JP2001358706A - Copyright protection system, enciphering device, decoding device and recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a system for preventing illegal decoding of digital contents which are recorded on a recording medium and have decoding limit. SOLUTION: In a communication system consisting of an enciphering device and a decoding device which share a contents key perform cipher communication by using the contents key, the enciphering device and the decoding device mutually authenticate that the opposite devices are a legitimate device with mutual authentication and also share a time varying key form a random number used for the mutual authentication. The decoding limit such as the number of reproducing times data stored in the decoding device is enciphered with the time varying key, transferred to the decoding device while security is conducted, also updated by both devices and the decoding limit is shared. In the case of loading contents, the cipher communication is performed by using a contents key generated from the updated decoding limitation.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a communication system for encrypting digital contents such as music, images, videos, games, and the like having a decryption restriction by sharing a common key between devices. A copyright protection system, an encryption device, a decryption device, and a recording medium for protecting a copyrighted work by associating a common key with decryption restriction update information. .

[0002]

2. Description of the Related Art In recent years, with the development of digital information compression technology and the explosive spread of a global communication infrastructure represented by the Internet, contents such as music, images, videos, games and the like have been used as digital information by using communication lines. Delivery to homes has begun to be realized.

A digital information distribution service using a communication line is a distribution form of only data that does not depend on a medium, so that the degree of freedom of the distribution service form is greatly improved.
More than just delivering content information,
It can be distributed in various forms, such as distribution with use restrictions such as use period.

[0004] In order to establish a distribution system that protects the rights of the copyright holder of digital contents and the interests of distributors, illegal acquisition by eavesdropping, eavesdropping, and spoofing of communications, and recording media on which received data is stored are used. The problem is to prevent illegal acts such as illegal duplication and tampering, and copyright protection technology such as encryption / authentication for discriminating an authorized system and data scrambling is required.

[0005] Various copyright protection techniques have been known in the past, and as a typical example, a random number and a response value are exchanged between a data encryption device and a data decryption device to mutually authenticate the legitimacy. There is a challenge-response mutual authentication technology that transmits data only when it is valid.

[0006] In the present specification, "decryption restriction" means information on whether the content transferred from the encryption device to the decryption device may be used (for example, to reproduce sound). For example, in the case of a content with the number of times of reproduction, the decryption limit is frequency information.

[0007] "Updating the decoding restriction" means the rule of updating the decoding restriction. For example, in the case of a content with the number of times of reproduction, this means that the number of times of information on the decryption limit (usable N times) transferred from the encryption device to the decryption device is reduced by one.

[0008] "Decryption restriction update information" means an updated decryption restriction. For example, in the case of a content with the number of times of reproduction, the decryption limit (usable N times) transferred from the encryption device to the decryption device becomes “N−1 times available” "Is the information rewritten.

[0009] In particular, in the case of a system in which digital content having a decryption restriction is encrypted using the above-described mutual authentication technology, mutual validity is authenticated between the encrypting device and the decrypting device, and the validity is verified. Only when it is confirmed that the decryption limit is transferred by encryption communication from the encryption device to the decryption device, the decryption device interprets the decryption limit and determines whether the decryption is possible and updates the decryption limit, In general, after transmitting the updated decryption restriction update information to the encryption device by encryption communication, the content is loaded from the encryption device to the decryption device by encryption communication, and the loaded content is decrypted and used. It is a method performed in.

[0010]

The problem here is that the decryption limit is updated normally, that is, the decryption limit update information updated by the decryption device is received by the authorized encryption device. That is. If the decryption limit has not been updated successfully, i.e., the decryption limit update information updated by the decryption device will not be received by the legitimate encryption device, but will instead impersonate the legitimate encryption device. When received by the impersonator's encryption device, a fraudulent act in which the content loaded from the authorized encryption device is decrypted by the decryption device without updating the decryption restriction by the authorized encryption device is established. Therefore, the decryption restriction update information updated by the decryption device is not received by the legitimate encryption device,
Instead, a system is needed that does not allow the decryption device to decrypt the content loaded from the legitimate encryption device if it is received by another fake encryption device impersonating the legitimate encryption device. Become.

In the above-described mutual authentication technique, it is only necessary to determine whether the communicating device is legitimate, and it is not possible to determine whether or not the decryption restriction has been updated normally, and to prevent fraudulent acts. That is, the decryption restriction is not updated by the legitimate encryption device as a result of the decryption restriction update information not being received by the legitimate encryption device and being received by another fake encryption device impersonating the legitimate encryption device. Nevertheless, the decryption device cannot prevent an act of illegally decrypting the content transmitted by the legitimate encryption device.

It is an object of the present invention to provide a copyright protection system, an encryption device, a decryption device, and a recording medium for reliably updating the decryption restriction and preventing unauthorized decryption of digital contents.

[0013] Another object of the present invention is to provide a system in which, when update information of a decryption restriction updated by a decryption device is received by another fake encryption device impersonating a legitimate encryption device, a legitimate cryptographic device is used. An object of the present invention is to provide a copyright protection system, an encryption device, a decryption device, and a recording medium in which a decryption device cannot decrypt contents loaded from a decryption device.

[0014]

A copyright protection system according to the present invention is a copyright protection system comprising an encryption device and a decryption device for performing encrypted communication using a content key. The apparatus includes: a content storage unit that stores a content; a first content key generation unit that generates the content key based on a second decryption restriction obtained by updating a first decryption restriction; First encryption means for encrypting based on the content and outputting encrypted content, the decryption device comprising: a second content key generation means for generating the content key from the second decryption restriction; A first decryption unit for decrypting the content using the content key generated by the second content key generation unit. The objects can be achieved.

[0015] The decryption device may include a decryption restriction updating unit that updates the first decryption restriction to the second decryption restriction based on a decryption restriction update rule, and encrypts the second decryption restriction based on a time-varying key. And second encryption means for outputting a first encryption / decryption restriction, wherein the encryption device sets the first encryption / decryption restriction transferred from the second encryption means to the time-variable key. Second decryption means for decrypting based on the second decryption restriction, the first content key generation means based on the second decryption restriction generated by the second decryption means. May be used to generate the content key.

