WO2004028230A2

WO2004028230A2 - System for protecting both copyrights and fair-use rights at the same time

Info

Publication number: WO2004028230A2
Application number: PCT/JP2003/016665
Authority: WO
Inventors: Makoto Saito; Rie Saito
Original assignee: Far East Engineering Co., Ltd.
Priority date: 2003-02-14
Filing date: 2003-12-25
Publication date: 2004-04-08
Also published as: JP2006517691A; WO2004028230A3; AU2003298496A8; AU2003298496A1

Abstract

System for protecting both copyrights of digital content which producers own and fair-use rights of digital content which consumers own at the same time. In addition to an authentication management unit, a copyrights management unit and a crypt key management unit, also a fair-use rights management unit is established in a key center. For copyrights protection, the authentication management unit, the copyrights management unit and the crypt key management unit are connected to each other to work. For fair-use rights protection, the authentication management unit, the copyrights management unit, the fair-use rights management unit and the crypt key management unit are connected to each other to work. The fair-use rights management unit confirms fair-use and permits to provide a consumer with a crypt key for re-decrypting according to the fair-use.

Description

System for protecting both copyrights and fair-use rights at the same time

BACKGROUND OF THE INVENTION

Field of the Invention

The present invention relates to a system for protecting copyrights of digital content, protecting fair-use rights of digital content, and usage of digital content. The present invention relates to protecting copyrights of digital content which producers own and fair-use rights of digital content which each individual owns at the same time, and promoting growth of a new market which enables secure electronic commerce and development of digital economy. In addition, the present invention also relates to contributing to society to provide a tax collection system and a function for investigation into a crime.

Description of Art Related to the Invention

Today, there are some conventional cryptosystems which use a method of common key cryptography for copyrights protection.

According to these conventional systems, a case of encrypting digital content M with a crypt key Ki into an encrypted format Ci of the digital content M is expressed as

and a case of decrypting the encrypted format Ci of the digital content M with a crypt key Ki into the digital content is expressed as

M = D (Cι, Ki).

Further more, a case of re-encrypting the digital content M into a re-encrypted format Ci of the digital content M is expressed as Ci = E ( D ( CM , KM ), KI )

and a case of re-decrypting a re-encrypted format Ci of the digital content M into the digital content M is expressed as

M = D (O, Ki).

These expressions are on condition that " i " is an integer which is 2 or over.

One of these conventional cryptosystems for digital content protection is a Content Protection Chain designed for a digital device at home. This system is realized as technologies of DTCP(Digital Transmission Content Protection), CPRM(Content Protection for Recordable Media) and HDCP(High-bandwidth Digital Content Protection) by CPTWG(Content Protection Technical Working Group), a group directed by Motion Picture Association of America.

According to these conventional technologies of DTCP, CPRM and HDCP, crypt keys protect digital content within home network. Digital content provided by a producer via Internet, CATV, Digital Satellite Broadcasting, recording mediums (for example, DVD, Digital Versatile Disc) and the like is encrypted with a crypt key Ki into an encrypted format of the digital content. And the encrypted format of the digital content is protected until the encrypted format of the digital content reaches at a consumer. The consumer pays for a crypt key Ki as charge of the digital content usage for decrypting the encrypted format of the digital content at a first digital device which the consumer wants to play on. The encrypted format of the digital content is decrypted by using the crypt key Ki into the digital content, then the consumer enjoys the digital content thanks to a decrypting function at the first digital device.

When the consumer wants to transmit the digital content which the consumer has ever enjoyed to a second digital device, for example that in a next room, via IEEE1394, USB, DVI, HDMI or wireless interface, and when the consumer wants to store the digital content for more enjoyment, a function of automatic and mandatory re-encrypting works within the first digital device. And then the digital content is re-encrypted with a crypt key K_ for re-encrypting.

The crypt key K2 for re-encrypting is originally equipped with or generated at the first digital device. The second digital device to which the re-encrypted format of the digital content is transmitted needs a crypt key K2 for re-decrypting the re-encrypted format of the digital content. Thus, the second digital device uses a crypt key K2 for re-decrypting originally equipped with, asks the first digital device to transmit a crypt key K2 for re-decrypting generated at the first digital device, or generates a crypt key K2 for re-decrypting by itself.

Also in a case of transmission of the digital content from the second digital device (for example, a record player) to a third digital device (for example, a TV display), procedure of re-encrypting and re-decrypting is also necessary. In this case, the digital content is re-encrypted with a crypt key K3. The second digital device is equipped with the crypt key K3 originally, or the second digital device generates the crypt key K3 by itself.

