U.S. patent application number 08/883337 was filed with the patent office on 2001-09-06 for method and apparatus of enciphering and deciphering data using multiple keys.
Invention is credited to ENDOH, NAOKI, HIRAYAMA, KOICHI, KATO, TAKEHISA, KOJIMA, TADASHI, UNNO, HIROAKI.
Application Number | 20010019615 08/883337 |
Document ID | / |
Family ID | 26470215 |
Filed Date | 2001-09-06 |
United States Patent
Application |
20010019615 |
Kind Code |
A1 |
KATO, TAKEHISA ; et
al. |
September 6, 2001 |
METHOD AND APPARATUS OF ENCIPHERING AND DECIPHERING DATA USING
MULTIPLE KEYS
Abstract
On a recording medium, first information obtained by enciphering
data with the first key and second information obtained by
enciphering the first key with each of the predetermined second
keys are recorded. A deciphering method is characterized by
comprising the steps of inputting the first and second information,
deciphering the first key using at least one of the second keys,
determining by a specific method that the obtained first key is
correct, and then deciphering the data using the first key to
obtain the data.
Inventors: |
KATO, TAKEHISA;
(YOKOHAMA-SHI, JP) ; ENDOH, NAOKI; (CHIBA-KEN,
JP) ; UNNO, HIROAKI; (YOKOHAMA-SHI, JP) ;
KOJIMA, TADASHI; (YOKOHAMA-SHI, JP) ; HIRAYAMA,
KOICHI; (YOKOHAMA-SHI, JP) |
Correspondence
Address: |
PILLSBURY MADISON & SUTRO
CUSHMAN DARBY & CUSHMAN IP GROUP
NINTH FLOOR
110O NEW YORK AVENUE, N.W.
WASHINGTON,
DC
200053918
|
Family ID: |
26470215 |
Appl. No.: |
08/883337 |
Filed: |
June 26, 1997 |
Current U.S.
Class: |
380/286 ;
386/E5.004; G9B/20.002; G9B/23.087 |
Current CPC
Class: |
G11B 23/284 20130101;
G11B 20/00557 20130101; H04N 5/913 20130101; G11B 20/00086
20130101; G11B 23/28 20130101; G11B 20/0021 20130101; H04N
2005/91364 20130101; G11B 20/00253 20130101 |
Class at
Publication: |
380/286 |
International
Class: |
H04K 001/00; H04L
009/00 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 28, 1996 |
JP |
8-170399 |
May 27, 1997 |
JP |
9-136709 |
Claims
1. An enciphering method comprising the steps of: enciphering data
with a first key; and enciphering said first key with each of a
plurality of predetermined second keys.
2. An enciphering method according to claim 1, wherein said data
includes at least one of key information, documents, sound, images,
and programs.
3. A recording medium having information items recorded thereon,
said information items comprising: first information obtained by
enciphering data with a first key; and second information obtained
by enciphering said first key with each of a plurality of
predetermined second keys.
4. A recording medium manufacturing method comprising the steps of:
obtaining first information by enciphering data with a first key;
obtaining second information obtained by enciphering said first key
with each of a plurality of predetermined second keys; and
recording said first and second information on the same recording
medium.
5. A deciphering method comprising the steps of: inputting first
information obtained by enciphering data with a first key and
second information obtained by enciphering said first key with each
of a plurality of predetermined second keys; deciphering said first
key using at least one of said second keys to obtain said first
key; determining by a specific method whether or not the obtained
first key is correct; and deciphering said data using said first
key after the determination to obtain said data.
6. A deciphering method according to claim 5, wherein said data
includes at least one of key information, documents, sound, images,
and programs.
7. A deciphering device comprising: input means for inputting first
information obtained by enciphering data with a first key and
second information obtained by enciphering said first key with each
of a plurality of predetermined second keys; storage means for
storing at least one of said second keys; and deciphering means for
deciphering said first key from said second information inputted
from said input means using at least one of said second keys in
said storage means, determining by a specific method whether or not
the obtained first key is correct, and deciphering said data from
said first information using said first key after the determination
to obtain said data.
8. A recording and reproducing device comprising: reading means for
reading first information and second information from a recording
medium on which said first information obtained by enciphering data
with a first key and said second information obtained by
enciphering said first key with each of a plurality of
predetermined second keys have been stored; storage means for
storing at least one of said second keys; and deciphering means for
deciphering said first key from said second information read by
said reading means using at least one of said second keys in said
storage means, determining by a specific method whether or not the
obtained first key is correct, and deciphering said data from said
first information using said first key after the determination to
obtain said data.
9. A key control method comprising the steps of: causing a first
caretaker to take custody of a plurality of predetermined second
keys; causing a second caretaker to take custody of first
information obtained by enciphering data with a first key and
second information obtained by enciphering said first key with each
of said predetermined second keys; and causing a third caretaker to
take custody of at least one of said second keys.
10. A deciphering device comprising: reading means for reading
first information, second information, and third information from a
recording medium on which said first information obtained by
enciphering data with a first key, said second information obtained
by enciphering said first key with each of a plurality of
predetermined second keys, and said third information used for key
determination have been stored; storage means for storing at least
one of said second keys; first deciphering means for deciphering
one of the enciphered first keys selected in the order determined
from said second information using one second key selected in the
order determined from said second keys stored in said storage
means, determining on the basis of said deciphering result and said
third information whether or not said first key obtained by said
deciphering is correct, and repeating said selection and said
determination until the first key determined to be correct has been
obtained; and second deciphering means for deciphering said data
from said first information using said first key said first
deciphering means has determined to be correct.
11. A deciphering device according to claim 10, wherein: said third
information is information obtained by enciphering said first key
with said first key itself; and when the key obtained by
deciphering one of said second information using one of said second
keys stored in said storage means coincides with the key obtained
by deciphering said third information using the former key, said
first deciphering means determines that the former key is the
correct first key.
12. A deciphering device according to claim 10, wherein said data
includes at least one of key information, documents, sound, images,
and programs.
13. A deciphering device comprising: a first unit built in a
driving unit of a recording medium or connected to the driving unit
of said recording medium without the CPU bus of a computer,
including: means for transferring first information obtained by
enciphering the data read from said recording medium with a first
key, second information obtained by enciphering said first key with
each of a plurality of predetermined second keys, and third
information used for key determination in such a manner that at
least said second information and third information are transferred
safely without being externally acquired; and a second unit
connected to said first unit via the CPU bus of said computer
including: means for receiving said first information, second
information, and third information from said first unit via the CPU
bus of said computer in such a manner that at least said second
information and third information are received safely without being
externally acquired; storage means for storing at least one of said
second keys; first deciphering means for deciphering one of the
enciphered first keys selected in the order determined from said
second information using one second key selected in the order
determined from said second keys stored in said storage means,
determining on the basis of said deciphering result and said third
information whether or not said first key obtained by said
deciphering is correct, and repeating said selection and said
determination until the first key determined to be correct has been
obtained; and second deciphering means for deciphering said data
from said first information using said first key said first
deciphering means has determined to be correct.
14. A deciphering device according to claim 13, wherein: said third
information is information obtained by enciphering said first key
with said first key itself; and when the key obtained by
deciphering one of said second information using one of said second
keys stored in said storage means coincides with the key obtained
by deciphering said third information using the former key, said
first deciphering means determines that the former key is the
correct first key.
15. A deciphering device according to claim 13, wherein said data
includes at least one of key information, documents, sound, images,
and programs.
16. A deciphering device comprising: reading means for reading
first information, second information, third information, and
fourth information from a recording medium on which said first
information obtained by enciphering a third key with a first key,
said second information obtained by enciphering said first key with
each of a plurality of predetermined second keys, said third
information used for key determination, and said fourth information
obtained by enciphering data with said third key have been stored;
storage means for storing at least one of said second keys; first
deciphering means for deciphering one of the enciphered first keys
selected in the order determined from said second information using
one second key selected in the order determined from said second
keys stored in said storage means, determining on the basis of said
deciphering result and said third information whether or not said
first key obtained by said deciphering is correct, and repeating
said selection and said determination until the first key
determined to be correct has been obtained; second deciphering
means for deciphering said third key from said first information
using said first key said first deciphering means has determined to
be correct; and third deciphering means for deciphering said data
from said fourth information using said third key obtained by said
second deciphering means.
17. A deciphering device according to claim 16, wherein: said third
information is information obtained by enciphering said first key
with said first key itself; and when the key obtained by
deciphering one of said second information using one of said second
keys stored in said storage means coincides with the key obtained
by deciphering said third information using the former key, said
first deciphering means determines that the former key is the
correct first key.
18. A deciphering device according to claim 16, wherein said data
includes at least one of key information, documents, sound, images,
and programs.
19. A deciphering method comprising the steps of: reading first
information, second information, and third information from a
recording medium on which said first information obtained by
enciphering data with a first key, said second information obtained
by enciphering said first key with each of a plurality of
predetermined second keys, and said third information used for key
determination have been stored; deciphering one of the enciphered
first keys selected in the order determined from said second
information using one second key selected in the order determined
from said second keys, determining on the basis of said deciphering
result and said third information whether or not said first key
obtained by said deciphering is correct, and repeating said
selection and said determination until the first key determined to
be correct has been obtained; and deciphering said data from said
first information using said first key determined to be
correct.
20. A deciphering method comprising the steps of: transferring
first information obtained by enciphering the data read from a
recording medium with a first key, second information obtained by
enciphering said first key with each of a plurality of
predetermined second keys, and third information used for key
determination from a first unit built in a driving unit of said
recording medium or connected to the driving unit of said recording
medium without the CPU bus of a computer to a second unit via the
CPU bus of the computer in such a manner that at least said second
information and third information are transferred safely without
being externally acquired; and in said second unit, deciphering one
of the enciphered first keys selected in the order determined from
said second information using one second key selected in the order
determined from said second keys stored in said storage means,
determining on the basis of said deciphering result and said third
information whether or not said first key obtained by said
deciphering is correct, repeating said selection and said
determination until the first key determined to be correct has been
obtained, and deciphering said data using said first key determined
to be correct.
21. A deciphering method comprising the steps of: reading first
information, second information, third information, and fourth
information from a recording medium on which said first information
obtained by enciphering at least a third key with a first key, said
second information obtained by enciphering said first key with each
of a plurality of predetermined second keys, said third information
used for key determination, and said fourth information obtained by
enciphering data with said third key have been stored; deciphering
one of the enciphered first keys selected in the order determined
from said second information using one second key selected in the
order determined from said second keys, determining on the basis of
said deciphering result and said third information whether or not
said first key obtained by said deciphering is correct, and
repeating said selection and said determination until the first key
determined to be correct has been obtained; deciphering said third
key from said first information using said first key determined to
be correct; and deciphering said data from said fourth information
using said third key obtained.