[0016] The encryption device may include a first key for storing a common key.
A common key storage unit, a decryption restriction storage unit that stores the first decryption restriction, a first random number generation unit that generates a first random number, and a second random number that is transferred from the first random number and the decryption device.
First mutual authentication processing means for performing mutual authentication processing with the decryption device using a random number, and receiving the authentication by the first mutual authentication processing means; A first time-varying key generating means for generating a key, and a third encrypting means for encrypting the first decryption restriction using the time-variable key and outputting a second encrypted decryption restriction, The decryption device includes a second common key storage unit that stores the common key, a second random number generation unit that generates the second random number, and the encryption device that uses the second random number and the first random number. Second mutual authentication processing means for performing mutual authentication with the second mutual authentication processing means, and second time-varying key generation for generating the time-variant key from the second random number and the first random number in response to the authentication being accepted by the second mutual authentication processing means Means for decrypting the second decryption restriction using the time-varying key Third decoding means and may further include a that.

[0017] The decryption device may further comprise a first decryption restriction updating means for updating the first decryption restriction to a second decryption restriction based on a decryption restriction update rule, and wherein the second content key generation means comprises: The content key is generated based on the second decryption restriction updated by the first decryption restriction update unit, and the encryption device receives the update of the decryption restriction in the first decryption restriction update unit of the decryption device. And a second decryption limit updating means for updating the first decryption limit to the second decryption limit in accordance with a decryption restriction update rule,
The content key generation unit may generate the content key based on the second decryption restriction updated by the second decryption restriction update unit.

[0018] The encryption device includes: first common key storage means for storing the common key; decryption restriction storage means for storing the first decryption restriction; first random number generation means for generating a first random number; A first mutual authentication processing unit for performing mutual authentication with the decryption device using the first random number and a second random number transferred from the decryption device, and receiving the authentication in the first mutual authentication processing unit. A first time-varying key generating means for generating a time-varying key from the first random number and the second random number; and a second means for encrypting the first decryption restriction using the time-variable key and outputting an encrypted decryption restriction. 2 encryption means, wherein the decryption device comprises: a second common key storage means for storing the common key; a second random number generation means for generating the second random number; A second step of performing mutual authentication with the encryption device using a first random number; Mutual authentication processing means; second time-variant key generation means for generating the time-variant key from the second random number and the first random number in response to the authentication being accepted by the second mutual authentication processing means; A second decryption means for decrypting the restriction by using the time-varying key, whereby the object is achieved.

The second decryption restriction update means updates the first decryption restriction to the second decryption restriction in advance, and the second decryption restriction update means updates the second decryption restriction updated by the first content key generation means. Outputting the decryption restriction, the first content key generation means generating the content key from the second decryption restriction, and the second decryption restriction updating means starting the processing of the first encryption means Then, the second decryption restriction may be stored in the decryption restriction storage means.

The first and second time-varying key generating means may generate the time-varying key based on the first and second random numbers and the common key.

[0021] The first and second content key generating means may generate the content key based on the second decryption restriction and the time-varying key.

The encryption device and the decryption device are
First and second data sequence key generation means for generating a data sequence key based on input / output data sequences of the encryption device and the decryption device, respectively,
And the second time-varying key generation means may generate the time-varying key based on the first and second random numbers and the data sequence key.

The encryption device and the decryption device are
First and second data sequence key generation means for generating a data sequence key based on input / output data sequences of the encryption device and the decryption device, respectively,
And the second time-varying key generation means may generate the time-varying key based on the first and second random numbers, the common key, and the data sequence key.

[0024] The encryption device and the decryption device may include:
First and second data sequence key generation means for generating a data sequence key based on input / output data sequences of the encryption device and the decryption device, respectively,
And the second content key generation means may generate the content generation key based on the second decryption restriction and the data sequence key.

[0025] The encryption device and the decryption device include:
First and second data sequence key generation means for generating a data sequence key based on input / output data sequences of the encryption device and the decryption device, respectively,
And the second content key generation means may generate the content generation key based on the second decryption restriction, the time-varying key, and the data sequence key.

The first and second mutual authentication processing means include:
It is also possible to mutually authenticate that the other device is a legitimate device by communication based on a challenge response type authentication protocol.

[0027] An encryption device according to the present invention is an encryption device for performing encrypted communication with a decryption device using a content key, wherein the encryption device includes a content storage means for storing content, and a first decryption device. Content key generation means for generating the content key based on a second decryption restriction obtained by updating the restriction; first encryption means for encrypting the content based on the content key and outputting encrypted content; Which achieves the above object.

[0028] The encryption device may further include a decryption means for decrypting the first decryption restriction transferred from the decryption device based on a time-varying key, and generating the second decryption restriction. The content key generation unit may generate the content key based on the second decryption restriction generated by the decryption unit.

The encryption device includes a common key storage unit that stores a common key, a decryption restriction storage unit that stores the first decryption restriction, a first random number generation unit that generates a first random number, and the first random number generation unit. Mutual authentication processing means for performing mutual authentication processing with the decryption device using a random number and a second random number transferred from the decryption device; and receiving the first random number upon authentication reception by the mutual authentication processing means. Time-varying key generation means for generating the time-varying key from a second random number, and second encryption means for encrypting the first decryption restriction using the time-variable key and outputting a second encrypted decryption restriction. May be further provided.

[0030] The encryption device further comprises a decryption restriction updating means for receiving the update of the decryption restriction of the decryption device and updating the first decryption restriction to the second decryption restriction in accordance with the decryption restriction update rule. The content key generation unit may generate the content key based on the second decryption restriction updated by the decryption restriction update unit.

The encryption device includes a common key storage unit that stores the common key, a decryption restriction storage unit that stores the first decryption restriction, a first random number generation unit that generates a first random number, 1 random number and the second transferred from the decryption device
Mutual authentication processing means for performing mutual authentication with the decryption device using a random number; and a time-variant key generating a time-variable key from the first random number and the second random number upon receiving authentication by the mutual authentication processing means. Key generating means, and a second means for encrypting the first decryption restriction using the time-varying key and outputting an encrypted decryption restriction
An encryption unit may be further provided.

The decryption restriction updating means updates the first decryption restriction to the second decryption restriction in advance, and the decryption restriction updating means outputs the updated second decryption restriction to the content key generation means, The content key generation means generates the content key from the second decryption restriction, and the decryption restriction updating means stores the decryption restriction storage means in response to the start of the processing of the first encryption means. The second decryption restriction may be stored.

[0033] The time-varying key generation means may generate the time-varying key based on the first and second random numbers and the common key.

[0034] The content key generation means may generate the content key based on the second decryption restriction and the time-varying key.

The encryption device further includes data sequence key generation means for generating a data sequence key based on the input / output data sequence of the encryption device, wherein the time-varying key generation means comprises The time-varying key may be generated based on two random numbers and the data sequence key.

The encryption device further includes data sequence key generation means for generating a data sequence key based on the input / output data sequence of the encryption device, wherein the time-varying key generation means comprises The time-varying key may be generated based on two random numbers, the common key, and the data sequence key.

