On the Design of Perceptual MPEG-Video Encryption Algorithms

In this paper, some existing perceptual encryption algorithms of MPEG videos are reviewed and some problems, especially security defects of two recently proposed MPEG-video perceptual encryption schemes, are pointed out. Then, a simpler and more effective design is suggested, which selectively encrypts fixed-length codewords (FLC) in MPEG-video bitstreams under the control of three perceptibility factors. The proposed design is actually an encryption configuration that can work with any stream cipher or block cipher. Compared with the previously-proposed schemes, the new design provides more useful features, such as strict size-preservation, on-the-fly encryption and multiple perceptibility, which make it possible to support more applications with different requirements. In addition, four different measures are suggested to provide better security against known/chosen-plaintext attacks.Comment: 10 pages, 5 figures, IEEEtran.cl

A High Resolution Survey of the Galactic Plane at 408 MHz

The interstellar medium is a complex 'ecosystem' with gas constituents in the atomic, molecular, and ionized states, dust, magnetic fields, and relativistic particles. The Canadian Galactic Plane Survey has imaged these constituents with angular resolution of the order of arcminutes. This paper presents radio continuum data at 408 MHz over the area 52 degrees < longitude < 193 degrees, -6.5 degrees < latitude < 8.5 degrees, with an extension to latitude = 21 degrees in the range 97 degrees < longitude < 120 degrees, with angular resolution 2.8' x 2.8' cosec(declination). Observations were made with the Synthesis Telescope at the Dominion Radio Astrophysical Observatory as part of the Canadian Galactic Plane Survey. The calibration of the survey using existing radio source catalogs is described. The accuracy of 408-MHz flux densities from the data is 6%. Information on large structures has been incorporated into the data using the single-antenna survey of Haslam (1982). The paper presents the data, describes how it can be accessed electronically, and gives examples of applications of the data to ISM research.Comment: Accepted for publication in the Astronomical Journa

Multiple channel maximum entropy spectral estimator and its application.

Thesis. 1977. M.S.--Massachusetts Institute of Technology. Dept. of Earth and Planetary Sciences.Microfiche copy available in Archives and Science.Bibliography : leaves 52-54.M.S

A size-dependent nanoscale metal–insulator transition in random materials

Insulators and conductors with periodic structures can be readily distinguished, because they have different band structures, but the differences between insulators and conductors with random structures are more subtle. In 1958, Anderson provided a straightforward criterion for distinguishing between random insulators and conductors, based on the \u27diffusion\u27 distance ζ for electrons at 0 K (ref. 3). Insulators have a finite ζ, but conductors have an infinite ζ. Aided by a scaling argument, this concept can explain many phenomena in disordered electronic systems, such as the fact that the electrical resistivity of \u27dirty\u27 metals always increases as the temperature approaches 0 K (refs 4–6). Further verification for this model has come from experiments that measure how the properties of macroscopic samples vary with changes in temperature, pressure, impurity concentration and applied magnetic field, but, surprisingly, there have been no attempts to engineer a metal–insulator transition by making the sample size less than or more thanζ. Here, we report such an engineered transition using six different thin-film systems: two are glasses that contain dispersed platinum atoms, and four are single crystals of perovskite that contain minor conducting components. With a sample size comparable to ζ, transitions can be triggered by using an electric field or ultraviolet radiation to tune ζ through the injection and extraction of electrons. It would seem possible to take advantage of this nanometallicity in applications

Cross-Monitoring and Corporate Governance

We take the view that corporate governance must involve more than corporate law. Despite corporate scholars\u27 nearly exclusive focus on corporate law mechanisms for controlling managerial agency costs, shareholders are not the only constituency concerned with such costs. Given the thick web of firms\u27 contractual commitments, it should not be a surprise that other financial claimants may also attempt to control agency costs in their contracts with the firm. We hypothesize that this cross-monitoring by other claimants has value for shareholders. We examine bank loans for empirical evidence of the value of cross-monitoring. Our approach builds on prior empirical work on the value of good corporate governance, to which we add data on the presence of bank loans and their interactions with free cash flow, governance indices, and individual corporate governance provisions. To our knowledge, ours is the first study to measure the performance effects of bank debt as a device for reducing managerial agency costs, and the first study on the interaction of ongoing bank monitoring with corporate governance arrangements. We find strong evidence that bank monitoring adds value. In effect, bank monitoring can counteract somewhat the value-decreasing effects of managerial entrenchment. Bank monitoring may substitute for good corporate governance