System for encoding a glass master to enable detection of a counterfeit optical CD-ROM

A device for enabling detection of a counterfeit optical CD-ROM is disclosed for use in a conventional mastering system. The device includes a signal source for providing a first signal for forming a predetermined defect in a glass master. The device also includes a switch for connecting a recorder of the mastering system to the signal source. In addition, the device includes a decoder for decoding encoded data and address information provided from an input source of the mastering system. Furthermore, the device includes a central processor unit which serves to detect whether a selected address from the decoded data is present. Upon detection of the selected address, the CPU controls the switch to connect the signal source to the recorder to enable the recorder to receive the first signal and form the predetermined defect at the selected address. When a CD-ROM manufactured from the glass master is played back, a desired error signal is generated at the predetermined address indicating that the CD-ROM is not counterfeit. Further, when a counterfeit CD-ROM is played back, the desired error signal is not generated at the predetermined address, thus enabling detection of the counterfeit CD-ROM. In addition, the defect is not visible to the unaided eye when the CD-ROM is viewed.

FIELD OF THE INVENTION 
This invention relates to the detection of counterfeit optical CD-ROMs, and 
more particularly, to a device for forming a predetermined defect at a 
predetermined location on an optical CD-ROM glass master used to 
manufacture a metal master from which duplicate CD-ROMs are fabricated, 
wherein when a duplicate CD-ROM is played back, a desired error signal is 
generated at a predetermined address and when a counterfeit CD-ROM is 
played back, the desired error signal is not generated at the 
predetermined address, thus enabling detection of the counterfeit CD-ROM. 
BACKGROUND OF THE INVENTION 
In conventional CD-ROM mastering, an input source is utilized to provide 
data which has been encoded .in a manner well known in the art. The 
encoded data is transmitted to a laser beam recorder (LBR) which utilizes 
the encoded data to selectively subject areas of a glass disk to a laser 
beam. The glass disk is then chemically treated in order to ultimately 
form an original glass master used to manufacture a metal master from 
which duplicate CD-ROMs are fabricated. In addition, with the advent of 
direct from disk mastering technology, a duplicate CD-ROM may also be 
utilized to manufacture a glass master. However, this technology also 
enables a counterfeiter to use a duplicate CD-ROM to form a counterfeit 
glass master in order to manufacture counterfeit CD-ROMs. Such illegal 
copying, or piracy, has caused great concern in the industry, resulting in 
the formation of organizations whose purpose is the elimination of piracy. 
Further, it has been estimated that such illegal copying costs legal 
manufacturers of CD-ROMs over $260 million per year. In this regard, 
reference is made to an article in the February 1994 edition of "One to 
One", page 16, entitled "GATT-TRIPS . . . And Falls Over". 
Various methods have been used to identify a CD-ROM in order to attempt to 
distinguish between a legally manufactured and counterfeit CD-ROM. One 
method includes forming a serial number on the CD-ROM by a process 
entitled "Maple Leaf" proposed by JVC. Another method includes using a 
code known as a Source Identification Code (SID Code) which identifies the 
manufacturing facility where a CD was replicated and where a master was 
originally manufactured. In this regard, reference is made to articles in 
the February 1994 and March/April 1994 editions of "One to One" entitled 
"SID code: Majors move ahead", page 5, and "SID Code finalised--now it's 
official", page 26, respectively. 
In addition, bar codes have been used to identify CD-ROMs. In this regard, 
reference is made to a publication by Optical Disc Corporation entitled 
"Disc Label Designer.TM. Graphic Editor & Disc Label Generator" which 
describes the insertion of text and bar code information near the inside 
of the disk. Further, although not described, the equipment utilized in 
this method could also be used to generate text or characters in the 
program area of the disk in order to distinguish counterfeit disks from 
legally manufactured disks. In addition, Sony Corporation manufactures a 
Bar Code/Text Generator which also forms bar code and text information 
near the inside of the disk. 
