Chosen-Ciphertext Secure Fuzzy Identity-Based Key Encapsulation Without ROM

The authors use hybrid encryption with Fuzzy Identity-Based Encryption (Fuzzy-IBE) schemes, and present the first and efficient Fuzzy Identity-Based Key Encapsulation Mechanism (Fuzzy-IB-KEM) schemes which are chosen-ciphertext secure (CCA) without random oracle in the selective-ID model. To achieve these goals, the authors consider Fuzzy-IBE schemes as consisting of separate Key and data Encapsulation Mechanisms (KEM-DEM), and then give the definition of Fuzzy-IB-KEM. The main idea is to enhance Sahai and Waters' "Large universe" construction, chosen-plaintext secure (CPA) Fuzzy-IBE, by adding some redundant information to the ciphertext to make it CCA-secure.