But, in a case that the re-encrypted format of the digital content is re-sent or re-distributed beyond home network, a crypt key for re-decrypting cannot be generated outside of home. It's impossible to re-send or re-distribute digital content to a third party due to the function of automatic and mandatory re-encrypting, and the third party as a receiver cannot re-decrypt by itself even if the third party receives a re-encrypted format of the digital content. And, the copyrights cannot be protected if a crypt key for re-decrypting is generated dishonestly within home network and provided beyond home network. Hence, these conventional technologies of DTCP, CPRM and HDCP provide a crypt key only within home network.

Another conventional cryptosystem which uses the method of common key cryptography for the digital content protection is pushed to be implemented. The cryptosystem is a system of a digital content protection invented by one of the present inventors, Makoto Saito, and disclosed in U.S. Pat. No. 6,438,694 and U.S. Pat. No. 6,069,952. This cryptosystem disclosed in the two U.S. patents includes not only a re-encrypting technology but also a key center to prevent from misuse. According to the cryptosystem disclosed in the two U.S. patents, when a consumer tries to decrypt a format of digital content which is encrypted with a crypt key Ki and provided for a digital device, the consumer accesses the key center via Internet and the like, and purchases a crypt key Ki for decrypting.

And, in a case of transmission to another digital device which is inside or outside of home network, digital content is re-encrypted automatically and mandatorily with a crypt key K2 provided by the key center. After the digital content is re-encrypted completely, the crypt key K2 is destroyed for security. Being different than the former system of the Content Protection Chain, the cryptosystem disclosed in the two U.S. patents needs consumers to pay the key center for a crypt key K2 for re-decrypting via Internet and the like. Misuse is prevented from because the key center manages a crypt key of digital content and the crypt key is available only for a consumer who has paid. Each crypt key provided by the key center is destroyed at a digital device of a consumer after usage. In other words, each crypt key is never stored at a digital device of a consumer and is never used again. When the key center provides a digital device of a consumer with a crypt key via Internet and the like, the crypt key itself is protected by a method of public and private key pairs.

Referring FIG.1 , an example of a digital content protection using the cryptosystem disclosed in the two U.S. patents in a case of that a certain number of consumers consume digital content is illustrated.

A consumer-A accesses the key center in order to obtain a crypt key Ki and enjoy digital content. The key center identifies the consumer-A, the consumer-A pays for a crypt key Ki, and then, the crypt key Ki is generated and sent to the consumer-A. At this time, a crypt key K2 for re-encrypting and protecting from misuse is also sent to the consumer-A.

When the consumer-A sends the digital content to a consumer-B for recommendation, the digital content is automatically and mandatorily re-encrypted with the crypt key K2 into a re-encrypted format of the digital content. The consumer-B accesses the key center in order to obtain a crypt key K2 and enjoy the digital content. As a result that the consumer-B has the same procedure as the consumer-A had, the consumer-B obtains a crypt key K2, the re-encrypted format of the digital content is re-decrypted with the crypt key K2 into the digital content, and the consumer-B enjoys the digital content. And a crypt key K3 for re-encrypting and protecting from misuse is sent to the consumer-B, in the same way as the crypt key K2 is sent to the consumer-A.

When the consumer-B sends the digital content to a consumer-C for recommendation, the digital content is automatically and mandatorily re-encrypted with the crypt key K3 into a re-encrypted format of the digital content. The consumer-C accesses the key center in order to obtain a crypt key K3 and enjoy the digital content. As a result that the consumer-C has the same procedure as the consumer-A and the consumer-B had, the consumer-C obtains a crypt key K3, the re-encrypted format of the digital content is re-decrypted with the crypt key K3 into the digital content, and the consumer-C enjoys the digital content. And a crypt key K4 for re-encrypting and protecting from misuse is sent to the consumer-C in the same way as the consumer-A and the consumer-B.

But, according to the cryptosystem disclosed in the two U.S. patents, when the automatic and mandatory re-encrypting prevents a consumer from enjoying digital content in a way the consumer likes, and then the consumer needs to obtain a crypt key newly, there is a problem. The problem is caused by a premise that a raison d'etre of the key center disclosed in the two U.S. patents is based on copyrights protection. Each crypt key for decrypting or re-decrypting is priced and needs to be paid for. A consumer is not able to obtain a crypt key for decrypting or re-decrypting without paying. Therefore, according to the cryptosystem disclosed in the two U.S. patents, fair-use rights of digital content which consumers have as personal usage rights are not protected, and more, assignment or presentation of digital content is impossible.

