Inventors: Thomas Lipscomb and Robert H Nagel

US patent number: 5,473,687

US patent application date: December 29, 1993
US patent issue date: December 5, 1995

SYNOPSIS OF THE INVENTION

An object of the present invention is to provide a system (method and apparatus) for discouraging and preventing unauthorized storage and retrieval (copying) of clear text information, which has been electronically retrieved by an authorized user from a secure information source. A further object of the present invention is to provide a system for electronic retrieval of a plurality of "information packets" from a secure information source in such a way as to discourage unauthorized use of these packets. It is a further object of the present invention to provide a system for discouraging electronic storage of clear text information packets for continued and continuouss availability to an information user. It is a further object of the present invention to provide a system for preventing repeated use and copying of clear text information, which is available in electronic storage.

These objects, as well as further objects which will become apparent from the discussion that follows, are achieved, in accordance with the present invention, by "decompressing" the information packet--that is, increasing the size of the information packet so that the long-term storage of this information packet would be awkward, inconvenient and expensive. For this reason, the information user is inclined to delete the information packet from electronic storage and then retrieve it again from the secure information source, paying the relatively nominal charge imposed by the information provider. When "decompressing," "expanding," of "exploding" the information, it is important that the information not be capable of being compressed again, for example, by means of the "zip" program, which looks for redundancy in the data. Accordingly, the information packet is preferably expanded by means of the following method: (a) producing a series of first pseudorandom digital data having a bit length which is at least twice the bit length of the information packet; and (b) combining the information packet with the first pseudorandom data to form second pseudorandom digital data having a bit length which is at least twice the bit length of the information packet.

The information packet and the first pseudorandom data are combined in such a way that the information data can be extracted from the second pseudorandom data. The information packet is thus expanded into a packet of pseudorandom data, which is sufficiently large to discourage permanent storage of this expanded data. In a preferred embodiment of the present invention, this final bit length is equal to at least 1.5 megabytes, which is greater than the amount of data, which can fit on a conventional 1.44-megabyte data diskette. All information packets, of whatever size, are preferably expanded ("exploded") to this final prescribed length. For a full understanding of the present invention, reference should now be made to the following detailed description of the preferred embodiments of the invention as illustrated in the accompanying drawings.