El otro día me quedé sin poder probar la conexión inalámbrica en Raspbmc porque los puertos USB de la Raspberry Pi no dan suficiente potencia para la antena WiFi USB que tengo. Cada puerto USB proporciona hasta 100mA, y parece que el consumo de la antena oscila entre 150mA y 200mA, por lo que no es suficiente. Quizá conectando un cable USB en Y desde los dos USB podría llegar a funcionar, pero nos quedaríamos sin puertos USB libres. ...

El pasado día 26 de junio asistí al evento ”Iniciativas Open Data en España”, atraído sin duda, por los grandes espadas en la materia que son Alberto Abella, Roberto Santos y Victoria Anderica, que además del reconocido prestigio que tienen, llevan años trabajando para que este país sea algo mejor. Como cabía esperar, no me defraudaron en sus intervenciones, que fueron tan correctas como acertadas. Como contrapartida, y diré el pecado, pero no el pecador, tuve que oír de boca de ”expertos” en la materia, estas dos afirmaciones, que me preocuparon y mucho, puesto que pueden afectar muy negativamente a la Ley de Transparencia y su desarrollo posterior: ...

Although the Enigma cipher as a whole is quite complex (it’s complexity is comparable to modern cryptographic algorithms) the individual transformations within it are relatively simple. In fact, they are simple enough that you can decipher an Enigma message with just a paper model. Our model is three-dimensional, to illustrate the wiring of a real Enigma machine. It needs only common household items to construct, and is completely compatible with all settings of a real Enigma machine (models I, M1, M2 and M3). ...

Raspbmc es una distribución basada en debian que permite ejecutar XBMC en la Raspberry Pi, lo que la transforma en un interesante reproductor multimedia casero (HTPC). Esta distribución recibe actualizaciones constantes que añaden mejoras, actualizaciones de drivers y nuevas funcionalidades. Además, permite compartir el contenido multimedia a través de NFS, SMB, FTP y HTTP. Raspbmc ha sido creada y está siendo mantenida por Sam Nazarko. Fuente retrocomputers.eu ...

Large projects can contain thousands of lines of code, distributed in multiple source files, written by many developers and arranged in several subdirectories. A project may contain several component divisions. These components may have complex inter-dependencies ” for example, in order to compile component X, you have to first compile Y; in order to compile Y, you have to first compile Z; and so on. For a large project, when a few changes are made to the source, manually recompiling the entire project each time is tedious, error-prone and time-consuming. ...

Las aplicaciones que se ejecutan al inicio tienen un archivo de configuración en el directorio /etc/xdg/autostart. Algunos de estos archivos de configuración tienen la variable NoDisplay=true, por lo que no aparecen en el listado de Aplicaciones al inicio, y por tanto no se pueden desactivar a golpe de ratón. Si queremos que estas aplicaciones se muestren y así poder desactivarlas mediante la interfaz gráfica, ejecutamos: $ sudo sed -i 's/NoDisplay=true/NoDisplay=false/' /etc/xdg/autostart/* Si además queremos que cada vez que instalamos un programa se ejecute este comando, podemos incluirlo en el archivo /etc/apt.conf: ...

El algoritmo de Dios es un término que surgió en la búsqueda de aquel algoritmo que indicara los pasos mínimos que resuelven un cubo de Rubik cualquiera. El término se usa profusamente, no sólo para el cubo de Rubik. Mucho antes de conocer dicho término, cuando me encontraba con diversos tipos de problemas, ya me asaltaba recurrentemente una pregunta irrelevante (para el caso que me ocupaba), pero que espero te haga pensar un poco en la importancia de algunas cuestiones que quizás no conoces: ...

Lock-free programming is a challenge, not just because of the complexity of the task itself, but because of how difficult it can be to penetrate the subject in the first place. I was fortunate in that my first introduction to lock-free (also known as lockless) programming was Bruce Dawson’s excellent and comprehensive white paper, Lockless Programming Considerations. And like many, I’ve had the occasion to put Bruce’s advice into practice developing and debugging lock-free code on platforms such as the Xbox 360. Since then, a lot of good material has been written, ranging from abstract theory and proofs of correctness to practical examples and hardware details. I’ll leave a list of references in the footnotes. At times, the information in one source may appear orthogonal to other sources: For instance, some material assumes sequential consistency, and thus sidesteps the memory ordering issues which typically plague lock-free C/C++ code. The new C++11 atomic library standard throws another wrench into the works, challenging the way many of us express lock-free algorithms. In this post, I’d like to re-introduce lock-free programming, first by defining it, then by distilling most of the information down to a few key concepts. I’ll show how those concepts relate to one another using flowcharts, then we’ll dip our toes into the details a little bit. At a minimum, any programmer who dives into lock-free programming should already understand how to write correct multithreaded code using mutexes, and other high-level synchronization objects such as semaphores and events. ...

The general thrust of this post is: use a MAC function like HMAC to sign data, don’t use hash functions. Although not all hash functions suffer from the problem I’m going to illustrate, in general using a hash function for message authentication comes with a lot of potential problems because those functions aren’t designed for this task. You shouldn’t try to work around it by creatively processing the inputs or inventing some fancy way of chaining hash functions. Just use the functions that were designed for this task instead of inventing your own crypto schemes. ...

This is a story that dates back to the earliest days of computers. The story has a plot, well, sort of. It has competition and intrigue, as well as traversing oodles of countries and languages. There is conflict and resolution, and a happyish ending. But the main focus is the characters ” 110,116 of them. By the end of the story, they will all find their own unique place in this world. This story (or article, as known on Smashing Magazine) will follow a few of those characters more closely, as they journey from Web server to browser, and back again. Along the way, you’ll find out more about the history of characters, character sets, Unicode and UTF-8, and why question marks and odd accented characters sometimes show up in databases and text files. ...