Fair-use rights are rights for consumers to use digital content, rights to use the digital content in a way the consumers like, and rights for the consumers themselves. There are copyright laws of each nation of the world or a part of international law. Though the copyright laws basically protect rights of copyright owners, there is an exception which enables freedom to use digital content when the usage is legal. Protecting rights of consumers as users, including bills which concern fair-use rights, has started in the U.S., and other nations are going to catch up.

Fair-use rights are new ideas which should be added to each copyright law, and are one part of rights which we people have in everyday life. Fair-use rights include representative six fair-use rights. The representative six fair-use rights will become apparent from the following description.

A first fair-use right is a right of freedom to decide when to consume (In other words, a right of time-shift). For example, in a case that a consumer tries to make a digital device play back a television program as digital content which has been broadcasted digitally and recorded the previous day, the consumer has paid for the digital content on recording, and an encrypted format of the digital content has been decrypted with a crypt key Ki in order to enable the digital device to record. But, the consumer needs to obtain a crypt key K2 in order to enjoy the digital content which the consumer has never enjoyed, because the digital content is automatically and mandatorily re-encrypted with a crypt key K2 in procedure of recording and storing the digital content. A crypt key K2 needs to be sent to the consumer on condition that the consumer does not need to pay. This first fair-use right gives consumers freedom to decide when to consume and enjoy digital content.

A second fair-use right is a right of freedom to choose which digital device for playing (In other words, a right of platform choice). For playing digital content of music, a consumer may use a personal computer or may use a digital audio device. For watching a program of digital broadcast, a consumer may use a digital television or may use a personal computer. A crypt key managed by a key center does not pick a particular digital device but is adapted to any digital device which is equipped with a function of encrypting, re-encrypting, decrypting and re-decrypting. This second fair-use right gives consumers freedom to choose which digital device for playing. A third fair-use right is a right to change a place to consume (In other words, a right of space-shift). For example, when digital content is a motion picture and is provided via Internet, television networks or tangible mediums, there is a question how the digital content is moved and played at a vacation house of a consumer which is far from home of the consumer. Digital content which a consumer owns is automatically and mandatorily re-encrypted with a crypt key for re-encrypting and protecting the copyrights into a re-encrypted format of the digital content. The consumer is able to store the re-encrypted format of the digital content in a recording medium (for example, DVD, Digital Versatile Disc), able to move the re-encrypted format of the digital content, and able to send the re-encrypted format of the digital content online or offline, but the format remains re-encrypted. Therefore, re-decrypting the re-encrypted format of the digital content needs to be permitted for no payment when a person who uses the digital content is the consumer. This third fair-use right allows consumers to change a place to enjoy digital content.

A fourth fair-use right is a right to copy for backup (In other words, a right of backup-copy). For example, when a personal computer or a digital device is broken, data of software in the personal computer or the digital device is vanished. This fourth fair-use right allows consumers who pay for digital content (e.g., software) to copy the digital content for backup.

A fifth fair-use right is a right to adjust for proper playing (In other words, a right of adjustment). For example, a person who does not have ability to see cannot enjoy a television program of digital broadcast as long as the program shows ordinarily. Hence, the person needs to change a format of visual information of the program into a format of sound information of the program. This fifth fair-use right allows to adjust digital content for proper playing.

Lastly, a sixth fair-use right is a right to process or modify. This fifth fair-use right gives consumers freedom to process or modify digital content as long as the consumers process or modify the digital content for their own enjoyment, even though the digital content is re-encrypted. Though there are fair-use rights including the six rights, the two U.S. patents, the U.S. Pat. No. 6,438,694 and the U.S. Pat. No. 6,069,952 do not disclose a cryptosystem which enables a consumer to have a crypt key without paying when the consumer has fair-use rights which are rights to use digital content without a duty to pay. The two U.S. patents do not have a solution for fair-use rights. In other words, a technology of the two U.S. patents does not have a function to protect fair-use rights. According to the two U.S. patents, a consumer always needs to pay for decrypting or re-decrypting because a primitive purpose of the two U.S. patents is encrypting and re-encrypting. The consumer has nothing to do but to pay again and buy a crypt key for re-decrypting in order to enable a re-encrypted format of digital content to be re-decrypted.

