Homomorphic Authenticated Encryption Secure Against Chosen-Ciphertext Attack.

Abstract

Abstract. We study homomorphic authenticated encryption, where privacy and authenticity of data are protected simultaneously. We define homomorphic versions of various security notions for privacy and authenticity, and investigate relations between them. In particular, we show that it is possible to give a natural definition of IND-CCA for homomorphic authenticated encryption, unlike the case of homomorphic encryption. Also, we construct a homomorphic authenticated encryption scheme sup-porting arithmetic circuits, which is chosen-ciphertext secure both for privacy and authenticity. Our scheme is based on the error-free approximate GCD assumption. Key words: homomorphic authenticated encryption, homomorphic MAC, homomorphic encryption, approximate GCD assumption 1