New cryptanalysis of LFSR-based stream ciphers and decoders for p-ary QC-MDPC codes

The security of modern cryptography is based on the hardness of solving certain problems. In this context, a problem is considered hard if there is no known polynomial time algorithm to solve it. Initially, the security assessment of cryptographic systems only considered adversaries with classical computational resources, i.e., digital computers. It is now known that there exist polynomial-time quantum algorithms that would render certain cryptosystems insecure if large-scale quantum computers were available. Thus, adversaries with access to such computers should also be considered. In particular, cryptosystems based on the hardness of integer factorisation or the discrete logarithm problem would be broken. For some others such as symmetric-key cryptosystems, the impact seems not to be as serious; it is recommended to at least double the key size of currently used systems to preserve their security level. The potential threat posed by sufficiently powerful quantum computers motivates the continued study and development of post-quantum cryptography, that is, cryptographic systems that are secure against adversaries with access to quantum computations. It is believed that symmetric-key cryptosystems should be secure from quantum attacks. In this manuscript, we study the security of one such family of systems; namely, stream ciphers. They are mainly used in applications where high throughput is required in software or low resource usage is required in hardware. Our focus is on the cryptanalysis of stream ciphers employing linear feedback shift registers (LFSRs). This is modelled as the problem of finding solutions to systems of linear equations with associated probability distributions on the set of right hand sides. To solve this problem, we first present a multivariate version of the correlation attack introduced by Siegenthaler. Building on the ideas of the multivariate attack, we propose a new cryptanalytic method with lower time complexity. Alongside this, we introduce the notion of relations modulo a matrix B, which may be seen as a generalisation of parity-checks used in fast correlation attacks. The latter are among the most important class of attacks against LFSR-based stream ciphers. Our new method is successfully applied to hard instances of the filter generator and requires a lower amount of keystream compared to other attacks in the literature. We also perform a theoretical attack against the Grain-v1 cipher and an experimental attack against a toy Grain-like cipher. Compared to the best previous attack, our technique requires less keystream bits but also has a higher time complexity. This is the result of joint work with Semaev. Public-key cryptosystems based on error-correcting codes are also believed to be secure against quantum attacks. To this end, we develop a new technique in code-based cryptography. Specifically, we propose new decoders for quasi-cyclic moderate density parity-check (QC-MDPC) codes. These codes were proposed by Misoczki et al.\ for use in the McEliece scheme. The use of QC-MDPC codes avoids attacks applicable when using low-density parity-check (LDPC) codes and also allows for keys with short size. Although we focus on decoding for a particular instance of the p-ary QC-MDPC scheme, our new decoding algorithm is also a general decoding method for p-ary MDPC-like schemes. This algorithm is a bit-flipping decoder, and its performance is improved by varying thresholds for the different iterations. Experimental results demonstrate that our decoders enjoy a very low decoding failure rate for the chosen p-ary QC-MDPC instance. This is the result of joint work with Guo and Johansson.Doktorgradsavhandlin

The palm tree in the landscape of the Bajo Segura basin irrigated area. An identity element in need of protection

La palmera, como aprovechamiento agrícola, ha estado estrechamente vinculada al espacio de la Huerta generado a lo largo de los siglos en la llanura aluvial del Segura. Los múltiples usos derivados de ésta han fortalecido su permanencia, a la vez que la imagen identitaria con que se asocia al territorio. Su presencia ha quedado plasmada en escritos de todo tipo desde la Ilustración hasta nuestros días, lo que permite contrastar la visión de entonces con la situación que atraviesa en la actualidad. Para ello se analizan tres ámbitos diferentes, San Isidro, una población entre palmeras tras la colonización de suelos salinos; el Palmeral de Orihuela, como pervivencia de un enclave histórico ligado a los rendimientos mixtos de la tierra; y finalmente, la dispersión generalizada de la palmera por el medio agrario.The palm tree, regarded as an agrarian resource, has been closely linked to the orchards, or spaces of "Huerta", developed over centuries in the Segura River fertile plains. The multiple uses of the palm tree have guaranteed its continuity and strengthened its association with the identity image related to this territory. Its presence has been captured in all types of written documents, from the Enlightenment to recent times, allowing us to compare ancient vision and present situation. To develop this comparison the paper analyses three different contexts: San Isidro, a town built between palms previously planted on saline soil, the Palmeral of Orihuela, a survival remain of a historic site associated with mixed cultivation of land and, finally, the generalized palm tree dispersion through the agrarian landscape

The palm tree, an identity-defining element in the Huerta landscape of Bajo Segura (SE of Spain)

La palmera, por sus múltiples aprovechamientos (agrícola, constructivo, ritual e industrial), ha sido tradicionalmente un elemento identitario en el paisaje huertano del Bajo Segura. En las últimas décadas su presencia se ha restringido, al perder las funciones que antaño cumplía, a lo que se ha unido la plaga del picudo rojo y la comercialización masiva con fines ornamentales para las nuevas áreas residenciales. El artículo aborda la presencia de esta especie en el territorio desde diversas visiones y en diferentes épocas: la estética de la literatura de viajes, la productiva de los tratados científicos o la emocional de las obras de creación.The palm tree, because of its numerous uses (agricultural, constructive, ritual and industrial), has been traditionally an identity-defining element in the landscape of the Bajo Segura irrigated area (SE of Spain). In recent decades, its presence has been limited, by the loss of functions that palm tree previously carried out, currently joined to the red palm weevil pest (Rhynchophorus ferrugineus) and the massive sale with ornamental purposes in the new built-up areas emerged from residential tourism boom. This article deals with the presence of the Palm in the territory from several views and in different times: the aesthetic of travel literature, the productive of scientific reports or the emotional of artistic works

