Documents filed in April 2000 with the U.S. Patent Office describe a method of copy protection by which the game system would verify a disc as legitimate, register the disc to that particular game console, then wipe out verification data so the disc would be rendered unreadable in other PlayStations.

"Since only titles for which legitimate software has actually been purchased and which have been initially registered in the machine table can be used, resale (so-called used software purchase) after purchase by an end user becomes practically impossible," according to the patent documents.

Although Sony has been vague about its plans for the technology, "I actually think they're toying with this idea," said Michael Pachter, a game industry analyst for Wedbush Morgan Securities.