Copyright protection for the electronic distribution of text documents

Each copy of a text document can be made different in a nearly invisible way by repositioning or modifying the appearance of different elements of text, i.e., lines, words, or characters. A unique copy can be registered with its recipient, so that subsequent unauthorized copies that are retrieved can be traced back to the original owner. In this paper we describe and compare several mechanisms for marking documents and several other mechanisms for decoding the marks after documents have been subjected to common types of distortion. The marks are intended to protect documents of limited value that are owned by individuals who would rather possess a legal than an illegal copy if they can be distinguished. We will describe attacks that remove the marks and countermeasures to those attacks. An architecture is described for distributing a large number of copies without burdening the publisher with creating and transmitting the unique documents. The architecture also allows the publisher to determine the identity of a recipient who has illegally redistributed the document, without compromising the privacy of individuals who are not operating illegally. Two experimental systems are described. One was used to distribute an issue of the IEEE JOURNAL ON SELECTED AREAS IN COMMUNICATIONS, and the second was used to mark copies of company private memoranda

Document copying deterrent method

The present invention is directed to a method of deterring the illicit copying of electronically published documents. It includes utilizing a computer system to electronically publish a plurality of copies of a document having electronically created material thereon for distribution to a plurality of subscribers and operating programming within the computer system so as to perform the identification code functions. The steps are to encode the plurality of copies each with a separate, unique identification code, the identification code being based on a unique arrangement of the electronically created material on each such copy; and, creating a codebook to correlate each such identification code to a particular subscriber. In some embodiments, decoding methods are included with the encoding capabilities. The unique arrangement of the electronically created material may be based on line-shift coding, word-shift coding, or feature enhancement coding (or combinations of these) and may be effected through bitmap alteration of document format file alteration

Capacity of Text Marking Channel

We have proposed earlier watermarking text documents by slightly shifting certain text lines. Such a text line represents a noisy channel and marking represents the transmission of a signal through this channel. The power of the signal represents the size of the shift and must be small for the marks to be imperceptible. In this paper we formulate the channel capacity under a constraint on individual signal power. We shows that to achieve the capacity the shifts should be normally distributed, have maximum power, and adjacent shifts should be negatively correlated. I. Introduction Many image watermarking methods have been proposed to protect motion and still pictures (see e.g. [5], [6] and references therein). Most of these works, however, are suitable for images with rich greyscale. For text documents, whose image is often binary, marks placed by some of these methods can be easily removed by binarization. We have proposed in [1], [7], [2] a different approach for marking text that i..

A Collusion Problem and its Solution

Consider a group of colluders each with certain knowledge such as identity of some other colluders, some cryptographic keys, and some data, possibly multiply encrypted. Two colluders can combine their knowledge if their current knowledge satisfies certain condition. Their cryptographic keys can help decrypt each other's encrypted data, expanding their knowledge and revealing more collusion opportunities, and the process of collusion continues. The question we address is whether it is possible for them to uncover a target set of unencrypted data. In this paper we formulate the collusion problem and provide an algorithm that determines whether a collusion problem has a solution and if so, computes one. A solution is a specific way by which the colluders can uncover the hidden information. The solution generated by our algorithm is generally not one that involves the minimum number of colluders. We show however that to find such a solution is NP-complete. Complex communications..

Collusion analysis of cryptographic protocols

As network applications such as electronic commerce proliferate, complex communications protocols that employ cryptographic building blocks, such as encryption and authentication, will become more common. We view a cryptographic protocol as a process by which information is transferred among some users and hidden from others. The collusion problem determines whether a subset of users can discover, through collusion, the information that is designed to be hidden from them after a protocol is executed. Earlier we introduced a model for cryptographic protocols and its collusion analysis, and solved a special case of the collusion problem. In this paper we present an algorithm that solves the general case

A Centralized, Tree-Based Approach to Network Repair Service for Multicast Streaming Media

IP multicast provides best-effort delivery. Packets encounter variable delays and may be lost because of transmission errors and buffer overflows. Real-time multimedia streaming services require that most packets arrive at the receivers prior to an application deadline. Multicast quality on the current Internet is often inadequate for these applications. We have solved this problem by placing repair servers inside the network. The repair servers recover missing packets by communicating with each other, then re-multicast the repaired stream to nearby receivers on a new address. Multicast reception in the constrained area is typically much better than in the wide area Internet. In this paper we address the problem of constructing a repair graph. The repair graph shows which repair servers each repair server communicates with to recover missing messages. Our objectives when constructing this graph conflict with each other. We want high reliability: every repair server to recover as many missing messages as possible, as quickly as possible. But we also want low cost: this recovery should use as little of the network bandwidth as possible. We present a centralized algorithm to generate repair graphs. We demonstrate through simulation that these graphs achieve a level of reliability that is almost as high as that achieved by repair graphs specifically designed for high reliability. At the same time, our graphs maintain a cost that is almost as low as the cost in repair graphs designed for low cost