Furthermore, dyes have been used for identifying a CD-ROM. In this method, 
a selected dye is added to a protective layer of the CD-ROM. The dye, when 
exposed to selected light sources, emits light having a color which 
identifies a selected manufacturing facility. This enables the use of 
selected colors to identify each manufacturing facility. 
However, a disadvantage with each of these methods is that such identifying 
information may be readily and accurately copied by counterfeiters 
utilizing available technology. As a result, illegally copied CD-ROMs are 
manufactured by counterfeiters which are essentially indistinguishable 
from legal CD-ROMs and thus undetectable. 
In this regard, hologram technology known as Nimbus, Replicate Stage or 
D.B.C./Holographic Label has been utilized for identifying the 
manufacturer of a CD-ROM. Essentially, this method includes the formation 
of a holographic image on the CD-ROM which is visible to the naked eye. 
The image formed is difficult to copy, thus enabling an illegally copied 
CD-ROM to be readily identifiable. Another method includes the use of 
"waterspot" technology introduced by Sonopress. In this method, a pattern 
is formed on the disk which is visible to the naked eye and difficult to 
copy. The pattern may be text or graphics and may be placed anywhere in 
the information area of the disk. However, a disadvantage with these 
methods is that the contents of the CD-ROM may still be accurately 
duplicated, thus not affecting playback of the illegal CD-ROM on 
conventional equipment. As a result, a counterfeiter is not substantially 
discouraged from illegally copying the disk. Further, it has been found 
that this technology is expensive to implement in CD-ROMs. 
As such, efforts have been made to inhibit copying of CD-ROMs. In this 
regard, copending patent application Serial No. 08/132,709, assigned to 
Digital Audio Disc Corporation, the assignee herein, describes a method 
wherein multiple information areas of a disk are destroyed in order to 
form a code which is detectable by software. Further, the information 
areas are destroyed after the disk has been manufactured. However, the 
destroyed information areas are sufficiently large such that they are 
visible to the unaided eye, thus enabling detection by a potential 
counterfeiter. 
Therefore, it is an object of the present invention to provide a system 
which does not enable accurate duplication of a CD-ROM by forming a 
predetermined defect, which cannot be accurately duplicated, at a 
predetermined location on an optical CD-ROM glass master wherein the 
defect is not visible to the unaided eye in a duplicate CD-ROM 
manufactured from the glass master, and when the duplicate CD-ROM is 
played back, a desired error signal is generated at a predetermined 
address indicating the CD-ROM is not counterfeit and when a counterfeit 
CD-ROM is played back, the desired error signal is not generated at the 
predetermined address, thus enabling detection of the counterfeit CD-ROM 
so as to render the CD-ROM unusable thus substantially discouraging a 
potential counterfeiter. 
SUMMARY OF THE INVENTION 
A device for encrypting a glass master to inhibit manufacture of a 
counterfeit optical CD-ROM. The device is used in conjunction with a 
mastering system having an input source for providing EFM encoded data 
which includes sector address information and a recorder for forming a 
glass master in accordance with a received signal. In particular, the 
device includes a signal source for providing a first signal for forming a 
predetermined defect in the glass master and a switch for connecting the 
recorder to either the input source or the signal source. The device 
further includes a decoder for decoding the EFM encoded data and the 
sector address information in order to provide decoded data. In addition, 
a central processor unit (CPU) is coupled to the decoder which serves to 
detect a sector address selected from the decoded data. Upon detection of 
the sector address by the CPU, the CPU controls the switch so as to 
connect the signal source to the recorder to thus enable the recorder to 
receive the first signal and form the predetermined defect at the selected 
sector address. This causes a predetermined error signal to be generated 
at the sector address when a CD-ROM manufactured from the glass master is 
played back indicating that the CD-ROM is not counterfeit and when a 
counterfeit CD-ROM is played back, the predetermined error signal is not 
generated at the sector address, thus indicating that the CD-ROM is 
counterfeit. Further, the defect on the CD-ROM is not visible to the 
unaided eye.

