Introduction

Right Hemisphere has developed a software system, called Em-bargo, aimed at protecting copyright of printed documents. It is applicable to word processing software and electronic document delivery. The basic idea, now covered by numerous patents around the world, is that confidential or copyright information can be invisibly marked with a "fingerprint" which links the document to its legitimate owner. Unauthorised copies of the document can be scanned to reveal their source, which provides a significant level of deterrence against security leaks or copyright violation.

HOW IT WORKS

Documents are fingerprinted by making a sequence of small variations to the spacing between words, characters, lines or other groups of printed elements of the document. These variations are very small and not visible to the eye, but can be read by a scanner and suitable software. The fingerprint is spread throughout the document, and kept through photocopying or faxing. The fingerprint can only be removed by re-keying the whole document.

WORD-PROCESSING APPLICATION

When combined with word-processing software, Em-bargo allows each copy of a document to be fingerprinted with the name of the authorised recipient. Any pirate copies can then be traced to their source. The fingerprint can also be arranged to indicate who printed the document. This is valuable for identifying employees who failed to use the shredder, or who sent a job to the wrong printer and didn't retrieve it. Many other applications suggest themselves, such as fingerprinting the document with its filename for later reference, and even applying the technology to photocopiers.

INTERNET APPLICATION

Em-bargo has enormous potential in the field of electronic document delivery and network publishing. To purchase a magazine, novel, business report, sheet music, or any other copyright document, the purchaser receives an encrypted file which can only be decrypted and printed by software which fingerprints the document with the purchaser's identity. If the purchaser gives a copy of the document to someone else, either by file transfer or photocopying of the hard copy, the pirate copy bears the purchaser's fingerprint.

This capability could be the key to making on-line publishing financially viable.

PHOTOCOPIER SECURITY

Em-bargo technology can be built into an electronic photocopier (the type of copier which scans the document electronically then prints it). Copies of documents produced by this copier can then contain invisible fingerprint information, such as the name of the person who made the copy. This could be invaluable for controlling document distribution, or preserving copyright in printed documents. This would be a huge benefit in libraries, where copying is allowed so long as numbers are limited, or in businesses where the ability to trace the person responsible for making each copy could be an important security asset.

SECURE PRINTERS

The technology can be incorporated into a printer's software, so that, for example, every document printed contains the name of the printer and the date, and possibly the name of the person requesting the printout.

Other Applications

Many other applications suggest themselves. Here are some examples:

• Document identification: Printed documents can be fingerprinted with text identifying the document for later reference. Just scan a page of the document to reveal the hidden information, which might include the filename, author, date or other useful identifying text.
  
• Document security: If the fingerprint indicates who printed the document, employees who failed to use the shredder, or who sent a job to the wrong printer and didn't retrieve it, can be readily identified.
  
• Software piracy: Em-bargo technology can be embedded into applications, such as word processors, so that every document printed carries within it the name of the licensed owner of the software. This would be a huge deterrent against "sharing" proprietary software, as legitimate owners of the software know that every document printed by pirated versions will contain their unique fingerprint, so the source of the breach can be identified from any hard copy subsequently generated.

FINGERPRINTING

This technique has been chosen as it offers a number of benefits:

• The appearance or readability of the document is not adversely affected.
• The fingerprint is spread throughout the document, so that any part leaked can be traced. It is not possible to remove the fingerprint, for example by whiting-out. It can only be removed by re-keying the entire document.
• The fingerprint is conveyed even through facsimile and multiple generations of photocopy including enlargements or reductions.

DECODING

A document's fingerprint is recovered by scanning it, using a conventional flat-bed scanner, and processing the bitmap image using Em-bargo decoding software. The hidden information is then displayed on the screen.