[0037] The encryption device further comprises a data sequence key generation means for generating a data sequence key based on the input / output data sequence of the encryption device. The content generation key may be generated based on the data sequence key.

[0038] The encryption device further includes data sequence key generation means for generating a data sequence key based on the input / output data sequence of the encryption device. The content generation key may be generated based on the time-varying key and the data sequence key.

[0039] A decryption device according to the present invention is a decryption device that performs cipher communication with an encryption device using a content key, wherein the decryption device generates a content key from a second decryption restriction. A key generation unit and a first decryption unit for decrypting the encrypted content using the content key generated by the content key generation unit are provided, whereby the object is achieved.

[0040] The decryption device may include a decryption restriction updating unit that updates the first decryption restriction to the second decryption restriction based on a decryption restriction update rule, and encrypts the second decryption restriction based on a time-varying key. , An encryption means for outputting the first encryption / decryption restriction.

The decryption device includes a common key storage unit for storing the common key, a random number generation unit for generating the second random number, and the encryption device using the second random number and the first random number. Mutual authentication processing means for performing mutual authentication, time-variant key generation means for generating the time-variant key from the second random number and the first random number in response to the authentication being accepted by the mutual authentication processing means, Second decryption means for decrypting the decryption restriction using the time-varying key may be provided.

The decryption device further comprises a decryption restriction updating means for updating the first decryption restriction to a second decryption restriction based on a decryption restriction update rule, and the content key generating means is provided by the decryption restriction updating means. The content key may be generated based on the updated second decryption restriction.

The decryption device includes a second common key storage unit that stores the common key, a second random number generation unit that generates the second random number, and the second random number generation unit that uses the second random number and the first random number. Mutual authentication processing means for performing mutual authentication with the encryption device, and receiving the authentication in the mutual authentication processing means,
The time-variant key generating means for generating the time-variable key from the random number and the first random number, and second decryption means for decrypting the encryption / decryption restriction using the time-variable key may be provided.

[0044] The time-varying key generation means may generate the time-varying key based on the first and second random numbers and the common key.

[0045] The content key generation means may generate the content key based on the second decryption restriction and the time-varying key.

The decryption device further comprises data sequence key generation means for generating a data sequence key based on the input / output data sequence of the decryption device, wherein the time-varying key generation means comprises The time-varying key may be generated based on a second random number and the data sequence key.

The decryption device further comprises data sequence key generation means for generating a data sequence key based on the input / output data sequence of the decryption device, wherein the time-varying key generation means comprises The time-varying key may be generated based on two random numbers, the common key, and the data sequence key.

[0048] The decryption device further comprises a data sequence key generation means for generating a data sequence key based on the input / output data sequence of the decryption device. The content generation key may be generated based on the data sequence key.

[0049] The decryption device further comprises a data sequence key generation means for generating a data sequence key based on the input / output data sequence of the decryption device. The content generation key may be generated based on the time-varying key and the data sequence key.

The recording medium according to the present invention is a recording medium for recording a program for causing a computer to function as means for performing encrypted communication with an encryption device using a content key. Content key generation means for generating the content key from the first, first decryption means for decrypting the encrypted content using the content key generated by the content key generation means,
The above function is achieved, thereby achieving the above object.

[0051] The program includes a decryption restriction updating means for updating the first decryption restriction to the second decryption restriction based on a decryption restriction update rule, and encrypts the second decryption restriction based on a time-varying key. Encryption means for outputting the decryption restriction,
The above-mentioned computer may further function.

The program performs common authentication with the encryption device using a common key storage unit for storing the common key, a random number generation unit for generating the second random number, and the second random number and the first random number. Mutual authentication processing means, time-variant key generation means for generating the time-variant key from the second random number and the first random number in response to the authentication being accepted by the mutual authentication processing means, and setting the first encryption / decryption restriction to the time-variable key. Second decryption using key
The computer may further function as decoding means.

[0053] The program further causes the computer to function as a decryption restriction update unit that updates the first decryption restriction to a second decryption restriction based on a decryption restriction update rule.
The content key generation unit may generate the content key based on the second decryption restriction updated by the decryption restriction update unit.

The program includes a second common key storage unit for storing the common key, a second random number generation unit for generating the second random number, and the encryption device using the second random number and the first random number. Mutual authentication processing means for performing mutual authentication, time-variant key generation means for generating the time-variant key from the second random number and the first random number in response to the authentication being accepted by the mutual authentication processing means, The computer may further function as second decryption means for decrypting using the time-varying key.

[0055] The time-varying key generation means may generate the time-varying key based on the first and second random numbers and the common key.

[0056] The content key generation means may generate the content key based on the second decryption restriction and the time-varying key.

[0057] The program further causes the computer to function as data sequence key generation means for generating a data sequence key based on the input / output data sequence of the decryption device. The time-varying key may be generated based on a second random number and the data sequence key.

The program further causes the computer to function as data sequence key generation means for generating a data sequence key based on the input / output data sequence of the decryption device. The time-varying key may be generated based on a second random number, the common key, and the data sequence key.

The program further causes the computer to function as data sequence key generation means for generating a data sequence key based on the input / output data sequence of the decryption device. And the content generation key may be generated based on the data sequence key.

[0060] The program further causes the computer to function as data sequence key generation means for generating a data sequence key based on the input / output data sequence of the decryption device. The content generation key may be generated based on the time-varying key and the data sequence key.

[0061]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The principle and embodiments of the present invention will be described below with reference to the accompanying drawings. In the present invention, decryption restriction is used for generating a common key used for digital content encryption communication.

(Embodiment 1) FIG. 1 shows a configuration diagram in Embodiment 1 of the present invention, and shows a system 100 in which an encryption device 101 and a decryption device 102 perform encrypted communication.

The encryption device 101 generates a common key storage unit 103 for storing a common key UK, a decryption restriction storage unit 111 for storing decryption restrictions, a content storage unit 121 for storing contents CT, and a random number R1. Random number generator 105
And the random number R1 and the random number R transferred from the decryption device 102
2 and a common key UK, a mutual authentication processing unit 107 that performs mutual authentication processing with the decryption device 102, and a mutual authentication processing is performed by the random number R1 and the random number R2 in response to the mutual authentication processing in the mutual authentication processing unit 107 A time-varying key generation unit 109 that generates a variable time-varying key VK each time it is executed, an encryption unit 113 that encrypts the decryption restriction S1 using the time-varying key VK and outputs an encrypted decryption restriction S2, The decryption limit S3 transferred from the encryption unit 116 of the decryption device 102 is
, And the decryption restriction storage unit 111
, A content key generation unit 117 that generates a content key CK from the decryption restriction S4, and encrypts the content CT based on the content key CK.
An encryption unit 119 that outputs the encrypted content S5.

