Electrical computers and digital processing systems: support – Data processing protection using cryptography – By stored data protection
Reexamination Certificate
1999-02-08
2003-07-01
Barrón, Gilberto (Department: 2132)
Electrical computers and digital processing systems: support
Data processing protection using cryptography
By stored data protection
C713S190000, C380S026000, C380S027000, C380S046000, C380S054000, C380S201000, C380S203000, C705S057000, C369S275300, C369S059240, C369S053210
Reexamination Certificate
active
06587948
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a recording method and a recording apparatus whereby digital data is recorded onto a disc as run-length limited code by modulating digital data used for modulating marks or spaces on the disc and, at the same time, the recorded digital data is encrypted by using key data which is also recorded onto the same disc by variation of the shape of marks or spaces with timing having no effect on the edges of the marks or the spaces. In addition, the present invention also relates to a playback method and a playback apparatus for reproducing the digital data and the key data recorded on the disc by the recording method and/or the recording apparatus from the disc with the key data used for decrypting the encrypted digital data.
In the commonly known related art compact disc, after completing data processing, audio data is subjected to EFM (Eight-to-Fourteen Modulation) to form a series of pits with a period in the range of 3T to 11T where the symbol T is a predetermined basic period. In this way, audio data or other information is recorded in the compact disc.
The compact disc player for playing back a signal from this compact disc radiates a laser beam to the disc and receives a light reflected by the compact disc. The compact disc player then obtains a playback signal having a level varying with the quantity of the received light and compares the playback signal with a predetermined slice level in order to convert the playback signal into a binary signal in a binary conversion process. A PLL circuit is driven to extract a playback clock signal from the binary signal. The extracted playback clock signal is in turn used for sequentially latching the binary signal to generate playback data with a period varying in the range of 3T to 11T corresponding to a series of pits formed on the compact disk.
The compact disc player then decodes the playback data generated in the way described above by carrying out data processing as a counterpart of the data processing performed in the recording operation. As a result, audio data or other information recorded on the compact disc is played back.
In order to effectively avoid an illegal copy in a transfer system for transferring audio data through such an optical-information recording medium, there have been proposed copy preventing systems like those shown in
FIGS. 1
or
2
.
An encoder
3
employed in a disc producing apparatus
2
in the copy preventing system
1
shown in
FIG. 1
carries out scramble processing on data D
1
to be recorded on an optical disc
5
by using a master key KM and then records the data completing the scramble processing on the optical disc
5
. On the other hand, a decoder
7
employed in a playback apparatus
6
carries out descramble processing on playback data reproduced from the optical disc
5
typically by using the shared master key as the disc producing apparatus
2
. Then, a decoder
8
complying with MPEG (Moving Picture Expert Group) specifications processes data obtained as a result of the descramble processing. Thus, in the copy preventing system
1
, the encoder
3
scrambles the data D
1
by using the predetermined master key KM shared with the playback apparatus
6
in order to prevent an illegal copy.
In the copy preventing system
10
shown in
FIG. 2
, on the other hand, data D
1
is scrambled by using a master key KM, a disc key DK unique to an optical disc
11
and a title key KT unique to a work recorded on the optical disc
11
. To put it in detail, an encoder
13
employed in a disc producing apparatus
12
carries out scramble processing on the disc key DK by using the master key KM and records the disc key DK completing the scramble processing on the optical disc
11
. Then, an encoder
14
employed in the disc producing apparatus
12
carries out scramble processing on the title key KT by using the disc key DK completing the scramble processing and records the title key KT completing the scramble processing on the. optical disc
11
.
Subsequently, an encoder
15
employed in the disc producing apparatus
12
carries out scramble processing on the data D
1
to be recorded by using the title key KT completing the scramble processing and records the data D
1
completing the scramble processing on the optical disc
11
. The disc producing apparatus
12
carries out multiple scramble processing on the data D
1
with the master key KM used as a reference and records the data D
1
completing the multiple scramble processing on the optical disc
11
.
A decoder
17
employed in a playback apparatus
16
carries out descramble processing on the disc key DK completing the scramble processing by using the master key KM to decode the disc key DK. A decoder
18
employed in a playback apparatus
16
then carries out descramble processing on the title key KT completing the scramble processing, by using the disc key DK to decode the title key KT. Subsequently, a decoder
19
employed in a playback apparatus
16
carries out descramble processing on the data D
1
completing the scramble processing by using the disk key DK.
The copy preventing system
10
adds the functional positions of the disc producer and the author of the work to the scramble and descramble processes, avoiding an illegal copy.
By the way, there are two types of illegal copy. An illegal copy of the first type is produced by using a result of decoding a master key. As a result, an illegal user is capable of reproducing a signal from the illegal copy by using a playback apparatus even if the illegal copy is produced as a result of piracy. An illegal copy of the second type is produced by physically copying a pit form created on a legal optical disc.
In a copy preventing system based on a master key, the problem of an illegal copy of the first type can be solved by making it difficult to decode the master key. This solution has a shortcoming, however, that once the master key has been decoded, it is no longer possible to avoid piracy of discs whatsoever. In addition, this solution is not applicable to piracy to produce an illegal copy of the second type.
SUMMARY OF THE INVENTION
It is thus an object of the present invention addressing the problems described above to provide a recording apparatus, a recording medium, a playback apparatus, a recording method and a playback method which are capable of effectively preventing illegal copies.
According to an aspect of the present invention, there is provided a recording apparatus for successively recording digital data as alternating marks and spaces on a disc by modulation of said marks or said spaces in a run-length direction thereof in accordance with said data, said recording apparatus comprising: a key data generating means for generating key data; an encryption means for encrypting said digital data on the basis of said key data generated by said key data generating means; a key data modulation means for modulating said marks or said spaces in a width direction thereof in accordance with said key data generated by said key data generating means; and a recording means for recording said key data used in modulation of said marks or said spaces carried out by said key data modulation means in a width direction thereof and digital data encrypted by said encryption means.
According to another aspect of the present invention, there is provided a disc-shaped recording medium for storing digital information encrypted by using predetermined key data on recording tracks by modulation of a series of alternating marks and spaces on each of said recording tracks, said disc-shape recording medium comprising: a program area having a plurality of said recording tracks wherein said encrypted digital information is recorded by modulation of said marks or said spaces in a run-length direction thereof; and a lead-in area for recording said key data by modulation of said marks or said spaces in a width direction thereof.
According to still another aspect of the present invention, there is provided a playback apparatus for reproducing key data and digi
Fukami Tadashi
Inazawa Yoshizumi
Yamaoka Keisuke
Barrón Gilberto
Darrow Justin T.
Maioli Jay H.
Sony Corporation
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