WO2004100443A1

WO2004100443A1 - Information management system

Info

Publication number: WO2004100443A1
Application number: PCT/JP2003/005844
Authority: WO
Inventors: Yukitoshi Maeda
Original assignee: Stark Co., Ltd.
Priority date: 2003-05-09
Filing date: 2003-05-09
Publication date: 2004-11-18
Also published as: AU2003235920A1

Abstract

It is possible to provide a technique for sharing a common key between an information transmission side and reception side without transmitting/receiving the common key between the information transmission side and the reception side. In order to achieve this object, an information management system used includes a server device for transmitting a content and content execution information associated with execution of the content and a terminal device for receiving these information. The server device and the terminal device respectively generate a common key according to use condition information which is information on the range where content execution is allowed in the terminal device. The use condition information is firstly shared by the server device and the terminal device and then updated and managed by the both devices according to the content execution information transmitted/received between the both devices. Accordingly, the use condition information firstly shared by the server device and the terminal device is shared by the both devices even after it is updated by the content execution information, and the both devices can share the common key generated according to the use condition information.

Description

Description Information management system Technical field

The present invention provides a server device that transmits content and content execution information relating to the execution of the content, and an encryption key (a common key scheme) for distributing the information secretly between terminal devices that receive the content and information. (A common key). Background art

Conventionally, encryption technology keys used to keep information confidential (a common key method is common) or the information generated by the key is transmitted between the information sending side and the receiving side through a communication network or the like. They were trying to share between the two by interacting through. For example, there are the following conventional technologies.

"The client has a common key of the common key method used for encrypting information and a public key of the public key method (corresponding to the secret key of the server) for encrypting the common key. The common key is encrypted with the public key and transmitted to the server The server decrypts the common key encrypted with the public key with its own private key, which allows the server and the client to share the common key. After that, information encrypted with the common key is exchanged with a server and a client (Japanese Patent Application Laid-Open No. 2002-305515).

Even when the common key is encrypted and transmitted as in the conventional technology, since the common key is transmitted and received between the information transmitting side and the information receiving side, the information is illegally transmitted through the distribution route. There is a possibility that the encryption obtained and applied to the common key may be illegally decrypted to obtain the common key. Therefore, in order to make it more difficult to illegally obtain a common key, a method of sharing the common key or the generated information of the common key between the sender and the receiver without transmitting / receiving the information between both parties Is desired.

In addition, if the same secret key is used, the risk of the secret key being decrypted increases. Therefore, in order to increase security, it is desirable to change the secret key periodically. In this regard, in the conventional technology, every time the common key is changed, the changed common key (or the information for generating the key) has to be transmitted and received between the information transmitting side and the information receiving side. Therefore, there is a possibility that the changed common key is illegally obtained through the distribution route as described above, and the encryption applied to the common key is illegally decrypted to obtain the common key.

Thus, the present invention provides a common key shared between a sender and a receiver of information without transmitting and receiving the common key between the sender and the receiver of the information. Provide a mechanism that can be easily changed.

In order to solve such a problem, the present invention utilizes an information management system or the like including a server device for transmitting content and content execution information relating to execution of the content, and a terminal device for receiving the server and the terminal device. The common key shared in the system of the present invention is mainly for protecting the content execution information.

The server device and the terminal device have the same usage condition information. The usage condition information is information relating to any one or more of the number of usages of the content, the usage period, the usage period, and the content ID that are allowed for the terminal device, that is, information indicating a range in which the execution of the content is allowed. The method by which the server device and the terminal device first have the same usage condition information does not matter. With this in mind, the server and terminal share a common key by the following mechanism. First, the server device and the terminal device share each other based on the usage condition information. Generate a passkey. As described above, since the server device and the terminal device share the usage condition information, a corresponding common key is generated for each. In this case, it goes without saying that the common key can be shared between the server device and the terminal device. The present invention further updates the usage condition information in each of the server device and the terminal device so that the server device and the terminal device have the same usage condition information even after the update. This is characterized in that a shared key newly generated based on the updated usage condition information can be shared between the server device and the terminal device. Update of usage condition information is performed as follows. The server device encrypts the content execution information, which is information relating to the execution of the content executed by the terminal device, using the common key generated by itself, and transmits the encrypted content execution information to the terminal device. Further, the server device updates its own use condition information based on the content execution information. The terminal device receives the encrypted content execution information transmitted from the server device, decrypts the content execution information with the common key generated based on the usage condition information (before updating) as described above, and executes the content execution information. Get. Then, the terminal device updates its own use condition information based on the decrypted content execution information. Since the server device and the terminal device update their own usage condition information based on the same content execution information, the updated usage condition information is also the same. Therefore, even when the server device and the terminal device newly generate a common key based on the updated usage condition information, respectively, the generated common key corresponds to the server device and the terminal device, and the shared key is generated between the two devices. Can share a common key. BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a diagram illustrating an example of the concept of the embodiment.

