A novel image encryption based on hash function with only two-round diffusion process

Reducing the Key Space of an Image Encryption Scheme Based on Two-Round Diffusion Process

“…However, the most-right column and bottom row must be padded to get a total number of rows and columns multiple of 8. Since the authors in [1] use 256 × 256 images for experimental purposes, we also consider, for simplicity reasons, 256 × 256 images to perform the security evaluation without loss of generality. We use the notations in [1].…”

“…The image encryption scheme proposed by Norouzi et al [1] is a symmetric scheme based on the application of two rounds of a diffusion process that is applied to each 8 × 8 patch composing the entire image. It uses a 512 bits secret key and it is designed for 256 grayscale images (grayscale images with a bit depth of 8 bits/pixel), of any size and aspect ratio.…”

“…Although it has been proposed for encryption, the operations defined over the 8 × 8 patches composing the entire image could also be applied for identification, since the encryption process is strongly dependent of the image content. However, although the scheme presents a good behavior, as the authors claim and justify in [1], we have analyzed the security of this scheme focusing our attention in the key space, since 512 bits secret keys are used, and no particular study appears regarding this aspect. The analysis we have performed is mainly applied to find weak and/or invalid keys.…”

“…Section 2 describes the encryption in [1]. Section 3 deals with the characterization of weak and invalid keys, allowing the computation, in Sect.…”

“…In 2014, Norouzi et al [1] propose an image encryption scheme that combines a hash function with two rounds of a diffusion process. Although it has been proposed for encryption, the operations defined over the 8 × 8 patches composing the entire image could also be applied for identification, since the encryption process is strongly dependent of the image content.…”