Image Encryption Using Dynamic S-Box Substitution in the Wavelet Domain

A number of image encryption techniques have been proposed in recent years. These techniques use either spatial or transform domain image processing. A major challenge when designing an image encryption scheme is to conceal the pixel of the input image, especially when the image has a low texture region. Another problem is the encryption computational time. In this paper, these two issues are addressed. As the use of a single substitution box (S-box) to encrypt digital images does not work well for greater as well as a lower number of gray levels. To solve this problem, a new substitution technique using multiple S-boxes with dynamic substitution is proposed. In the second part of this paper, the proposed discrete wavelet transform based scheme is employed to reduce the encryption computational time. A number of parameters like correlation, entropy, energy, contrast, homogeneity, MSE and PSNR are used to analyze the quality of cipher images.