Though technologies of cryptosystem need not only to protect digital content from misuse but also to give freedom to a personal usage or a family usage, conventional technologies have a limit and take only one side. And, the conventional technologies do not enable a representative to collect taxes imposed on a user, because the key center disclosed in the two U.S. patents does not know conditions of each electronic commerce. When misuse and a crime related to digital content are committed, the conventional technologies do not tell the misuse and the crime are an actual fact or not. The conventional technologies leave misuse and a crime beyond perception.

According to a conventional idea of decrypting, each crypt key for decrypting is priced, and there is a limit for re-decrypting because a point of the conventional idea is only protecting copyrights. The conventional technologies protect only digital content, collect only charge of the digital content usage, and are a partial solution that a system of the technologies gives advantage only to a producer. A partial economic system may be founded on absolute initiative of producers when fair-use rights which allow a consumer to enjoy purchased digital content as the consumer likes are not protected. The partial economic system is immature and not suitable for digital economy as new development of economy. A primitive solution seeking what to protect is being pursued. BRIEF SUMMERY OF THE INVENTION

The present invention enables what the conventional technologies do not, the present invention is for protecting both copyrights of digital content owned by producers and fair-use rights of digital content owned by consumers at the same time, and for contributing to society to provide a tax collection system and a function for criminal investigation. Coupling with re-encrypting and a key center, a crypt key for no payment protects rights of consumers.

BRIEF DISCRETION OF THE DRAWINGS

FIG.1 is a flowchart illustrating the digital content protection of the prior arts.

FIG.2 is a flowchart illustrating an embodiment of basic practice of the present invention.

FIG.3 is a flowchart illustrating an embodiment of applied practice of the present invention.

FIG.4 is a flowchart illustrating another embodiment of applied practice of the present invention.

FIG.5 is an example of display illustrating an embodiment of the present invention.

FIG.6 is another example of display illustrating an embodiment of the present invention.

FIG.7 is an overview illustrating a function of a key center of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

A key center is necessary for the present invention to protect both copyrights of digital content owned by producers and fair-use rights of digital content owned by consumers at the same time when digital content is sent, re-sent, distributed, re-distributed via Internet, home network or the like. A key center is firstly disclosed in the U.S. Pat. No. 6,069,952.

A key center of the present invention is a third party as a go-between of a producer of digital content and a consumer of the digital content. Management of a crypt key is entrusted to the key center when the producer wants to encrypt and protect the digital content for copyright protection and also wants to know conditions of consumption. Structuring a system of the key center is centralized or distributed. One of the two types may be selected according to a business model.

The digital content is protected thanks to encrypting. When an encrypted format of the digital content is provided by the producer, the consumer who tries to consume the digital content pays the key center in order to obtain a crypt key, and then the encrypted format of the digital content is decrypted into the digital content for the consumer's enjoyment. And more, the digital content is re-encrypted in order to protect copyrights of the digital content.

An authentication management unit, a copyrights management unit and a crypt key management unit are in the key center and enable this procedure of decrypting and re-encrypting. The authentication management unit authenticates one of or both the consumer and a digital device of the consumer. The authentication management unit identifies and authenticates who or which digital device accesses the key center by communicating.

Having a function of charging, the copyrights management unit permits to send a crypt key for decrypting by charging. On charging, the copyrights management unit makes registration of the consumer who has paid for the digital content. In order to protect and re-encrypt the digital content, the copyrights management unit commands the crypt key management unit to generate and send a crypt key for re-encrypting via communication network. And, the digital content is automatically and mandatorily re-encrypted with the crypt key at the digital device of the consumer for copyrights protection.

The copyrights management unit protects the digital content from misuse by making the consumer use a crypt key for re-encrypting automatically and mandatorily. And the copyrights management unit gives usage rights of the digital content to the consumer according to payment by the consumer.

The payment includes not only charge of the digital content usage but also charge of the key center usage. The charge of the key center usage may be paid by income of advertising. The payment is possible when advertisements are added to a crypt key.

In a case that a person who is not a producer of digital content provides an encrypted or re-encrypted format of the digital content for a consumer, the consumer pays the key center and obtains a crypt key in order to have the encrypted or re-encrypted format of the digital content decrypted or re-decrypted.

When a person presents an encrypted or re-encrypted format of digital content as a gift to a consumer, the person as a presenter may pays instead of the consumer as a receiver. When the presenter pays, the key center recognizes that the presenter has done the payment and a usage rights holder of the digital content is the receiver. The recognition is done by the copyrights management unit in the key center.

