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

In this work, we analyze the security of the image encryption scheme proposed by Norouzi et al. (Multimedia Syst 20:45–64, 2014) [1]. The encryption scheme is based on a hash function and a two-round diffusion process applied to each 8 × 8 patches that compose the entire image. The analysis reveals the existence of a huge number of weak keys, allowing us to compute the effective key length, thus reducing the key space from 2512 to 2195 keys.