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Digital.CSIC (59,605 recursos)
Repositorio institucional del Consejo Superior de Investigaciones Científicas. Digital.CSIC es un depósito de documentos digitales, cuyo objetivo es organizar, archivar, preservar y difundir en modo de acceso abierto la producción intelectual resultante de la actividad investigadora del CSIC.

(IFA) Comunicaciones congresos

Mostrando recursos 1 - 20 de 47

1. Deterministic Cryptanalysis of some Stream Ciphers - Caballero-Gil, P.; Fúster-Sabater, A.; Hernández-Goya, C.
A new graph-based approach to edit distance cryptanalysis of some clock-controlled generators is here presented in order to simplify search trees of the original attacks. In particular, the proposed improve- ment is based on cut sets de¯ned on some graphs so that only the most promising branches of the search tree have to be analyzed because cer- tain shortest paths provide the edit distances. The strongest aspects of the proposal are: a) the obtained results from the attack are absolutely deterministic and b) many inconsistent initial states are recognized be- forehand and avoided during search.

2. Digital identity-based multisignature scheme implementation - Buenasmañanas Domínguez, Francisco Javier; Hernández Encinas, Ascensión; Queiruga Dios, Araceli; Hernández Encinas, Luis
Digital signature, as an official signature, have many applications in information security, including authentication, data integrity, and non-repudiation. When a private or public document must be signed by a group of people, we call it multisignature scheme if all and every single member of the group signs the document. An identity-based digital multisignature is a multi signer digital signature so that the multiple private keys are generated by a trusted third part from signer’s identities. In this paper, an efficient Java implementation to a recent identity-based multisignature scheme based on RSA is proposed.

3. Optoelectronics properties of Silicon photodiodes - Muñoz Zurita, Ana Luz; Campos Acosta, Joaquín; Pons, Alicia; Shcherbakov, Alexandre S.; Gómez Jiménez, Ramón
To measure a photodiode reflectance, the reference detector is placed first at position A and its reading is recorded. Afterward the photodiode to be tested is introduced in the laser beam at half way between the shutter and position A, with an angle of incidence about 3º and the reference photodiode is moved to position B and its response recorded. Then the reflectance is given by the ratio between the reference detector reading at position B and the reading at position A. Placing the photodiode to be tested a that position assures that the beam seen by the reference detector runs the same distance in both...

4. On the skew tent map as base of a new image chaos-based encryption scheme - Arroyo Guardeño, David; Rhouma Rhouma; Gonzalo Alvarez; Veronica Fernandez; Safya Belghith
Second Workshop on Mathematical Cryptology, pages 113–117. Universidad de Cantabria, Santander, Spain.

5. Real time monitoring of railway traffic using fiber bragg grating sensors - Filograno, Massimo L.; Rodríguez Barrios, Alberto; González Herráez, Miguel; Corredera Guillén, Pedro; Martín López, Sonia; Rodríguez-Plaza, M.; Andrés-Alguacil, A.
In this work we present field tests concerning the application of Fiber Bragg Grating (FBG) sensors for the monitoring of railway traffic. The test campaigns are performed on the Spanish high speed line Madrid–Barcelona, with different types of trains (S-102 TALGO–BOMBARDIER, S- 103 SIEMENS-VELARO and S-120 CAF). We located the FBG sensors in the rail track at 70 km from Madrid in the country side, where the trains primarily are tested during commercial operation with maximum speeds between 250-300 km/h. The FBG sensor interrogation system used allows the simultaneous monitoring of four FBG sensors at 8000 samples/s. The different position of the FBG sensors in relation with the rail can be used with...

