DESCRIPTION
COPYRIGHT PROTECTION SYSTEM, REPRODUCTION DEVICE, AND REPRODUCTION
METHOD
Technical Field
[0001]
The present invention relates to services provided through
cooperation between a recording medium on which digital contents
such as movie and music are recorded and a reproduction terminal
apparatus that is connected to an external network. In particular,
the present invention relates to a technique to prevent unauthorized
acquisition of viewing histories of the reproduction terminal
apparatus.
Background Art
[0002]
In recent years, systems for distributing digital contents
(hereinafter simply called "contents"), specifically digitized
copyrighted works such as movie and music, by recording contents
on a recording medium or transmitting contents via abroadband network,
have been spreading widely in accordance with increasing capacity
of recording media and spread of broadband networks. In such systems,
it is required to allow playback and copying of contents only under
limitations based on agreement with copyright holders, in order to
protect copyrights of contents. As a prior art to protect copyrighted
works against unauthorized copying without permission of copyright
holders, a method of using cryptographic technology is well known.
[0003]
Meanwhile, in accordance with rapid spread of the Internet,
the number of systems whose communication infrastructures are
established based on the Internet has been increasing. For example,

there is an e-commerce system for trading via the Internet. Moreover,
trends of providing new services with linking recording media and
the Internet have been accelerating. For example, there is a service
of transmitting extra contents (e.g. subtitles and related game
programs) relating to a recording medium to a user, in response to
an identifier that uniquely identifies the recording medium to a
server via the Internet. Also, it is possible to transmit content
viewing histories and the likes of the user, stored in/held by a
reproduction apparatus, to the server via the Internet. Accordingly,
the user can enjoy services that suit the user's likes and tastes.
As a prior art for protecting data to be transmitted to the server,
a method of using authentication techniques and signature techniques
is well known. Such techniques are disclosed in detail by Non-patent
Document 1.
[Non-Patent Document 1]
"Secure Electronic Commerce: Building the Infrastructure for
Digital Signatures and Encryption", translated into Japanese by
Shinichiro Yamada, published by Pearson Education Japan.
Disclosure of the Invention
Problems to be solved by the Invention
[0004]
As explained above, the user transmits the viewing histories
of the user to the server to enjoy services that suit the user's
likes and tastes. However, this is problematic because the set of
viewing histories, which is a kind of personal information of the
user, is collected by the server regardless of whether the manager
of the server is malicious or not. As a result, if the server manager
is malicious, there are possibilities that the set of viewing histories,

which is a kind of personal information of the user, will be abused
behind the user's back, for example.
[0005]
Accordingly, to solve the problem described above, the present
invention aims to provide a copyright protection system, a
reproduction apparatus and a reproduction method that are capable
of preventing personal information of a user from being transmitted
to an external server that is under management of a malicious party.
Means for solving the problems
[0006]
To fulfill the above-described obj ect, one aspect of the present
invention is a reproduction apparatus that reproduces a content,
comprising: a reading unit operable to read, from a recording medium,
a content, a program including an instruction to connect to an external
network, and a certificate for use in verification of validity of
the program; a first verification unit operable to verify validity
of the program, using the certificate; an execution unit operable
to execute the program verified by the first verification unit; a
second verification unit operable to verify validity of the
certificate; a communication unit operable to connect to the external
network and operate according to the instruction included in the
program; and a control unit operable to perform control to restrain
the communication unit from connecting to the external network if
the second verification unit judges that the certificate is invalid,
even if the first verification unit has judged that the program is
valid.
Advantageous effects of the Invention

[0007]
With the stated structure, the reproduction apparatus verifies
validity of the certificate for the program that includes the
instruction to connecting to the external network, and if judged
that the certificate is invalid, performs the control to restrain
the communication unit from connecting to the external network.
Accordingly, the reproduction apparatus is capable of preventing
information that pertains to viewing of the content by the user from
being transmitted to another apparatus.
[0008]
Here, if the certificate is invalid, there are possibilities
that the instruction included in the program has been tampered with
and rewritten with an instruction to transmit the information that
pertains to the viewing of the content by the user to an external
server that is under management of a malicious party. Therefore,
in the case the certificate has been proved to be invalid as a result
of the verification, the reproduction apparatus performs the control
such that the communication unit is restrained from connecting to
the external network. With this operation, the present invention
achieves an advantageous effect that the information pertaining to
the viewing by the user is prevented from being transmitted to a
server that is under management of a malicious party.
Brief Description of the Drawings
[0009]
FIG. 1 is a block diagram showing the structure of a copyright
protection system pertaining to an embodiment of the present
invention;
FIG. 2 is a block diagram showing the structure of a CA terminal

apparatus pertaining to the embodiment;
FIG. 3 is an example of a revocation list pertaining to the
embodiment ;
FIG. 4 is an example of a white list pertaining to the embodiment ;
FIG. 5 is an example of a certificate pertaining to the
embodiment ;
FIG. 6 is a block diagram showing the structure of a
content-provider terminal apparatus pertaining to the embodiment;
FIG. 7 is an example of data to be recorded on a recording
medium pertaining to the embodiment;
FIG. 8 is a block diagram showing the structure of a reproduction
apparatus pertaining to the embodiment;
FIG. 9 is a flowchart showing operations performed by the
reproduction apparatus pertaining to the embodiment;
FIG. 10 is a flowchart showing operations performed by the
reproduction apparatus pertaining to the embodiment; and
FIG. 11 is a diagram showing the structure of an LSI that realizes
the reproduction apparatus pertaining to the embodiment.
Explanations of References
[0010]
101 CA terminal apparatus
102 content-provider terminal apparatus
103 recording medium
104 reproduction apparatus
Best Mode for Carrying Out the Invention
[0011]
One aspect of the present invention is a reproduction apparatus

that reproduces a content, comprising: a reading unit operable to
read, from a recording medium, a content, a program including an
instruction to connect to an external network, and a certificate
f oruse inverif icationof validity of the program; a first verification
unitoperable to verify validity of the program, using the certificate;
an execution unit operable to execute the program verified by the
first verification unit; a second verification unit operable to verify
validity of the certificate; a communication unit operable to connect
to the external network and operate according to the instruction
included in the program; and a control unit operable to perform control
to restrain the communication unit from connecting to the external
network if the second verification unit judges that the certificate
is invalid, even if the first verification unit has judged that the
program is valid.
[0012]
The second verification unit may store therein a certificate
list that includes an identifier of at least one certificate that
is to be judged as having been revoked, judge whether an identifier
of the certificate read by the reading unit is included in the
certificate list, and determine that the certificate has been revoked
if judged that the identifier of the certificate is included in the
certificate list.
[0013]
The program may further include an acquisition instruction
to acquire the certificate list from an external apparatus via the
external network, when the execution unit executes the acquisition
instruction by executing the program, the control unit may perform
the control such that the communication unit connects to the external