22. A deciphering unit device that receives information via the CPU
bus of a computer from a bus transfer unit built in a driving unit
of a recording medium or connected to the driving unit of said
recording medium without the CPU bus of the computer and deciphers
data on the basis of the information, said deciphering unit device
comprising: means for receiving first information obtained by
enciphering the data read from said recording medium with a first
key, second information obtained by enciphering said first key with
each of a plurality of predetermined second keys, and third
information used for key determination from said bus transfer unit
via the CPU bus of said computer in such a manner that at least
said second information and third information are received safely
without being externally acquired; storage means for storing at
least one of said second keys; first deciphering means for
deciphering one of the enciphered first keys selected in the order
determined from said second information using one second key
selected in the order determined from said second keys stored in
said storage means, determining on the basis of said deciphering
result and said third information whether or not said first key
obtained by said deciphering is correct, and repeating said
selection and said determination until the first key determined to
be correct has been obtained; and second deciphering means for
deciphering said data from said first information using said first
key said first deciphering means has determined to be correct.
Description
BACKGROUND OF THE INVENTION
[0001] The present invention relates to an enciphering method,
deciphering method, recording and reproducing device, deciphering
device, deciphering unit device, recording medium, recording-medium
manufacturing method, and key control method which are for
preventing the digitally recorded data from being copied from a
recording medium.
[0002] Compact disks and laser disks have been available as
recording mediums that record digitized data (e.g., documents,
sound, images, or programs). Floppy disks and hard disks have been
used as recording mediums for computer programs and data. In
addition to those recording mediums, a DVD (digital video disk),
which is a large-capacity recording medium, has been developed.
[0003] Since the aforementioned various digital recording mediums
record the digital data (including the compressed or encoded data,
which can be decoded later) as it is, the recorded data can be
copied easily to another recording medium without impairing the
quality of sound or the quality of image, which enables a large
number of reproductions to be made, contributing to literary
piracy.
[0004] In summary, when the data is copied from a digital recording
medium, the data can be copied with the sound quality and picture
quality of the master remaining unchanged, or without the
deterioration of sound quality or picture quality. This has caused
the problem of permitting the wrongful conduct of making
unauthorized copies of the original and selling them without paying
a royalty.
BRIEF SUMMARY OF THE INVENTION
[0005] Accordingly, it is an object of the present invention to
provide an enciphering method, deciphering method, recording and
reproducing device, deciphering device, deciphering unit device,
recording medium, recording-medium manufacturing method, and key
control method which are for preventing an unauthorized copy of
digital recording mediums.
[0006] According to one aspect of the present invention, there is
provided an enciphering method comprising the steps of: enciphering
data with a first key; and enciphering the first key with each of a
plurality of predetermined second keys.
[0007] According to another aspect of the present invention, there
is provided a recording medium having information items recorded
thereon, the information items comprising: first information
obtained by enciphering data with a first key; and second
information obtained by enciphering the first key with each of a
plurality of predetermined second keys.
[0008] According to another aspect of the present invention, there
is provided a recording medium manufacturing method comprising the
steps of: obtaining first information by enciphering data with a
first key; obtaining second information obtained by enciphering the
first key with each of a plurality of predetermined second keys;
and recording the first and second information on the same
recording medium.
[0009] According to another aspect of the present invention, there
is provided a deciphering method comprising the steps of: inputting
first information obtained by enciphering data with a first key and
second information obtained by enciphering the first key with each
of a plurality of predetermined second keys; deciphering the first
key using at least one of the second keys to obtain the first key;
determining by a specific method whether or not the obtained first
key is correct; and deciphering the data using the first key after
the determination to obtain the data.
[0010] According to another aspect of the present invention, there
is provided a deciphering device comprising: input means for
inputting first information obtained by enciphering data with a
first key and second information obtained by enciphering the first
key with each of a plurality of predetermined second keys; storage
means for storing at least one of the second keys; and deciphering
means for deciphering the first key from the second information
inputted from the input means using at least one of the second keys
in the storage means, determining by a specific method whether or
not the obtained first key is correct, and deciphering the data
from the first information using the first key after the
determination to obtain the data.
[0011] According to another aspect of the present invention, there
is provided a recording and reproducing device comprising: reading
means for reading first information and second information from a
recording medium on which the first information obtained by
enciphering data with a first key and the second information
obtained by enciphering the first key with each of a plurality of
predetermined second keys have been stored; storage means for
storing at least one of the second keys; and deciphering means for
deciphering the first key from the second information read by the
reading means using at least one of the second keys in the storage
means, determining by a specific method whether or not the obtained
first key is correct, and deciphering the data from the first
information using the first key after the determination to obtain
the data.
[0012] According to another aspect of the present invention, there
is provided a key control method comprising the steps of: causing a
first caretaker to take custody of a plurality of predetermined
second keys; causing a second caretaker to take custody of first
information obtained by enciphering data with a first key and
second information obtained by enciphering the first key with each
of the predeter- mined second keys; and causing a third caretaker
to take custody of at least one of the second keys.
[0013] According to another aspect of the present invention, there
is provided a deciphering device comprising: reading means for
reading first information, second information, and third
information from a recording medium on which the first information
obtained by enciphering data with a first key, the second
information obtained by enciphering the first key with each of a
plurality of predetermined second keys, and the third information
used for key determination have been stored; storage means for
storing at least one of the second keys; first deciphering means
for deciphering one of the enciphered first keys selected in the
order determined from the second information using one second key
selected in the order determined from the second keys stored in the
storage means, determining on the basis of the deciphering result
and the third information whether or not the first key obtained by
the deciphering is correct, and repeating the selection and the
determination until the first key determined to be correct has been
obtained; and second deciphering means for deciphering the data
from the first information using the first key the first
deciphering means has determined to be correct.
[0014] According to another aspect of the present invention, there
is provided a deciphering device comprising: a first unit built in
a driving unit of a recording medium or connected to the driving
unit of the recording medium without the CPU bus of a computer,
including: means for transferring first information obtained by
enciphering the data read from the recording medium with a first
key, second information obtained by enciphering the first key with
each of a plurality of predetermined second keys, and third
information used for key determination in such a manner that at
least the second information and third information are transferred
safely without being externally acquired; and a second unit
connected to the first unit via the CPU bus of the computer
including: means for receiving the first information, second
information, and third information from the first unit via the CPU
bus of the computer in such a manner that at least the second
information and third information are received safely without being
externally acquired; storage means for storing at least one of the
second keys; first deciphering means for deciphering one of the
enciphered first keys selected in the order determined from the
second information using one second key selected in the order
determined from the second keys stored in the storage means,
determining on the basis of the deciphering result and the third
information whether or not the first key obtained by the
deciphering is correct, and repeating the selection and the
determination until the first key determined to be correct has been
obtained; and second deciphering means for deciphering the data
from the first information using the first key the first
deciphering means has determined to be correct.
[0015] According to another aspect of the present invention, there
is provided a deciphering device comprising: reading means for
reading first information, second information, third information,
and fourth information from a recording medium on which the first
information obtained by enciphering a third key with a first key,
the second information obtained by enciphering the first key with
each of a plurality of predetermined second keys, the third
information used for key determination, and the fourth information
obtained by enciphering data with the third key have been stored;
storage means for storing at least one of the second keys; first
deciphering means for deciphering one of the enciphered first keys
selected in the order determined from the second information using
one second key selected in the order determined from the second
keys stored in the storage means, determining on the basis of the
deciphering result and the third information whether or not the
first key obtained by the deciphering is correct, and repeating the
selection and the determination until the first key determined to
be correct has been obtained; second deciphering means for
deciphering the third key from the first information using the
first key the first deciphering means has determined to be correct;
and third deciphering means for deciphering the data from the
fourth information using the third key obtained by the second
deciphering means.
[0016] According to another aspect of the present invention, there
is provided a deciphering method comprising the steps of: reading
first information, second information, and third information from a
recording medium on which the first information obtained by
enciphering data with a first key, the second information obtained
by enciphering the first key with each of a plurality of
predetermined second keys, and the third information used for key
determination have been stored; deciphering one of the enciphered
first keys selected in the order determined from the second
information using one second key selected in the order determined
from the second keys, determining on the basis of the deciphering
result and the third information whether or not the first key
obtained by the deciphering is correct, and repeating the selection
and the determination until the first key determined to be correct
has been obtained; and deciphering the data from the first
information using the first key determined to be correct.
[0017] According to another aspect of the present invention, there
is provided a deciphering method comprising the steps of:
transferring first information obtained by enciphering the data
read from a recording medium with a first key, second information
obtained by enciphering the first key with each of a plurality of
predetermined second keys, and third information used for key
determination from a first unit built in a driving unit of the
recording medium or connected to the driving unit of the recording
medium without the CPU bus of a computer to a second unit via the
CPU bus of the computer in such a manner that at least the second
information and third information are transferred safely without
being externally acquired; and in the second unit, deciphering one
of the enciphered first keys selected in the order determined from
the second information using one second key selected in the order
determined from the second keys stored in the storage means,
determining on the basis of the deciphering result and the third
information whether or not the first key obtained by the
deciphering is correct, repeating the selection and the
determination until the first key determined to be correct has been
obtained, and deciphering the data using the first key determined
to be correct.
[0018] According to another aspect of the present invention, there
is provided a deciphering method comprising the steps of: reading
first information, second information, third information, and
fourth information from a recording medium on which the first
information obtained by enciphering at least a third key with a
first key, the second information obtained by enciphering the first
key with each of a plurality of predetermined second keys, the
third information used for key determination, and the fourth
information obtained by enciphering data with the third key have
been stored; deciphering one of the enciphered first keys selected
in the order determined from the second information using one
second key selected in the order determined from the second keys,
determining on the basis of the deciphering result and the third
information whether or not the first key obtained by the
deciphering is correct, and repeating the selection and the
determination until the first key determined to be correct has been
obtained; deciphering the third key from the first information
using the first key determined to be correct; and deciphering the
data from the fourth information using the third key obtained.
[0019] According to another aspect of the present invention, there
is provided a deciphering unit device that receives information via
the CPU bus of a computer from a bus transfer unit built in a
driving unit of a recording medium or connected to the driving unit
of the recording medium without the CPU bus of the computer and
deciphers data on the basis of the information, the deciphering
unit device comprising: means for receiving first information
obtained by enciphering the data read from the recording medium
with a first key, second information obtained by enciphering the
first key with each of a plurality of predetermined second keys,
and third information used for key determination from the bus
transfer unit via the CPU bus of the computer in such a manner that
at least the second information and third information are received
safely without being externally acquired; storage means for storing
at least one of the second keys; first deciphering means for
deciphering one of the enciphered first keys selected in the order
determined from the second information using one second key
selected in the order determined from the second keys stored in the
storage means, determining on the basis of the deciphering result
and the third information whether or not the first key obtained by
the deciphering is correct, and repeating the selection and the
determination until the first key determined to be correct has been
obtained; and second deciphering means for deciphering the data
from the first information using the first key the first
deciphering means has determined to be correct.
