28 research outputs found
Active control of sound inside a sphere via control of the acoustic pressure at the boundary surface
Here we investigate the practical feasibility of performing soundfield
reproduction throughout a three-dimensional area by controlling the acoustic
pressure measured at the boundary surface of the volume in question. The main
aim is to obtain quantitative data showing what performances a practical
implementation of this strategy is likely to yield. In particular, the
influence of two main limitations is studied, namely the spatial aliasing and
the resonance problems occurring at the eigenfrequencies associated with the
internal Dirichlet problem. The strategy studied is first approached by
performing numerical simulations, and then in experiments involving active
noise cancellation inside a sphere in an anechoic environment. The results show
that noise can be efficiently cancelled everywhere inside the sphere in a wide
frequency range, in the case of both pure tones and broadband noise, including
cases where the wavelength is similar to the diameter of the sphere. Excellent
agreement was observed between the results of the simulations and the
measurements. This method can be expected to yield similar performances when it
is used to reproduce soundfields.Comment: 28 pages de text
Chaotic iterations versus Spread-spectrum: chaos and stego security
A new framework for information hiding security, called chaos-security, has
been proposed in a previous study. It is based on the evaluation of
unpredictability of the scheme, whereas existing notions of security, as
stego-security, are more linked to information leaks. It has been proven that
spread-spectrum techniques, a well-known stego-secure scheme, are chaos-secure
too. In this paper, the links between the two notions of security is deepened
and the usability of chaos-security is clarified, by presenting a novel data
hiding scheme that is twice stego and chaos-secure. This last scheme has better
scores than spread-spectrum when evaluating qualitative and quantitative
chaos-security properties. Incidentally, this result shows that the new
framework for security tends to improve the ability to compare data hiding
scheme
Lyapunov exponent evaluation of a digital watermarking scheme proven to be secure
In our previous researches, a new digital watermarking scheme based on
chaotic iterations has been introduced. This scheme was both stego-secure and
topologically secure. The stego-security is to face an attacker in the
"watermark only attack" category, whereas the topological security concerns
other categories of attacks. Its Lyapunov exponent is evaluated here, to
quantify the chaos generated by this scheme.
Keywords : Lyapunov exponent; Information hiding; Security; Chaotic
iterations; Digital Watermarking.Comment: 10 page
Chapitre 6 : la qualification au cœur des droits sociaux : les enjeux salariaux de la réforme des retraites
Jean-Pascal Higelé (dir.) et avec la collaboration de Nicolas CastelLa réforme des pensions, en les indexant sur les prix, en gelant les taux de cotisation, en distinguant le contributif et le non contributif, en augmentant la durée de la carrière complète, s'emploie à interrompre leur évolution vers la poursuite du salaire pour les remplacer par un dispositif non salarial conjuguant revenu garanti, revenu différé de prévoyance et rente de la propriété financière
Application of Steganography for Anonymity through the Internet
In this paper, a novel steganographic scheme based on chaotic iterations is
proposed. This research work takes place into the information hiding security
framework. The applications for anonymity and privacy through the Internet are
regarded too. To guarantee such an anonymity, it should be possible to set up a
secret communication channel into a web page, being both secure and robust. To
achieve this goal, we propose an information hiding scheme being stego-secure,
which is the highest level of security in a well defined and studied category
of attacks called "watermark-only attack". This category of attacks is the best
context to study steganography-based anonymity through the Internet. The
steganalysis of our steganographic process is also studied in order to show it
security in a real test framework.Comment: 14 page
Chaotic Iterations for Steganography - Stego-security and chaos-security
International audienceChaotic neural networks have received a great deal of attention these last years. In this paper we establish a precise correspondence between the so-called chaotic iterations and a particular class of artificial neural networks: global recurrent multi-layer perceptrons. We show formally that it is possible to make these iterations behave chaotically, as defined by Devaney, and thus we obtain the first neural networks proven chaotic. Several neural networks with different architectures are trained to exhibit a chaotical behavior
A new secure process for steganography: CI2. Stego and topological security
International audienceIn this paper is proposed a novel steganographic scheme based on chaotic iterations which offer a solution facing the main limitation of the previous one. This research work takes place into the information hiding security fields. We show that the proposed scheme is stego-secure, which is the highest level of security in a well defined and studied category of attack called "watermark-only attack". Additionally, we prove that this scheme presents topological properties so that it is one of the firsts able to face, at least partially, an adversary when considering the others categories of attacks defined in the literature