network before the second verification unit verifies validity of
the certificate, in order that the second verification unit receives
the certificate list according to the acquisition instruction, and
the second verification unit may store therein the certificate list
received from the external apparatus.
[0014]
The program may be either a program that includes an acquisition
instruction to acquire the certificate list from an external apparatus
via the external network or a program that does not include the
acquisition instruction, and if the program does not includes the
acquisition instruction to acquire the certificate list from the
external apparatus via the external network, the control unit may
perform the control to restrain the communication unit from connecting
to the external network, before the second verification unit verifies
validity of the certificate.
[0015]
The certificate may include a public key, the program may be
given a signature based on a private key corresponding to the public
key, the first verification unit may verify validity of the program
by verifying the signature given to the program, the control unit
may perform the control to restrain the communication unit from
connecting to the external network if the second verification unit
judges that the identifier of the certificate is included in the
certificate list, even if the first verification unit has judged
that the program is valid.
[0016]
With the stated structure, the reproduction apparatus is
capable of control the communication unit according to the result

of the verification of the certificate. If the certificate read by
the reading unit is judged as having been revoked based on the
certificate list showing the identifier of at least one certificate
that is to be judged as having been revoked, the control unit restrains
the communication unit from connecting to the external network.
Accordingly, it is possible to prevent the information pertaining
to the viewing of the content from being transmitted to another
apparatus via the external network. Note that a certificate that
is to be judged as having been revoked means a certificate that has
been exposed or hacked at a certain timing and whose validity should
be revoked.
[0017]
The reproduction apparatus may further comprise a confirmation
unit operable to confirm whether the recording medium is an old
recording medium that has been manufactured before the certificate
has been revoked, wherein the control unit may perform the control
such that the communication unit connects to the external network
if the confirmation unit judges that the recording medium is the
old medium, even if the second verification unit has judged that
the certificate has been revoked.
[0018]
The recording medium may further store thereon first
information that pertains to the recording medium, and the
confirmation unit may acquire second information that indicates an
old recording medium that has been manufactured before the certificate
has been revoked, and compare the first information with the second
information to judge whether the recording medium is the old recording
medium.

[0019]
The first information may be an identifier of the recording
medium, the second information may be a recording medium list that
includes an identifier of at least one recording medium that has
been manufactured before the certificate has been revoked, and the
confirmation unit may confirm whether the identifier of the recording
medium is included in the recording medium list, and determine that
the recording medium is the old recording medium if confirmed that
the identifier of the recording medium is included in the recording
medium list.
[0020]
The program may further include an acquisition instruction
to acquire the recording medium list from an external apparatus via
the external network, when the execution unit executes the acquisition
instruction by executing the program, the control unit may perform
the control such that the communication unit connects to the external
network before the confirmation unit judge whether the recording
medium is the old recording medium, in order that the confirmation
unit receives the recording medium list according to the acquisition
instruction, and the conf irmation unit may store therein the recording
medium list received from the external apparatus.
[0021]
If the communication unit is simply restrained from connecting
to the external network in the case the certificate has been revoked,
the following problem occurs with respect to an old recording medium
that has been manufactured before the certificate is judged as having
been revoked. That is, in the case of such an old recording medium,
although it has been able to transmit the information pertaining

to the viewing of the content recorded on the old recording medium
to another apparatus via the external network before the certificate
is judged as having been revoked by execution of the program
corresponding to the certificate, it becomes impossible to transmit
the information after the certificate is judged as having been revoked.
In this regard, with the structure stated above, the reproduction
apparatus judges a revoked certificate as having been revoked while
allowing transmission of the information pertaining to the viewing
of the content recorded on the old recording medium that has been
manufactured before the certificate is judged as having been revoked,
in the same manner as before the judgment. This realizes both the
security and the user convenience at the same time.
[0022]
Another aspect of the present invention is a copyright
protection system that includes a Certificate Authority terminal
apparatus, a content-provider terminal apparatus, and a reproduction
apparatus that reproduces a content, the Certificate Authority
terminal apparatus comprising a certificate generation unit operable
to generate a certificate for use in verification of validity of
a program that includes an instruction to transmit information that
pertains to viewing of a content to another apparatus via an external
network, the content-provider terminal apparatus comprising a
recording unit operable to record the content, the certificate
generated by the Certificate Authority terminal apparatus and the
program onto a recording medium, and the reproduction apparatus
comprising: a reading unit operable to read, fromtherecordingmedium,
the content, the program and the certificate; a first verification
unit operable to verify validity of the program, using the certificate;

an execution unit operable to execute the program verified by the
first verification unit; a second verification unit operable to verify
validity of the certificate; a communication unit operable to connect
to the external network and operate according to the instruction
included in the program; and a control unit operable to perform control
to restrain the communication unit from connecting to the external
network if the second verification unit judges that the certificate
is invalid, even if the first verification unit has judged that the
program is valid.
[0023]
With the stated structure, the reproduction apparatus included
in the copyright protection system verifies validity of the
certificate for the program that includes the instruction to transmit
the information to another apparatus, and if judged that the
certificate is invalid, performs the control to restrain the
communication unit from connecting to the external network.
Accordingly, the reproduction apparatus is capable of preventing
information that pertains to viewing of the content by the user from
being transmitted to another apparatus.
[0024]
The following describes a preferred embodiment of the present
invention, with reference to the drawings.
[0025]
Embodiment 1
1.1 Structure of copyright protection system
As FIG. 1 shows, a copyright protection system includes a CA
terminal apparatus 101, a content-provider terminal apparatus 102,
a recording medium 103 and a reproduction apparatus 104.

[0026]
The CA terminal apparatus 101 provides the content-provider
terminal apparatus 102 with a pair of a certificate and a private
key. Also, inresponsetoarequestfromthecontent-providerterminal
apparatus 102, the CA terminal apparatus 101 provides the
content-provider terminal apparatus 102 with a white list signed
by the CA. Further, the CA terminal apparatus 101 provides the
reproduction apparatus 104 with a public key owned by the CA (a CA
public key) and a revocation list signed by the CA. The details of
the white list are described later.
[0027]
In response to a request from the reproduction apparatus 104,
the content-provider terminal apparatus 102 provides the reproduction
apparatus 104 with the white list signed by the CA. Also, the
content-provider terminal apparatus 102 signs a program to be recorded
on the recording medium 103 using the private key received from the
CA terminal apparatus 101, and records the signed program on the
recording medium 103. At this moment, the content-provider terminal
apparatus 102 also records the certificate corresponding to the
private key used for generation of the signature, on the recording
medium 103. Finally, the content-provider terminal apparatus 102
records a content that has been encrypted (hereinafter also referred
to as "the encrypted content") on the recording medium 103. The
program to be recorded on the recording medium 103 is a program for
reproduction of contents, such as a program for showing navigation
information, menu information, and so on.
[0028]
The reproduction apparatus 104 receives the CA public key and
the revocation list from the CA terminal apparatus 101, receives

the white list from the content-provider terminal apparatus 102,
and reproduces the contents recorded on the recording medium 103
using the lists.
1.2 Structure of CA terminal apparatus 101
The following describes the structure of the CA terminal
apparatus 101 in detail.
[0029]
As FIG. 2 shows, the CA terminal apparatus 101 includes a
reception unit 201, a transmission unit 202, a revocation list storage
unit 203, a signature generation unit 204, a public key/private key
generation unit 205, a certificate generation unit 206, a CA public
key/private key generation unit 207, and a CA public key/private
key storage unit 208.
[0030]
The CA terminal apparatus 101 is structured from a
microprocessor, a RAM, a ROM, a hard disk and so on, which are not
specifically illustrated. The RAM, the ROM and the hard disk store
computer programs. The CA terminal apparatus 101 carries out
functions thereof as a result of the microprocessor operating in
accordance with the computer programs.
[0031]
As FIG. 2 shows, regarding the CA terminal apparatus 101, the
functional blocks, such as the reception unit 201, the transmission
unit 202, the revocation list storage unit 203, the signature
generation unit 204, the public key/private key generation unit 205,
the certificate generation unit 206, the CA public key/private key
generation unit 207 and the CA public key/private key storage unit
208, are typically realized as LSI (s), which is an integrated circuit.

