New color image cryptosystem via SHA-512 and hybrid domain

Most current image encryption algorithms directly confuse and/or diffuse the image pixels only in spatial domain which results in reducing storage efficiency and making the cipher-image incompressible. In this paper, we introduce a new color image encryption scheme based on the hash function SHA-512, discrete wavelet transform (DWT) and chaotic maps with excellent performance. Combining with the plain-image and the secret keys, the SHA-512 is employed to generate the new keys. In the proposed algorithm, both the 2D-LASM and the 2D-SIMM are used to generate the keystreams, where the initial values and parameters are produced by the SHA-512 hash value. The single-level DWT is applied to decompose the plain-image into four image sub-bands. Then these sub-bands are shuffled, minified, reversed and swapped by the keystreams. The image after inverse discrete wavelet transform (IDWT) reconstruction is further divided and diffused using the keystreams (more than 2(349)) in spatial domain. Experimental results and performance analysis demonstrate the proposed scheme is an efficient, secure and robust encryption mechanism. Besides, the duration of the experiment was relatively short and required only 0.3628 s on average.