Flexible symmetric predicate encryption for data privacy in IoT environments

Internet of Things (IoT) applications are revolutionizing lifestyles and social management. In IoT environments, there is a need to deploy a large number of sensing devices, which are typically resource-constrained, with limited computational power and communication resources. Due to its open nature, IoT applications confront potential security and privacy risks in exchange for convenience, with data privacy being a significant concern. Predicate encryption (PE) offers a promising approach to address this concern. However, most PE schemes are public-key cryptosystems, which are more expensive compared to symmetric cryptography. These costs are burdensome for resource-constrained devices, especially when dealing with massive amounts of data. A recent study by Viet et al. (ESORICS'2022) introduced a symmetric PE scheme. However, this scheme's representation of attributes and predicates is limited. To overcome this limitation, we propose a flexible symmetric PE scheme. In the proposed scheme, predicates and attributes are represented using vectors. Tokens are related to predicates, while ciphertexts are associated with attributes. The encrypted message can be decrypted when the values of the predicate vector and attribute vector are pairwise unequal. This scheme enables fine-grained access control over encrypted data, ensuring that users with any attribute value in the vector embedded in the ciphertext cannot decrypt it. The security analysis demonstrates that the proposed scheme effectively protects data privacy. Additionally, performance evaluations indicate that the scheme is efficient, providing a lightweight solution for data privacy in IoT environments.