2,226 research outputs found
On the data hiding theory and multimedia content security applications
This dissertation is a comprehensive study of digital steganography for multimedia content protection. With the increasing development of Internet technology, protection and enforcement of multimedia property rights has become a great concern to multimedia authors and distributors. Watermarking technologies provide a possible solution for this problem.
The dissertation first briefly introduces the current watermarking schemes, including their applications in video,, image and audio. Most available embedding schemes are based on direct Spread Sequence (SS) modulation. A small value pseudo random signature sequence is embedded into the host signal and the information is extracted via correlation. The correlation detection problem is discussed at the beginning. It is concluded that the correlator is not optimum in oblivious detection. The Maximum Likelihood detector is derived and some feasible suboptimal detectors are also analyzed. Through the calculation of extraction Bit Error Rate (BER), it is revealed that the SS scheme is not very efficient due to its poor host noise suppression. The watermark domain selection problem is addressed subsequently. Some implications on hiding capacity and reliability are also studied. The last topic in SS modulation scheme is the sequence selection. The relationship between sequence bandwidth and synchronization requirement is detailed in the work. It is demonstrated that the white sequence commonly used in watermarking may not really boost watermark security.
To address the host noise suppression problem, the hidden communication is modeled as a general hypothesis testing problem and a set partitioning scheme is proposed. Simulation studies and mathematical analysis confirm that it outperforms the SS schemes in host noise suppression. The proposed scheme demonstrates improvement over the existing embedding schemes.
Data hiding in audio signals are explored next. The audio data hiding is believed a more challenging task due to the human sensitivity to audio artifacts and advanced feature of current compression techniques. The human psychoacoustic model and human music understanding are also covered in the work. Then as a typical audio perceptual compression scheme, the popular MP3 compression is visited in some length. Several schemes, amplitude modulation, phase modulation and noise substitution are presented together with some experimental results. As a case study, a music bitstream encryption scheme is proposed. In all these applications, human psychoacoustic model plays a very important role. A more advanced audio analysis model is introduced to reveal implications on music understanding. In the last part, conclusions and future research are presented
Use and Abuse of the Fisher Information Matrix in the Assessment of Gravitational-Wave Parameter-Estimation Prospects
The Fisher-matrix formalism is used routinely in the literature on
gravitational-wave detection to characterize the parameter-estimation
performance of gravitational-wave measurements, given parametrized models of
the waveforms, and assuming detector noise of known colored Gaussian
distribution. Unfortunately, the Fisher matrix can be a poor predictor of the
amount of information obtained from typical observations, especially for
waveforms with several parameters and relatively low expected signal-to-noise
ratios (SNR), or for waveforms depending weakly on one or more parameters, when
their priors are not taken into proper consideration. In this paper I discuss
these pitfalls; show how they occur, even for relatively strong signals, with a
commonly used template family for binary-inspiral waveforms; and describe
practical recipes to recognize them and cope with them.
Specifically, I answer the following questions: (i) What is the significance
of (quasi-)singular Fisher matrices, and how must we deal with them? (ii) When
is it necessary to take into account prior probability distributions for the
source parameters? (iii) When is the signal-to-noise ratio high enough to
believe the Fisher-matrix result? In addition, I provide general expressions
for the higher-order, beyond--Fisher-matrix terms in the 1/SNR expansions for
the expected parameter accuracies.Comment: 24 pages, 3 figures, previously known as "A User Manual for the
Fisher Information Matrix"; final, corrected PRD versio
Covert Wireless Communication with a Poisson Field of Interferers
In this paper, we study covert communication in wireless networks consisting
of a transmitter, Alice, an intended receiver, Bob, a warden, Willie, and a
Poisson field of interferers. Bob and Willie are subject to uncertain shot
noise due to the ambient signals from interferers in the network. With the aid
of stochastic geometry, we analyze the throughput of the covert communication
between Alice and Bob subject to given requirements on the covertness against
Willie and the reliability of decoding at Bob. We consider non-fading and
fading channels. We analytically obtain interesting findings on the impacts of
the density and the transmit power of the concurrent interferers on the covert
throughput. That is, the density and the transmit power of the interferers have
no impact on the covert throughput as long as the network stays in the
interference-limited regime, for both the non-fading and the fading cases. When
the interference is sufficiently small and comparable with the receiver noise,
the covert throughput increases as the density or the transmit power of the
concurrent interferers increases
Considerations in the Interpretation of Cosmological Anomalies
Anomalies drive scientific discovery -- they are associated with the cutting
edge of the research frontier, and thus typically exploit data in the low
signal-to-noise regime. In astronomy, the prevalence of systematics --- both
"known unknowns" and "unknown unknowns" --- combined with increasingly large
datasets, the widespread use of ad hoc estimators for anomaly detection, and
the "look-elsewhere" effect, can lead to spurious false detections. In this
informal note, I argue that anomaly detection leading to discoveries of new
physics requires a combination of physical understanding, careful experimental
design to avoid confirmation bias, and self-consistent statistical methods.
These points are illustrated with several concrete examples from cosmology.Comment: An informal summary of an invited talk given at the IAU symposium
"Statistical Challenges in 21st Century Cosmology", accepted in the
Proceedings IAU Symposium No. 306, 2014 (A.F. Heavens, J.-L. Starck, A.
Krone-Martins eds.). 7 pages, 1 figure. Comments welcom
Non-linear echo cancellation - a Bayesian approach
Echo cancellation literature is reviewed, then a Bayesian model is introduced and it is shown how how it can be used to model and fit nonlinear channels. An algorithm for cancellation of echo over a nonlinear channel is developed and tested. It is shown that this nonlinear algorithm converges for both linear and nonlinear channels and is superior to linear echo cancellation for canceling an echo through a nonlinear echo-path channel
Current and future constraints on Higgs couplings in the nonlinear Effective Theory
We perform a Bayesian statistical analysis of the constraints on the
nonlinear Effective Theory given by the Higgs electroweak chiral Lagrangian. We
obtain bounds on the effective coefficients entering in Higgs observables at
the leading order, using all available Higgs-boson signal strengths from the
LHC runs 1 and 2. Using a prior dependence study of the solutions, we discuss
the results within the context of natural-sized Wilson coefficients. We further
study the expected sensitivities to the different Wilson coefficients at
various possible future colliders. Finally, we interpret our results in terms
of some minimal composite Higgs models.Comment: 45 pages, 9 figures, 8 tables; v2: updated references, experimental
input now includes data of Moriond 2018, extended discussion of projection to
future colliders; v3: added Appendix, matches Journal versio
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