The authentication management unit authenticates the presenter, and the payment is done at the copyrights management unit. The presenter registers the receiver as a usage rights holder of the digital content. After that, the receiver asks for a crypt key for decrypting or re-decrypting, and then the copyrights management unit recognizes the receiver as a usage rights holder of the digital content. The crypt key management unit sends the crypt key for decrypting or re-decrypting after confirmation of the presenter's payment.

In a case that digital content is decrypted and consumed by a consumer and then the consumer as an assignor assigns a re-encrypted format of the digital content to a person as an assignee and renounces usage rights of the digital content, the assignment is possible when the key center removes the usage rights of the digital content from the assignor to the assignee. The removal is done by the copyrights management unit. The copyrights management unit receives the assignor's expression of will to assign, and registers the expression after confirmation of the assignor's payment.

According to the assignee's demand for a crypt key and a declaration of the assignment, the copyrights management unit confirms the assignment, the assignor's expression of will to assign, and the assignor's payment. After that, the assignor renounces the usage rights and the assignee gets the usage rights. The crypt key management unit sends a crypt key for re-decrypting to the assignee who accepts the assignment according to permission of crypt key generation.

The key center entrusted by a producer has information about the producer, but the key center also has information about a consumer. The key center can be deputed to collect taxes imposed on a user of the key center. A producer of digital content and a consumer of the digital content are the user of the key center.

In a case of misuse or a crime related to digital content, the key center can prove when and who uses the digital content because the key center has information about condition of consumption of the digital content.

In other words, when authority of each nation or International asks or enforces law, the key center can disclose traces of the consumer who uses the digital content, and the key center can provide concrete proof of the misuse or the crime. At the time of the application of the present invention, there are convention on cyber crime and some Acts in the U.S., Japan, and other nations. Though working on legislation has just started, the key center can provide proof at any time of law enforcement.

In a case of protection of fair-use rights, in other words, a case that a consumer buys digital content and tries to use the digital content according to a fair-use right, the consumer demands a crypt key for re-decrypting from the key center. Though the digital content once consumed is re-encrypted and protected, the consumer who tries to consume the digital content according to the fair-use right can enjoy the digital content by obtaining permission of fair-use and the crypt key for re-decrypting from the key center.

The authentication management unit, the copyrights management unit, the crypt key management unit and a fair-use rights management unit are in the key center and enable this procedure of re-decrypting. The fair-use rights management unit identifies the demand of the consumer for the crypt key according to the fair-use right, the fair-use rights management unit commands the crypt key management unit to generate and send the crypt key for re-decrypting to a digital device of the consumer via communication network, and then re-decrypting is possible at the digital device of the consumer.

The first fair-use right to decide when to consume is realized in a way that a consumer declares that digital content has not played yet at a digital device of the consumer and the key center receives the declaration therefore sends a crypt key for re-decrypting to the consumer for no payment.

The second fair-use right to choose a digital device for playing is realized in a way that a crypt key is enabled to be adapted to any digital device which is equipped with the function of encrypting, decrypting and others and the crypt key does not pick a particular digital device.

The third fair-use right to change a place to consume is realized in a way that the key center authenticates and identifies a consumer and then sends a crypt key for re-decrypting to the consumer for no payment.

The fourth fair-use right to copy for backup is realized in a way that a consumer declares that the consumer copies digital content for backup and the key center receives the declaration therefore sends a crypt key for re-decrypting to the consumer for no payment.

The fifth fair-use right to adjust for proper playing is realized in a way that a consumer declares that the consumer changes a format of digital content for adjustment and the key center receives the declaration therefore sends a crypt key for re-decrypting to the consumer for no payment.

The sixth fair-use right to process or modify is realized in a way that a consumer declares that the consumer processes or modifies digital content and the key center receives the declaration therefore sends a crypt key for re-decrypting to the consumer for no payment. In these six fair-use cases, a crypt key for re-decrypting is sent for no payment and the fair-use rights management unit permits to send a crypt key or not. In a case that digital content is not allowed to be processed or modified but the digital content is processed or modified and the processed or modified format of the digital content is re-encrypted and provided for a third party beyond a personal usage, there is an exception that the copyrights management unit decides not to permit to send a crypt key for re-decrypting to the third party.

