PHP-CABE: Partially Hidden Policy Comparable Attribute-Based Encryption with Computation Outsourcing

With the widespread application of Internet of Things (IoT) devices, an increasing number of edge users are utilizing these devices to collect various types of data, such as health data and e-government data. To achieve convenient and efficient data interconnection, massive user data is stored in central cloud service providers (CSPs). However, this storage method poses new challenges for user privacy and data security protection. Cipher-text-Policy Attribute-Based Encryption (CPABE) schemes are effective methods for achieving fine-grained access control in cloud storage scenarios. However, existing CPABE methods cannot provide flexible access control policies, and access policies exposed in public cloud environments also threaten data security. Based on this, we propose a Partially Hidden Policy with Comparable Attributes-Based Encryption (PHP-CABE) scheme that combines computation outsourcing. To realize access control policies for comparable attributes, we perform special encoding of the numerical ranges of comparable attributes. Simultaneously, to achieve system flexibility while safeguarding user privacy, we design a partial hiding mechanism tailored for this flexible encoding scheme. Additionally, we outsource most of the attribute verification and decryption computations to the CSP. We rigorously prove that the PHP-CABE scheme is secure and demonstrate our scheme’s high efficiency via performance analysis.