Controllable forward secure identity-based encryption with equality test in privacy-preserving text similarity analysis

Text similarity measures have become increasingly pivotal in text -related research and applications, encompassing tasks such as information retrieval, text classification, document clustering. Unveiling the equality relationship between encrypted words is fundamental for ensuring privacypreserving text similarity. Identity -based encryption with equality test (IBEET) emerges as a promising solution for computing similarity over encrypted data in cloud environment. However, prevalent IBEET schemes often lack control over the lifespan of trapdoors, potentially leading to misuse and unauthorized disclosure of users' privacy. In this paper, we introduce a novel primitive known as controllable forward secure identity -based encryption with equality test (CFS-IBEET), designed to support both permanent trapdoor and temporary trapdoor. We present a concrete CFS-IBEET scheme based on bilinear pairing and conduct a comprehensive security analysis against two types of adversaries in random oracle model. The comprehensive performance evaluation shows that our CFS-IBEET scheme offers significant advantages of high efficiency of encryption, decryption, trapdoor generation and test algorithms as well as the guarantee of controllable forward security, showcasing its applicability for collaborative filtering recommendation system in E -commerce age.