United States Patent [w]
Sollish et al.
US006029259A [ii] Patent Number:  Date of Patent:
 METHOD AND SYSTEM FOR
AUTHENTICATING DIGITAL OPTICAL
 Inventors: Baruch Sollish, Emmanuel, Israel;
Craig Schwarz, Churchville, N.Y.
 Assignee: T.T.R. Technologies Ltd., Klar-Saba, Israel
 Appl. No.: 09/103,682
 Filed: Jun. 15, 1998
 Int. C I. G11C 29/00
 U.S. CI 714/719; 714/718
 Field of Search 714/719, 718
 References Cited
U.S. PATENT DOCUMENTS
5,400,319 3/1995 Fite et al 369/275.5
5,563,947 10/1996 Kikimis 380/4
5,590,768 1/1997 Hilton et al 206/308.1
5,703,858 12/1997 Mitchell et al 369/58
Primary Examiner—Phung M. Chung Attorney, Agent, or Firm—Darby & Darby
A method for authenticating a digital optical medium to determine il it is original or an unauthorized copy. One or more special bistable data subunits are written onto the original digital optical medium by recording bistable data symbols and other intentional errors into the data subunit such that the data subunit will be on the error-correction limit threshold. A bistable data symbol is a data symbol for which a player will randomly read at least two different values. Depending on which values are read for the bistable data symbols, the bistable data subunit will either be errorfree and readable (at or below the error-correction limit) or will be erroneous or unreadable (above the error-correction limit). When an unauthorized copy of the digital optical medium is made, the data subunit with the address of the bistable data subunit on the original digital optical medium will be a monostable data subunit with constant data, because special hardware equipment is needed to record bistable data symbols. Thus, by testing the stability of the appropriate data subunits, the undetermined digital optical medium can be authenticated as either original or an unauthorized copy. Methods for writing a bistable data subunit include replacing one or more data symbols in the data subunit with bistable data symbols and zero or more data symbols in the data subunit with erroneous data symbols. Methods for testing the stability of a data subunit include multiple readings and checking for error as well as measuring the time for a successful read using a player with a multiple retry capability.
8 Claims, 10 Drawing Sheets