE) for non-monotonic access structure. All the searchable encryption schemes based on ABE which have developed so far considers the access structure to be monotonic which does not support negative attributes. To support non-monotonic access structure, we have used a reduced ordered binary decision diagram (ROBDD) which efficiently supports all the Boolean operations (AND, OR, NOT) over attributes. The first attempt of using ordered binary decision diagram for the construction of ABE was done by Li et al. (2017). But the access structure represented by OBDD contains many redundant nodes which leads to increased computation cost. Hence, to reduce this cost we have used ROBDD which does not contain any redundant node and developed a CP-ABSE scheme which is efficient in terms of computational and storage cost.