[0020] In each of the above categories, the data may include at
least one of key information, documents, sound, images, and
programs.
[0021] With the present invention, only the correct party having at
least one of the second keys can get the first key and therefore
can get the plain data of the data enciphered using the first key.
As a result, the wrongful conduct of making unauthorized copies and
selling the thus copied mediums can be prevented, thereby
protecting copyrights.
[0022] Moreover, with the present invention, even if the data
flowing over the signal line connecting the enciphering unit to the
deciphering unit is stored, the stored data cannot be reproduced or
used, because the data is the enciphered data. In addition, because
the information necessary for enciphering the data is created on
the basis of, for example, random numbers, and cannot be reproduced
later, the stored data cannot be reproduced or used, even if the
second key (master key) in the deciphering unit has been broken. As
a result, the wrongful conduct of making unauthorized copies and
selling the thus copied mediums can be prevented, thereby
protecting copyrights.
[0023] Still furthermore, with the present invention, because the
enciphering unit and deciphering unit can be designed separately
from the essential portion of the reproducing section of the
digital recording and reproducing apparatus, even if the cipher is
broken, the enciphering unit and deciphering unit have only to be
replaced to overcome this problem.
[0024] Additional objects and advantages of the present invention
will be set forth in the description which follows, and in part
will be obvious from the description, or may be learned by practice
of the present invention. The objects and advantages of the present
invention may be realized and obtained by means of the
instrumentalities and combinations particularly pointed out in the
appended claims.
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING
[0025] The accompanying drawings, which are incorporated in and
constitute a part of the specification, illustrate presently
preferred embodiments of the present invention and, together with
the general description given above and the detailed description of
the preferred embodiments given below, serve to explain the
principles of the present invention in which:
[0026] FIG. 1 is a block diagram of a system according to a first
embodiment of the present invention;
[0027] FIG. 2 is a flowchart for the operation of the first
embodiment;
[0028] FIG. 3 illustrates an example of a format in which the
enciphered key and the enciphered data are stored on a recording
medium;
[0029] FIG. 4 is a diagram to help explain a case where the data is
stored from the CPU BUS;
[0030] FIG. 5 is a block diagram of a system according to a second
embodiment of the present invention;
[0031] FIGS. 6A and 6B show examples of the internal structure of
the key judging section;
[0032] FIG. 7 is a flowchart for the operation of the second
embodiment;
[0033] FIG. 8 is a flowchart for the operation of the second
embodiment;
[0034] FIG. 9 is a block diagram of a system according to a third
embodiment of the present invention;
[0035] FIG. 10 is a flowchart for the operation of the third
embodiment;
[0036] FIG. 11 is a diagram t o help explain the key control
method; and
[0037] FIG. 12 is a diagram to help explain the enciphering
operation.
DETAILED DESCRIPTION OF THE INVENTION
[0038] Hereinafter, referring to the accompanying drawings,
embodiments of the present invention will be explained.
[0039] In the embodiments, the operation of enciphering a certain
data item a using key K is expressed as E.sub.K(a) and the
operation of deciphering a certain data item a using key K is
expressed as D.sub.K(a). By this way of expression, the operation
of enciphering and deciphering a certain data item a using key K is
expressed as D.sub.K(E.sub.K(a)), for example.
[0040] In the embodiments, there is a case where a certain data
item is first deciphered and then the deciphered data item is
enciphered to restore the original data item. This is based on the
fact that the deciphering of the data has the same function as the
enciphering of the data. Specifically, to return the enciphered
data to the original data, the key used for deciphering must be
known. Once the key is known, enciphering the deciphered data
produces the original data that was first deciphered. If the cipher
key is x and the data item is y, the operation will be expressed
as:
E.sub.X(D.sub.X(y))=y
[0041] In the embodiments, explanation will be given using an
example of a system that reads the image data compressed and
enciphered according to the MPEG 2 data compression standard from a
DVD and enciphers, decodes, and reproduce the read-out data.
[0042] (First Embodiment)
[0043] Hereinafter, a first embodiment of the present invention
will be explained.
[0044] FIG. 1 is a block diagram of a system according to a first
embodiment of the present invention. FIG. 2 is a flowchart for the
operation of the first embodiment.
[0045] The system related to the first embodiment is connected to
the CPU BUS of the CPU (not shown) used for reproduction in a
computer, such as a personal computer. The system is designed to
allow the enciphered data (ESK(Data) explained later) to flow over
the CPU BUS. FIG. 1 shows only the sections related to the CPU used
for reproduction.
[0046] As shown in FIG. 1, the system of the first embodiment
comprises a DVD driving unit (not shown) that reads the data from a
DVD 101, an enciphering unit 107 that is connected to the DVD
driving unit without the CPU BUS or is built in the DVD driving
unit, and a deciphering unit 114.
[0047] The enciphering unit 107 and deciphering unit 114 are
connected to the CPU BUS 110. The deciphering unit 114 outputs the
data via, for example, an I/O port, not via the CPU BUS. That is,
in the embodiment, the input and output of the data is carried out
without the CPU BUS, whereas the CPU BUS is used for the data
transfer between the enciphering unit 107 and the deciphering unit
114.
[0048] The enciphering unit 107 includes a demodulation/error
correction circuit 117, a demodulation/error correction circuit
118, and an enciphering circuit 104. Although in FIG. 1, the
enciphering unit 107 has two enciphering circuits 104, it is
assumed that it actually has one enciphering circuit. The
enciphering unit 107 is assumed to be composed of a single
independent IC chip. The demodulation/error correction circuit 117
and demodulation/error correction circuit 118 may be provided in
the unit (the DVD driving unit) in the preceding stage, not in the
enciphering unit 107.
[0049] The deciphering unit 114 includes a deciphering circuit 112
and a session key creation circuit 111 that creates a second
session key S.sub.K'. In the embodiment, the deciphering unit 114
is assumed to include an MPEG decoder circuit 115 and a converter
circuit 116 that converts the digital enciphered image data into
analog data. Although in FIG. 1, the deciphering unit 114 has four
deciphering circuits 112, it is assumed that it actually has one
deciphering circuit. The deciphering unit 114 is assumed to be
composed of a single independent IC chip.
[0050] In each of the enciphering unit 107 and deciphering unit
114, a master key, explained later, has been registered. It is
assumed that the master key has been recorded in a secret area in
each of the enciphering unit chip and the deciphering unit chip so
that the user cannot externally take out the master key.
[0051] A control section (not shown) is assumed to control the
entire system. The control section is realized by, for example,
executing a program on the CPU in the computer. Concrete examples
of control by the control section include an instruction to read
the data from a DVD, the specification of data transfer
destination, and an instruction to output the data from the
deciphering unit 114. The control section may be triggered, for
example, by the user via a user interface, or by a process in an
application program.
[0052] In the first embodiment, a first session key is represented
by S.sub.K, a second session key S.sub.K', the master key M.sub.K,
and image data (i.e., the data to be enciphered) Data.
[0053] In FIG. 1, numeral 102 indicates E.sub.MK(S.sub.K) created
by enciphering the first session key S.sub.K using the master key
M.sub.K, 103 E.sub.SK(Data) created by enciphering the image data
Data using the first session key S.sub.K, 105 the master key
M.sub.K, 106 a second session key S.sub.K', 108 D.sub.MK(S.sub.K')
created by deciphering the second session key S.sub.K' using the
master key M.sub.K, 109 E.sub.SK'(E.sub.MK(S.sub.K)) created by
enciphering the first session key E.sub.MK(S.sub.K) enciphered with
the master key M.sub.K using the second session key S.sub.K', and
113 the first session key S.sub.K.
[0054] As shown in FIG. 3, it is assumed that on the DVD 101,
E.sub.MK(S.sub.K) created by enciphering the first session key
S.sub.K using the master key M.sub.K is recorded in the key
recording area (lead-in area) in the innermost circumference
portion and the E.sub.SK(Data) created by enciphering the image
data Data using the first session key S.sub.K is recorded in the
data recording area (data area).
[0055] Hereinafter, the operation of the first embodiment will be
explained by reference to the flowchart of FIG. 2.
[0056] At step S1, the first session key E.sub.MK(S.sub.K)
enciphered using the master key M.sub.K is read from the DVD 101,
on which the DVD driving unit (not shown) has recorded the first
session key, and then is loaded into the enciphering unit 107. At
that time, the demodulation/error correction circuit 117 performs
demodulation and data error correction.
[0057] At step S2, in the deciphering unit 114, the session key
creation circuit 111 creates a second session key S.sub.K' using
random numbers, such as time data from a clock (not shown). Then,
the deciphering circuit 112 deciphers the created second session
key S.sub.K' using the master key M.sub.K to create
D.sub.MK(S.sub.K') and sends it to the enciphering unit 107 via the
CPU BUS 110.
[0058] As the timing of generating random numbers (e.g., the timing
of inputting time information), for example, the timing with which
the signal indicating that the DVD 101 has been loaded into the DVD
driving unit is asserted may be used.
[0059] The session creation circuit 111 may be composed of a
random-number generator that is as long as the key. When a key is
created using random numbers all of whose bits may take 0s or 1s,
it is necessary to perform a check process to prevent all of the
bits from taking 0s or 1s.
[0060] At step S3, using the master key M.sub.K, the enciphering
circuit 104 of the enciphering unit 107 enciphers
D.sub.MK(S.sub.K') received via the CPU BUS 110.
[0061] Namely, from
E.sub.MK(D.sub.MK(S.sub.K'))=S.sub.K'
[0062] a second session key S.sub.K' created at the session key
creation circuit 111 of the deciphering unit 114 can be
obtained.
[0063] The second session key S.sub.K' created at the session key
creation circuit 111 is designed to prevent its contents from being
known even if it is stolen on the CPU BUS 110.
[0064] Then, at step S4, using the second session key S.sub.K', the
enciphering unit 107 enciphers the enciphered first session key
E.sub.MK(S.sub.K) recorded on the DVD 101 to create
E.sub.SK'(E.sub.MK(S.sub.K)), and sends this to deciphering unit
114.
[0065] Then, at step S5, the deciphering circuit 112 of the
deciphering unit 114 deciphers E.sub.SK'(E.sub.MK(S.sub.K))
received via the CPU BUS 110 using the second session key S.sub.K'
and produces:
D.sub.SK'(E.sub.SK'(E.sub.MK(S.sub.K)))=E.sub.MK(S.sub.K)
[0066] Furthermore, E.sub.MK(S.sub.K) obtained at the deciphering
circuit 112 is deciphered using the master key M.sub.K to
produce:
D.sub.MK(E.sub.MK(S.sub.K))=S.sub.K
[0067] Thus, this gives the first session key S.sub.K.
