Electronic marking and identification techniques to discourage document copying

Modern computer networks make it possible to distribute documents quickly and economically by electronic means rather than by conventional paper means. However, the widespread adoption of electronic distribution of copyrighted material is currently impeded by the ease of illicit copying and dissemination. In this paper we propose techniques that discourage illicit distribution by embedding each document with a unique codeword. Our encoding techniques are indiscernible by readers, yet enable us to identify the sanctioned recipient of a document by examination of a recovered document. We propose three coding methods, describe one in detail, and present experimental results showing that our identification techniques are highly reliable, even after documents have been photocopied

The Minimum Shared Edges Problem on Grid-like Graphs

We study the NP-hard Minimum Shared Edges (MSE) problem on graphs: decide whether it is possible to route $p$ paths from a start vertex to a target vertex in a given graph while using at most $k$ edges more than once. We show that MSE can be decided on bounded (i.e. finite) grids in linear time when both dimensions are either small or large compared to the number $p$ of paths. On the contrary, we show that MSE remains NP-hard on subgraphs of bounded grids. Finally, we study MSE from a parametrised complexity point of view. It is known that MSE is fixed-parameter tractable with respect to the number $p$ of paths. We show that, under standard complexity-theoretical assumptions, the problem parametrised by the combined parameter $k$, $p$, maximum degree, diameter, and treewidth does not admit a polynomial-size problem kernel, even when restricted to planar graphs

An Adaptive Intraframe DPCM Codec based Upon Nonstationary Image Model

This Paper Introduces a Nonstationary Model for Images and Develops an Adaptive Intrafield Dpcm Codec based Upon the Model. the Codec Attempts to Minimize the Mean‐square Coding Error at Each Sample Point in the Picture. the Quantizer in the Resulting Adaptive Codec is Found to Be Similar to that Previously Obtained from Visual Masking Considerations. Comparative Simulation Results using 256 X 256 Pixel Rasters Are Given for Two‐ and Three‐bit/pixel Versions of the Adaptive Codec, the Three‐bit/pixel Graham Codec, and Three‐bit/pixel Previous Element Dpcm. © 1979 the Bell System Technical Journa

Reduction of Transmission Error Propagation in Adaptively Predicted, DPCM Encoded Pictures

A New Technique for Reducing Transmission Error Propagation in Adaptively Predicted, dpcm‐encoded Pictures is Described. the Basis for the Technique is a Generalization of the Notion of Predictor Output Attenuation, Described by Graham, to Include Attenuation of the Adaptive Prediction Function. Simulation Results Are Presented that Show that Application of the Technique to Graham\u27s Codec Results in Significant Reduction in Error Propagation Without Degradation of Picture Quality. the Technique Requires No Increase in Transmission Rate. © 1979 the Bell System Technical Journa