Trinidad, producto turístico integral y sostenible en Cuba

With the Soviet Union dismantling, Cuba pledges to the development of the tourism industry. Due to its historical legacy typical of a colonial town and its location between the coast and the mountain, Trinidad has become an important touristic destination that combi- nes sun and beach, cultural and environment tourism. In this article we are going to analyze the factors that turn Trinidad into an international reference and the impact of this activity in the family finances, in the recovery of the local heritage and in the environment. All of them are the factors why Trinidad has been declared as a World Heritage.Con el desmantelamiento de la Unión Soviética, Cuba apostó claramente por el desarro- llo del sector turístico. Trinidad, debido a su histórico conjunto urbano propio de la ciudad colonial y su enclave geográfico entre la montaña y el litoral, se ha convertido en un impor- tante destino que aúna el turismo de playa con el de naturaleza y el cultural. En el presente artículo se analizarán los factores que hacen de Trinidad un referente internacional, así como la repercusión que esta actividad ejerce tanto en la economía familiar como en la recupera- ción del patrimonio local y su entorno ambiental; por ello ha sido declarado Patrimonio de la Humanidad

El desarrollo turístico de Orihuela y su incidencia en el poblamiento (1910-2010)

The century 1910-2010 represents to Orihuela municipality (SE of Spain) a momentous change that is reflected both in social aspects as in economic. Agriculture, the most determinant factor on wealth, has been pushed into the background in favour of the secondary and tertiary sectors. In this process, tourism has generated an alteration in the traditional distribution of population, which has caused the current antagonism that exists between interior lands and the coast. A group of foreign residents has been encouraged by this urban duality reaching 42,2% of total municipality population.La centuria de 1910 a 2010 representa para el municipio de Orihuela un cambio trascendental que se refleja tanto en los aspectos sociales como económicos. La agricultura, factor condicionante de la riqueza, ha quedado relegada frente a los sectores secundario y terciario. En este proceso, el turismo ha generado una alteración en la tradicional distribución del poblamiento que origina el antagonismo actual entre el interior y la costa. Esta dualidad urbana está motivada por la presencia de un colectivo de residentes extranjeros que alcanza el 42,2% de la población municipal

Poly-nuclear urban system, landscape identity and economic development: The Vega Baja of the Segura River (Alicante) case study

[EN] The geographical area of this study -the Vega Baja alluvial plainis characterized by its intensively irrigated agricultural pattern. It is one of the last remaining Huerta European landscapes identified in the Dobris Report and dates back to the ninth-century. Since the 1990s, the introduction of new land uses has modified the configuration patterns of otherwise stable traditional settlements. The exceptionally rapid pace of this process has had a significant impact on the landscape, the environment, and on how the local population relates to their surroundings. Moreover, in the last twenty-five years, the local economy has undergone restructuring, producing a mind-shift among local communities and resulting in a meaningful loss of crop production surface to make way for town-planning developments. The preservation of the Huerta’s landscape identity requires a comprehensive and integrated reference framework to ensure sustainable development which is a goal advanced by this work. To this end, four key categories -Landscape, Agriculture, Habitat and Tourism- are defined and analyzed over three separate time periods that reflect the evolution of the territory. The aim of this paper is to provide an analytical territorial framework that can inform and guide future decision making —in the context of sustainable economic development— that should embrace a comprehensive approach to Huerta landscape identity values.Garcia-Mayor, C.; Canales Martínez, G. (2018). Poly-nuclear urban system, landscape identity and economic development: The Vega Baja of the Segura River (Alicante) case study. En 24th ISUF International Conference. Book of Papers. Editorial Universitat Politècnica de València. 47-53. https://doi.org/10.4995/ISUF2017.2017.5933OCS475

Almoradi, independent municipality of Orihuela in 1583: analysis of privilege conferred by category of University

Almoradí consigue independizarse de Orihuela en 1583 al obtener el vecindario el Privilegio Real de Universidad, mediante una compensación económica de 5.000 libras a la corona. En el Antiguo Régimen dicha categoría de población representaba para un lugar la obtención de una demarcación territorial propia y ejercer en ella el autogobierno. El desencadenante fue la riqueza generada por la colonización agraria, a raíz de la construcción del Azud de Alfeitamí en 1571 que amplió notablemente el regadío a costa de la reducción del almarjal.Almoradí gets independence from Orihuela in 1583 thanks to the villagers, who were granted the Royal Privilege of University, by £ 5,000 compensation to the Crown. In the Old Regime, with this category the town gets its own territorial demarcation and exercising self-government. The cause was the wealth generated by the agricultural colonization, motivated by the construction of the dam of Alfeitamí in 1571 which expanded signifi cantly irrigated land and reduced a swampy area widely

Software for determining dripline irrigation pipes using a Pocket PC

This communication presents the development of a freeware for mobile devices (Smartphone and Pocket PC). It was developed with a LabVIEW program, and enables engineers and installers to calculate commercial diameters to be used in laterals of drip irrigation, without the need for being at the personal computer. Input data required: drippers flow rates, number of drippers, spacing between the drippers, medium pressure in the lateral and pressure tolerance. As results, it shows commercial diameters that can be used with diode LED, maximum and minimum pressures for each lateral, and a graphic that shows, on a comparative, wether it exceeds each lateral of the pressure tolerance or not