[0068] After the first session key S.sub.K has been obtained as
described above, at step S6, the image data E.sub.SK(Data)
enciphered using the first session key SK recorded on the DVD 101
by the DVD driving unit (not shown) is read out and loaded into the
enciphering unit 107. At that time, the demodulation/error
correction circuit 118 performs demodulation and corrects errors in
the data. Then, E.sub.SK(Data) is sent to the enciphering unit 107
via the CPU BUS 110.
[0069] At step S7, the deciphering circuit 112 of the deciphering
unit 114 deciphers E.sub.SK(Data) received via the CPU BUS 110
using the first session key S.sub.K and produces:
D.sub.SK(E.sub.SK(Data)=Data
[0070] Then, the enciphered image data is deciphered to produce
Data.
[0071] Then, step S6 and step S7 are repeated until for example,
the process of the data to be deciphered (i.e., E.sub.SK(Data)) has
been completed or the stop of the process has been requested.
[0072] When the image data Data thus obtained has been compressed
according to, for example, the MPEG2 data compression standard, the
image data is decoded at an MPEG decoder circuit 115. After the
decoded signal has been converted by a D/A converter circuit 116
into an analog signal, the analog signal is sent to an imaging
device (not shown), such as a television, which reproduces the
image.
[0073] Step 1 may be executed before or after step S2 and step
S3.
[0074] Step S6 and step S7 may be executed by the method of
carrying out the steps in units of E.sub.SK(Data), the method of
reading a specific number of E.sub.SK(Data) at step S6, storing the
read-out data in a buffer temporarily, and then deciphering
E.sub.SK(Data) in the buffer at step S7, or the method of carrying
out step S6 and step S7 in a pipeline processing manner.
[0075] Moreover, the deciphering circuit 112 may transfer the image
data E.sub.SK(Data) to the MPEG decoder circuit 115 in units of one
Data item or a specific number of Data items.
[0076] As described above, with the first embodiment, when the data
is reproduced from a medium on which the digitized data has been
enciphered and recorded (when the enciphered data is deciphered),
the deciphered data is prevented from flowing over the CPU BUS of
the computer and the second session key S.sub.K' used to encipher
the first session key necessary for deciphering the enciphered data
flowing over the CPU BUS is created on the basis of information
that changes each time the data is reproduced, such as time
information. Therefore, even when the data flowing over the CPU BUS
110 is stored from signal lines 210 into a digital storage medium
211 as shown in FIG. 4, the data cannot be reproduced of used.
[0077] As a result, the wrongful conduct of making unauthorized
copies and selling the thus copied mediums can be prevented,
thereby protecting copyrights.
[0078] Furthermore, with the embodiment, as seen from FIG. 1,
because the circuits used for enciphering and deciphering can be
designed separately from the essential portion of the reproducing
section of the digital recording and reproducing apparatus, such as
a DVD, even if the cipher is broken, the deciphering unit 114 (or
the enciphering unit 107 and deciphering unit 114) has only to be
replaced to overcome this problem.
[0079] While in the first embodiment, the enciphering unit 107 has
one enciphering circuit, it may have two enciphering circuits.
Moreover, although in the embodiment, the deciphering unit 114 has
one deciphering circuit, it may have two, three, or four
deciphering circuits. In these cases, it is desirable that the
enciphering circuits should be paired with the corresponding
deciphering circuits and each pair be used independently or in a
shared manner.
[0080] When a set of an enciphering circuit and the corresponding
deciphering circuit is used independently, an enciphering method
different from that in another enciphering circuit and deciphering
circuit may be used in the enciphering circuit and its
corresponding deciphering circuit in the independent set.
[0081] (Second Embodiment)
[0082] Hereinafter, a second embodiment of the present invention
will be explained.
[0083] What will be explained in the second embodiment is an
example suitable for a case where a plurality of predetermined
master keys are prepared and one or more of them are allocated to
deciphering unit makers (or DVD makers and distributors).
[0084] FIG. 5 is a block diagram of the system according to the
second embodiment of the present invention. An example of the
operation of the second embodiment is shown in the flowchart of
FIGS. 7 and 8.
[0085] The system related to the second embodiment is connected to
the CPU BUS of the CPU (not shown) used for reproduction in a
computer, such as a personal computer. The system is designed to
allow the enciphered data (E.sub.SK(Data)) to flow over the CPU
BUS. FIG. 5 shows only the sections related to the CPU used for
reproduction.
[0086] As shown in FIG. 5, the system of the second embodiment
comprises a DVD driving unit (not shown) that reads the data from a
DVD 101, an enciphering unit 107 that is connected to the DVD
driving unit without the CPU BUS or is built in the DVD driving
unit, and a deciphering unit 114a.
[0087] The enciphering unit 107 and deciphering unit 114a are
connected to the CPU BUS 110. The deciphering unit 114a outputs the
data via, for example, an I/O port, not via the CPU BUS. That is,
in the second embodiment, the input and output of the data is
carried out without the CPU BUS, whereas the CPU BUS is used for
the data transfer between the enciphering unit 107 and the
deciphering unit 114a.
[0088] The enciphering unit 107 includes a demodulation/error
correction circuit 117, a demodulation/error correction circuit
118, and an enciphering circuit 104. Although in FIG. 5, the
enciphering unit 107 has two enciphering circuits 104, it is
assumed that it actually has one enciphering circuit. The
enciphering unit 107 is assumed to be composed of a single
independent IC chip. The demodulation/error correction circuit 117
and demodulation/error correction circuit 118 may be provided in
the unit (the DVD driving unit) in the preceding stage, not in the
enciphering unit 107.
[0089] The deciphering unit 114a includes a deciphering circuit 112
and a session key creation circuit 111 that creates a second
session key S.sub.K', and a key judging circuit 120.
[0090] FIGS. 6A and 6B show examples of the structure of the key
judging circuit 120. The key judging circuit 120 includes a
deciphering circuit 112, a comparison circuit 121, and a gate
circuit 122. In the second embodiment, it is assumed that the
deciphering unit 114a incorporates an MPEG decoder circuit 115 and
a conversion circuit 116 that converts the deciphered digital image
data into analog image data.
[0091] Although in FIG. 5 and FIGS. 6A and 6B, the deciphering unit
114a has a total of five deciphering circuits 112, including the
two deciphering circuits 112 in the key judging circuit 120, it is
assumed that it actually has one deciphering circuit.
[0092] The deciphering unit 114a is composed of a single
independent IC chip.
[0093] In each of the enciphering unit 107 and deciphering unit
114a, master keys, explained later, have been registered. It is
assumed that the master keys have been recorded in a secret area in
each of the enciphering unit chip and the deciphering unit chip so
that the user cannot externally take out the master keys.
[0094] A control section (not shown) is assumed to control the
entire system. The control section is realized by, for example,
executing a program on the CPU in the computer. Concrete examples
of control by the control section include an instruction to read
the data from a DVD, the specification of data transfer
destination, and an instruction to output the data from the
deciphering unit 114a. The control section may be triggered, for
example, by the user via a user interface, or by a process in an
application program.
[0095] In the second embodiment, there are an n number of types of
master keys. A first session key is represented by S.sub.K, a
second session key S.sub.K', the n-th master key M.sub.Kt (t s in
the range of 1 to n), and image data (i.e., the data to be
enciphered) Data.
[0096] In FIG. 5, numeral 102-1 indicates E.sub.MKi(S.sub.K)
created by enciphering the first session key S.sub.K using the
master key M.sub.Ki, 102-2 E.sub.SK(S.sub.K) created by enciphering
the first session key S.sub.K using the first session key S.sub.K
itself, 103 E.sub.SK(Data) created by enciphering the image data
Data using the first session key S.sub.K, 105 the master key
M.sub.Ki, 106 a second session key S.sub.K', 108
D.sub.MKj(S.sub.K') created by deciphering the second session key
S.sub.K' using the master key M.sub.Kj, 109-1
E.sub.SK'(E.sub.MKi(S.sub.K- )) created by enciphering the first
session key E.sub.MKi(S.sub.K) enciphered with the master key
M.sub.Ki using the second session key S.sub.K', 109-2
E.sub.SK'(E.sub.SK(S.sub.K)) created by enciphering the first
session key E.sub.SK(S.sub.K) enciphered with the first session key
S.sub.K itself using the second session key S.sub.K' and 113 the
first session key S.sub.K.
[0097] Several methods can be considered as to how to set the
number of types of E.sub.MKi(S.sub.K) created by enciphering the
first session key S.sub.K recorded on the DVD 101 using the master
key M.sub.Ki and how to set the number of types of master key
M.sub.Kj the deciphering unit 114a has in it. For example, they are
as follows.
[0098] (Method 1) One master key E.sub.MKi(S.sub.K) (i is in the
range of 1 to n) is recorded on the DVD 101. The deciphering unit
114a has an n number of master keys M.sub.Kj (j=1 to n) in it.
[0099] (Method 2) An n number of master keys E.sub.MKi(S.sub.K)
(i=1 to n) are recorded on the DVD 101. The deciphering unit 114a
has one master key M.sub.Kj (j is in the range of 1 to n) in
it.
[0100] (Method 3) This is an expansion of Method 2. An n number of
master keys E.sub.MKi(S.sub.K) (i=1 to n) are recorded on the DVD
101. The deciphering unit 114a has an m (2<m<n) number of
master keys M.sub.Kj (j=1 to n) in it. The m number of master keys
have been selected from the n number of master keys beforehand.
[0101] As a concrete example, n=100 or n=400 and m=2, 3, 4, or 10.
The present invention is not limited to these values.
[0102] (Method 4) This is the reverse of Method 3. An m
(2<m<n) number of master keys E.sub.MKi(S.sub.K) (i=1 to n)
are recorded on the DVD 101. The m number of master keys have been
selected from an n number of master keys M.sub.Kj (j=1 to n)
beforehand. The deciphering unit 114a has an n number of master
keys M.sub.Kj (j=1 to n) in it.
[0103] (Method 5) An n number of master keys E.sub.MKi(S.sub.K)
(i=1 to n) are recorded on the DVD 101. The deciphering unit 114a
has an n number of master key M.sub.Kj (j=1 to n) in it.
[0104] Method 3 to Method 5 have the same deciphering
procedure.
[0105] As shown in FIG. 3, it is assumed that on the DVD 101, one
(in the case of Method 1) or more (in the case of Method 2 to
Method 5) E.sub.MKi(S.sub.K) created by enciphering the first
session key S.sub.K using the master key M.sub.Ki are recorded in
the key recording area (lead-in area) in the innermost
circumference portion and E.sub.SK(Data) created by enciphering the
image data Data using the first session key S.sub.K is recorded in
the data recording area (data area).