Each of the units may be individually realized as one chip. Also,
two or more units, or part of each unit may be realized as one chip.
[0032]
Note that although an LSI is used here, the circuit may be
variously described as an IC# a system LSI, a super LSI or an ultra
LSI depending on the level of integration.
[0033]
Note also that the technique used for the integration does
not have to be LSI. A special-purpose circuit or general-purpose
processor may be used instead. LSI circuits whose configurations
can be altered after production such as the programmable FPGA (Field
Programmable Gate Array) or a reconf igurable processor whose circuit
cell connections and settings are reconf igurable may also be used.
[0034]
Moreover, if, due to progress in the field of semiconductor
technology or the derivation of another technology, a technology
to replace LSI emerges, such a technology may be used to integrate
the functional blocks. The use of biotechnology or the like is
considered to be a possibility.
[0035]
Finally, each functional block may be realized with software,
or a combination of an LSI and software. The software may be
tamper-resistant.
[0036]
(1) Reception unit 201
The recpeptionunit 201 receives a white list to which a signature
has not been given {an unsigned white list) from the content-provider
terminal apparatus 102. A white list is a list showing whether
contents recorded on a recording medium are valid or not, independently

from whether a certificate recorded on the same recording medium
has been revoked or not by the revocation list. In this embodiment,
the white list is a list of contents that should be considered as
valid, independently from whether the certificate is invalid or not.
However, the same function may be realized in various manners. For
example, contents that should be considered as invalid may be listed
so that other contents that are not listed are considered as valid.
The details of the white list are described later.
[0037]
(2) Transmission unit 202
The transmision unit 202 transmits a pair of a certificate
and a private key, generated by the public key/private key generation
unit 205 and the ceritifcate generation unit 206, and a white list
to which a signature has been given, to the content-provider terminal
apparatus 102. The transmision unit 202 also transmits a CA. public
key generated by the CA public key/private key generation unit 207,
and a revocation list to which a signature has been given, to the
reproduction apparatus 104.
[0038]
(3) Revocation list storage unit 203
The revocation list storage unit 203 stores a revocation list
that has not been signed yet, and the revocation list is to be signed
by the signature generation unit 204. Here, the revocation list is
a list showing whether a certificate has been revoked or not. The
certificate is described later. In this embodiment, the revocation
list is realized as a list showing only certificates that are to
be revoked. However, the same function may be realized in various
manners. For example, the list may show only certificates that have
not been revoked.

[0039]
FIG. 3 shows an example of a revocation list to which a signature
has been given. A version number field 301 holds a version number
that shows a version of the revocation list. Certificate ID fields
302 and 303 each hold an ID of a certificate that should be revoked.
A signature field 304 holds a signature that has been given to
concatenated data formed from the version number and the certificate
IDs. Here, Sig (X, Y) is a function for generating a signature for
data Y, using a secret key X. SK_CA is a CA private key, and a sign
u | |" means concatenation of data.
[0040]
As described above, the revocation list is a list showing whether
the certificate has been revoked or not. The example of FIG. 3 shows
that the certificates having a certificate ID 0x0011 and a certificate
ID 0x0034 have been revoked.
[0041]
(4) Signature generation unit 204
The signature generation unit 204 generates a signature, using
a CA private key stored in the CA public key/private key storage
unit 208. Specifically, the signature generation unit 204 gives a
signature to a revocation list stored in the revocation list storage
unit 203, and gives a signature to an unsigned white list that the
reception unit 201 has received from the content-provider terminal
apparatus 102. Note that the signature described in this embodiment
is a general digital signature. Since the technique for giving a
signature is well known, an explanation thereof is omitted here.
[0042]
FIG. 4 shows an example of a white list to which a signature
has been given. A version number field 401 holds a version number

that shows a version of the white list. Content ID fields 402, 403
and 404 each hold an ID of a content that should be considered as
valid. A signature field 405 holds a signature that has been given
to concatenated data formed from the version number and the content
IDs.
[0043]
As described above, the white list is a list showing that the
contents recorded on the recording medium are valid. The example
of FIG. 4 shows that the three contents identified by a content ID
OxOOOC, a content ID 0x0027 and a content ID 0x00A2 are valid.
[0044]
(5) Public key/private key generation unit 205
The public key/private key generation unit 205 generates a
pair of a public key and a private key corresponding thereto. The
public key is part of a certificate to be transmitted to the
content-provider terminal apparatus 102.
[0045]
(6) Certificate generation unit 206
The certificate generation unit 206 generates a certificate
by generating a signature using a CA private key stored in the CA
public key/private key storage unit 208 and giving the signature
to a public key generated by the public key/private key generation
unit 205.
[0046]
FIG. 5 shows an example of a certificate. A certificate ID
field 501 holds an ID that uniquely identifies the certificate. A
public key field 502 holds a public key generated by the public
key/private key generation unit 205. A signature field 503 holds
a signature that has been given to concatenated data formed from

the certificate ID and the public key.
[0047]
(7) CA public key/private key generation unit 207
The CA. public key/private key generation unit 207 generates
a pair of a public key, to be used by the CA, and a private key
corresponding thereto.
[0048]
(8) CA. public key/private key storage unit 208
The CA public key/private key storage unit 208 stores a pair
of a CA public key and a CA private key generated by the CA public
key/private key generation unit 207. The CA public key is transmitted
to the reproduction apparatus 104 via the transmission unit 202.
The CA private key is used by the signature generation unit 204 or
the certificate generation unit 206 to generate signature of the
CA.
1.3 Structure of content-provider terminal apparatus 102
The following describes the structure of the content-provider
terminal apparatus 102 in detail.
[0049]
As FIG. 6 shows, the content-provider terminal apparatus 102
includes a reception unit 601, a transmission unit 602, an unsigned
white list generation unit 603, an unsigned white list storage unit
604, a white list storage unit 605, a certificate/private key storage
unit 606, a program storage unit 607, a signature generation unit
608, a content ID generation unit 609, a content storage unit 610,
an encryption key storage unit 611, an encryption unit 612, and a
recording unit 613.
[0050]

