Privacy protection of digital speech based on homomorphic encryption

Abstract

This paper presents a digital speech encryption scheme based on homomorphic encryption, which uses a symmetrical key cryptosystem (MORE-method) with probabilistic statistics and fully homomorphic properties to encrypt speech signals. In the proposed scheme, each sample of speech signal is firstly multiplied one weight, and then encrypted, the normalization is exploited to make the data expend lossy compression. Finally, a recombination method of the cipher-text is proposed to obtain the corresponding speech cipher-text with good performances. Experimental results show that the proposed scheme is homomorphism, which has strong diffusibility and a large key-space. What’s more, it is robustness to statistical analysis attacks, decreased the residual intelligibility as small as possible. Moreover, the encrypted speech can be decrypted completely. Compared with two dimensional chaotic and Paillier cryptosystem, the proposed scheme is more security and lower complexity, so the proposed scheme especially meets the sensitive speech security in the cloud.