## 1 Introduction  
With rapid development of digital communication and computer networks, it becomes feasible to guarantee transmission security against malicious tampering or copyright infringement. Information security plays a critical role in data transmission. Watermarking, cryptography, or steganography could protect transmitted information. Since digital images are easy to modify, a secure authentication system is needed to ensure that no tampering is made. Digital watermarking is a simple way to protect intellectual property. Watermarking schemes should be designed to provide integrity authentication for digital images. Chaotic watermarks are better alternatives than pseudorandom signals that possess white spectra. The chaotic theory has been widely applied in the fields of cryptography for information security and varying feature representation. An encryption scheme based on chaotic logistic maps is proposed for secure transmission. A secret key of 80 bits and two chaotic logistic maps has been employed. To enhance the robustness of ciphering against various attacks, the secret key was updated after encrypting each block of sixteen pixels of the source image. The statistical analysis and key sensitivity tests demonstrated that the encryption scheme provided an efficient and secure way for real-time image processing [1; 2; 3]. Applications of both deterministic and chaotic digital image cryptosystems in the spatial domain and frequency domain have been introduced. The results of these applications were compared in both qualitative and quantitative points of view, using symmetric deterministic and chaotic encryption schemes. The 64-bit block ciphers were proceeded in secret key cryptography. Differential scrambling was applied in both cases where Exclusive OR operations between the plaintext and either deterministic key or chaotic key were made. Outcomes were evaluated using both qualitative and quantitative analysis. The chaotic scheme was shown to be better than deterministic schemes against entropy attack and ciphertext attack [4]. In the present paper, a pixel shuffling method is proposed for image encryption. Based on the unpredictable characteristics of chaotic systems, the chaotic sequences are used as encryption codes to implement digital image encryption with high security. The method, covering four differential chaotic systems and pixel shuffling, can fully banish outlines of the host image, disorder distributive characteristics of intensity levels, and dramatically reduce the probability of exhaustive attacks. The scheme has great encryption performance that reaches high confidential security [5]. A double image encryption method has been proposed by utilizing discrete multiple-parameter fractional Fourier transform and chaotic maps. The image scrambled by one chaotic map is encoded into the amplitude of complex signals. The complex signal, multiplied by another chaotic random phase mask, is encrypted by multi-parameter fractional Discrete Fourier Transform (DFT). Parameters in chaotic maps serve as the keys of this encryption scheme [6]. In another study an efficient scheme was applied for embedding the compressed binary watermark logo on a basis of based integer wavelet-based watermarking. The Peak Signal to Noise Ratio (PSNR) and Normalized Correlation Coefficient (NCC) analyses indicated a better performance than existing methods on protecting document image contents [7]. Recently, an overview of digital video watermarking has thoroughly summarized current state of the art techniques for 3D video watermarking. Watermarking, in the frequency domain, was one of their main areas of focus, where DFT, Discrete Sine Transform (DST), Discrete Cosine Transform (DCT), and Discrete Wavelet Transform (DWT) were highlighted. The DFT function produced a set of complex coefficients covering real and imaginary parts at each frequency, with translational invariance of the magnitude, where the DST function focuses on its imaginary coefficients and the DCT function focuses on its real coefficients.