The content-provider terminal apparatus 102 is structured from
a microprocessor, a RAM, a ROM, a hard disk and so on, which are
not specifically illustrated. The RAM, the ROM and the hard disk
store computer programs. The content-provider terminal apparatus
102 carries out functions thereof as a result of the microprocessor
operating in accordance with the computer programs.
[0051]
As FIG. 6 shows, regarding the content-provider terminal
apparatus 102, the functional blocks, such as the reception unit
601, the transmission unit 602, the unsigned white list generation
unit 603, the unsigned white list storage unit 604, the white list
storage unit 605, the certificate/private key storage unit 606, the
program storage unit 607, the signature generation unit 608, the
content ID generation unit 609, the content storage unit 610, the
encryption key storage unit 611, the encryption unit 612, and the
recording unit 613, are typically realized as LSl(s) , which is an
integrated circuit. Each of the units may be individually realized
as one chip. Also, two or more units, or part of each unit may be
realized as one chip.
[0052]
Note that although an LSI is used here, the circuit may be
variously described as an IC, a system LSI, a super LSI or an ultra
LSI depending on the level of integration.
[0053]
Note also that the technique used for the integration does
not have to be LSI. A special-purpose circuit or general-purpose
processor may be used instead. LSI circuits whose configurations
can be altered after production such as the programmable FPGA (Field
Programmable Gate Array) or a reconf igurable processor whose circuit

cell connections and settings are reconfigurable may also be used.
[0054]
Moreover, if, due to progress in the field of semiconductor
technology or the derivation of another technology, a technology
to replace LSI emerges, such a technology may be used to integrate
the functional blocks. The use of biotechnology or the like is
considered to be a possibility.
[0055]
Finally, each functional block may be realized with software,
or a combination of an LSI and software. The software may be
tamper-resistant.
[0056]
(1) Reception unit 601
The reception unit 601 receives, from the CA terminal apparatus
101, a certificate, a private key corresponding thereto, and a white
list to which a signature has been given.
[0057]
(2) Transmission unit 602
The transmission unit 602 transmits an unsigned white list
generated by the unsigned white list generation unit 603 to the CA
terminal apparatus 101, and transmits the white list to which a
signature has been given by the CA terminal apparatus 101 to the
reproduction apparatus 104.
[0058]
(3) Unsigned white list generation unit 603
The unsigned white list generation unit 603 generates a white
list that shows IDs of contents that should be considered as valid
even if the certificates are invalid.
[0059]

(4) Unsigned white list storage unit 604
The unsigned white list storage unit 604 stores therein an
unsigned white list generated by the unsigned white list generation
unit 603. The stored unsigned white list is to be transmitted to
the CA. terminal apparatus 101 via the transmission unit 602.
[0060]
(5) White list storage unit 605
The white list storage unit 605 receives, via the transmission
unit 602, a white list to which the CA terminal apparatus 101 has
given a signature, and stores the white list therein. The stored
white list (which has been signed) is to be transmitted to the
reproduction apparatus 104 via the transmission unit 602.
[0061]
(6) Certificate/private key storage unit 606
The certificate/private key storage unit 606 receives, via
the reception unit 601, a pair of a certificate and a private key
corresponding thereto. The certificate has been generated and signed
by the CA terminal apparatus 101.
[0062]
(7) Program storage unit 607
The program storage unit 607 stores therein programs to be
used for reproduction of contents recorded on the recording medium
103.
[0063]
(8) Signature generation unit 608
The signature generation unit 608 generates, using a private
key stored in the certificate/private key storage unit 606, a signature
to be given to programs stored in the program storage unit 607.
[0064]

(9) Content ID generation unit 609
The content ID generation unit 609 generates an ID that uniquely
identifies a content to be recorded on the recording medium 103.
The content IDs to be shown in the white list are generated at this
moment.
[0065]
(10) Content storage unit 610
The content storage unit 610 stores therein contents to be
recorded on the recording medium 103.
[0066]
(11) Encryption key storage unit 611
The encrypt ion key storage unit 611 stores therein an encryption
key used for encrypting contents to be recorded on the recording
medium 103.
[0067]
(12) Encryption unit 612
The encryption unit 612 encrypts contents stored in the content
storage unit 610, using an encryption key stored in the encryption
key storage unit 611.
[0068]
(13) Recording unit 613
The recording unit 613 records, on the recording medium 103,
aprogram to whicha signature has beengivenby the signature generation
unit 608, a certificate stored in the certificate/private key storage
unit 606, a content ID generated by the content ID generation unit
609, and a content encrypted by the encryption unit 612.
[0069]
FIG. 7 shows an example of the recording medium 103 on which
the above-mentioned pieces of data have been recorded. Programs to

which signatures have been given are recorded in a signed program
recording area 701. Certificates are recorded in a certificate
recording area 702. Content IDs are recorded in a content ID recording
area 703. Encrypted contents are recorded in an encrypted contents
recording area 704.
1.4 Structure of reproduction apparatus 104
The following describes the structure of the reproduction
apparatus 104 in detail.
[0070]
As FIG. 8 shows, the reproduction apparatus 104 includes a
transmission/reception unit 801, a reading unit 802, a program
verifying unit 803, a program execution unit 804, a revocation list
storage unit 805, a certificate verifying unit 806, a CA public key
storage unit 807, a white list storage unit 808, a content ID checking
unit 809, a decryption key storage unit 810, a decryption unit 811,
a control unit 812, and an external communication unit 813.
[0071]
The reproduction apparatus 104 is structured from a
microprocessor, a RAM, a ROM, a hard disk and so on, which are not
specifically illustrated. The RAM, the RDM and the hard disk store
computer programs. The reproduction apparatus 104 carries out
functions thereof as a result of the microprocessor operating in
accordance with the computer programs.
[0072]
As FIG. 8 shows, regarding the reproduction apparatus 104,
the functional blocks, such as the transmission/reception unit 801,
the reading unit 802, the program verifying unit 803, the program
execution unit 804, the revocation list storage unit 805, the

certificate verifying unit 806, the CA public key storage unit 807,
the white list storage unit 808, the content ID checking unit 809,
the decryption key storage unit 810, the decryption unit 811, the
control unit 812, and the external communication unit 813, are
typically realized as LSI(s), which is an integrated circuit. Each
of the units may be individually realized as one chip. Also, two
or more units, or part of each unit may be realized as one chip.
FIG. 11 shows an example.
[0073]
Note that although an LSI is used here, the circuit may be
variously described as an IC, a system LSI, a super LSI or an ultra
LSI depending on the level of integration.
[0074]
Note also that the technique used for the integration does
not have to be LSI. A special-purpose circuit or general-purpose
processor may be used instead. LSI circuits whose configurations
can be altered after production such as the programmable FPGA (Field
Programmable Gate Array) or a reconf igurable processor whose circuit
cell connections and settings are reconf igurable may also be used.
[0075]
Moreover, if, due to progress in the field of semiconductor
technology or the derivation of another technology, a technology
to replace LSI emerges, such a technology may be used to integrate
the functional blocks. The use of biotechnology or the like is
considered to be a possibility.
[0076]
Finally, each functional block may be realized with software,
or a combination of an LSI and software. The software may be
tamper-resistant.