Fair-use rights including representative six rights are rights executed by a consumer of digital content. On the other hand, copyrights are rights executed by a producer of digital content. Fair-use rights are brought into effect by sending a crypt key for re-decrypting for no payment, and copyrights are brought into effect by paying for a crypt key for decrypting or re-decrypting and by re-encrypting automatically and mandatorily in addition to encrypting. The present invention relates to a system for simultaneous protection and coexistence of both copyrights and fair-use rights. The coexistence is realized by multiple executions of three technologies. The three technologies are sending a crypt key for decrypting or re-decrypting according to payment, mandatory re-encrypting by sending a crypt key for re-encrypting, and sending a crypt key for re-decrypting for no payment.

A crypt key which needs to be paid for executes re-decrypting, but also a crypt key which does not need to be paid for executes re-decrypting. Though re-decrypting has these two types of execution, it costs to manage the key center which enables protection of fair-use rights. In order to pay the cost, a crypt key for re-decrypting based on a fair-use right may be paid for, or the cost may be paid by income of advertising. In a case that a television program is accompanied by advertisements therefore non-encrypted and broadcasted for no payment, encrypting and decrypting with a crypt key Ki is omitted and the copyrights management unit enforces re-encrypting the television program with a crypt key K2 in order to protect copyrights of the television program. And the fair-use rights management unit provides a crypt key K2 for re-decrypting in order to protect fair-use rights of the television program. In the same way as this case, protection of fair-use rights can be applied to digital content which is non-encrypted and accompanied by advertisements (e.g., an ordinarily broadcasted television program). The crypt keys are destroyed for security after usage and the crypt keys themselves are protected by the method of public and private key pairs in the same way as crypt keys of the conventional technologies are protected. The authentication management unit, the copyrights management unit, the crypt key management unit and the fair-use rights management unit are in the key center but do not need to exist at the same place. For example, each unit may be distributed throughout Internet to exist and may be connected to each other to construct the key center.

DETAILED DISCRETION OF EMBODIMENTS

Embodiments of the present invention are shown by FIG.2 through FIG.7. FIG.5 and FIG.6 are examples of display.

Referring to FIG.2, an embodiment that a consumer obtains a crypt key according to fair-use rights is illustrated. A consumer-A has ever paid for digital content but the digital content is automatically and mandatorily re-encrypted with a crypt key K2. The consumer-A wants to use the digital content according to one fair-use right or a plural number of fair-use rights.

The consumer-A has already paid for a crypt key Ki by a demand for a crypt key (1). The digital content is re-encrypted with the crypt key K2 for re-encrypting into a re-encrypted format of the digital content, and the re-encrypted format of the digital content is stored. The consumer-A requests a crypt key K2 for re-decrypting by a demand for a crypt key (2) and practices a fair-use declaration because the consumer-A wants to execute fair-use. The authentication management unit in the key center authenticates the consumer-A and contacts the copyrights management unit in order to confirm that the consumer-A has already paid. After the confirmation of usage rights of the consumer-A at the copyrights management unit, the fair-use rights management unit confirms why and how the consumer-A needs and uses a crypt key according to the fair-use declaration.

When the fair-use rights management unit accepts the fair-use of the consumer-A as legal according to information about the fair-use of the consumer-A, the fair-use rights management unit gives permission to send a crypt key K2 for re-decrypting. Receiving the permission, the crypt key management unit generates and sends the crypt key K2 to the consumer-A. The provided crypt key K2 is used to re-decrypt the re-encrypted format of the digital content at a digital device of the consumer-A. At that time, a crypt key K3 for re-encrypting is also provided in order to prevent misuse. After re-decrypting, the crypt key K3 is used to re-encrypt.

Referring to FIG.3, an embodiment that protection of fair-use rights is applied to the conventional copyrights protection systems (e.g., systems of CPTWG) is illustrated. A consumer-A of digital content has already paid for a crypt key Ki by a demand for a crypt key (1). The consumer-A declares to the key center that the consumer-A will use a cryptosystem of CPTWG or the like within home network of the consumer-A, and asks the key center not to generate and provide a crypt key K2 until the consumer-A needs. Re-encrypting the digital content into a re-encrypted format of the digital content is executed by using a crypt key K2' provided at digital device of the consumer-A within the home network based on technologies of CPTWG (e.g., DTCP, HDCP, CPRM and the like). The re-encrypting is executed at the digital device of the consumer-A.

The re-encrypted format of the digital content is re-decrypted into the digital content at the digital device of the consumer-A or another digital device of the consumer-A within the home network. The re-decrypting is executed by using a crypt key K2^' provided at one of digital devices of the consumer-A within the home network. When the consumer-A uses the conventional technologies, re-decrypting and re-encrypting are repeatable according to the technologies as long as the consumer-A uses within the home network.