6. Free-space Mbps quantum key distribution link in Madrid - María José, García-Martínez; Natalia, Denisenko; Diego, Soto; Alberto, Carrasco-Casado; Verónica, Fernández-Mármol

7. High-speed free-space quantum key distribution with automatic tracking for short-distance urban links - Alberto, Carrasco-Casado; María-José, García-Martínez; Natalia, Denisenko; Verónica, Fernández-Mármol

8. High-speed free-space quantum key distribution system for urban applications - García-Martínez, María José; denisenko, natalia; soto, diego; Fernandez-Marmol, Veronica

9. Towards a Short-range Free-space GHz-clocked Quantum Key Distribution System - García-Martínez, María José; Denisenko, Natalia; Soto, Diego; Fernandez-Marmol, Veronica
A free-space quantum key distribution system that operates at a wavelength of 850 nm is presented. The system is designed to implement the B92 protocol at high transmission rates between two locations in urban areas.

10. Analysis of Quantum Key Distribution as a Disruptive Technology - García-Martínez, María José; Soto, Diego; Denisenko, Natalia; Fernandez-Marmol, Veronica
Various considerations about the present and future of quantum cryptography together with a security analysis are discussed in this paper. We also present a free-space GHz-clocked QKD system designed for urban links.

11. Electron-multiplying CCD astronomical photometry - Ferrero, Alejandro; Campos Acosta, Joaquín; Pons, Alicia
Electron Multiplying CCD is a CCD technology sensor reduces read-out noise to less than one electron. We study the way the usage of this technology affects to the astronomical photometry and to the improvement of the temporal resolution of the measurements. We show the effect of this technology on individual celestial sources and in the limiting magnitude. We propose a criterion to choose the optimal EM gain for a specific integration time. We explain a straightforward procedure to characterize the actual EM gain and the readout noise expressed in photo-electrons for every software-displayed gain, and we applied this procedure to the Andor Ixon DU-888E-C00-BV EMCCD.

12. Linealización del Generador Auto-Shrinking e Implementación con FPGA - Pazo-Robles, M.E.; Fúster-Sabater, Amparo; Tinetti, F.G.
En este trabajo se presenta una modelización del generador Auto-Shrinking mediante autómatas celulares. La implementación del modelo ya linealizado puede llevarse a práctica mediante lógica FPGA. La linealidad y las propiedades de simetría que aparecen en este modelo celular pueden utilizarse de manera conveniente para el análisis y/o criptoanálisis de este tipo de generador criptográfico.

We present an approach to the characterization of low‐power bright picosecond optical pulses with an internal frequency modulation in both time and frequency domains in practically important cases of exploiting semiconductor heterolasers operating in near‐infrared range in the active mode‐locking regime. This approach uses the joint Wigner time‐frequency distributions, which can be found for this regime due to involving the interferometric technique under consideration. In so doing, the modified scanning Michelson interferometers were chosen for shaping the field‐strength auto‐correlation functions peculiar to the above‐mentioned types of infrared light radiation. We consider in principle the key features of a new experimental...

We make an attempt to develop a novel approach to experimental investigations of highrepetition‐ rate trains of picosecond optical pulses. For this purpose an opto‐electronic system for detecting train‐average time parameters had been created. The scheme of this system consists of optical auto‐correlator, electronic controller, and a set of the checking units. The computer admits several regimes for operation: calibration of optical autocorrelator, measuring cycle, and data processing and display. Initially, pulse trains arrive at the optical auto‐correlator, i.e. at a two‐beam scanning Michelson interferometer, which is formed by two total‐internal‐reflection prisms and a 50%‐mirror. The prismatic optical circuit permits keeping out the backward scattering from basic reflecting...

15. A NEW TECHNIQUE OF MEASURING LOW‐POWER PICOSECOND OPTICAL PULSE TRAINS - Muñoz Zurita, Ana Luz; Shcherbakov, Alexandre S.; Campos Acosta, Joaquín; Gómez Jiménez, Ramón
We present a theoretic approach to the characterization of low‐power bright ultrashort optical pulses with an internal frequency modulation simultaneously in both time and frequency domains. The analysis and computer simulations are applied to studying the capability of Wigner distribution to characterize solitary pulses in practically important case of the sech‐pulses. Then, the simplest two‐beam scanning Michelson interferometer is selected for shaping the field‐strength auto‐correlation function of low‐power picosecond pulse trains. We are proposing the key features of a new interferometric experimental technique for accurate and reliable measurements of the train‐average width as well as the value and sign of...

