Linear solutions for cryptographic nonlinear sequence generators

This letter shows that linear Cellular Automata based on rules 90/150 generate all the solutions of linear difference equations with binary constant coefficients. Some of these solutions are pseudo-random noise sequences with application in cryptography: the sequences generated by the class of shrinking generators. Consequently, this contribution show that shrinking generators do not provide enough guarantees to be used for encryption purposes. Furthermore, the linearization is achieved through a simple algorithm about which a full description is provided

Global Linear Complexity Analysis of Filter Keystream Generators

An efficient algorithm for computing lower bounds on the global linear complexity of nonlinearly filtered PN-sequences is presented. The technique here developed is based exclusively on the realization of bit wise logic operations, which makes it appropriate for both software simulation and hardware implementation. The present algorithm can be applied to any arbitrary nonlinear function with a unique term of maximum order. Thus, the extent of its application for different types of filter generators is quite broad. Furthermore, emphasis is on the large lower bounds obtained that confirm the exponential growth of the global linear complexity for the class of nonlinearly filtered sequences

The cosmic evolution of radio-AGN feedback to z=1

This paper presents the first measurement of the radio luminosity function of 'jet-mode' (radiatively-inefficient) radio-AGN out to z=1, in order to investigate the cosmic evolution of radio-AGN feedback. Eight radio source samples are combined to produce a catalogue of 211 radio-loud AGN with 0.5<z<1.0, which are spectroscopically classified into jet-mode and radiative-mode (radiatively-efficient) AGN classes. Comparing with large samples of local radio-AGN from the Sloan Digital Sky Survey, the cosmic evolution of the radio luminosity function of each radio-AGN class is independently derived. Radiative-mode radio-AGN show an order of magnitude increase in space density out to z~1 at all luminosities, consistent with these AGN being fuelled by cold gas. In contrast, the space density of jet-mode radio-AGN decreases with increasing redshift at low radio luminosities (L_1.4 < 1e24 W/Hz) but increases at higher radio luminosities. Simple models are developed to explain the observed evolution. In the best-fitting models, the characteristic space density of jet-mode AGN declines with redshift in accordance with the declining space density of massive quiescent galaxies, which fuel them via cooling of gas in their hot haloes. A time delay of 1.5-2 Gyr may be present between the quenching of star formation and the onset of jet-mode radio-AGN activity. The behaviour at higher radio luminosities can be explained either by an increasing characteristic luminosity of jet-mode radio-AGN activity with redshift (roughly as (1+z) cubed) or if the jet-mode radio-AGN population also includes some contribution of cold-gas-fuelled sources seen at a time when their accretion rate was low. Higher redshifts measurements would distinguish between these possibilities.Comment: Accepted for publication in MNRA

Analysis of the generalized self-shrinking generator

AbstractThis work shows that the output sequences of a well-known cryptographic generator, the so-called generalized self-shrinking generator, are particular solutions of homogeneous linear difference equations with binary coefficients. In particular, all those generated sequences are just linear combinations of primary sequences weighted by binary values. Furthermore, the complete class of solutions of these difference equations includes other balanced sequences with the same period and even greater linear complexity than that of the generalized self-shrinking sequences. Cryptographic parameters of all above mentioned sequences are here analyzed in terms of linear equation solutions. In addition, this work describes an efficient algorithm to synthesize the component primary sequences as well as to compute the linear complexity and period of any generalized self-shrinking sequence

Protocol: Triple Diamond method for problem solving and design thinking. Rubric validation

[EN] There is a set of tools that we can use to improve the results of each of the phases that continuous improvement projects must go through (8D, PDCA, DMAIC, Double diamond, etc.). These methods use divergent techniques, which help generate multiple alternatives, and convergent techniques that help analyze and filter the generated options. However, the tools used in all those frameworks are often very similar. Our goal, in this research, is to develop a comprehensive model that allows it to be used both for problem-solving and for taking advantage of opportunities. This protocol defines the main terms related to our research, makes a framework proposal, proposes a rubric that identifies observable milestones at each stage of the model and proposes the action plan to validate this rubric and the model in a given context. The action plan will be implemented in a future research.Marin-Garcia, JA.; Garcia-Sabater, JJ.; Garcia-Sabater, JP.; Maheut, J. (2020). Protocol: Triple Diamond method for problem solving and design thinking. Rubric validation. WPOM-Working Papers on Operations Management. 11(2):49-68. https://doi.org/10.4995/wpom.v11i2.14776OJS496811

Estudio de algunas Secuencias pseudoaleatorias de aplicación criptográfica

Sin resume

Los Papiros de Herculano en la España de finales del siglo XVIII y comienzos del XIX

The aim of this article is to explore the interest aroused by the Herculaneum papyri among Spanish intellectuals in the 18th and 19th centuries. For this purpose, the authors draw on the testimony of travellers, scholars and prominent writers like Francisco Pérez Báyer, Nicolás de Azara, Esteban de Arteaga, Leandro Fernández de Moratín, Pedro Antonio de Alarcón, Pedro Montengón and Juan Andrés y Morell. While the first five writers reflect upon the topic in a general manner, Montegón and Andrés do deal with it in greater detail