A Non-adaptive Partial Encryption of Grayscale Images based on Chaos

AbstractResearch papers published in recent times have focused towards different kinds of image encryption techniques. Image encryption based on Chaos became very popular for cryptography since properties of Chaos are related to two basic properties of good cipher-Confusion and Diffusion. In this paper, A Non-adaptive Partial Encryption of Grayscale Images Based on Chaoshas been proposed. In Partial encryption speed and time is the main factor. We decompose the original grayscale image into its corresponding binary eight bit planes then encrypted using couple tent map based pseudorandom binary number generator (PRBNG). The four significant bit planes, determined by 5% level of significance on contribution of a bit-plane in determination of a pixel value, are encrypted using keys which are obtained by applying the recurrence relation of tent map based PRBNG. Then the four insignificant bit planes along with encrypted significant bit planes are combined to form the final cipher image. In order to evaluate performance, the proposed algorithm was measured through a series of tests to measure the security and effectiveness of the proposed algorithm. These tests includes visual test through histogram analysis, measures of central tendency and dispersion, correlation-coefficient analysis, key sensitivity test, key space analysis, information entropy test, Measurement of Encryption Quality – MSE, PSNR, NPCR, UACI. Experimental results show that the new cipher has satisfactory security and efficient

Periodicity of chaotic trajectories in realizations of finite computer precisions and its implication in chaos communications

Fundamental problems of periodicity and transient process to periodicity of chaotic trajectories in computer realization with finite computation precision is investigated by taking single and coupled Logistic maps as examples. Empirical power law relations of the period and transient iterations with the computation precisions and the sizes of coupled systems are obtained. For each computation we always find, by randomly choosing initial conditions, a single dominant periodic trajectory which is realized with major portion of probability. These understandings are useful for possible applications of chaos, e.g., chaotic cryptography in secure communication.Comment: 10 pages, 3 figures, 2 table

Asymptotic expansions for the escape rate of stochastically perturbed unimodal maps

The escape rate of a stochastic dynamical system can be found as an expansion in powers of the noise strength. In previous work the coefficients of such an expansion for a one-dimensional map were fitted to a general form containing a few parameters. These parameters were found to be related to the fractal structure of the repeller of the system. The parameter alpha, the "noise dimension", remains to be interpreted. This report presents new data for alpha showing that the relation to the dimensions is more complicated than predicted in earlier work and oscillates as a function of the map parameter, in contrast to other dimension-like quantities.Comment: 7 pages, 5 figure