The decryption device 102 includes a common key storage unit 104 for storing a common key UK, a random number generation unit 106 for generating a random number R2, and an encryption device 101 using the random number R2, the random number R1, and the common key UK. A mutual authentication processing unit 108 for performing a mutual authentication process, a time-varying key generation unit 110 for generating a time-varying key VK from the random number R2 and the random number R1 in response to the mutual authentication process in the mutual authentication processing unit 108, A decryption unit 114 that decrypts the restriction S2 using the time-varying key VK, and a decryption restriction update unit 112 that updates the decryption restriction S1 decrypted by the decryption unit 114 to the decryption restriction S4 based on the decryption restriction update rule.
An encryption unit 116 that encrypts the decryption restriction S4 using the time-varying key VK and outputs an encrypted decryption restriction S3; a content key generation unit 118 that generates a content key CK from the decryption restriction S4; S5 is the content key CK
And a decryption unit 120 that decrypts the content CT and outputs the content CT.

Both the encryption device 101 and the decryption device 102 have common key storage units 103 and 104 and hold the same common key UK. The common key UK may be stored in advance in the common key storage units 103 and 104 as the same common key, or the same common key UK may be created by a creation process.

The encryption apparatus 101 includes a decryption restriction storage unit 111 for storing the decryption restriction S1 and a content storage unit 121 for storing the content CT. The common key storage unit 103, the decryption restriction storage unit 111, and the content storage unit 121 are arranged in a protected area that cannot be directly accessed from outside.

FIG. 2 is a flowchart showing a processing procedure of the system according to the first embodiment. The processing procedure of the system 100 including the encryption device 101 and the decryption device 102 will be described below with reference to FIGS.

The encryption device 101 and the decryption device 102
A random number generator 10 for generating random numbers R1 and R2 independently of each other
5 and 106, exchange each other's random numbers R1 and R2, create a response value V1 using the random number R1 and the common key UK, create a response value V2 using the random number R2 and the common key UK, A challenge-response mutual authentication is performed by exchanging and comparing the response values V1 and V2 to mutually authenticate that the other device is a legitimate device.
8 (S201).

It is determined by the mutual authentication processing units 107 and 108 whether or not authentication has been established for confirming that the other device is valid (S202). If it is determined that the authentication has not been established (NO in S202), the process ends. If it is determined that the authentication has been established (S
(YES in 202), the time-varying key generation units 109 and 110 generate the same time-varying key VK that changes for each mutual authentication from the mutual random numbers R1 and R2 (S203). After that, the encryption device 1
01, the decryption restriction S1 stored in the decryption restriction storage unit 111 is encrypted by the encryption unit 113 using the time-varying key VK, and the encrypted decryption restriction S2 is transferred to the decryption device 102 (S204).

The decryption unit 114 decrypts the received decryption restriction S2 using the same time-varying key VK (S20).
5). The decryption restriction update unit 112 updates the decryption restriction S1 decrypted by the decryption unit 114 according to the decryption restriction update rule (S206), and encrypts the updated decryption restriction S4 using the time-varying key VK (S207). ) Transfer the decryption restriction S3 to the encryption device 101. The decryption unit 115 decrypts the transferred encrypted decryption restriction S3 using the time-varying key VK to obtain an updated decryption restriction S4, and
1 (S208).

The content key generation unit 117 determines the decryption limit S4
Then, a content key CK is generated (S209). When transferring the content CT stored in the content storage unit 121 from the encryption device 101 to the decryption device 102,
The encryption unit 119 encrypts the content CT using the content key CK (S210). Content key generation unit 1
18 generates a content key CK from the decryption restriction S4 (S211). The decryption unit 120 in the decryption device decrypts the encrypted content S5 using the content key CK (S
212).

In this embodiment, an example has been described in which the content is transferred from the encryption device to the decryption device after one authentication is established. However, after the authentication is established, the content transfer occurs between the transmission and decryption devices. Mutual authentication for confirming that the partner device is valid may be performed each time. In addition, the time-varying key VK
Are generated using the random numbers R1 and R2 used for mutual authentication, but the response values V1 and V2 may be used.

The same algorithm may be used for the decryption restriction and the content encryption / decryption, even if different algorithms are used. For example, DES (Da
taEncryption Standard) or the like may be used.

The same algorithm may be used for generating the time-varying key and the content key, even if different algorithms are used. For example, SHA (Secure Ha
A one-way function such as (shAlgorithm) may be used.

In this embodiment, transmission and reception are performed by mutual authentication processing sections 107 and 1 in order to easily explain the present invention.
08, encryption unit 113, decryption unit 114, decryption unit 11
5, encryption unit 116, encryption unit 119, decryption unit 120
Shows an example of what is going on. In general, actual transmission and reception are managed by the control units 122 and 123. The same applies to embodiments described later.

As described above, the copyright protection system of the present embodiment performs content encryption communication in connection with the decryption restriction update information (decryption restriction S4) in the transfer of the content CT which is a literary work. , Correctly decryption restrictions S1
Unless the update process is performed, the content CT cannot be decrypted.

(Embodiment 2) FIG. 3 shows a copyright protection system 200 according to Embodiment 2 of the present invention. FIG.
In FIG. 7, the same components as those in FIG. 1 are denoted by the same reference numerals, and description thereof will be omitted.

In the copyright protection system 200, the decryption restriction S4 updated by the decryption restriction update unit 112 is encrypted / decrypted and transferred as in the copyright protection system 100 shown in FIG. A decryption restriction update unit 223 is provided in the encryption device 201 instead of being stored in the unit 111.

The decryption limit update unit 212 of the decryption device 202
Is a decryption limit update command C for instructing the update of the decryption limit S1.
Only C is transferred to the decryption limit update unit 223. The decryption restriction update unit 223 receives the transferred decryption restriction update command CC, updates the decryption restriction S1, and stores the updated decryption restriction S4 in the decryption restriction storage unit 211.

As described above, the copyright protection system 200 of the present embodiment does not need to transfer the updated decryption restriction S4 related to the generation of the content key CK from the decryption device 202 to the encryption device 201. Therefore, the confidentiality of the decryption restriction S4 can be improved. Further, since the encryption unit and the decryption unit related to the transfer of the updated decryption restriction S4 can be deleted, there is an effect that the system scale can be reduced.

(Embodiment 3) FIG. 4 shows a copyrighted work protection system 300 according to Embodiment 3 of the present invention. FIG.
In FIG. 7, the same components as those in FIG.

