PT-CPABKS – Secure Multi-User Keyword Search in Cloud Using Policy-Tiered CP-ABE with Optimized Indexing

Cloud computing faces several challenges in balancing data confidentiality with efficient retrieval and fine-grained access control. Conventional searchable encryption models enable keyword search but lack fine-grained access control, whereas traditional model-based solutions enforce policies at the cost of computational and communication overhead. To address these drawbacks, this manuscript proposes a Policy-Tiered Ciphertext-Policy Attribute-Based Keyword Search (PT-CPABKS) model that integrates Ciphertext-Policy Attribute-Based Encryption (CP-ABE), Advanced Encryption Standard with Galois/Counter Model (AES-GCM), and Public-key Encryption with Keyword Search (PEKS) with a policy-tiered index structure. The proposed model supports secure multi-keyword search, enforces fine-grained access policies, and optimizes the encryption, decryption, and key generation process by minimizing per-attribute operations. The incorporation of the policy-tiered index reduces redundant attribute processing and accelerates query processing. The proposed model achieved a competitive performance by obtaining an overall execution time of 544 ms when compared with CP-ABE and MRSE models.