[0106] It is assumed that an n number of master keys M.sub.Kj (in
the case of Method 1, Method 4, or Method 5), one master key
M.sub.Kj (in the case of Method 2), or an m number of master keys
M.sub.Kj (in the case of Method 3) have been registered in the
deciphering unit 114a.
[0107] A predetermined master key is assumed to have been
registered in the deciphering unit 107.
[0108] Hereinafter, Method 1, Method 2, and Method 3 to Method 5
will be explained in that order.
[0109] First, the operation of the second embodiment in the case of
Method 1 will be explained by reference to the flowcharts of FIGS.
7 and 8.
[0110] At step S11, the first session key E.sub.SK(S.sub.K)
enciphered using the first session key S.sub.K itself is read from
the DVD 101, on which the DVD driving unit (not shown) has recorded
the first session key, and then is loaded into the enciphering unit
107. At that time, the demodulation/error correction circuit 117
performs demodulation and data error correction.
[0111] At step S12, the first session key E.sub.MKi(S.sub.K) (i in
the range of 1 to n, where i is unknown here) enciphered using the
master key M.sub.Ki is read from the DVD 101, on which the DVD
driving unit (not shown) has recorded the master key, and then is
loaded into the enciphering unit 107. At that time, the
demodulation/error correction circuit 117 performs demodulation and
data error correction.
[0112] At step S13, the session key creation circuit 111 of the
deciphering unit 114 creates a second session key S.sub.K' using
random numbers, such as time data from a clock (not shown). Then,
the deciphering circuit 112 deciphers the created second session
key S.sub.K' using the master key M.sub.Kj (j is in the range of 1
to n, where j is predetermined) to create D.sub.MKj(S.sub.K') and
sends it to the enciphering unit 107 via the CPU BUS 110.
[0113] As the timing of generating random numbers (e.g., the timing
of inputting time information), for example, the timing with which
the signal indicating that the DVD 101 has been loaded into the DVD
driving unit is asserted may be used.
[0114] The session creation circuit 111 may be composed of a
random-number generator that is as long as the key, for example.
When a key is created using random numbers all of whose bits may
take 0s or 1s, it is necessary to perform a check process to
prevent all of the bits from taking 0s or 1s.
[0115] At step S14, using the master key M.sub.Kj (j has a
predetermined value in the range of 1 to n), the enciphering
circuit 104 of the enciphering unit 107 enciphers
D.sub.MKj(S.sub.K') received via the CPU BUS 110.
[0116] Namely, from
E.sub.MKj(D.sub.MKj(S.sub.K'))=S.sub.K'
[0117] a second session key S.sub.K' created at the session key
creation circuit 111 of the deciphering unit 114a can be
obtained.
[0118] The second session key S.sub.K' created at the session key
creation circuit 111 is designed to prevent its contents from being
known even if it is stolen on the CPU BUS 110.
[0119] Then, at step S15, using the thus obtained second session
key S.sub.K', the enciphering unit 107 enciphers the enciphered
first session key E.sub.SK(S.sub.K) recorded on the DVD 101 to
create E.sub.SK'(E.sub.SK(S.sub.K)), and sends this to deciphering
unit 114a in via CPU BUS 110.
[0120] Similarly, at step S16, using the thus obtained second
session key S.sub.K', the enciphering unit 107 enciphers the
enciphered first session key E.sub.MKi(S.sub.K) recorded on the DVD
101 to create E.sub.SK'(E.sub.MKi(S.sub.K)), and sends this to
deciphering unit 114a.
[0121] Then, at step S17, the deciphering circuit 112 of the
deciphering unit 114a deciphers E.sub.SK'(E.sub.SK(S.sub.K))
received via the CPU BUS 110 using the second session key S.sub.K'
and produces:
D.sub.SK'(E.sub.SK'(E.sub.SK(S.sub.K)))=E.sub.SK(S.sub.K)
[0122] Similarly, at step S18, the deciphering circuit 112 of the
deciphering unit 114a deciphers E.sub.SK'(E.sub.MKi(S.sub.K))
received via the CPU BUS 110 using the second session key S.sub.K'
and produces:
D.sub.SK'(E.sub.SK'(E.sub.MKi(S.sub.K)))=E.sub.MKi(S.sub.K)
[0123] Because the master key M.sub.Ki used in creating
E.sub.MKi(S.sub.K) is unknown, the first session key S.sub.K is
found using the key judging circuit 120 as follows.
[0124] First, the principle of the key judging process will be
explained.
[0125] When E.sub.MKi(S.sub.K) is deciphered using all of the
master keys M.sub.Kj (j=1 to n), this gives:
S.sub.Kij=D.sub.MKj(E.sub.MKi(S.sub.K)) (j=1 to n)
[0126] Of these, one S.sub.Kij (j=1 to n) is the first session key
S.sub.K.
[0127] Using the E.sub.SK(S.sub.K), it is determined which one of
the created S.sub.Kij (j=1 to n) is the first session key
S.sub.K.
[0128] Then, when E.sub.SK(S.sub.K) is deciphered using all of the
candidates S.sub.Kij (j=1 to n) of the first session key, this
gives:
S.sub.K"(i, j)=D.sub.SKij(E.sub.SK(S.sub.K))
[0129] Here, when the same master key M.sub.Kj as the master key
M.sub.Ki used in creating E.sub.MKi(S.sub.K) is used in the
deciphering unit, or when i=j, this gives S.sub.K"(i,
j)=S.sub.Kij=S.sub.K.
[0130] Therefore, when a check is made to see if S.sub.K"(i,
j)=S.sub.Kij (j=1 to n) holds for each S.sub.Kij (j=1 to n), this
gives S.sub.Kij that meets S.sub.K"(i, j)=S.sub.Kij (j=1 to n) as
the first session key S.sub.K. The one corresponding to j giving
the S.sub.Kij is the master key used in the present session.
[0131] The operation is expressed in C language notation as
follows:
1 for (i=1; i<n+1; i++) { DS1[i]=DMK[i](EM.sub.Ki(S.sub.K));
DS2[i]=DSK[i](E.sub.SK(S.sub.K- )); if(DS1[i]==DS2[i]) {
SK1=DS2[i]; break; } else EXIT_MISMATCH; }
[0132] The second line in the above procedure indicates the
operation of deciphering E.sub.MKi(S.sub.K) using M.sub.Ki and
substituting the result into DS1[i].
[0133] The third line in the procedure indicates the operation of
deciphering E.sub.SK(S.sub.K) using S.sub.Ki and substituting the
result into DS2[i].
[0134] The fourth line in the procedure indicates the operation of
judging whether nor not DS1[i] coincides with DS2[i].
[0135] The ninth line in the procedure indicates the operation
executed when DS1[i] does not coincide with DS2[i].
[0136] For example, in FIGS. 6A and 6B, the deciphering circuit 112
in the key judging circuit 120 deciphers E.sub.MKi(S.sub.K) for j=1
using master key M.sub.Kj, giving:
S.sub.Kij=D.sub.MKj(E.sub.MKi(S.sub.K))
[0137] Then, the deciphering circuit 112 deciphers
E.sub.SK(S.sub.K) using S.sub.Kij, giving:
S.sub.K"=D.sub.SKij(E.sub.SK(S.sub.K))
[0138] Next, the comparison circuit 121 compares S.sub.K" with
S.sub.Kij. If they coincide with each other, the gate circuit 122
will be controlled so as to output the stored S.sub.Kij (FIG. 6A)
or S.sub.K" (FIG. 6B) as the first session key S.sub.K.
[0139] If they do not coincide, j is incremented by one and the
same operation will be carried out until the first session key
S.sub.K has been obtained.
[0140] After the first session key S.sub.K has been obtained as
described above, at step S20, the image data E.sub.SK(Data)
enciphered using the first session key S.sub.K recorded on the DVD
101 by the DVD driving unit (not shown) is read out and loaded into
the enciphering unit 107. At that time, the demodulation/error
correction circuit 118 performs demodulation and corrects errors in
the data. Then, E.sub.SK(Data) is sent to the enciphering unit 107
via the CPU BUS 110.
[0141] At step S21, the deciphering circuit 112 of the deciphering
unit 114a deciphers E.sub.SK(Data) received via the CPU BUS 110
using the first session key S.sub.K and produces:
D.sub.SK(E.sub.SK(Data)=Data
[0142] Then, the enciphered image data is deciphered to produce
Data.
[0143] Then, step S20 and step S21 are repeated until for example,
the process of the data to be deciphered (i.e., E.sub.SK(Data)) has
been completed or the stop of the process has been requested.
[0144] When the image data Data thus obtained has been compressed
according to, for example, the MPEG2 data compression standard, the
image data is decoded at an MPEG decoder circuit 115. After the
decoded signal has been converted by a D/A converter circuit 116
into an analog signal, the analog signal is sent to an imaging
device (not shown), such as a television, which reproduces the
image.
[0145] Any one of step S11, step S12, and steps S13 and S4 may be
executed first.
[0146] Moreover, either step S15 and step S17 or step S16 and S18
may be executed first.
[0147] Step S20 and step S21 may be executed by the method of
carrying out the steps in units of E.sub.SK(Data), the method of
reading a specific number of E.sub.SK(Data) at step S20, storing
the read-out data in a buffer temporarily, and then deciphering
E.sub.SK(Data) in the buffer at step S21, or the method of carrying
out step S20 and step S21 in a pipeline processing manner.
[0148] Moreover, the deciphering circuit 112 may transfer the image
data E.sub.SK(Data) to the MPEG decoder circuit 115 in units of one
Data item or a specific number of Data items.
[0149] As described above, with the second embodiment, even when
the data flowing over the CPU BUS 110 is stored, the data cannot be
reproduced of used, as in the first embodiment.
[0150] As a result, the wrongful conduct of making unauthorized
copies and selling the thus copied mediums can be prevented,
thereby protecting copyrights.
[0151] Furthermore, with the second embodiment, the information
that directly indicates the master key used to encipher the first
session key recorded on the recording medium is not necessary,
which enables a suitable master key to be selected and used in a
predetermined range in recording the data on a DVD. In addition,
the second embodiment has the advantage that it can allocate master
keys in a specific unit, such as a DVD maker or a DVD
distributor.
[0152] With the second embodiment, because the circuits used for
enciphering and deciphering can be designed separately from the
essential portion of the reproducing section of the digital
recording and reproducing apparatus, such as a DVD, even if the
cipher is broken, the deciphering unit 114a (or the enciphering
unit 107 and deciphering unit 114a) has only to be replaced to
overcome this problem.