[0077]
(1) Transmission/reception unit 801
The transmission/ reception unit 801 communicates with external
apparatuses. Specifically, the transmission/reception unit 801
transmits a request for a revocation list to the CA terminal apparatus
101, and receives the revocation list from the CA terminal apparatus
101. Also, the transmission/reception unit 801 transmits a request
for a white list to the content-provider terminal apparatus 102,
and receives the white list from the content-provider terminal
apparatus 102.
[0078]
(2) Reading unit 802
The reading unit 802 reads data recorded on the recording medium
103.
[0079]
(3) Program verifying unit 803
The program verifying unit 803 verifies validity of a program
read from the recording medium 103 by the reading unit 802.
Specifically, the program verifying unit 803 verifies a signature
given to the program, to verify validity of the program.
[0080]
(4) Program execution unit 804
The program execution unit 804 executes a program verified
by the program verifying unit 803. If the program includes an
instruction to make a request for a revocation list or an instruction
to make a request for a white list, the program execution unit 804
transmits a request via the transmission/reception unit 801.
[0081]
(5) Revocation list storage unit 805

The revocation list storage unit 805 stores therein a revocation
list received via the transmission/reception unit 801.
[0082]
(6) Certificate verifying unit 806
The certificate verifying unit 806 verifies validity of a
certificate read by the reading unit 802 from the recording medium
103. Specifically, the certificate verifying unit 806 verifies a
signature given to the certificate read from the recording medium
103, using a CA public key stored in the CA public key storage unit
807. Moreover, the certificate verifying unit 806 checks whether
an ID included in the certificate is on the revocation list stored
in the revocation list storage unit 805. If the ID is included in
the list, the certificate verifying unit 806 judges that the
certificate has been revoked, regardless of the result of the
verification of the signature. These verification results are to
be transmitted to the control unit 812, and used for judging whether
to activate the external communication unit 813.
[0083]
(7) CA public key storage unit 807
The CA public key storage unit 807 stores therein a public
key corresponding to private key held by the CA. The CA public key
is to be used for verifying a signature given by the CA.
[0084]
(8) White list storage unit 808
The white list storage unit 808 stores therein a white list
received via the transmission/reception unit 801.
[0085]
(9) Content ID checking unit 809
The content ID checking unit 809 checks whether a content ID

read by the reading unit 802 from the recording medium 103 is on
the white list stored in the white list storage unit 808. If the
ID is included in the list, the content ID checking unit 809 judges
that the content corresponding to the content ID (or a recording
medium on which the content ID is recorded) is valid, regardless
of the result of the verification of the certificate performed by
the certificate verifying unit 806. These verification results are
to be transmitted to the control unit 812, and used for judging whether
to activate the external communication unit 813.
[0086]
(10) Decryption key storage unit 810
The decryption key storage unit 810 stores therein a decryption
key to be used for decrypting a content read by the reading unit
802 from the recording medium 103.
[0087]
(11) Decryption unit 811
The decryption unit 811 decrypts a content read by the reading
unit 802 from the recording medium 103, using a decryption key stored
in the decryption key storage unit 810.
[0088]
(12) Control Unit 812
The control unit 812 receives a verification result from the
certificate verifying unit 806 and a checking result from the content
ID checking unit 809, and controls whether to activate the external
communication unit 813 based on the results. If receiving results
showing "the certificate is valid" and "the ID of the certificate
is not on the revocation list", the control unit 812 activates the
external communication unit 813. Even if receiving results showing
"the certificate is valid" and "the ID of the certificate is on the

revocation list", if receiving a result showing "the ID is on the
white list", the control unit 812 activates the external communication
unit 813. In other words, regardless the certif icate has been revoked
or not, the control unit 812 judges that the content is valid if
the ID of the content is on the white list, and enables services
that use the external communication. As a result, regarding contents
that were produced before the certificate has been revoked, it is
possible to enjoy services with use of the network even if the same
certificate has been revoked due to unauthorized acts. Note that
if the ID is on the white list, the external communication unit 813
should be activated regardless of the judgment as to whether the
certificate has been revoked or not. Accordingly, if the ID is on
the white list, the judgment as to whether "the ID of the certificate
is on the revocation list" can be omitted.
[0089]
In the examples of FIG. 4 and FIG. 5, when the recording medium
on which the certificate having a certificate ID 0x0011 is inserted
in the reproduction apparatus 104, the external communication unit
813 will not be activated, because the certificate ID is on the
revocation list. Accordingly, it is impossible to connect to the
external network to enjoy services such as download of extra contents
and additional subtitles. On the other hand, even if the certificate
having the certificate ID 0x0011 is recorded on the recording medium,
if the content recorded on the recording medium has a content ID
OxOOOC, 0x0027 or 0x00A2, the external communication unit 813 will
be activated, because these content IDs are on the white list.
Accordingly, it is possible to enjoy the services with use of the
external network.
[0090]

(13) External communication unit 813
The external communication unit 813 connects to an external
network under control of the control unit 812. After activated by
the control unit 812, the external communication unit 813 communicates
with an external server and performs data transmission and so on
in accordance with instructions included in a program being executed
by the program execution unit 804.
1.5 Operations of reproduction apparatus 104
The following explains operations performed by the
reproduction apparatus 104 with reference to FIG. 9 and FIG. 10.
Note that operations performed by the other apparatuses have been
made clear in the detailed explanations. Accordingly, explanations
of the operations of the other apparatus are omitted here.
[0091]
Firstly, the program execution unit 804 executes a program
read by the reading unit 802 from the recording medium 103 and verified
by the program verifying unit 803 (Step S901) . Next, the
transmission/reception unit 801 transmits requests for a revocation
list and a white list to the CA terminal apparatus 101 and the
content-provider terminal apparatus 102 respectively in accordance
with instructions by the program being executed by the program
execution unit 804, and receives the revocation list and the white
list (Step S902) . The certificate verification unit 806 verifies
a signature that has been given to the certificate, using a CA public
key stored in the CA public key storage unit 807. Furthermore, the
certificate verification unit 806 checks whether the certificate
has been revoked, using a revocation list stored in the revocation
list storage unit 805 (Step S903) . As a result of the verification

and the checking, if the certificate verification unit 806 judges
that the verification of the signature has been successful and the
certificate has not been revoked (Step S904: NO), the control unit
812 activates the external communication unit 813 (Step S905) . If
it is judged that the verification of the signature has been successful
but the certificate has been revoked (Step S904, YES), the content
ID checking unit 809 checks the white list. The content ID checking
unit 809 checks a signature that has been given to the white list
stored in the white list storing unit 808, using a CA public key-
stored in the CA public key storage unit 807. If the verification
of the signature of the white list has been successful, the content
ID checking unit 809 further judges whether a content ID read by
the reading unit 802 is on the white list. If it is judged that the
content ID is on the white list (YES in Step S907) , the control unit
812 activates the external communication unit 813 (Step S908) . If
it is judged that the content ID is not on the white list (No in
Step S907), the control unit 812 does not activate the external
communication unit 813 (Step S909) . If the verification of the
signature given to the white list has not been successful, the
processing moves to Step S909 regardless of the judgment result as
to whether the content ID is on the white list (or without performing
the judgment).
[0092]
Other Modifications
The present invention is explained above based on the embodiment.
However, the present invention is not limited to the embodiment.
The following modifications are included in the present invention
as well.
(1) In the embodiment above, the content ID is recorded on the