DETAILED DESCRIPTION OF THE INVENTION 
The present invention will now be described by referring to FIGS. 1-3B, 
wherein like elements are designated by like reference numerals. Referring 
to FIG. 1, a block diagram for a system 10 for encoding a glass master to 
enable the detection of a counterfeit optical CD-ROM is shown. In 
conventional CD-ROM mastering, an input source 12 is utilized to provide 
data which has been encoded using eight to fourteen modulation (EFM) in a 
manner well known in the art. The EFM encoded data is then transmitted to 
a laser beam recorder (LBR) 14 which utilizes the EFM encoded data to 
selectively subject areas of a glass disk to a laser beam. The glass disk 
is then chemically treated in order to ultimately form an original glass 
master used to fabricate a metal master from which CD-ROMs are replicated. 
In accordance with the present invention, the system 10 is located between 
the input source 12 and the LBR 14. The system 10 includes a switching 
device 16 which enables the ultimate formation of a desired defect on the 
glass master at a predetermined location. A CD-ROM may include 333,000 
blocks, or sectors, each having 2048 bytes of user data. In a preferred 
embodiment, at least one sector is destroyed in order to form the defect. 
Further, the configuration and size of the defect is preferably such that 
the defect is not visible to the unaided eye when a CD-ROM having the 
defect is viewed. The system 10 further includes a signal source 18 for 
providing random high frequency (HF) or other signal suitable for 
producing data errors in the desired sector or sectors. In addition, the 
system 10 includes a computer terminal 20 which enables a user to define 
the location or sector address of the sector to be destroyed. 
Referring to FIG. 2, a schematic for the switching device 16 is shown. The 
switching device 16 includes an EFM decoder 22, an analog switch 24 having 
first 26, second 28 and third 30 switch terminals and a CPU 32 for 
controlling the analog switch 24 having control line 34. The switching 
device 16 further includes data 36, sector address 38 and signal 40 input 
terminals and an output terminal 42. The data input terminal 36 is 
connected to the first switch terminal 26 and to the EFM decoder 22. The 
CPU 32 is connected to the sector address input terminal 38 and coupled to 
the EFM decoder 22. The signal input terminal 40 is connected to the 
second switch terminal 28. The data 36, sector address 38 and signal 40 
input terminals are connected to the input source 12, the computer 
terminal 20 and the signal source 18, respectively (FIG. 1). Further, the 
output terminal 42 is connected between the third switch terminal 30 and 
the LBR 14. The analog switch 24 serves to electrically connect the first 
26 and third 30 switch terminals when the analog switch 24 is turned on 
through control line 34 or to electrically connect the second 28 and third 
30 switch terminals when the analog switch 24 is turned off through 
control line 34. 
In normal operation, the analog switch 24 is on, thus enabling EFM encoded 
data having encoded address information provided by the input source 12 to 
be transmitted as a data stream to the output terminal 42 and ultimately 
to the LBR 14. The LBR 14 is then driven to selectively subject areas of 
the glass disk to a laser beam in accordance with the EFM encoded data. 
Further, EFM encoded data from the input source 12 is also transmitted to 
the EFM decoder 22 where the address information is decoded and then 
provided to the CPU 32. In accordance with the present invention, the user 
employs the computer terminal 20 to input to the CPU 32 a sector address 
for a desired sector to be destroyed. The CPU 32 then monitors the decoded 
address information and detects whether the sector address is present. 
Upon detection of the sector address, the CPU 32 controls the analog 
switch 24 through control line 34 so as to turn off analog switch 24. This 
interrupts the data stream supplied by the input source 12 and connects 
the signal source 18, thus enabling the transmittance of a random HF or 
other signal to the LBR 14. The LBR 14 is then driven to subject areas of 
the glass disk to the laser beam in accordance with the random HF signal. 