[0153] While in the second embodiment, the enciphering unit 107 has
one enciphering circuit, it may have two enciphering circuits.
Moreover, although in the embodiment, deciphering unit 114a has one
deciphering circuit, it may have two, three, four, or five
deciphering circuits. In these cases, it is desirable that the
enciphering circuits should be paired with the corresponding
deciphering circuits and each pair be used independently.
[0154] When a set of an enciphering circuit and its corresponding
deciphering circuit is used independently, an enciphering method
different from that in another enciphering circuit and deciphering
circuit may be used in the enciphering circuit and its
corresponding deciphering circuit in the independent set.
[0155] Next, the operation of the second embodiment in the case of
Method 2 where an n number of E.sub.MKi(S.sub.K) (i=1 to n) have
been recorded on the DVD 101 and the deciphering unit 114a includes
one M.sub.Kj (j has a value in the range of 1 to n) will be
explained by reference to the flowcharts of FIGS. 7 and 8.
[0156] At step S11, the first session key E.sub.SK(S.sub.K)
enciphered using the first session key S.sub.K itself is read from
the DVD 101, on which the DVD driving unit (not shown) has recorded
the first session key, and then is loaded into the enciphering unit
107. At that time, the demodulation/error correction circuit 117
performs demodulation and data error correction.
[0157] At step S12, the first session key E.sub.MKi(S.sub.K) (i =1
to n) enciphered using the master key M.sub.Ki is read from the DVD
101, on which the DVD driving unit (not shown) has recorded the
master key, and then is loaded into the enciphering unit 107. At
that time, the demodulation/error correction circuit 117 performs
demodulation and data error correction.
[0158] At step S13, the session key creation circuit 111 of
deciphering unit 114a creates a second session key S.sub.K' using
random numbers, such as time data from a clock (not shown). Then,
the deciphering circuit 112 deciphers the created second session
key S.sub.K' using the master key M.sub.Kj (j has a predetermined
value in the range of 1 to n) to create D.sub.MKj(S.sub.K') and
sends it to the enciphering unit 107 via the CPU BUS 110.
[0159] As the timing of generating random numbers (e.g., the timing
of inputting time information), for example, the timing with which
the signal indicating that the DVD 101 has been loaded into the DVD
driving unit is asserted may be used.
[0160] At step S14, using the master key M.sub.Kj (j has a
predetermined value in the range of 1 to n), the enciphering
circuit 104 of the enciphering unit 107 enciphers
D.sub.MKj(S.sub.K') received via the CPU BUS 110.
[0161] Namely, from
E.sub.MKj(D.sub.MKj(S.sub.K'))=S.sub.K'
[0162] a second session key S.sub.K' created at the session key
creation circuit 111 of the deciphering unit 114a can be
obtained.
[0163] The second session key S.sub.K' created at the session key
creation circuit 111 is designed to prevent its contents from being
known even if it is stolen on the CPU BUS 110.
[0164] Then, at step S15, using the thus obtained second session
key S.sub.K', the enciphering unit 107 enciphers the enciphered
first session key E.sub.SK(S.sub.K) recorded on the DVD 101 to
create E.sub.SK'(E.sub.SK(S.sub.K)), and sends this to deciphering
unit 114a.
[0165] Similarly, at step S16, using the thus obtained second
session key S.sub.K', the enciphering unit 107 enciphers an n
number of enciphered first session keys E.sub.MKi(S.sub.K) recorded
on the DVD 101 to create E.sub.SK'(E.sub.MKi(S.sub.K)), and sends
these to deciphering unit 114a via the CPU BUS 110.
[0166] Then, at step S17, the deciphering circuit 112 of the
deciphering unit 114a deciphers E.sub.SK'(E.sub.SK(S.sub.K))
received via the CPU BUS 110 using the second session key S.sub.K'
and produces:
D.sub.SK'(E.sub.SK'(E.sub.SK(S.sub.K)))=E.sub.SK(S.sub.K)
[0167] Similarly, at step S18, the deciphering circuit 112 of the
deciphering unit 114a deciphers E.sub.SK'(E.sub.MKi(S.sub.K))
received via the CPU BUS 110 using the second session key S.sub.K'
and produces:
D.sub.SK'(E.sub.SK'(E.sub.MKi(S.sub.K)))=E.sub.MKi(S.sub.K)
[0168] Because the master key M.sub.Ki used in creating each of the
n number of E.sub.MKi(S.sub.K) (i=1 to n) recorded on the DVD 101
is unknown, it cannot be known whether the master key M.sub.Ki
corresponds to the master key M.sub.Kj in the deciphering unit
114a. At step S19, the first session key S.sub.K is found using the
key judging circuit 120 as follows.
[0169] First, the principle of the key judging process will be
explained.
[0170] When all of E.sub.MKi(S.sub.K) (i=1 to n) are deciphered
using the master key M.sub.Kj, this gives:
S.sub.Kij=D.sub.MKj(E.sub.MKi(S.sub.K)) (i=1 to n)
[0171] Of these, one S.sub.Kij (i is in the range of 1 to n) is the
first session key S.sub.K.
[0172] Using the E.sub.SK(S.sub.K), it is determined which one of
the created S.sub.Kij (i=1 to n) is the first session key
S.sub.K.
[0173] Then, when E.sub.SK(S.sub.K) is deciphered using all of the
candidates S.sub.Kij (i=1 to n) of the first session key, this
gives:
S.sub.K"(i, j)=D.sub.SKij(E.sub.SK(S.sub.K))
[0174] Here, when the same master key M.sub.Kj as the master key
M.sub.Ki used in creating E.sub.MKi(S.sub.K) is used in the
deciphering unit, or when i=j, this gives S.sub.K"(i,
j)=S.sub.Kij=S.sub.K.
[0175] Therefore, when a check is made to see if S.sub.K"(i,
j)=S.sub.Kij (j=1 to n) holds for each S.sub.Kij (i=1 to n), this
gives S.sub.Kij that meets S.sub.K"(i, j)=S.sub.Kij (j=1 to n) as
the first session key S.sub.K. The one corresponding to i giving
the S.sub.Kij is the master key used in the present session.
[0176] For example, in FIGS. 6A and 6B, the deciphering circuit 112
in the key judging circuit 120 deciphers E.sub.MKi(S.sub.K) for i=1
using master key M.sub.Kj, giving:
S.sub.Kij=D.sub.MKj(E.sub.MKi(S.sub.K))
[0177] Then, the deciphering circuit 112 deciphers
E.sub.SK(S.sub.K) using S.sub.Kij, giving:
S.sub.K"=D.sub.SKij(E.sub.SK(S.sub.K))
[0178] Next, the comparison circuit 121 compares S.sub.K" with
S.sub.Kij. If they coincide with each other, the gate circuit 122
will be controlled so as to output the stored S.sub.Kij (FIG. 6A)
or S.sub.K" (FIG. 6B) as the first session key S.sub.K.
[0179] If they do not coincide, i is incremented by one and the
same operation will be carried. This will be continued until the
first session key S.sub.K has been obtained.
[0180] After the first session key S.sub.K has been obtained as
described above, at steps S20 to S22, the image data Data is
extracted from the image data E.sub.SK(Data) enciphered using the
first session key S.sub.K.
[0181] As described earlier, the image data Data is decoded at the
MPEG decoder circuit 115. After the decoded signal has been
converted by the D/A converter circuit 116 into an analog signal,
the analog signal is sent to the imaging device (not shown), such
as a television, which reproduces the image.
[0182] In Method 2, too, any one of step S11, step S12, and step
S13 and step S14 may be executed first.
[0183] Moreover, either step S15 and step S17 or step S16 and S18
may be executed first.
[0184] Furthermore, steps S12, S16, S18, and S19 may be executed in
a batch processing manner using all the n number of (enciphered)
master keys recorded on the DVD or using a specific number of
master keys at a time. They may be executed one after another for
each master key.
[0185] When they are executed sequentially every third master key,
the second session key S.sub.K' may be created for each master
key.
[0186] Step S20 and step S21 may be executed by the method of
carrying out the steps in units of E.sub.SK(Data), the method of
reading a specific number of E.sub.SK(Data) at step S20, storing
the read-out data in a buffer temporarily, and then deciphering
E.sub.SK(Data) in the buffer at step S21, or the method of carrying
out step S20 and step S21 in a pipeline processing manner.
[0187] Moreover, the deciphering unit 114a may transfer the image
data E.sub.SK(Data) to the MPEG decoder circuit 115 in units of one
Data item or a specific number of Data items.
[0188] As described above, with the second embodiment, even when
the data flowing over the CPU BUS 110 is stored, the data cannot be
reproduced or used, as in the first embodiment.
[0189] As a result, the wrongful conduct of making unauthorized
copies and selling the thus copied mediums can be prevented,
thereby protecting copyrights.
[0190] Furthermore, with the second embodiment, because the first
session keys enciphered using more than one master key and the
first session key enciphered with the first session key itself are
stored on the recording medium, the master keys built in the
deciphering unit can be allocated in a specific unit, such as to
each unit manufacturer.
[0191] With the second embodiment, because the circuits used for
enciphering and deciphering can be designed separately from the
essential portion of the reproducing section of the digital
recording and reproducing apparatus, such as a DVD, as seen from
FIG. 1, even if the cipher is broken, the deciphering unit 114b (or
the enciphering unit 107 and deciphering unit 114b) has only to be
replaced to overcome this problem.
[0192] While in the second embodiment, the enciphering unit 107 has
one enciphering circuit, it may have two enciphering circuits.
Moreover, although in the embodiment, the deciphering unit 114a has
one deciphering circuit, it may have two, three, four, or five
deciphering circuits. In these cases, it is desirable that the
enciphering circuits should be paired with the corresponding
deciphering circuits and each pair be used independently or be
shared.
[0193] When a set of an enciphering circuit and its corresponding
deciphering circuit is used independently, an enciphering method
different from that in another enciphering circuit and deciphering
circuit may be used in the enciphering circuit and its
corresponding deciphering circuit in the independent set.
[0194] Next, explanation will be given about Method 3 where an n
number of E.sub.MKi(S.sub.K) (i=1 to n) have been recorded on the
DVD 101 and the deciphering unit 114a includes an m number of
M.sub.Kj (j takes m values in the range of 1 to n (m<n)).
[0195] Since Method 3 is the same as Method 2 in basic
configuration, operation, and effect, only the difference between
them will be explained.
[0196] While in Method 2, the deciphering unit 114a includes one
predetermined master key M.sub.Kj (j has a value in the range of 1
to n), in Method 3, the deciphering unit 114a includes an m number
of predetermined master keys M.sub.Kj (m.gtoreq.2). The order in
which the m number of master keys M.sub.Kj (j takes m values in the
range of 1 to n) are used in the key judgment has been
determined.
