CCA-secure keyed-fully homomorphic encryption

• Main Authors: LAI, Junzuo, DENG, Robert H., MA, Changshe, SAKURAI, Kouichi, WENG, Jian
• Format: text
• Language: English
• Published: Institutional Knowledge at Singapore Management University 2016
• Subjects: Chosen ciphertext security; Fully homomorphic encryption; Convertible identity-based fully homomorphic encryption; Information Security
• Online Access: https://ink.library.smu.edu.sg/sis_research/3352; https://ink.library.smu.edu.sg/context/sis_research/article/4354/viewcontent/CCA_Secure_Keyed_Fully_Homomorphic_Encryption.pdf
• Institution: Singapore Management University

To simultaneously achieve CCA security and homomorphic property for encryption, Emura et al. introduced a new cryptographic primitive named keyed-homomorphic encryption, in which homomorphic ciphertext manipulations can only be performed by someone holding a devoted evaluation key which, by itself, does not enable decryption. A keyed-homomorphic encryption scheme should provide CCA2 security when the evaluation key is unavailable to the adversary and remain CCA1-secure when the evaluation key is exposed. While existing keyed-homomorphic encryption schemes only allow simple computations on encrypted data, our goal is to construct CCA-secure keyed-fully homomorphic encryption (keyed-FHE) capable of evaluating any functions on encrypted data with an evaluation key.In this paper, we first introduce a new primitive called convertible identity-based fully homomorphic encryption (IBFHE), which is an IBFHE with an additional transformation functionality, and define its security notions. Then, we present a generic construction of CCA-secure keyed-FHE from IND-sID-CPA-secure convertible IBFHE and strongly EUF-CMA-secure signature. Finally, we propose a concrete construction of IND-sID-CPA-secure convertible IBFHE, resulting in the first CCA-secure keyed-FHE scheme in the standard model.