Double Security to Colour Images with DCT based Watermarking and Chaos based Encryption

Abstract

Copyright protection, content authentication, and other applications have benefited from color image watermarking. Color image encryption can be used to secure color images and prevent unauthorized access. To protect a color image’s copyright, the paper proposes a powerful watermarking in CIE La*b* space using a block-based DCT approach. Initially, the color image has been transformed to CIE La*b* space and the watermark has been implanted into the b* channel because any changes made to the b* channel are almost undetectable by the human eye. Before the watermark embedding the b* channel is sub-divided into non-overlapping blocks of size [8$\times$ 8]. By making sure that the difference among two middle band frequencies is +ve within the situation where the encoded value is 1, the algorithm embeds a single bit of the watermark which is binary into the DCT coefficients of each sub-block of the original image. After watermarking, Encryption is done on the watermarked image before sending it to the receiver. This paper proposed a novel cryptographic system by constructing a new chaotic map for producing the key. The proposed method has been compared with different current works, and the experimental outcome shows the superiority of the work presented in this paper.