Secure image encryption technique based on jigsaw transform and chaotic scrambling using digital image watermarking

Abstract

In this paper, an enhanced symmetric hybrid digital cryptosystem method based on jigsaw transform, digital domain watermarking using discrete cosine domain is proposed. To further enhance the security of the cryptosystem chaotic scrambling with sorting technique is used in order to create chaos. In proposed technique, watermark image is scrambled using jigsaw transform. The plain image is watermarked in discrete cosine domain using jigsawed watermark, then the resultant image is scrambled using chaotic scrambling algorithm. The security of system is strengthened by using additional parameters i.e. jigsaw technique, watermarking and chaotic scrambling using sorting thereby increasing complexity and key space that makes hard for the cyber hacker to derive the secret key to and retrieve the original image. The proposed cryptosystem is designed for 2D gray scale images. The proposed system is implemented digitally and watermark has good imperceptibility and robustness. The real strength of proposed methodology is investigated on the basis of different criteria using Matlab R2018a for experimental results. The computed values of mean squared error, correlation coefficient, peak signal-to-noise ratio, structural similarity Index, between recovered and the original image shows the efficiency of the suggested scheme. The experimental results and numerical simulations are given to highlight the key ruggedness and strength of proposed methodology. Therefore, the obtained simulation results demonstrate that the proposed cryptosystem is robust against known attacks, such as statistical attack (uniform histograms of different encrypted images, Correlation coefficients between plain and the encrypted image is as low as 0.01, brute force attack (large keyspace). Moreover, the ruggedness of the watermark is also proved against Geometric attack, Compression attack, statistical attack (correlation coefficients between the original and encrypted watermark is as low as 0.01) and gaussian noise attack, plaintext attack (secret keys are also encrypted thereby increasing robustness). The proposed method can be used in secure image transmission in healthcare, multimedia transmission etc.