RESUMO
Despite that many image encryption systems based on chaotic or hyperchaotic systems have been proposed to protect different kinds of information, it has been crucial to achieve as much security as possible in such systems. In this sense, we numerically implement a known image encryption system with some variants, making special emphasis when two operations are considered in the scrambling stage. The variants of such an encryption system are based on some hyperchaotic systems, which generated some substitution boxes and the keys of the system. With the aim to have a more complete evaluation, some internal stages of the image encryption scheme have been evaluated by using common statistical tests, and also the scaling behavior of the encrypted images has been calculated by means of a two-dimensional detrended fluctuation analysis (2D-DFA). Our results show that the image encryption systems that include two operations or transformations in the scrambling stage present a better performance than those encryption systems that consider just one operation. In fact, the 2D-DFA approach was more sensitive than some common statistical tests to determine more clearly the impact of multiple operations in the scrambling process, confirming that this scaling method can be used as a perceptual security metric, and it may contribute to having better image encryption systems.
RESUMO
Esta patología afecta principalmente a varones alrededor de la cuarta década de la vida. El trastornos simula signos y síntomas de una insuficiencia arterial crónica. La etiología de esta rara enfermedad no ha sido aún definida. Se presenta el caso de una paciente de 40 años de edad, multigesta, deportista, cuya primera manifestación fue la claudicación intermitente progresiva. Se realizaron varios estudios como arteriografía, angioplastia fallida y TAC. Se encontró en el transoperatorio, tumoración quística que envolvía el 100 por ciento del tercio medio de la arteria, practicándose resección del mismo con retiro de adventicia normal