683 research outputs found
Wide spread spectrum watermarking with side information and interference cancellation
Nowadays, a popular method used for additive watermarking is wide spread
spectrum. It consists in adding a spread signal into the host document. This
signal is obtained by the sum of a set of carrier vectors, which are modulated
by the bits to be embedded. To extract these embedded bits, weighted
correlations between the watermarked document and the carriers are computed.
Unfortunately, even without any attack, the obtained set of bits can be
corrupted due to the interference with the host signal (host interference) and
also due to the interference with the others carriers (inter-symbols
interference (ISI) due to the non-orthogonality of the carriers). Some recent
watermarking algorithms deal with host interference using side informed
methods, but inter-symbols interference problem is still open. In this paper,
we deal with interference cancellation methods, and we propose to consider ISI
as side information and to integrate it into the host signal. This leads to a
great improvement of extraction performance in term of signal-to-noise ratio
and/or watermark robustness.Comment: 12 pages, 8 figure
Watermarking for multimedia security using complex wavelets
This paper investigates the application of complex wavelet transforms to the field of digital data hiding. Complex wavelets offer improved directional selectivity and shift invariance over their discretely sampled counterparts allowing for better adaptation of watermark distortions to the host media. Two methods of deriving visual models for the watermarking system are adapted to the complex wavelet transforms and their performances are compared. To produce improved capacity a spread transform embedding algorithm is devised, this combines the robustness of spread spectrum methods with the high capacity of quantization based methods. Using established information theoretic methods, limits of watermark capacity are derived that demonstrate the superiority of complex wavelets over discretely sampled wavelets. Finally results for the algorithm against commonly used attacks demonstrate its robustness and the improved performance offered by complex wavelet transforms
Statistical Watermarking for Networked Control Systems
Watermarking can detect sensor attacks in control systems by injecting a
private signal into the control, whereby attacks are identified by checking the
statistics of the sensor measurements and private signal. However, past
approaches assume full state measurements or a centralized controller, which is
not found in networked LTI systems with subcontrollers. Since generally the
entire system is neither controllable nor observable by a single subcontroller,
communication of sensor measurements is required to ensure closed-loop
stability. The possibility of attacking the communication channel has not been
explicitly considered by previous watermarking schemes, and requires a new
design. In this paper, we derive a statistical watermarking test that can
detect both sensor and communication attacks. A unique (compared to the
non-networked case) aspect of the implementing this test is the state-feedback
controller must be designed so that the closed-loop system is controllable by
each sub-controller, and we provide two approaches to design such a controller
using Heymann's lemma and a multi-input generalization of Heymann's lemma. The
usefulness of our approach is demonstrated with a simulation of detecting
attacks in a platoon of autonomous vehicles. Our test allows each vehicle to
independently detect attacks on both the communication channel between vehicles
and on the sensor measurements
Authentication with Distortion Criteria
In a variety of applications, there is a need to authenticate content that
has experienced legitimate editing in addition to potential tampering attacks.
We develop one formulation of this problem based on a strict notion of
security, and characterize and interpret the associated information-theoretic
performance limits. The results can be viewed as a natural generalization of
classical approaches to traditional authentication. Additional insights into
the structure of such systems and their behavior are obtained by further
specializing the results to Bernoulli and Gaussian cases. The associated
systems are shown to be substantially better in terms of performance and/or
security than commonly advocated approaches based on data hiding and digital
watermarking. Finally, the formulation is extended to obtain efficient layered
authentication system constructions.Comment: 22 pages, 10 figure
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