recording medium without being protected. However, the present
invention is not limited to this. For example, the content ID may
be used to affect encryption of contents, or used to generate encryption
key to be used for encryption of contents, or may be used to change
the encryption key. Moreover, the content ID may be concatenated
with the content, or signature may be given to data formed from the
content ID and a hash value of the contents to protect the content
ID from tampering. Furthermore, the content ID may be recorded by
a special method of writing in which the procedure for writing into
the recording medium and the procedure for reading the recording
medium are kept secret.
[0093]
(2) In the embodiment above, IDs to be on the white list are content
IDs that can identify contents. However, the present invention is
not limited to this. For example, they may be media IDs that can
identify the recording media, or IDs of manufacturers that manufacture
the recordingmedia, or IDs for identif yingmanuf acturing apparatuses.
Alternatively, any other IDs may be used as long as they can identify
the contents or the recording media.
[0094]
(3) In the embodiment above, the external communication unit is
activated if the certificate has not been revoked or the content
ID is on the white list even if the certificate has been revoked.
However, the present invention is not limited to this. For example,
the program to be executed by the program execution unit may include
an instruction to acquire a revocation list from the CA terminal
apparatus, and execution of this program may be one of conditions
for activating the external communication unit. Furthermore, the
program to be executed by the program execution unit may include

an instruction to acquire a white list from the content-provider
terminal apparatus, and execution of this program may be one of
conditions for activating the external communication unit.
[0095]
(4) In the embodiment above, the revocation list and the white
list are acquired from the CA terminal apparatus and the
content-provider terminal apparatus respectively. However, the
present invention is not limited to this. For example, both of the
revocation list and the white list may be acquired from the CA terminal
apparatus, or conversely, both of them may be acquired from the content
provider terminal apparatus. Also, it is not necessary that the
revocation list and the white list are separate lists. They may be
combined as a single list.
[0096]
(5) In the embodiment above, the certificate verifying unit
verifies the certificate, and the content ID checking unit checks
the content ID, and the control unit controls the external
communication unit in accordance with results of the verification
and the checking. However, the present invention is not limited to
this. For example, it is possible to use a structure that allows
the user of the reproduction apparatus to determine which to be
performed between the verification of the certificate and the checking
of the content ID. Also, it is possible to use a structure in which
the user of the reproduction apparatus can activate the external
communication unit even if the control unit does not activate the
external communication unit.
[0097]
(6) In the embodiment above, the control unit controls only whether
to activate the external communication unit or not. However, the

present invention is not limited to this. For example, the control
unit may change the way of controlling in accordance with the type
of a function that uses the external communication unit. Specifically,
in order to disable only a function of transmitting information
relating to users' preference, the control unit does not activate
the external communication unit if an instruction in the program
to transmit user's information is being executed by the program
execution unit, and activates the external communication unit if
a different instruction (e.g. an instruction to transmit an ID of
a recording medium (a media ID) to a server) in the program is being
executed by the program execution unit. Further, a list showing,
for each function, whether the external communication unit is to
be activated may be transmitted from the CA. terminal apparatus, the
content -provider terminal apparatus, or other apparatuses. Further,
when updating the firm ware, the manufacturer of the reproduction
apparatus may notify the reproduction apparatus of which function
is to be disabled.
[0098]
In the case of a system that stops reproduction of contents,
copying and so on if the certificate is not valid, the system may
control whether to enable reproduction and copying, in the same manner
as controlling whether to activate the external communication unit.
[0099]
(7) In the embodiment above, if a request instruction for a
revocation list or a white list is issued from the program to be
executed by the program execution unit, the revocation list or the
white list is acquired via the transmission/reception unit. However,
the present invention is not limited to this. For example, acquis it ion
of a list may be permitted only once between insertion and ejection

of a recording medium, and even if a request for acquiring a list
is issued a plurality of times from the program to be executed by
the program execution unit, the transmission/reception unit may not
follow the second instruction and later. Alternatively, time limit
(once in a hour, once in a week, etc.) may be set, and the
transmission/reception unit may not follow the instruction from the
program if the limit is not satisfied.
[0100]
(8) In the embodiment above, a single apparatus has a plurality
of functions (components). However, the present invention is not
limited to this. The functions (components) may be divided into a
plurality of apparatuses respectively. The present invention
includes a case where the same effect and function may be realized
by combinations of such apparatuses.
[0101]
(9) Part or all of the components included in each of the apparatuses
described above may be structured from an IC card or a single module
which is attachable to the apparatus. The IC card or the module is
a computer system structured from a microprocessor, a ROM, a RAM
and so on. The IC card or the module may include the
super-multifunctional LSI described above. The IC card or the module
carries out functions thereof as a result of the microprocessor
operating in accordance with computer programs. The IC card or the
module may be tamper-resistant.
[0102]
(10) The present invention may be the methods indicated above.
Further, these methods may be a computer program executed by a computer
and further be the digital signal of the computer program.
[0103]

Further, the present invention may be the above-mentioned
computer program and the digital signal recorded onto a recording
medium that can be read by a computer. Examples of such recording
media include a flexible disk, a hard disk, a CD-ROM, an MO, a DVD,
a DVD-ROM, a DVD-RAM, a BD (Blu-ray Disc), a semiconductor memory
and the like.
[0104]
Further, the present invention may be realized such that the
computer program and the digital signal are transmitted across
telecommunications networks, wired and wireless communication lines,
networks such as the Internet, data broadcasting, and so on.
[0105]
Further, the present invention may be a computer system having
a microprocessor and a memory, the memory holding the above-mentioned
computer program and the microprocessor performing operations
according to the computer program.
[0106]
Further, the computer program and the digital signal may be
installed on an independent computer system by either recording the
digital signal one of the recording medium and transferring the
recording medium, or transferring the computer program and digital
signal via one of the networks.
(11) The present invention may include various combinations of the
embodiment and the modifications.
Summary
(l) One aspect of the present invention is a reproduction apparatus
that reproduces a content recorded on a recording medium that has
the content and a certificate recorded thereon, the reproduction

apparatus comprising: a reading unit operable to read the content
and the certificate from the recording medium; a verifying unit
operable to verify validity of the certificate; a communication unit
operable to communicate with external apparatuses via a network;
and a control unit operable to control the communication unit to
activate or not to activate the communication unit in accordance
with a result of verification performed by the verifying unit.
[0107]
(2) In the reproduction apparatus of (1), the control unit may
not activate the communication unit when the verifying unit judges
that the certificate is invalid.
[0108]
(3) The reproduction apparatus of (1) may further comprise a
revocation list storage unit operable to store a revocation list
that shows an identifier of a certificate to be revoked, wherein
the verifying unit may verify whether an identifier of the certificate
read from the recording medium is on the revocation list.
[0109]
(4) In the reproduction apparatus of (3), the control unit may
not activate the communication unit when the verifying unit judges
that the identifier of the certificate is on the revocation list.
[0110]
(5) In the reproduction apparatus of (1), the recording medium
may further have a content identifier recorded thereon, and the
reproduction apparatus may further comprise: a valid-content list
storage unit operable to store a valid-content list that shows an
identifier of a valid content; and a checking unit operable to check
whether the content read from the recording medium is valid.
[0111]