It's impossible to use the conventional technologies such as those of CPTWG when the consumer-A wants to execute the fair-use right to change a place to consume and the consumer-A wants to transmit the digital content to an outside digital device which is owned by the consumer-A beyond the home network, including a case of transmission via Internet. A crypt key to use beyond the home network is necessary when the consumer-A transmits the digital content to outside of the home network. Hence, one of digital devices of the consumer-A within the home network practices a demand for a crypt key (2) and obtains a crypt key K2 for re-encrypting. The digital content is re-encrypted with the crypt key K2 and transmitted to the outside digital device which is owned by the consumer-A beyond the home network.

After the transmission, a demand for a crypt key (3) and a fair-use declaration are practiced in order to execute re-decrypting at the outside digital device. And in the same way as the case of FIG.2, the key center manages the fair-use declaration, a crypt key K2 for re-decrypting is provided for the outside digital device according to permission of sending a crypt key, and then re-decrypting is executed by using the crypt key K2 for re-decrypting.

In a case of CPRM, in order to protect fair-use rights safely, it is more desirable to use a crypt key K2 of the key center, not a crypt key K2' generated at a digital device, because CPRM enables offline transmission beyond home network.

Referring to FIG.4, obtaining a crypt key based on assignment is illustrated. A consumer-A of digital content has already obtained a crypt key Ki. In a case of FIG.4, the consumer-A assigns the digital content to a consumer-B. The digital content is re-encrypted with a crypt key K2 provided for the consumer-A into a re-encrypted format of the digital content, and the re-encrypted format of the digital content is sent to the consumer-B. At the same time of the sending, the consumer-A practices an assignment declaration of assignor.

The consumer-B practices a demand for a crypt key and an assignment declaration of assignee in order to enjoy the digital content. The authentication management unit in the key center authenticates the consumer-B, and in addition to the authentication, the copyrights management unit confirms payment of the consumer-A and an agreement of the consumer-A to assign.

After these confirmations, registration of the consumer-A as a usage rights holder is erased, and the consumer-A renounces the usage rights. Hence, A crypt key for fair-use is never provided for the consumer-A after the erasure. At the same time of the erasure, the consumer-B is registered as a usage rights holder, and the crypt key management unit generates and sends a crypt key K2 for re-decrypting to the consumer-B according to permission of generation. A crypt key K3 for re-encrypting is also sent to the consumer-B in order to prevent misuse.

Referring to FIG.5, questioning display is shown when a consumer demands a crypt key from the key center. The consumer chooses one of four choices to declare which category a demand of the consumer belongs to. In a case of consumption by the consumer, the consumer chooses 1 as purchase. In a case that the consumer needs a crypt key for decrypting or re-decrypting an encrypted or re-encrypted format of digital content which is assigned by someone as an assignor, the consumer chooses 2 as assignment. In a case that the consumer obtains a crypt key for the first time because someone as a presenter has paid for and presented an encrypted or re-encrypted format of digital content to the consumer and then the consumer is registered as a usage rights holder, the consumer chooses 3 as presentation. In a case of fair-use, the consumer chooses 4 as fair-use. In a case that the consumer pays for digital content to present someone as a presentee, the consumer chooses 1 as purchase. In this case, the consumer registers the presentee as a usage rights holder, and the consumer is registered as a payer. And then, the usage rights are given to the presentee automatically.

Referring to FIG.6, questioning display is shown when the consumer chooses 4 as fair-use according to a display of FIG.5. The consumer chooses one of five choices to declare which category a fair-use right of the consumer belongs to. In a case that the consumer wants a crypt key according to the fair-use right of freedom to decide when to consume, the consumer chooses 1. In a case that the consumer wants a crypt key according to the fair-use right to change a place to consume, the consumer chooses 2. In a case that the consumer wants a crypt key according to the fair-use right to copy for backup, the consumer chooses 3. In a case that the consumer wants a crypt key according to the fair-use right to adjust for proper playing, the consumer chooses 4. In a case that the consumer wants a crypt key according to the fair-use right to process or modify, the consumer chooses 5. Referring to FIG.7, an overview of a function of the key center, which is integration of FIG.1 through FIG.6, is illustrated. This overview shows that a digital device of a consumer accesses the key center in order to obtain a crypt key for decrypting or re-decrypting. First, the authentication management unit authenticates the digital device of the consumer, and then the digital device of the consumer tells which of purchase, assignment, presentation and fair-use is the purpose of obtaining a crypt key.