In the copyright protection system 300, like the copyright protection system 200 shown in FIG. 2, the decryption restriction update unit 223 in the encryption apparatus 201 receives the update command CC from the decryption restriction update unit 212. Instead of updating S1, the decryption restriction updating unit 323 updates the decryption restriction S1 previously stored in the decryption restriction storage unit 311 in the encryption device 301. Content key generation unit 117
Generates the content key CK using the updated decryption restriction S4, and in response to the encryption unit 319 starting encrypting the content CT, the decryption restriction update unit 323 is updated to the decryption restriction storage unit 311. The decryption limit S4 is stored.

As described above, the copyright protection system 300 according to the present embodiment does not update the decryption limit S1 with the command from the decryption device 302, but instead updates the decryption limit update unit 3 in advance.
23 updates the decryption restriction S1, and the content key generation unit 117 generates the data transfer key CK, so that the processing steps can be shortened.

(Embodiment 4) FIG. 5 shows a copyright protection system 400 according to Embodiment 4 of the present invention. FIG.
In FIG. 7, the same components as those in FIG.

In the copyright protection system 400, in generating the time-varying key VK in the time-varying key generation units 409 and 410, the common key UK is used in addition to the random numbers R1 and R2. The time-varying key VK is, for example, a random number R1, R2, a common key U
K may be generated by combining K by exclusive OR and performing conversion by a one-way function.

As described above, according to the copyright protection system 400 of the present embodiment, the random number R
The time-varying key VK is not generated from only R1 and R2, but the time-varying key VK is generated by associating the secret common key UK. Therefore, it is not easy to analogize the time-varying key VK. There is an effect that the confidentiality of VK can be improved.

(Embodiment 5) FIG. 6 shows a copyright protection system 500 according to Embodiment 5 of the present invention. FIG.
In FIG. 7, the same components as those in FIG.

In the copyright protection system 500, in generating the content key CK in the content key generation units 517 and 518, a time-varying key VK is used in addition to the updated decryption restriction S4. The content key CK may be generated, for example, by combining the decryption restriction S4 and the time-varying key VK with an exclusive OR, and performing conversion using a one-way function.

As described above, according to the copyright protection system 500 of the present embodiment, instead of generating the time-varying key CK only from the updated decryption restriction S4, the Since the time-varying key VK is associated with the time-varying key CK and the time-varying key CK is generated, there is an effect that the strength of content encryption can be further improved.

(Embodiment 6) FIG. 7 shows a copyright protection system 600 according to Embodiment 6 of the present invention. FIG.
In FIG. 7, the same components as those in FIG.

In the copyright protection system 600, the whole or a part of the input / output data input or output to the encryption device 601 and the decryption device 602 (here, the random number R
1, R2, response values V1, V2, encryption / decryption restrictions S2, S
3. The encryption device 601 and the decryption device 602 include data sequence key generation units 625 and 626 that generate the data sequence key TK1 from the encrypted content S5). Time-varying key generation units 609 and 610 and content key generation units 617 and 6
The data sequence key TK1 is added to the key generation at 18.

The data series key TK1 may be generated, for example, by counting High or Low of each input / output data. The time-varying key VK is, for example, a random number R
1, R2, and the data series key TK1 may be combined by exclusive OR, and may be generated by performing conversion using a one-way function. Further, the content key CK may be generated by combining the decryption restriction S4 and the data sequence key TK1 with an exclusive OR, and performing a conversion using a one-way function. Further, it is not necessary to generate the data sequence key TK1 from all of the input / output data to be input / output, and it is also possible to generate the data series key TK1 from a part of them.

As described above, the copyright protection system 600 according to the present embodiment monitors input / output data input / output to / from an encryption device and a decryption device, and, based on the input / output data, a data sequence common to each device. A key TK1 is generated, and the generated data sequence key TK1 is associated with generation of each content key. Since the input / output data needs to be the same between the encryption device and the decryption device to be encrypted, there is an effect that communication spoofing can be prevented.

(Embodiment 7) FIG. 8 is a block diagram showing Embodiment 7 of the present invention, and shows a system 800 in which an encryption device 101 and a decryption device 102 perform encrypted communication.
With reference to FIG. 8, an aspect in which the encryption device and the decryption device are directly connected and used will be described. The same components as those described in the first embodiment are denoted by the same reference numerals. A detailed description of these components will be omitted.

The system 800 includes a content reproducing device 801 for reproducing content and a content reproducing device 801.
Encryption device 101 described in the first embodiment attached to
And The content reproducing device 801 is similar to the content reproducing device 801 of the first embodiment.
And the playback unit 802 that plays back the content decrypted by the decryption device 102.

As described above, the decoding device 102 described in the first embodiment can be included in the content reproducing device 801 that reproduces content. The encryption device 101 described in the first embodiment is used by being attached to the content reproduction device 801. The encryption device 101 mounted on the content playback device 801 and the decryption device 102 included in the content playback device 801 perform the encryption communication as described in the first embodiment.

[0097] Content reproduction device 801 can be a mobile phone. The content reproduction device 801 may be an audio player or a personal computer. The encryption device 101 can be a memory card. The encryption device 101 may be any of the encryption devices 201 to 601 described in Embodiments 2 to 6,
It goes without saying that the decoding device 102 may be any of the decoding devices 202 to 602 described in the second to sixth embodiments.

The decoding apparatus 102 can operate by a program read from the recording medium 803 on which a program for operating the decoding apparatus is recorded as described in the first to sixth embodiments. The recording medium 803 can be a CD-ROM.

FIG. 9 shows another configuration diagram according to the seventh embodiment of the present invention, and shows a system 800 in which the encryption device 101 and the decryption device 102 perform encrypted communication. With reference to FIG. 8, an aspect in which the encryption device and the decryption device are used by being connected by an electric communication line will be described. The same components as those described in the first and seventh embodiments with reference to FIG. 8 are denoted by the same reference numerals. A detailed description of these components will be omitted.

Referring to FIG. 9, system 900 includes a content reproducing device 801 for reproducing content, a server 901, and an electric communication line 903 for connecting content reproducing device 801 and server 901. The content reproduction device 801 is a decryption device 1 described in the first embodiment.
02 and a playback unit 802 that plays back the content decrypted by the decryption device 102. The server 901 includes the encryption apparatus 101 mounted on the server 901 and described in the first embodiment.

The content reproducing apparatus 801 for reproducing the content and the server 901 are connected to the electric communication line 9.
03 is connected. The encryption device 101 is mounted on a server 901 and used. The encryption device 101 mounted on the server 901 and the decryption device 102 included in the content reproduction device 801 perform encrypted communication via the electric communication line 903 as described in the first embodiment.