(6) in the reproduction apparatus of (5), the control unit may
activate the communication unit when the checking unit judges that
the content identifier is on the valid-content list.
[0112]
(7) In the reproduction apparatus of (5), even when the verifying
unit judges that the identifier of the certificate is on the revocation
list, the control unit may activate the communication unit when the
checking unit judges that the content identifier is on the
valid-content list.
[0113]
(8) In the reproduction apparatus of (1), the recording medium
may further have a program recorded thereon, which pertains to
reproduction of the content, the reproduction apparatus may further
comprise an execution unit operable to execute the program, and the
control unit may activate the communication unit when the program
provides an instruction for acquiring a revocation list from outside.
[0114]
(9) In the reproduction apparatus of (8), the control unit may
not activate the communication unit if the program does not include
the instruction for acquiring a revocation list from outside.
[0115]
(10) In the reproduction apparatus of (8), a signature may have
been given to the program, and the reproduction apparatus may further
comprise a signature verifying unit operable to verify the signature,
using the certificate.
[0116]
(11) Another aspect of the present invention is a copyright
protection system that includes a Certificate Authority terminal

apparatus that generates and issues a certificate, a content-provider
terminal apparatus that records a content and a certificate on a
recording medium and provides a user with the content, and a
reproduction apparatus that reproduces the content recorded on the
recording medium, the Certificate Authority terminal apparatus
comprising a certificate generation unit operable to generate a
certificate, the content-provider terminal apparatus comprising a
recording unit operable to record a content and a certificate on
the recording medium, and the reproduction apparatus comprising:
a reading unit operable to read the content and the certificate from
the recording medium; a verifying unit operable to verify validity
of the certificate; a communication unit operable to communicate
with external apparatuses via a network; and a control unit operable
to control the communication unit to activate or not to activate
the communication unit in accordance with a result of verification
performed by the verifying unit.
[0117]
(12) In the copyright protection system of (11), the control unit
of the reproduction apparatus may not activate the communication
unit when the verifying unit judges that the certificate is invalid.
[0118]
(13) In the copyright protection system of (11), the reproduction
apparatus may further comprise a revocation list storage unit operable
to store a revocation list that shows an identifier of a certificate
to be revoked, and the verifying unit may verify whether an identifier
of the certificate read from the recording medium is on the revocation
list.
[0119]
(14) In the copyright protection system of (13), the control unit

of the reproduction apparatus may not activate the communication
unit when the verifying unit judges that the identifier of the
certificate is on the revocation list.
[0120]
(15) In the copyright protection system of (11), the recording unit
of the content-provider terminal apparatus may further record a
content identifier on the recording medium, and the reproduction
apparatus may further comprise: a valid-content list storage unit
operable to store a valid-content list that shows an identifier of
a valid content; and a checking unit operable to check whether the
content read from the recording medium is valid.
[0121]
(16) In the copyright protection system of (15), the control unit
of the reproduction apparatus may activate the communication unit
when the checking unit judges that the content identifier is on the
valid-content list.
[0122]
(17) In the copyright protection system of (15), even when the
verifying unit judges that the identifier of the certificate is on
the revocation list, the control unit of the reproduction apparatus
may activate the communication unit when the checking unit judges
that the content identifier is on the valid-content list.
[0123]
(18) In the copyright protection system of (11), even when the
verifying unit judges that the identifier of the certificate is on
the revocation list, the control unit of the reproduction apparatus
activates the communication unit when the checking unit judges that
the content identifier is on the valid-content list.

[0124]
(19) In the copyright protection system of (18), the control unit
of the reproduction apparatus may not activate the communication
unit when a program provides an instruction for acquiring a revocation
list from outside.
[0125]
(20) In the copyright protection system of (18), even when the
verifying unit judges that the identifier of the certificate is on
the revocation list, the control unit of the reproduction apparatus
may activate the communication unit when the checking unit judges
that the content identifier is on the valid-content list.
[0126]
(21) In the copyright protection system of (15), the recording unit
of the content-provider terminal apparatus may record the content
identifier on the recording medium such that the content identifier
can not be tampered with.
[0127]
(22) In the copyright protection system of (21), the
content-provider terminal apparatus may further comprise an
encryption unit operable to encrypt the content based on the content
identifier.
[0128]
(23) In the copyright protection system of (21), the
content-provider terminal apparatus may further comprise a signature
generation unit operable to give a signature to the content identifier
and a hash value of the content.
[0129]
(24) Another aspect of the present invention is a reproduct ionmethod

for reproducing a content recorded on a recording medium that has
the content and a certificate recorded thereon, the reproduction
method comprising: a reading step of reading the content and the
certificate from the recording medium; a verifying step of verifying
validity of the certificate; a communication step of communicating
with external apparatuses via a network; and a control step of
controlling the communication step to activate or not to activate
the communication step in accordance with a result of verification
performed in the verifying step.
[0130]
(25) In the reproduction method of (24), the control step may not
activate the communication step when the verifying step judges that
the certificate is invalid.
[0131]
(26) The reproduction method of (24) may further comprise a
revocation list storage step of storing a revocation list that shows
an identifier of a certificate to be revoked, wherein the verifying
step may verify whether an identifier of the certificate read from
the recording medium is on the revocation list.
[0132]
(27) The reproduction method of (24) may further comprise a
revocation list storage step of storing a revocation list that shows
an identifier of a certificate to be revoked, wherein the verifying
step may verify whether an identifier of the certificate read from
the recording medium is on the revocation list.
[0133]
(28) Another aspect of the present invention is a program that
reproduces a content recorded on a recording medium that has the
content and a certificate recorded thereon, the program comprising:

a reading step of reading the content and the certificate from
the recording medium; a verifying step of verifying validity of the
certificate; a communication step of communicating with external
apparatuses via a network; and a control step of controlling the
communication step to activate or not to activate the communication
step in accordance with a result of verification performed in the
verifying step.
[0134]
(29) The program of (28) may be recorded on a computer-readable
recording medium.
[0135]
(30) Another aspect of the present invention is an integrated circuit
that reproduces a content recorded on a recording medium that has
the content and a cert i f icate recorded thereon, the integrated circuit
comprising: a reading unit operable to read the content and the
certificate from the recording medium; a verifying unit operable to
verify validity of the certificate; a communication unit operable
to communicate with external apparatuses via a network; and a control
unit operable to control the communication unit to activate or not
to activate the communication unit in accordance with a result of
verification performed by the verifying unit.
[0136]
(31) With the stated structure, it is possible to control the
communication unit, to control communications with the server in
accordance with a result of verification of the certificate.
Therefore, if the certificate is to be revoked, it is possible to
prevent personal information such as a user's viewing history
collected by the reproduction apparatus from being transmitted to
the server. The certificate to be revoked means that it has been

exposed or hacked at a certain timing. If only simply inhibiting
reproduction of a content when the certificate has been revoked,
there is a disadvantage that the content that has been manufactured
before it becomes necessary to revoke the certificate will be not
able to enjoy services via a network, in spite of the fact that it
was able to enjoy such services at the time of the manufacture. For
this reason, the present invention uses the revocation list and the
valid-content list in combination. In the present invention,
certificates that should be revoked are listed in the revocation
list, and contents that have been produced before the certificates
are revoked are listed in the valid-content list to enable use of
such contents. As a result, it is possible to realize both security
and user convenience.
Industrial Applicability
[0137]
The reproduction apparatus described above can be used for
business purposes i.e., can be used repeatedly and continuously,
in the industry where the digital contents are provided to users,
in the manufacturing industry where reproduction apparatuses for
reproducing digital contents are manufactured, and the selling
industry where the reproduction apparatuses for reproducing digital
contents are sold.

