Abstract
Nonlinear dynamic cryptosystems or chaos-based cryptosystems have been attracting a large amount of research since 1990. The critical aspect of cryptography is to face the growth of communication and to achieve the design of fast and secure cryptosystems. In this paper, we introduce three versions of a chaos-based cryptosystem based on a similar structure of the Zhang and Fridrich cryptosystems. Each version is composed of two layers: a confusion layer and a diffusion layer. The confusion layer is achieved by using a modified 2-D cat map to overcome the fixed-point problem and some other weaknesses, and also to increase the dynamic key space. The 32-bit logistic map is used as a diffusion layer for the first version, which is more robust than using it in 8-bit. In the other versions, the logistic map is replaced by a modified Finite Skew Tent Map (FSTM) for three reasons: to increase the nonlinearity properties of the diffusion layer, to overcome the fixed-point problem, and to increase the dynamic key space. Finally, all versions of the proposed cryptosystem are more resistant against known attacks and faster than Zhang cryptosystems. Moreover, the dynamic key space is much larger than the one used in Zhang cryptosystems. Performance and security analysis prove that the proposed cryptosystems are suitable for securing real-time applications.
Highlights
Today, chaos-based encryption algorithms have been widely used in image and video encryption systems [Hamidouche et al, 2015]
Confusion property aims to make the statistical relationship between the cipher image and the secret key as complex and involved as possible, whereas the diffusion property aims to make the statistical relationship between the plain image and the cipher image as complex and involved as possible
Since the fixed-point problem was not solved in the 2-D cat map, Baker or standard maps were used in the Fridrich model, and so the cipher of the first plain pixel of any image will remain in the first position
Summary
Chaos-based encryption algorithms have been widely used in image and video encryption systems [Hamidouche et al, 2015]. Any cryptosystem must achieve diffusion and confusion effects, in order to be robust and secure against several types of attacks. The nonlinear process is achieved by a nonlinear feedback register In this way, Masuda et al [2006] considered two classes of chaotic finite-state maps: key-dependent chaotic S-boxes and chaotic mixing transformation. Fast and secure cryptosystems were proposed: Chen et al [2015] have proposed a fast chaos-based image encryption scheme using a dynamic state variables selection mechanism. Murillo-Escobar et al [2015] have proposed a color image encryption algorithm based on total plain image characteristics, and 1-D logistic map with optimized distribution. They claim that their structure can be implemented in real-time applications.
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