Electronic marking and identification techniques to discouragedocument copying

摘要

Modern computer networks make it possible to distribute documentsquickly and economically by electronic means rather than by conventionalpaper means. However, the widespread adoption of electronic distributionof copyrighted material is currently impeded by the ease of illicitcopying and dissemination. The authors propose techniques thatdiscourage illicit distribution by embedding each document with a uniquecodeword. The encoding techniques are indiscernible by readers, yetenable one to identify the sanctioned recipient of a document byexamination of a recovered document. The authors propose three codingmethods, describe one in detail, and present experimental resultsshowing that their identification techniques are highly reliable, evenafter documents have been photocopied