[0197] Because an n number of E.sub.MKi (S.sub.K) (i=1 to n) have
been recorded on the DVD 101, using the master key first in order
of use in the deciphering unit 114b produces the first session key
S.sub.K. Therefore, in this case, the operation is the same as in
Method 2.
[0198] With Method 3, if one of the master keys is broken, the
master key is made unusable. From this time on, E.sub.MKi(S.sub.K)
corresponding to the unusable master key is not allowed to be
recorded on the DVD 101. This case will be explained below.
[0199] When the unusable master key is not the master key first in
order of use, the first session key S.sub.K can be obtained. In
this case, too, the operation is the same as in Method 2.
[0200] When the master key first in order of use is made unusable,
E.sub.MKi(S.sub.K) corresponding to the unusable master key has not
been recorded on the DVD 101. Even if the master key first in order
of use is used, the first session key S.sub.K cannot be obtained in
step S19. In such a case, when the deciphering unit 114a carries
out the same operation using the master key second in order of use
as in Method 2, this produces the first session key S.sub.K,
provided that this master key is not unusable.
[0201] Even when the master key r-th in order of use is made
unusable, the first session key S.sub.K can be obtained similarly,
provided that one of the master keys (r+1)-th or later in order of
use is not unusable.
[0202] In this way, the deciphering unit 114a can be used until the
predetermined m number of master keys (m.gtoreq.2) in the
deciphering unit 114a have all been made unusable.
[0203] The operation of Method 5 is the same as that of Method
3.
[0204] Because in Method 4, the information corresponding to all
the master keys has not been stored on the DVD 101, when the
information corresponding to the master key selected in the
deciphering unit has not been recorded on the DVD 101, deciphering
cannot be effected as in the case where the master key is unusable.
In this case, the master key next in order of use is selected and
deciphering is tried. Therefore, the operation of Method 4 is also
the same as that of Method 3.
[0205] In the embodiment, to encipher the information and transfer
it safely over the CPU BUS 110, the second session key S.sub.K' has
been used. The second session key S.sub.K' is created in the
deciphering unit 114a and is transferred to the enciphering unit
107 through the procedure of using master keys. At that time, one
predetermined master key is supposed to have been registered in the
enciphering unit 107.
[0206] Instead, a plurality of master keys may be registered in the
enciphering unit 107 and the second session key S.sub.K' may be
transferred from the deciphering unit 114a to the enciphering unit
107, using the procedure as described in Method 1 to Method 5 using
key judgment.
[0207] For example, when the same master key as that registered in
the deciphering unit 114a is also registered in the enciphering
unit 107, the operation is the same as that of Method 5.
[0208] When part of the master keys registered in the deciphering
unit 114a are registered in the enciphering unit 107, the operation
is the same as that of Method 3.
[0209] When one master key is registered in the enciphering unit
107, the procedure of Method 2 can be used.
[0210] In these cases, however, in the procedure of each of Method
1 to Method 5, enciphering is replaced with deciphering.
Specifically, D.sub.MKi(S.sub.K) and DSK(S.sub.K) are transferred
from the deciphering unit 114a to the enciphering unit 107.
[0211] In addition to the configuration using the master key,
various suitable configurations may be used as the configuration
that safely transfers the second session key S.sub.K' from the
deciphering unit 114a to the enciphering unit 107 over the CPU BUS
110. For example, the techniques disclosed in Nikkei Electronics,
No. 676, Nov. 18, 1996, pp. 13-14. In this case, it is not
necessary to register a master key in the enciphering unit 107.
[0212] (Third Embodiment)
[0213] Hereinafter, a third embodiment of the present invention
will be explained.
[0214] The third embodiment is, for example, a single DVD
player.
[0215] FIG. 9 is a block diagram of a system according to the third
embodiment of the present invention. An example of the operation of
the third embodiment is shown in the flowchart of FIG. 10.
[0216] The third embodiment is what is obtained by eliminating from
the configuration of the second embodiment the portion related to
the operation of exchanging an enciphered key between the
enciphering unit and deciphering unit by use of the second session
key.
[0217] As shown in FIG. 9, the system of the third embodiment
comprises a DVD driving unit (not shown) that reads the data from a
DVD 101 and a deciphering unit 114b.
[0218] The deciphering unit 114b includes a deciphering circuit
112, a key judging circuit 120, a demodulation/error correction
circuit 117, and a demodulation/error correction circuit 118. In
the third embodiment, the deciphering unit 114b is assumed to
include an MPEG decoder circuit 115 and a conversion circuit 116
that converts the digital deciphered data into analog data.
[0219] As shown in FIGS. 6A and 6B, the key judging circuit 120
includes a deciphering circuit 112, a comparison circuit 121, and a
gate circuit 122.
[0220] Although in FIG. 9 and FIGS. 6A and 6B, the deciphering unit
114b has a total of three deciphering circuits 112, including the
two deciphering circuits 112 in the key judging circuit 120, it is
assumed that it actually has one deciphering circuit. Each of the
demodulation/error correction circuit 117 and the
demodulation/error correction circuit 118 may be provided in the
unit in the preceding stage, not in the enciphering unit 107.
[0221] The deciphering unit 114b is composed of a single
independent IC chip.
[0222] In the deciphering unit 114b, a master key, explained later,
has been registered. It is assumed that the master key has been
recorded in a secret area in the deciphering unit chip so that the
user cannot externally take out the master key.
[0223] In the third embodiment, there are an n number of master
keys. A first session key is represented by S.sub.K, a second
session key S.sub.K', the i-th master key M.sub.Ki (i is in the
range of 1 to n), and image data (i.e., the data to be enciphered)
Data.
[0224] In FIG. 9, numeral 102-1 indicates E.sub.MKi(S.sub.K)
created by enciphering the first session key S.sub.K using the
master key M.sub.Ki, 102-2 E.sub.SK(S.sub.K) created by enciphering
the first session key S.sub.K using the first session key S.sub.K
itself, 103 E.sub.SK(Data) created by enciphering the image data
Data using the first session key S.sub.K, 105 the master key
M.sub.Ki, and 113 the first session key S.sub.K.
[0225] As in the second embodiment, several methods can be
considered as to how to set the number of types of
E.sub.MKi(S.sub.K) created by enciphering the first session key
S.sub.K recorded on the DVD 101 using the master key M.sub.Ki and
how to set the number of types of master key M.sub.Kj the
deciphering unit 114b has in it. For example, they are as
follows.
[0226] (Method 1) One master key E.sub.MKi(S.sub.K) (i is in the
range of 1 to n) is recorded on the DVD 101. The deciphering unit
114b has an n number of master keys M.sub.Kj (j=1 to n) in it.
[0227] (Method 2) An n number of master keys E.sub.MKi(S.sub.K)
(i=1 to n) are recorded on the DVD 101. The deciphering unit 114b
has one master key M.sub.Kj (j has a value in the range of 1 to n)
in it.
[0228] (Method 3) An n number of master keys E.sub.MKi(S.sub.K)
(i=1 to n) are recorded on the DVD 101. The deciphering unit 114b
has an m (2<m<n) number of master keys M.sub.Kj (j is in the
range of 1 to n) in it.
[0229] (Method 4) An m (2<m<n) number of master keys
E.sub.MKi(S.sub.K) (i is in the range of 1 to n) are recorded on
the DVD 101. The deciphering unit 114b has an n number of master
keys M.sub.Kj (j=1 to n) in it.
[0230] (Method 5) An n number of master keys E.sub.MKi(S.sub.K)
(i=1 to n) are recorded on the DVD 101. The deciphering unit 114b
has an n number of master key M.sub.Kj (j=1 to n) in it.
[0231] As shown in FIG. 3, it is assumed that on the DVD 101, one
(in the case of Method 1) or more (in the case of Method 2 to
Method 5) E.sub.MKi(S.sub.K) created by enciphering the first
session key S.sub.K using the master key M.sub.Ki are recorded in
the key recording area (lead-in area) in the innermost
circumference portion and the E.sub.SK(Data) created by enciphering
the image data Data using the first session key S.sub.K is recorded
in the data recording area (data area).
[0232] Next, the operation of the third embodiment will be
explained by reference to the flowchart of FIG. 10. The operation
of the third embodiment is what is obtained by eliminating from the
operation of the second embodiment the portion related to the
operation of exchanging an enciphered key between the enciphering
unit and deciphering unit by use of the second session key.
[0233] At step S31, the first session key E.sub.SK(S.sub.K)
enciphered using the first session key S.sub.K itself is read from
the DVD 101, on which the DVD driving unit (not shown) has recorded
the first session key, and then is loaded into the deciphering unit
114b. At that time, the demodulation/error correction circuit 117
performs demodulation and data error correction.
[0234] At step S32, the first session key E.sub.MKi(S.sub.K)
enciphered using the master key M.sub.Ki is read from the DVD 101,
on which the DVD driving unit (not shown) has recorded the master
key, and then is loaded into the deciphering unit 114b. At that
time, the demodulation/error correction circuit 117 performs
demodulation and data error correction.
[0235] At step S33, the first session key S.sub.K is obtained using
the key judging circuit 120.
[0236] The operation of obtaining the first session key S.sub.K
differs depending on Method 1, Method 2, or Method 3 to Method 5.
Each case is the same as explained in the second embodiment, so
explanation of them will not be given.
[0237] After the first session key S.sub.K has been obtained, the
image data Data is extracted from the enciphered image data
E.sub.SK(Data) using the first session key S.sub.K at steps S34 to
S36. The operation at step S34 to S36 are the same as that of steps
S20 to S22 explained in the second embodiment (i.e., that of steps
S6 to S8 explained in the first embodiment) except that there is no
exchange of the image data Data between the units via the CPU
BUS.
[0238] As described earlier, the image data Data is decoded at the
MPEG decoder circuit 115. After the decoded signal has been
converted by the D/A converter circuit 116 into an analog signal,
the analog signal is sent to the imaging device (not shown), such
as a television, which reproduces the image.
[0239] In Method 3, too, step S31 may be executed before step S32
or vice versa.
[0240] Furthermore, in method 2 and in method 3 to method 5, step
S32 and step S33 may be executed in a batch processing manner using
all the n number of (enciphered) master keys (in the case of
Methods 2, 3, and 5) or all the m number of (enciphered) master
keys (in the case of Method 4) recorded on the DVD or using a
specific number of master keys at a time. They may be executed one
after another for each master key.
[0241] Step S34 and step S35 may be executed by the method of
carrying out the steps in units of E.sub.SK(Data), the method of
reading a specific number of E.sub.SK(Data) at step S34, storing
the read-out data in a buffer temporarily, and then deciphering
E.sub.SK(Data) in the buffer at step S35, or the method of carrying
out step S34 and step S35 in a pipeline processing manner.
