Catálogo de publicaciones - libros

In this paper, we present a new pseudo-random sequence generator, constructed by the generalized discrete Baker transformation. This new generator is called Cascaded Baker Register Machine (CBRM), which uses the sensitivity of chaotic behaviour and allows the application of automata- and shift-register theory. It is shown that a CBRM has good properties of randomness, such as large periods and high linear complexity. It can provide high cryptographic security with fast encryption speed, and can be realized effectively by both hardware and software.

Permutations are a core component of almost every cipher. No matter if we consider the DES, AES or most of the other encryption algorithms relevant nowadays, we always find permutation operators as essential building blocks inside. In this contribution we will introduce key-dependent permutation operators of provably excellent quality inspired by chaotic Kolmogorov flows.

From chaotic systems theory it is known that the class of Kolmogorov flows exhibits the highest degree of instability among all dynamical systems. As will be derived and proven in detail in this paper, these outstanding properties make them a perfect inspiration for developing a novel class of strong cryptographic permutation operators.

In this paper we examine the immunity of ElGamal signature scheme and its variants against fault cryptanalysis. Although such schemes have been already widely adopted, their resistance against fault cryptanalysis has not been verified in detail yet. However, at least some of them are not immune to fault cryptanalysis and can be broken without solving discrete logarithm problem. We will show that the selected signature schemes can be broken in (2) steps if single bit-flip errors are inducted during computations. We also present two modifications that can be used to improve security of ElGamal scheme.

In the theory of symmetric cipher design, criteria for the choice of Boolean functions with good behavior have been thoroughly studied. The character of these criteria is mainly statistiscal. We survey the often conflicting propoerties which are generally acknowledged, which shows the almost universal neglect of complexity-theoretic techniques. Of these, we propose the most prominent complexity measure concerning Boolean functions, to wit, , as a means to assess Boolean function behavior in the context of symmetric algorithm design. The connection between BCC of the non-linear elements of a design and the pseudorandom stream generated with their help is shown by scrutiny of linear complexity profiles.

A new protocol is presented that allows to convince of the knowledge of a solution to the Independent Vertex Set Problem without revealing anything about it. It is constructed from a bit commitment scheme based on the hardness of the Discrete Logarithm Problem, which guarantees its efficient performance and formal security. One of its possible applications is node identification in ad-hoc wireless network because it does not require any authentication servers. Furthermore, recent works on network security has pointed out the importance of the design of efficient Zero Knowledge Proofs of Knowledge for the Independent Vertex Set Problem in broadcast models.

The main idea behind this paper is to improve a known plaintext divide-and-conquer attack that consists in guessing the initial state of a Linear Feedback Shift Register component of a keystream generator, and then trying to determine the other variables of the cipher based on the intercepted keystream. While the original attack requires the exhaustive search over the set of all possible initial states of the involved register, this work presents a new and simple heuristic optimization of such an approach that avoids the evaluation of an important number of initial states when launching a constrained edit distance attack on irregularly clocked shift registers.

For protocol analysis, we have to capture the protocol specification, the security goals of the protocol, and the communications environment it is expected to run in. In the research literature, the emphasis is usually on verification techniques and on the modelling of security properties, while in most cases the default for the communications environment is an unstructured network totally controlled by the attacker. This paper will argue that for the analysis of the kind of protocols developed today, more specific models of the communications network are required. To support this argument, a number of recently proposed security protocols with novel features will be briefly discussed.

The main goal of this work is to improve the automatic interpretation of ocean satellite images. We present a comparative study of different classifiers: Graphic Expert System (GES), ANN-based Symbolic Processing Element (SPE), Hybrid System (ANN – Radial Base Function & Fuzzy System), Neuro-Fuzzy System and Bayesian Network.. We wish to show the utility of hybrid and neuro-fuzzy system in recongnition of oceanic structures. On the other hand, other objective is the feature selection, which is considered a fundamental step for pattern recognition. This paper reports a study of learning Bayesian Network for feature selection [1] in the recognition of oceanic structures in satellite images.

In this paper we present the development of a system able to speak from Braille writing. By means of dynamic thresholding, adaptive Braille grid, recovery dots techniques and TTS software (Text-To-Speech), translates Braille scanned images into normal text, and not only that, it speaks the translated text. is a robust application with innovative thersholding and Braille grid creation algorithms which detects and read Braille characters with 99.9% of correct symbols and an error variance below 0.012. The conversion time is only 26 secs for double-sided documents by MATLAB programming language.

Traditional authentication systems, employed to gain access to a private area in a building or to data stored in a computer, are based on something the user (an authentication card, a magnetic key) or something the user (a password, an identification code). But emerging technologies allow for more reliable and comfortable for the user, authentication methods, most of them based on biometric parameters. Much work could be found in literature about biometric based authentication, using parameters like iris, voice, fingerprints, face characteristics, and others. We have developed a new methodology for personal authentication, where the biometric parameter employed for the authentication is the retinal vessel tree, acquired through a retinal angiography. It has already been asserted by expert clinicians that the configuration of the retinal vessels is unique for each individual and that it does not vary in his life, so it is a very well suited identification characteristic. In this work we will present the design and implementation stages of an application which allows for a reliable personal authentication in high security environments based on the retinal authentication method.