Watermarking-Based Perceptual Hashing Search Over Encrypted Speech

Privacy-preserving search over encrypted speech has come into being an important and urgent research field in cloud storage. In this paper, a speech scrambling encryption method based on the Chua’s circuit chaotic system with memristor is proposed, and then a watermarking-based perceptual hashing search algorithm over encrypted speech is proposed based on the zero-crossing rate. In the proposed scheme, the zero-crossing rate is extracted from the digital speech to generate the perceptual hashing as the search digest. The perceptual hashing digest as a watermark is embedded into the encrypted speech signal. The search results can be obtained by matching and computing the normalized Hamming distance of the perceptual hashing digests between the search target and the extracted one without loading and decrypting the encrypted speech. Experimental results show that the proposed scheme has good discrimination, uniqueness, and perceptual robustness to common speech processing. In addition, the security and computation complexity are all satisfactory. The precision ratio is 100 %, and the recall ratio is more than 98 %.