[0102] Telecommunications line 903 can be the Internet. The electric communication line 903 may be a local area network (LAN).

As in the embodiment shown in FIG. 8, content reproducing apparatus 801 can be a mobile phone. The content reproduction device 801 may be an audio player or a personal computer. Encryption device 10
1 may be a memory card. The encryption device 101
Encryption devices 201 to 601 described in the second to sixth embodiments
Needless to say, the decoding device 102 may be any of the decoding devices 202 to 602 described in the second to sixth embodiments.

As in the case of the embodiment shown in FIG.
02 can be operated by a program read from the recording medium 803 in which the program for operating the decoding device 102 as described in the first to sixth embodiments is recorded.

FIG. 9 illustrates the mode in which the encryption device 101 and the decryption device 102 are connected and used via the electric communication line 903, but the present invention is not limited to this. The encryption device 101 and the decryption device 102 may be connected via a wireless communication line.

[0106]

As described above, according to the present invention, a copyright protection system, an encryption device, a decryption device, and a recording medium for securely updating the decryption restriction and preventing unauthorized decryption of digital contents are provided. can do.

Further, according to the present invention, if the decryption restriction update information updated by the decryption device is received by another forgery encryption device impersonating the legitimate encryption device, the legitimate encryption It is possible to provide a copyright protection system, an encryption device, a decryption device, and a recording medium in which a decryption device cannot decrypt content loaded from the device.

Further, according to the present invention, in the transfer of the content which is a literary work, the encrypted communication is performed in association with the update information of the decryption restriction. It is possible to provide a copyrighted work protection system, an encryption device, a decryption device, and a recording medium that provide advantageous effects.

Further, according to the present invention, it is not necessary to transfer the updated decryption restriction relating to the generation of the data transfer key from the decryption device to the encryption device, so that the confidentiality of the decryption restriction can be improved. Also, a copyright protection system, an encryption device, a decryption device, and a recording medium that can reduce the system scale because the encryption unit and the decryption unit related to the transfer of the updated decryption restriction can be deleted. Can be provided.

Further, according to the present invention, the decryption limit is not updated by a command from the decryption device, but the decryption limit is updated in advance and the data transfer key is generated. , A copyright protection system, an encryption device, a decryption device, and a recording medium can be provided. .

Further, according to the present invention, a time-varying key is generated not only from a random number that can be monitored externally but from a time-variable key so as to associate a secret common key. It is possible to provide a copyrighted work protection system, an encryption device, a decryption device, and a recording medium that are not easy to use and can improve the confidentiality of a time-varying key.

Further, according to the present invention, input / output data input / output to / from the encryption device and the decryption device is monitored, a data sequence key common to each device is generated from the input / output data, and the generated data sequence key is generated. Since the key is associated with the generation of each content key, a copyright protection system that has an effect of preventing communication spoofing,
An encryption device, a decryption device, and a recording medium can be provided.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing a configuration of a system according to a first embodiment.

FIG. 2 is a flowchart showing a processing procedure of the system according to the first embodiment.

FIG. 3 is a configuration diagram showing a configuration of a system according to a second embodiment.

FIG. 4 is a configuration diagram showing a configuration of a system according to a third embodiment.

FIG. 5 is a configuration diagram showing a configuration of a system according to a fourth embodiment.

FIG. 6 is a configuration diagram showing a configuration of a system according to a fifth embodiment.

FIG. 7 is a configuration diagram showing a configuration of a system according to a sixth embodiment.

FIG. 8 is a configuration diagram showing a configuration of a system according to a seventh embodiment.

FIG. 9 is a configuration diagram showing another configuration of the system according to the seventh embodiment.

[Explanation of symbols]

101, 201, 301, 401, 501, 601
Encryption device 102, 202, 302, 402, 502, 602
Decryption devices 103, 104 Common key storage units 105, 106 Random number generation units 107, 108 Mutual authentication processing units 109, 110, 609, 610 Time-varying key generation units 111, 211, 311 Decryption restriction storage units 112, 212, 223, H.323 Analysis restriction update unit 113, 116, 119 Encryption unit 114, 115, 120 Decryption unit 117, 118, 617, 618 Content key generation unit 625, 626 Data sequence key generation unit

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) G06F 17/60 302 G06F 17/60 512 512 H04L 9/00 601B 601E F-term (Reference) 5B017 AA03 AA07 BA07 BB10 CA15 CA16 5B082 EA11 GA11 5J104 AA01 AA13 AA16 EA01 EA04 EA18 JA03 NA02

Claims (47)