In a case of purchase, after the digital device of the consumer has paid, the copyrights management unit gives permission to send a crypt key for decrypting or re-decrypting. Receiving the permission, the crypt key management unit generates and provides the digital device of the consumer with the crypt key for decrypting or re-decrypting and a crypt key for re-encrypting.

In a case of assignment, after the copyrights management unit confirms payment by an assignor, the copyrights management unit erases registration of the assignor as a usage rights holder according to confirmation of an assignment declaration of the assignor, and newly registers the consumer who is an assignee as a usage rights holder. And then, the copyrights management unit gives permission to send a crypt key for re-decrypting. Receiving the permission, the crypt key management unit generates and provides the digital device of the consumer with the crypt key for re-decrypting and a crypt key for re-encrypting.

In a case of presentation, the copyrights management unit confirms payment by a presenter and identifies the consumer as a usage rights holder after the presenter registers the consumer. And, the copyrights management unit gives permission to send a crypt key for decrypting. Receiving the permission, the crypt key management unit generates and provides the digital device of the consumer with the crypt key for decrypting and a crypt key for re-encrypting.

In a case of fair-use, the copyrights management unit confirms payment by the consumer and registration of the consumer as a usage rights holder. After these confirmations, the fair-use rights management unit questions the digital device of the consumer about which fair-use right is the purpose of obtaining a crypt key. When the fair-use rights management unit accepts a fair-use right which the digital device of the consumer declares as legal, the fair-use rights management unit gives permission to send a crypt key for re-decrypting. Receiving the permission, the crypt key management unit generates and provides the digital device of the consumer with the crypt key for re-decrypting and a crypt key for re-encrypting.

As regards a tax collection system, the key center can be deputed to collect taxes because the key center has information about condition of consumption of digital content. The copyrights management unit which includes a function of charging can be deputed to calculate taxes and collect the taxes.

In a case of misuse or a crime related to digital content, the authentication management unit may specify the offender, the copyrights management unit may disclose the details, and the crypt key management unit may have a crypt key chain trace the digital content and the offender.

When these embodiments are practiced, the present invention may promote growth of a new market which enables secure electronic commerce and development of digital economy by protecting producers' copyrights of digital content and each individual's fair-use rights of digital content at the same time. In addition, the present invention may contribute to society to provide the tax collection system and the function for investigation into a crime.

Claims

CLAIM

What is claimed is: l. A system comprising:

a key center that provides at least one crypt key for encrypting, decrypting, re-encrypting or re-decrypting; and

means for encrypting or re-encrypting digital content into an encrypted or re-encrypted format of said digital content in order to protect copyrights.

2. The system of claim 1 , wherein said encrypted or re-encrypted format of said digital content is decrypted or re-decrypted into said digital content at a digital device in order to execute at least one fair-use right of time-shift, platform choice, space-shift, backup-copy, adjustment, processing and modification.

3. The system of claim 2, wherein said digital content is re-encrypted in order to protect copyrights after at least one fair-use right of time-shift, platform choice, space-shift and backup-copy is executed.

4. The system of claim 2, wherein an adjusted format of said digital content, a processed format of said digital content, or a modified format of said digital content is re-encrypted in order to protect copyrights after at least one fair-use right of adjustment, processing and modification is executed.

5. The system of claim 1 , wherein said encrypted or re-encrypted format of said digital content is assigned to an accepting digital device from an assigning digital device and decrypted or re-decrypted into said digital content at said accepting digital device.

6. The system of claim 5, wherein said digital content is re-encrypted after the assignment in order to protect copyrights.

7. The system of claim 6, wherein the key center refuses a decrypting or re-decrypting key to said assigning digital device after the assignment if said encrypted or re-encrypted format is produced by using an encrypting or re-encrypting key which is provided by the key center in order to prevent misuse at said assigning digital device.

8. The system of claim 1 , wherein said encrypted or re-encrypted format of said digital content is presented to a receiving digital device and decrypted or re-decrypted into said digital content at said receiving digital device.

9. The system of claim 8, wherein said digital content is re-encrypted after the presentation in order to protect copyrights.

10. The key center comprising:

an authentication management unit that identifies a user or a digital device of said user;

a copyrights management unit that confirms usage rights of said user or said digital device of said user;

a fair-use rights management unit that confirms fair-use rights of said user or said digital device of said user; and

a crypt key management unit that generates at least one crypt key for encrypting, decrypting, re-encrypting or re-decrypting.