16. Applying the triple correlation functions to characterizing high-frequency repetition trains of picosecond optical pulses - Muñoz Zurita, Ana L.; Shcherbakov, Alexandre S.; Campos Acosta, Joaquín
The triple correlation of an ordinary function on the real time is the integral of the product of that function with two independently shifted copies of itself. Triple correlation methods are frequently used in signal processing for treating signals that are corrupted by additive Gaussian noise; in particular, triple correlation techniques perform well when multiple observations of the signal are available and the signal may be translating in between the observations, e.g. a sequence of images of an object translating on a noisy background.

17. Mejora del rango dinámico de un sensor Brillouin distribuido de temperatura y strain en fibra óptica mediante amplificación Raman - Rodríguez-Barrios, Félix; Martín-López, Sonia; Carrasco-Sanz, Ana; Corredera, Pedro; Hernanz, Mª Luisa; González-Herráez, Miguel
En el ámbito de la ingeniería civil, la monitorización del estado de sus infraestructuras, tanto en fase de construcción como en fase de explotación resulta de gran interés social y económico. Para este propósito tradicionalmente se han utilizado de manera casi exclusiva sensores de tipo eléctrico y mecánico. En los últimos tiempos el uso de sensores ópticos ha proporcionado una solución de compromiso para su instalación en ambientes en los que los sensores eléctricos presentan mermadas sus capacidades óptimas, por ejemplo por el nivel de ruido electromagnético y los mecánicos resultan poco prácticos y versátiles. En muchas aplicaciones, la necesidad de sensado de una elevada cantidad...

18. Diseño y Construcción de un Novedoso Espectro-Gonio-Fotómetro - Rabal, Ana M.; Fontecha, José Luis; Pons, Alicia; Campos, Joaquín; Zafra, Rafael
Ser capaz de predecir y reproducir la apariencia de los objetos es un problema que tiene repercusiones en múltiples áreas de actividad. Para llegar a resolver este problema es necesario especificar bien la percepción de apariencia y basarla en medidas físicas. El concepto de apariencia está relacionado con el color, el brillo, la translucidez y la textura de los objetos, por lo que la medida de la apariencia tiene que estar relacionada con la de esas otras magnitudes.

19. Criptosistemas basados en curvas hiperelípticas - Hernández Encinas, Luis
La seguridad de la mayoría de los criptosistemas de clave pública se basa en la supuesta intratabilidad computacional de un problema matemático, considerado difícil, como el de la factorización, el de la suma de un subconjunto o el del logaritmo discreto. En este último problema, utilizando el grupo multiplicativo Z*p, se fundamentan criptosistemas como el de ElGamal y esquemas de autenticación y de firma digital.

20. Una mirada al criptoanálisis actual: tendencias y casos prácticos - Fúster Sabater, Amparo
Se podría decir que existen tantos criptoanálisis distintos como criptosistemas puedan diseñarse. Sin embargo, las actuales técnicas criptoanalíticas pueden agruparse en diferentes familias que cubren el rango completo de criptosistemas encontrados en la literatura. Con el fin de presentar una panorámica amplia del Criptoanálisis actual vamos a señalar tres métodos criptoanalíticos bien diferenciados: la técnica de la "edit-distance generalizada" para el criptoanálisis de generadores binarios (cifrado en flujo), el denominado "slide attack" para el criptoanálisis de cifrados iterativos (cifrado en bloque) y el criptoanálisis de software criptográfico como el GNU Privacy Guard (Criptografía de clave pública).

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