[Claims] 1. A copyright protection system comprising an encryption device and a decryption device that perform encrypted communication using a content key, wherein the encryption device includes: a content storage unit that stores content; First content key generation means for generating the content key based on the second decryption restriction obtained by updating the decryption restriction; and first encryption for encrypting the content based on the content key and outputting encrypted content. The decryption device comprises: a second content key generation unit configured to generate the content key from the second decryption restriction; and the encrypted content generated by the second content key generation unit. A copyright protection system comprising: first decryption means for decrypting using a content key. 2. The decryption device according to claim 1, wherein the decryption device updates the first decryption restriction to the second decryption restriction based on a decryption restriction update rule; and the second decryption restriction is based on a time-varying key. Second encryption means for encrypting and outputting a first encryption / decryption restriction, wherein the encryption device changes the first encryption / decryption restriction transferred from the second encryption means to the time-varying A second decryption unit that decrypts based on the key to generate the second decryption restriction, wherein the first content key generation unit performs the second decryption restriction generated by the second decryption unit. The copyright protection system according to claim 1, wherein the content key is generated based on the content key. 3. The encryption device includes: a first common key storage unit that stores a common key; a decryption restriction storage unit that stores the first decryption restriction; and a first random number generation unit that generates a first random number. Using the first random number and the second random number transferred from the decryption device to perform a mutual authentication process with the decryption device;
Mutual authentication processing means; first time-variable key generation means for generating the time-variant key from the first random number and the second random number in response to authentication acceptance by the first mutual authentication processing means; The restriction is encrypted using the time-varying key and the second
A third encryption unit that outputs an encryption / decryption limit; the decryption device stores a second common key storage unit that stores the common key; and a second random number generation unit that generates the second random number. Second mutual authentication processing means for performing mutual authentication with the encryption device using the second random number and the first random number; and receiving the authentication in the second mutual authentication processing means, A second time-varying key generation unit that generates the time-varying key from the first random number, and a third decryption unit that decrypts the second encryption / decryption restriction using the time-varying key. The copyright protection system according to claim 2. 4. The decoding apparatus according to claim 1, wherein the decoding device updates the first decryption restriction to a second decryption restriction based on a decryption restriction update rule.
Further comprising a decryption restriction update unit, wherein the second content key generation unit generates the content key based on the second decryption restriction updated by the first decryption restriction update unit; A second decryption restriction updating unit configured to update the first decryption restriction to the second decryption restriction in accordance with the decryption restriction update rule in response to the update of the decryption restriction in the first decryption restriction updating unit of the decoding device; The copyright protection system according to claim 1, wherein the first content key generation unit generates the content key based on the second decryption restriction updated by the first decryption restriction update unit. 5. The encryption device, wherein: the first common key storage means for storing the common key; a decryption restriction storage means for storing the first decryption restriction; and a first random number generation means for generating a first random number. First mutual authentication processing means for performing mutual authentication with the decryption device using the first random number and a second random number transferred from the decryption device; and accepting authentication in the first mutual authentication processing device. And generating a time-varying key from the first random number and the second random number.
A time-variable key generating unit; and a second encrypting unit that encrypts the first decryption restriction using the time-variable key and outputs an encrypted decryption restriction. Second random number storage means for generating the second random number, and a second mutual key for performing mutual authentication with the encryption device using the second random number and the first random number. Authentication processing means; second time-varying key generation means for generating the time-variant key from the second random number and the first random number in response to the authentication being accepted by the second mutual authentication processing means; 5. The copyright protection system according to claim 4, further comprising: a second decryption unit that decrypts the encrypted data using the time-varying key. 6. The second decryption restriction update unit updates the first decryption restriction to a second decryption restriction in advance, and the second decryption restriction update unit updates the first decryption restriction update unit to the first content key generation unit. The second decryption restriction is output, the first content key generation unit generates the content key from the second decryption restriction, and the second decryption restriction update unit starts processing of the first encryption unit. 6. The copyright protection system according to claim 5, wherein the second decryption restriction is stored in the decryption restriction storage means in response to the request. 7. The first and second time-varying key generation means,
The copyright protection system according to claim 3, wherein the time-varying key is generated based on the first and second random numbers and the common key. 8. The copyright protection system according to claim 3, wherein the first and second content key generation means generates the content key based on the second decryption restriction and the time-varying key. 9. The encryption device and the decryption device include first and second data sequence key generation means for generating a data sequence key based on an input / output data sequence of the encryption device and the decryption device. 4. The copyrighted work protection according to claim 3, further comprising: each of the first and second time-varying key generation means generating the time-varying key based on the first and second random numbers and the data sequence key. 5. system. 10. The encryption device and the decryption device are provided with first and second data sequence key generation means for generating a data sequence key based on input / output data sequences of the encryption device and the decryption device. The first and second time-varying key generation means each further comprising: the first and second time-varying key generation means generating the time-variant key based on the first and second random numbers, the common key, and the data sequence key. Copyright protection system. 11. The encryption device and the decryption device include first and second data sequence key generation means for generating a data sequence key based on input / output data sequences of the encryption device and the decryption device. The first and second content key generation means further comprises:
The copyright protection system according to claim 3, wherein the content generation key is generated based on a decryption restriction and the data sequence key. 12. The encryption device and the decryption device include first and second data sequence key generation means for generating a data sequence key based on an input / output data sequence of the encryption device and the decryption device. The first and second content key generation means further comprises:
The copyright protection system according to claim 3, wherein the content generation key is generated based on decryption restrictions, the time-varying key, and the data sequence key. 13. The copyright protection device according to claim 3, wherein said first and second mutual authentication processing means mutually authenticate that the other device is a valid device by communication based on a challenge response type authentication protocol. system. 14. An encryption device that performs encrypted communication with a decryption device using a content key, wherein the encryption device is obtained by updating content storage means for storing content and a first decryption restriction. Content key generating means for generating the content key based on a second decryption restriction; and first encrypting means for encrypting the content based on the content key and outputting encrypted content. Encryption device. 15. The encryption device further includes a decryption unit that decrypts the first decryption restriction transferred from the decryption device based on a time-varying key and generates the second decryption restriction. 15. The encryption device according to claim 14, wherein the content key generation unit generates the content key based on the second decryption restriction generated by the decryption unit. 16. The encryption device, wherein: a common key storage unit that stores a common key; a decryption restriction storage unit that stores the first decryption restriction; a first random number generation unit that generates a first random number; Mutual authentication processing means for performing mutual authentication processing with the decryption device using a first random number and a second random number transferred from the decryption device; and receiving the authentication by the mutual authentication processing means, the first random number A time-varying key generating means for generating the time-varying key from the second random number, and encrypting the first decryption restriction using the time-varying key.