When this is complete, the CPU 32 controls the analog switch through 
control line 34 so as to turn on analog switch 24. This resumes 
transmittance of EFM encoded data to again selectively subject areas of 
the glass disk to a laser beam in accordance with the EFM encoded data. 
Upon completion, the glass disk is then chemically treated in a well known 
manner in order to ultimately form an encrypted glass master having a 
defect at a predetermined address. The encrypted glass master is then used 
to form a metal master from which encrypted CD-ROMs, each having the 
defect at the predetermined address, may be manufactured. 
CD-ROM verification equipment having a CD-ROM drive is frequently utilized 
during the manufacturing process to check data. It has been found that 
when an encrypted CD-ROM having the defect is played back on a CD-ROM 
drive, the defect causes the generation of an error message, known as a 
device medium error, at a predetermined address thus indicating that 
sector data is missing or difficult to obtain. When an encrypted CD-ROM 
having the defect is utilized to form a second, or counterfeit, glass 
master, the duplicating equipment attempts to reconstruct the missing data 
in order to keep the integrity of the sector intact. However, since random 
HF was used to form the defect, the reconstructed data will not be an 
accurate duplication. It has been found that upon playback of a second, or 
counterfeit, CD-ROM fabricated from the counterfeit glass master, a 
different error message indicating that data is incorrect or missing is 
generated. 
This is shown by a test in which an encrypted CD-ROM having a defect at a 
predetermined address (designated as Test -A) and a counterfeit CD-ROM 
(designated as Test-B) are each played back on CD-ROM verification 
equipment. In order to form the encrypted CD-ROM, an encrypted glass 
master was formed by interrupting an EFM signal used for forming the glass 
master at approximately 40:00:00 minutes, absolute time, in order to 
enable insertion of random HF to form the defect. The encrypted glass 
master was then utilized to ultimately manufacture the encrypted CD-ROM. 
Subsequently, the encrypted CD-ROM was utilized to form a counterfeit 
glass master from which the counterfeit CD-ROM was ultimately formed. 
The encrypted and counterfeit CD-ROMs were then tested for high frequency 
(HF), block error rate (BER) and track pitch parameters by using test 
equipment used to certify stampers as acceptable for production use. 
Further, the test equipment serves to detect and correct data errors by 
using a scheme known as the Cross-Interleave Reed-Solomon Code (CIRC). The 
test results are as shown in Table 1: 
TABLE 1 
______________________________________ 
Test-A Test-B 
TEST DATA (encrypted CD-ROM) 
(counterfeit CD-ROM) 
______________________________________ 
HF Results 
Good Good 
BER Results 
C2 error & Drop Out @ 
Good 
40:00 min 
Track Pitch 
Good Good 
______________________________________ 
Referring to Table 1, the BER Results show that the encrypted CD-ROM had a 
"C2" error at 40:00 minutes. This indicates an unrecoverable error which 
could not be corrected by the CIRC. However, no errors were detected when 
the second master was tested, thus indicating that data was reconstructed 
when the second master was manufactured. 
Subsequently, the encrypted and counterfeit CD-ROMs were each played back 
on four different CD-ROM drives used in conjunction with the verification 
equipment. In particular, the drives utilized were a Philips LMS CM212 
drive, a Toshiba XM-3401TA 2 speed drive, a Sony CDU-541 drive and a Sony 
CDU-561 2 speed drive, although it is noted that other drives may be used. 
