Secure and robust color image watermarking scheme using partial homomorphic cryptosystem in ASWDR compressed domain

Abstract

The primary requirement of Secure Signal Processing (SSP) is to protect the identity and content of the transmitted data. To this end, various encryption techniques are employed. Homomorphic encryption in general and Paillier cryptosystem in particular is found to be one such algorithm suitable for image processing applications. It offers additive privacy homomorphism. In this paper, the Paillier encryption is employed for watermarking of six different compressed images in ASWDR (Adaptively Scanned Wavelet Difference Reduction) domain. The results are found to be encouraging both in terms of visual quality and the correlation coefficient values. The proposed watermarking scheme ensures robustness towards selected image processing attacks. The encryption parameters like NPCR (Number of Pixels Change Rate), UACI (Unified Average Changing Intensity) and Encryption Speed are evaluated. The proposed technique is compared with the one in SPIHT (Set Partitioning in Hierarchical Trees) domain. The experimental results obtained for ASWDR compression are better placed in comparison to those obtained by SPIHT compression. The proposed scheme is further analyzed in view of other recent schemes carried out by using RSA as an encryption tool in DWT domain. It is concluded that our proposed scheme is better placed in comparison to this scheme.