[0242] Moreover, the deciphering unit 114b may transfer the image
data E.sub.SK(Data) to the MPEG decoder circuit 115 in units of one
Data item or a specific number of Data items.
[0243] With the third embodiment, the wrongful conduct of making
unauthorized copies and selling the thus copied mediums can be
prevented, thereby protecting copyrights.
[0244] Furthermore, with the third embodiment, it is possible to
select and use a suitable master key in a predetermined range in
recording the data on a DVD. The master keys can be allocated in a
specific unit, such as to a DVD player maker, a DVD maker, or a DVD
distributor.
[0245] Still furthermore, with the third embodiment, because the
circuits used for enciphering and deciphering can be designed
separately from the essential portion of the reproducing section of
the digital recording and reproducing apparatus, such as a DVD, as
seen from FIG. 1, even if the cipher is broken, the deciphering
unit 114b has only to be replaced to overcome this problem.
[0246] While in the third embodiment, the deciphering unit 114b has
one deciphering circuit, it may have two or three deciphering
circuits. In these cases, it is desirable that the enciphering
circuits should be paired with the corresponding deciphering
circuits and each pair be used independently or be shared.
[0247] When a set of an enciphering circuit and its corresponding
deciphering circuit is used independently, an enciphering method
different from that in another enciphering circuit and deciphering
circuit may be used in the enciphering circuit and its
corresponding deciphering circuit in the independent set.
[0248] Until now, the first embodiment, the second embodiment
(specifically, the three types of configuration), and the third
embodiment (specifically, the three types of configuration) have
been explained. The present invention is not limited to these
embodiments, but may be practiced or embodied in still other ways
without departing from the spirit or essential character
thereof.
[0249] Although the embodiments have been explained using a DVD as
information recording medium, the present invention may be applied
to other recording mediums, such as CD-ROMs.
[0250] While in the embodiments, the image data has been used as
the information to be deciphered, the present invention may be
applied to reproducing devices of other types of information, such
as sound, text, or programs.
[0251] While in the embodiments, the data Data is image data, the
configuration may be designed to use key information S.sub.Kt as
the data Data. Specifically, E.sub.SK(S.sub.Kt) and E.sub.SKt(Data)
may be recorded on a recording medium, such as a DVD, beforehand in
place of E.sub.SK(Data), then S.sub.Kt is first obtained at the
deciphering units 114, 114a, 114b through the procedure in each of
the embodiments, and E.sub.SKt(Data) is deciphered using the
S.sub.Kt to produce the actual contents of the data. The
hierarchization of keys may be carried out over any number of
levels of hierarchy.
[0252] While in the embodiments, the information to be deciphered
has been compressed according to the MPEG2 standard, the present
invention is not restricted to this. The data may be compressed or
enciphered according to another standard. In this case, a decoder
circuit corresponding to another standard has to be provided
instead of the MPEG decoder circuit 115. The data may not be
enciphered. In this case, the MPEG decoder circuit 115 is
eliminated.
[0253] To output any data items compressed by various methods (or
data items requiring no deciphering), several types of decoder
circuits may be provided and switched suitably. In this case, a
method can be considered which reads an identifier indicating the
decoder to be used from a recording medium, such as a DVD, and
selects a suitable decoder circuit according to the identifier.
[0254] The configurations of the key judging circuit 120 shown in
FIGS. 6A and 6B in the second and third embodiments are
illustrative and not restrictive. Other configurations of the key
judging circuit may be considered.
[0255] Various types of the configuration that uses
E.sub.SK(S.sub.K) as key judgment information may be considered.
For instance, D.sub.SK(S.sub.K) is used as information used for key
judgment. The key judging circuit 120 deciphers E.sub.MKi(S.sub.K)
read from a recording medium, such as a DVD, using master key
M.sub.Kj to produce S.sub.Kij=D.sub.MKj(E.sub.MKi(S.sub.K)),
deciphers the S.sub.Kij using the S.sub.Kij itself to produce
S.sub.K'"=D.sub.SKij(S.sub.Kij), and compares the S.sub.K' with
DSK(S.sub.K) read from a recording medium, such as a DVD. When they
coincide with each other, the key judging circuit judges that the
first session key S.sub.K=S.sub.Kij is correct and outputs it.
[0256] As other examples of key judgment information, the one
enciphered or deciphered twice or more times, such as
E.sub.SK(E.sub.SK(S.sub.K)) or D.sub.SK(D.sub.SK(S.sub.K)) may be
considered. In addition, E.sub.MKi(E.sub.MKi(S.sub.K)) may be
provided for each E.sub.MKi(S.sub.K).
[0257] In the embodiments, on the basis of the key judgment
information, a judgment is made through the procedure shown in each
of Method 1 to Method 5 as to whether the key obtained by
deciphering is the correct first session key. However, the key
judgment information, key judging procedure, and the structure for
key judgment can be eliminated by recording all the
E.sub.MKi(S.sub.K) on a recording medium, such as a DVD, in order
of i and registering them in the deciphering unit in such a manner
that i corresponds to M.sub.Ki. When M.sub.Ki for a certain i
becomes unusable, it is desirable that information indicating
invalidity should be stored on a recording medium, such as a DVD,
in place of E.sub.MKi(S.sub.K).
[0258] A key control method followed by disk makers (assumed to be
makers that produce DVDs for writings, including movies and music),
player makers (assumed to be makers that produce DVD players), and
a key control organization that controls master keys will be
described taking a DVD-ROM as example, by reference to FIG. 11.
Here, in addition to the contents, Data may be key information, as
described earlier (explanation of the case where enciphering or
deciphering is done using key information S.sub.Kt when Data is key
information S.sub.Kt will be omitted). In FIG. 11, a computer used
for processing is not shown.
[0259] FIG. 12 is a diagram to help explain a system for
deciphering. Enciphering circuits 301, 312, 303 in FIG. 12 may be
on the same unit (e.g., a computer) or on different units (e.g.,
computers). In the latter case, information is exchanged between
the units. The enciphering circuits 301, 312, 303 may be
constructed in hardware or in software.
[0260] Explanation will be given about a case where an n number of
master keys E.sub.MKi(S.sub.K) (i=1 to n) are recorded on a DVD. A
DVD player (a deciphering unit 114b) has an m (2<m<n) number
of master keys M.sub.Kj (j is in the range of 1 to n) in it. The m
number of master keys have been selected from the n number of
master keys beforehand. The master keys M.sub.Kj are assumed to be
allocated exclusively to the DVD player maker. It is assumed that
n=100 and m=10.
[0261] A method of recording E.sub.SK(S.sub.K) on a DVD as key
judgment information is used (the section indicated by numeral 302
in FIG. 12 uses E.sub.SK(S.sub.K) as key judgment information).
[0262] A key control organization 200 keeps master keys
M.sub.Ki(i=1 to 100). It is desirable that the number of master
keys should be set at a larger value than necessary in preparation
for the entry of a new player maker or in case a master key is
broken.
[0263] The key control organization 200 exclusively allocates the
master keys M.sub.Ki (i=1 to 100) to the individual player makers
201 to 203. For example, as shown in FIG. 11, it allocates master
keys M.sub.Ki (i=10 to 19) to player maker A, master keys M.sub.Ki
(i=20 to 29) to player maker B, and master keys M.sub.Ki (i=30 to
39) to player maker C. The key control organization 200 sends the
allocated master keys to the individual player makers by means of
communication mediums or recording mediums. At that time, it is
desirable that they should be exchanged safely by enciphered
communication.
[0264] Each player maker controls the master keys allocated by the
key control organization 200. Using the allocated master keys, each
player maker manufactures DVD players with the configuration as
shown in the third embodiment and sells the resulting products.
[0265] It is assumed that the key control organization 200 does not
give the plain data on the master keys to disk makers 221 to
223.
[0266] First, each disk maker (e.g., maker a) determines the first
session key S.sub.K (e.g., for each disk) by itself, and gives the
first session key S.sub.K to the key control organization 200. The
key control organization 200 enciphers the received first session
key S.sub.K using all the master keys M.sub.Ki (i=1 to 100) to
produce E.sub.MKi(S.sub.K) (i=1 to 100) (using the enciphering unit
301 of FIG. 12). Then, the key control organization 200 gives
E.sub.MKi(S.sub.K) (i=1 to 100) to disk maker a.
[0267] It is desirable that the exchange of the allocated master
keys between the key control organization 200 and the disk maker
should be made by means of communication mediums or recording
mediums through enciphered communication.
[0268] Disk maker a records E.sub.MKi(S.sub.K) (i=1 to 100),
E.sub.SK(S.sub.K), and E.sub.SK(Data) on a DVD 231. The operation
of enciphering S.sub.K with S.sub.K itself to produce
E.sub.SK(S.sub.K) is carried out by the disk maker side or by the
key control organization 200 side (using the enciphering circuit
321 of FIG. 12) in the case of enciphering with a mater key. It is
assumed that at least the enciphering of the contents is done at
the disk maker side (using the enciphering circuit 303 of FIG.
12).
[0269] Disk maker a controls the received E.sub.MKi(S.sub.K), key
judgment information E.sub.SK(S.sub.K), and E.sub.SK(Data) (or
Data) for S.sub.K, for example.
[0270] The same is true for the other disk makers.
[0271] In case it is found that the master key has been broken,
from that time on, DVDs are manufactured without using the broken
master key. For example, if the master key for i=19 has been
broken, ninety-nine E.sub.MKi(S.sub.K) corresponding to i=1 to 18
and 20 to 100 are recorded on a DVD.
[0272] In case it is found that the master key has been broken, it
is desirable that the player maker to which the broken master key
has been allocated should manufacture and sell DVD players
excluding the broken master key. For example, if the master key for
i=19 has been broken, player maker A manufactures DVD players using
the master keys for i=10 to 18 and sells the resulting
products.
[0273] The already sold DVD player having the master key for i=19
may be used without any modification. It may be modified so as not
to have the master key for i=19.
[0274] Consequently, the master keys can be controlled safely and
effectively. In addition, the risk of the master key being
deciphered in an unauthorized manner can be dispersed and even
after the deciphering of the master key, the system can function
safely and effectively.
[0275] As describe in detail, with the present invention, only the
correct maker having at least one of a plurality of second keys can
get the first key and therefore can get the plain data of the data
enciphered using the first key.
[0276] As a result, the wrongful conduct of making unauthorized
copies and selling the thus copied mediums can be prevented,
thereby protecting copyrights.
[0277] Additional advantages and modifications will readily occur
to those skilled in the art. Therefore, the present invention in
its broader aspects is not limited to the specific details,
representative devices, and illustrated examples shown and
described herein. Accordingly, various modifications may be made
without departing from the spirit or scope of the general inventive
concept as defined by the appended claims and their
equivalents.
* * * * *