The encryption device according to claim 15, further comprising: a second encryption unit that outputs a decryption restriction. 17. The encryption apparatus further comprises a decryption restriction update unit that receives the update of the decryption restriction of the decryption apparatus and updates the first decryption restriction to the second decryption restriction according to a decryption restriction update rule. 15. The encryption device according to claim 14, wherein the content key generation unit generates the content key based on the second decryption restriction updated by the decryption restriction updating unit. 18. The encryption device, comprising: a common key storage unit that stores the common key; a decryption restriction storage unit that stores the first decryption restriction; a first random number generation unit that generates a first random number; Mutual authentication processing means for performing mutual authentication with the decryption device using the first random number and a second random number transferred from the decryption device; and receiving the authentication by the mutual authentication processing means, the first random number Time-variant key generation means for generating a time-variant key from the second random number, and second encryption means for encrypting the first decryption restriction using the time-variable key and outputting an encrypted decryption restriction. 18. The encryption device according to claim 17, further comprising: 19. The decryption restriction update means updates the first decryption restriction to the second decryption restriction in advance, and the decryption restriction update means outputs the updated second decryption restriction to the content key generation means. The content key generation means generates the content key from the second decryption restriction, and the decryption restriction updating means receives the processing of the first encryption means and stores the decryption restriction storage. 18. The encryption device according to claim 17, wherein said second decryption restriction is stored in a means. 20. The encryption apparatus according to claim 16, wherein said time-varying key generation means generates said time-varying key based on said first and second random numbers and said common key. 21. The encryption device according to claim 16, wherein said content key generation means generates said content key based on said second decryption restriction and said time-varying key. 22. The encryption device further includes a data sequence key generation unit that generates a data sequence key based on an input / output data sequence of the encryption device, wherein the time-varying key generation unit includes the first key. 17. The encryption device according to claim 16, wherein the time-varying key is generated based on a second random number and the data sequence key. 23. The encryption device further includes data sequence key generation means for generating a data sequence key based on an input / output data sequence of the encryption device, wherein the time-varying key generation means comprises 17. The encryption device according to claim 16, wherein the time-varying key is generated based on a second random number, the common key, and the data sequence key. 24. The encryption device further includes a data sequence key generation unit that generates a data sequence key based on an input / output data sequence of the encryption device, wherein the content key generation unit is configured to execute the second decryption. 17. The encryption device according to claim 16, wherein the content generation key is generated based on a restriction and the data sequence key. 25. The encryption device further includes a data sequence key generation unit that generates a data sequence key based on an input / output data sequence of the encryption device, wherein the content key generation unit is configured to execute the second decryption. 17. The encryption device according to claim 16, wherein the content generation key is generated based on a restriction, the time-varying key, and the data sequence key. 26. A decryption device for performing encrypted communication with an encryption device using a content key, wherein the decryption device generates the content key from a second decryption restriction, and a decryption device. A first decryption unit for decrypting content using the content key generated by the content key generation unit. 27. The decryption device, comprising: a decryption restriction updating unit that updates the first decryption restriction to the second decryption restriction based on a decryption restriction update rule; and the second decryption restriction is based on a time-varying key. 27. The decryption device according to claim 26, further comprising: encryption means for encrypting and outputting the first decryption restriction. 28. The decryption device, wherein: the common key storage means for storing the common key; a random number generation means for generating the second random number; and the encryption using the second random number and the first random number. Mutual authentication processing means for performing mutual authentication with a device; time-variable key generation means for generating the time-variant key from the second random number and the first random number in response to acceptance of authentication by the mutual authentication processing means; 28. The decryption device according to claim 27, further comprising: second decryption means for decrypting the decryption restriction using the time-varying key. 29. The decryption device further comprises a decryption restriction update unit that updates the first decryption restriction to a second decryption restriction based on a decryption restriction update rule, and the content key generation unit performs the decryption restriction update. The decryption device according to claim 26, wherein the content key is generated based on the second decryption restriction updated by a means. 30. A decryption device comprising: a second common key storage unit that stores the common key; a second random number generation unit that generates the second random number; and a second random number and a first random number. Authentication processing means for performing mutual authentication with the encryption device, and time-varying key generation means for generating the time-varying key from the second random number and the first random number upon receiving authentication from the mutual authentication processing means. 30. The decryption device according to claim 29, further comprising: a second decryption unit configured to decrypt the decryption restriction using the time-varying key. 31. The decryption apparatus according to claim 28, wherein said time-varying key generation means generates said time-varying key based on said first and second random numbers and said common key. 32. The decryption device according to claim 28, wherein said content key generation means generates said content key based on said second decryption restriction and said time-varying key. 33. The decryption device further comprises a data sequence key generation means for generating a data sequence key based on an input / output data sequence of the decryption device, wherein the time-varying key generation means comprises: 29. The decryption device according to claim 28, wherein the time-varying key is generated based on first and second random numbers and the data sequence key. 34. The decryption device further comprises data sequence key generation means for generating a data sequence key based on the input / output data sequence of the decryption device, wherein the time-varying key generation means 29. The decryption device according to claim 28, wherein the time-variant key is generated based on a second random number, the common key, and the data sequence key. 35. The decryption device further comprises a data sequence key generation unit that generates a data sequence key based on an input / output data sequence of the decryption device, wherein the content key generation unit is configured to perform the second decryption. The decryption device according to claim 28, wherein the content generation key is generated based on a restriction and the data sequence key. 36. The decryption device further comprises data sequence key generation means for generating a data sequence key based on an input / output data sequence of the decryption device, wherein the content key generation means is configured to execute the second decryption. The decryption device according to claim 28, wherein the content generation key is generated based on a restriction, the time-varying key, and the data sequence key. 37. A recording medium recording a program for causing a computer to function as means for performing encrypted communication with an encryption device using a content key, wherein the program generates the content key from a second decryption restriction. A storage medium for causing the computer to function as first content decryption means for decrypting the encrypted content using the content key generated by the content key generation means. 38. A decryption restriction updating means for updating the first decryption restriction to the second decryption restriction based on a decryption restriction update rule, encrypting the second decryption restriction based on a time-varying key, 38. The recording medium according to claim 37, further causing the computer to function as encryption means for outputting the first decryption restriction. 39. The program, comprising: a common key storage unit that stores the common key; a random number generation unit that generates the second random number; and a mutual authentication with the encryption device using the second random number and the first random number. A time-varying key generating means for generating the time-varying key from the second random number and the first random number in response to the authentication being accepted by the mutual authentication processing means; 39. The recording medium according to claim 38, further causing the computer to function as second decryption means for decrypting using a time-varying key. 40. The program further causes the computer to function as a decryption restriction update unit that updates the first decryption restriction to a second decryption restriction based on a decryption restriction update rule. The recording medium according to claim 37, wherein the content key is generated based on the second decryption restriction updated by the restriction updating unit. 41. The program, wherein the program stores a second common key storing means for storing the common key, a second random number generating means for generating the second random number, and the encryption using the second random number and the first random number. Mutual authentication processing means for performing mutual authentication with a device; time-variable key generation means for generating the time-variant key from the second random number and the first random number in response to the authentication being accepted by the mutual authentication processing means; 41. The recording medium according to claim 40, further causing the computer to function as a second decryption unit that decrypts the data using the time-varying key. 42. The recording medium according to claim 39, wherein said time-varying key generation means generates said time-varying key based on said first and second random numbers and said common key. 43. The recording medium according to claim 39, wherein said content key generation means generates said content key based on said second decryption restriction and said time-varying key. 44. The program further causes the computer to function as data sequence key generation means for generating a data sequence key based on an input / output data sequence of the decryption device, wherein the time-varying key generation means 40. The recording medium according to claim 39, wherein the time-varying key is generated based on first and second random numbers and the data sequence key. 45. The program further causes the computer to function as data sequence key generation means for generating a data sequence key based on an input / output data sequence of the decryption device, wherein the time-varying key generation means 40. The recording medium according to claim 39, wherein the time-varying key is generated based on first and second random numbers, the common key, and the data sequence key. 46. The program further causes the computer to function as a data sequence key generation unit that generates a data sequence key based on an input / output data sequence of the decryption device. The recording medium according to claim 39, wherein the content generation key is generated based on a decryption restriction and the data sequence key. 47. The program further causes the computer to function as data sequence key generation means for generating a data sequence key based on an input / output data sequence of the decryption device, wherein the content key generation means The recording medium according to claim 39, wherein the content generation key is generated based on a decryption restriction, the time-varying key, and the data sequence key.