One-Encryption Multilevel Output: Attribute-Driven Dynamic Differential Privacy Binding in CP-ABE

Existing ciphertext-policy attribute-based encryption (CP-ABE) schemes primarily determine who is authorized to decrypt, yet they do not guarantee privacy once ciphertexts are decrypted. Differential privacy (DP) protects released results through noise perturbation, but its privacy budget ε is usually configured independently of access attributes, which hinders fine-grained multi-level privacy protection in hierarchical IoT data sharing. To bridge this gap, a single-encryption multi-level output framework is proposed, where an attribute-driven noise key derivation function establishes a chained mapping among access attributes, noise keys, and noise intensity, enabling one ciphertext to yield differently perturbed outputs at distinct ε levels for users with varying privileges. Authenticated encryption with associated data (AEAD) is further incorporated to enforce strong cross-version and cross-policy binding, preventing low-noise outputs from being forged or replayed across authorization levels. Theoretical analysis proves that the framework achieves IND-CPA confidentiality, ε-differential privacy and tamper-resistant noise binding, while experiments demonstrate superior privacy–utility trade-offs, multi-level adaptability, and tamper resistance, indicating that the framework is well suited for practical IoT data sharing scenarios.