CLAIMS
1. A reproduction apparatus that reproduces a content, comprising:
a reading unit operable to read, from a recording medium, a
content, a program including an instruction to connect to an external
network, and a certificate for use in verification of validity of
the program;
a first verification unit operable to verify validity of the
program, using the certificate;
an execution unit operable to execute the program verified
by the first verification unit;
a second verification unit operable to verify validity of the
certificate;
a communication unit operable to connect to the external network
and operate according to the instruction included in the program;
and
a control unit operable to perform control to restrain the
communication unit from connecting to the external network if the
second verification unit judges that the certificate is not valid,
even if the first verification unit has judged that the program is
valid.
2. The reproduction apparatus of Claim 1, wherein
the second verification unit stores therein a certificate list
that includes an identifier of at least one certificate that is to
be judged as having been revoked, judges whether an identifier of
the certificate read by the reading unit is included in the certificate
list, and determines that the certificate has been revoked if judged
that the identifier of the certificate is included in the certificate

list.
3. The reproduction apparatus of Claim 2, wherein
the program further includes an acquisition instruction to
acquire the certificate list from an external apparatus via the
external network,
when the execution unit executes the acquisition instruction
by executing the program, the control unit performs the control such
that the communication unit connects to the external network before
the second verification unit verifies validity of the certificate,
in order that the second verification unit receives the certificate
list according to the acquisition instruction, and
the second verification unit stores therein the certificate
list received from the external apparatus.
4. The reproduction apparatus of Claim 2, wherein
the program is either a program that includes an acquisition
instruction to acquire the certificate list from an external apparatus
via the external network or a program that does not include the
acquisition instruction, and
if the program does not includes the acquisition instruction
to acquire the certificate list from the external apparatus via the
external network, the control unit performs the control to restrain
the communication unit from connecting to the external network, before
the second verification unit verifies validity of the certificate.
5. The reproduction apparatus of Claim 2, wherein
the certificate includes a public key.

the program is given a signature based on a private key-
corresponding to the public key,
the first verification unit verifies validity of the program
by verifying the signature given to the program,
the control unit performs the control to restrain the
communication unit from connecting to the external network if the
second verification unit judges that the identifier of the certificate
is included in the certificate list, even if the first verification
unit has judged that the program is valid.
6. The reproduction apparatus of Claim 1, further comprising
a confirmation unit operable to confirm whether the recording
medium is an old recording medium that has been manufactured before
the certificate has been revoked, wherein
the control unit performs the control such that the
communication unit connects to the external network if the
confirmation unit judges that the recording medium is the old medium,
even if the second verification unit has judged that the certificate
has been revoked.
7. The reproduction apparatus of Claim 6, wherein
the recording medium further stores thereon first information
that pertains to the recording medium, and
the confirmation unit acquires second information that
indicates an old recording medium that has been manufactured before
the certificate has been revoked, and compares the first information
with the second information to judge whether the recording medium
is the old recording medium.

8. The reproduction apparatus of Claim 7, wherein
the first information is an identifier of the recording medium,
the second information is a recording medium list that includes
an identifier of at least one recording medium that has been
manufactured before the certificate has been revoked, and
the confirmation unit confirms whether the identifier of the
recording medium is included in the recording medium list, and
determines that the recording medium is the old recording medium
if confirmed that the identifier of the recording medium is included
in the recording medium list.
9. The reproduction apparatus of Claim 7, wherein
the program further includes an acquisition instruction to
acquire the recording medium list from an external apparatus via
the external network,
when the execution unit executes the acquisition instruction
by executing the program, the control unit performs the control such
that the communication unit connects to the external network before
the confirmation unit judge whether the recording medium is the old
recording medium, in order that the confirmation unit receives the
recording medium list according to the acquisition instruction, and
the confirmation unit stores therein the recording medium list
received from the external apparatus.
10. A copyright protection system that includes a Certificate
Authority terminal apparatus, a content -provider terminal apparatus,
and a reproduction apparatus that reproduces a content,

the Certificate Authority terminal apparatus comprising
a certificate generation unit operable to generate a
certificate for use in verification of validity of a program, the
program including an instruct ion to transmit information that pertains
to viewing of a content to another apparatus via an external network,
the content-provider terminal apparatus comprising
a recordingunit operable to record the content, the certificate
generated by the Certificate Authority terminal apparatus and the
program onto a recording medium, and
the reproduction apparatus comprising:
a reading unit operable to read, from the recording medium,
the content, the program and the certificate;
a first verification unit operable to verify validity of the
program, using the certificate;
an execution unit operable to execute the program verified
by the first verification unit;
a second verification unit operable to verify validity of the
certificate;
a communication unit operable to connect to the external network
and operate according to the instruction included in the program;
and
a control unit operable to perform control to restrain the
communication unit from connecting to the external network if the
second verification unit judges that the certificate is not valid,
even if the first verification unit has judged that the program is
valid.
11. A control methodforusebyareproduction apparatus that reproduces

a content, the control method comprising:
a reading step of reading, from a recording medium, a content,
a program including an instruction to connect to an external network,
and a certificate for use in verification of validity of the program;
a first verification step of verifying validity of the program,
using the certificate;
an execution step of executing the program verified in the
first verification step;
a second verification step of verifying validity of the
certificate;
a communication step of connecting to the external network
and operating according to the instruction included in the program;
and
a control step of performing control to restrain the
communication unit from connecting to the external network if the
second verification step judges that the certificate is not valid,
even if the first verification step has judged that the program is
valid.
12. A computer- readable recording medium that stores thereon a
computer program for use by a reproduction apparatus that reproduces
a content, the computer program causing a computer to perform:
a reading step of reading, from a recording medium, a content,
a program including an instruction to connect to an external network,
and a certificate for use in verification of validity of the program;
a first verification step of verifying validity of the program,
using the certificate;
an execution step of executing the program verified in the

first verification step;
a second verification step of verifying validity of the
certificate;
a communication step of connecting to the external network
and operating according to the instruction included in the program;
and
a control step of performing control to restrain the
communication unit from connecting to the external network if the
second verification step judges that the certificate is not valid,
even if the first verification step has judged that the program is
valid.
13. An integrated circuit for use in a reproduction apparatus that
reproduces a content, the integrated circuit comprising:
a reading unit operable to read, from a recording medium, a
content, a program including an instruction to connect to an external
network, and a certificate for use in verification of validity of
the program;
a first verification unit operable to verify validity of the
program, using the certificate;
an execution unit operable to execute the program verified
by the first verification unit;
a second verification unit operable to verify validity of the
certificate;
a communication unit operable to connect to the external network
and operate according to the instruction included in the program;
and
a control unit operable to perform control to restrain the

communication unit from connecting to the external network if the
second verification unit judges that the certificate is not valid,
even if the first verification unit has judged that the program is
valid.

The object of the present invention is to provide a reproduction apparatus that is capable of preventing personal information of users
from being transmitted to an external apparatus that is under management of a malicious person.
The reproduction apparatus uses a revocation list and a valid-content list in combination in order to prevent transmission of personal information of users. It is possible to prevent
transmission of personal information by revoking certificates to be revoked because of being exposed or hacked at a certain timing, by listing them in the revocation list. Meanwhile, it is possible to allowuse of contents that have been manufactured before the exposure, by listing them in the valid-content list. Accordingly, it is possible to realize both the security and the user convenience at the same
time.