Magdalena Romera

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We discuss a tagging schema and a tagging tool for labeling the rhetorical structure of texts. We also propose a statistical method for measuring agreement of hierarchical structure annotations and we discuss its strengths and weaknesses. The statistical measure we use suggests that annotators can achieve good levels of agreement on the task of determining(More)
We present a tagging schema and a tagging tool for labeling the rhetorical structure of texts. We focus on presenting the difficulties that we faced in designing a discourse annotation manual and on discussing the choices that we made in order to address these difficulties. We report reliability results concerning our agreement on building the rhetorical(More)
In recent years, a growing number of cryptosystems based on chaos have been proposed, many of them fundamentally flawed by a lack of robustness and security. In this Letter, we explain how to break a very recent block cipher algorithm based on the logistic map. This cryptosystem uses a 128-bit external key to derive the initial condition and number of(More)
This paper describes the security weakness of a recently proposed improved chaotic encryption method based on the modulation of a signal generated by a chaotic system with an appropriately chosen scalar signal. The aim of the improvement is to avoid the breaking of chaotic encryption schemes by means of the return map attack introduced by Pérez and(More)
The external argument theory of Douady and Hubbard allows us to know both the potential and the field-lines in the exterior of the Mandelbrot set. Nonetheless, there are no explicit formulae to operate with external arguments, and the external argument theory is difficult to apply. In this paper we introduce some tools in order to obtain formulae to operate(More)
This paper describes the security weaknesses of a recently proposed secure communication method based on chaotic masking using projective synchronization of two chaotic systems. We show that the system is insecure and how to break it in two different ways, by high-pass filtering and by generalized synchronization.