The results for the verification test are as shown in Table 2: 
TABLE 2 
______________________________________ 
CD-ROM Test-A Test-B 
Verification 
(encrypted CD-ROM) 
(counterfeit CD-ROM) 
______________________________________ 
Phillips communication failure @ 
Mismatch found @ block 
LMS CM 212 block 179851 179850 
Toshiba SCSI device medium 
SCSI blank block 
XM-3401TA (2X) 
error @ block 179851 
encountered @ 179850 
Sony CDU-541 
SCSI device medium 
Mismatch found @ block 
error @ block 179851 
179850 
Sony SCSI device medium 
Mismatch found @ block 
CDU-561 (2X) 
error @ block 179851 
179850 
______________________________________ 
Referring to Table 2, the error messages generated for the Toshiba and both 
Sony drives are the same for the encrypted CD-ROM. In particular, the 
error message generated, i.e. "SCSI device medium error @ block 179851", 
indicates that the drive had difficulty reading data from the encrypted 
master at block 179851. In regard to the Philips drive, although the error 
message indicated at block 179851 is different, the message generated 
indicates a similar type of error. Further, an error message identical to 
that indicated for the Toshiba and both Sony drives, i.e. "SCSI device 
medium error" was generated at a later block, i.e. block 179853. 
In regard to the counterfeit CD-ROM, the error messages generated, i.e. 
"Mismatch found @ block 179850" for the Philips and both Sony drives and 
"SCSI blank block encountered @ 179850" for the Toshiba drive, indicate an 
error that may categorized as data being incorrect or missing. 
Therefore, playback of an encrypted CD-ROM formed from the encrypted glass 
master will cause the generation of a device medium or similar type of 
error. However, upon playback of a counterfeit CD-ROM formed from the 
counterfeit glass master, the reconstructed data causes the generation of 
a different error message indicating a different type of error. In 
accordance with the present invention, error detecting software is stored 
on the CD-ROM or the drive which is adapted to detect whether or not the 
device medium or similar type of error occurs at the predetermined 
address. Therefore, detection of the device medium error at the 
predetermined address indicates that the encrypted CD-ROM is not 
counterfeit. 
However, upon playback of a counterfeit CD-ROM, the error detecting 
software will not detect a device medium or similar type error at the 
predetermined address to thus indicate that the CD-ROM is counterfeit. 
Once a counterfeit CD-ROM is indicated, the error detecting software may 
be adapted to deny further access to the CD-ROM or other suitable options 
which render the counterfeit CD-ROM unusable. In this manner, a potential 
counterfeiter would be discouraged from illegally copying an encrypted 
CD-ROM. Further, the defect does not create any visible cosmetic flaws on 
the encrypted CD-ROM and does not substantially affect tracking and servo 
focus systems of the CD-ROM drive utilized. 
Referring to FIG. 3A, an encrypted CD-ROM 44 in accordance with the present 
invention is shown. The CD-ROM 44 includes a signal surface 46 for storing 
digitally encoded data represented by pits and lands formed on the signal 
surface 46 which may be read by an optical device. A CD-ROM may include 
333,000 blocks, or sectors, each having 2048 bytes of user data. In a 
preferred embodiment, at least one sector is destroyed in order to form 
the defect. Further, the configuration and size of the defect is 
preferably such that the defect is not visible to the unaided eye when the 
CD-ROM 44 is viewed. By way of example, the defect may be formed within 
balloon section 48 of FIG. 3A and is not visible to the unaided eye. 
Referring to FIG. 3B, an enlarged view of balloon section 48 of FIG. 3A is 
shown. In this view, a defect 50 is shown on a portion of the signal 
surface 46 corresponding to at least one sector destroyed by a suitable 
signal such as a random high frequency signal. When this occurs, the 
signal surface 46 is formed such that an error signal is produced when the 
CD-ROM 44 is played back. The error signal serves to indicate that the 
CD-ROM 44 is not counterfeit, wherein a counterfeit CD-ROM is indicated if 
the error signal is not generated. 
Thus it is apparent that in accordance with the present invention, an 
apparatus that fully satisfies the objectives, aims and advantages is set 
forth above. While the invention has been described in conjunction with 
specific embodiments, it is evident that many alternatives, modifications, 
permutations and variations will become apparent to those skilled in the 
art in light of the foregoing description. Accordingly, it is intended 
that the present invention embrace all such alternatives, modifications 
and variations as fall within the scope of the appended claims.