FIG. 2 is a diagram illustrating an example of the configuration of the embodiment.

Figure 3 shows an example of updating the usage condition information based on the content execution information. It is a figure showing an example of an example.

FIG. 4 is a diagram illustrating an example of a processing flow according to the embodiment.

FIG. 5 is a diagram illustrating an example of the configuration of the embodiment.

FIG. 6 is a diagram illustrating an example of content execution information used in the embodiment. BEST MODE FOR CARRYING OUT THE INVENTION

An embodiment of the present invention will be described with reference to FIGS.

(Concept)

FIG. 1 is a diagram showing an example of the concept of the present invention. An example of the concept of the present invention will be described with reference to FIG.

The present invention relates to a key (common key) used for encrypting and decrypting the content execution information and the like in a system including a server device that transmits the content and the content execution information and a terminal device that receives the content and the content execution information. ) Is shared between the server device and the terminal device.

As shown in Fig. A, the server device and the terminal device shared usage condition information A. The usage condition information is information relating to one or more of the number of usages, the usage expiration date, the usage period, and the content ID in which the terminal device is allowed to execute the content. The content could not be executed only with this usage condition information, and content execution information regarding the execution of the content was required for each individual content. Therefore, the terminal device requested the super device to deliver the content execution information A. The server generates a common key A of the common key system based on the usage condition information A shared with the terminal, and transmits the encrypted content execution information A obtained by encrypting the content execution information A to the terminal. . The terminal device received the encrypted content execution information A and generated a common key A based on the usage condition information A shared with the server device. Server as described above Since the device also generated the common key A based on the same usage condition information A, the server device and the terminal device could share the common key A. Then, the terminal device decrypts the encrypted content execution information A with the common key A.

Then, as shown in FIG. B, the server device updates its own use condition information A to use condition information B based on the content execution information A that has been encrypted. In other words, the usage condition information A was managed based on the content execution information A. The terminal device also updates its own use condition information A to use condition information B based on the decrypted content execution information A. In other words, the usage condition information A was managed based on the content execution information A in the same manner as the server device.

Then, as shown in Fig. C, in the same procedure as described above, the terminal device requested the server device to deliver the content execution information B relating to the execution of another content. The server device encrypted the content execution information B with the common key B generated based on the updated usage condition information B and transmitted it to the terminal device. The terminal device also generated a common key B based on the updated usage condition information B. As described above, since both the server device and the terminal device generated the common key B based on the usage condition information B, the server device and the terminal device could share the common key B. At this time, the common key B or the generated information of the common key B was not transmitted and received between the server device and the terminal device.

(Constitution)

FIG. 2 is a diagram illustrating an example of a functional block according to the present embodiment. An example of the configuration of the present embodiment will be described with reference to FIG.

The present embodiment is an information management system including a server device 0200 and a terminal device 0210. '

(Server device)

“Server device 0 2 0 0” is a server device side use condition information management unit 0 2 0 1, a server-side common key generation unit 202, an encryption unit 202, and a transmission unit 204.

The “server device usage condition information management unit 0 201” associates the terminal device 0 210 with the number of times of use of content, the usage period, the usage period, Use condition information, which is information about one or more of the content IDs, is managed based on the content rate information, which is information about the execution of content. “Managing usage condition information based on content execution information” means that the present embodiment mainly updates usage condition information based on content execution information. For example, as shown in the figure, the use condition information A is updated to the use condition information B based on the content execution information.

As described above, the “usage condition information” is information relating to any one or more of the number of times of use, the expiration date, the usage period, and the content ID permitted for the terminal device 0210. The use condition information indicates a range in which the content execution is permitted in the terminal device 0 210, but the content cannot be executed only by the terminal device 0 210 having this use condition information. In order to execute content, content execution information is required. The usage condition information may be, for example, information indicating that the number of times the content is allowed to be used by the terminal device 210 is 10 times. Further, the usage condition information may be, for example, information obtained by converting the number of times of use and the like into points. For example, if the content requires 10 points for one use, and if the usage condition information is converted to 100 points, the content is used 10 times. It becomes. This usage condition information has the same contents in the server-side usage condition information management unit 0201 and the terminal device-side usage condition information management unit 0221 of the terminal device 210 described later. Prerequisite, that is, sharing. First, share the usage condition information. There is no particular limitation on the method for having it. For example, the same usage condition information may be input to the server device 0210 and the terminal device 0200 without passing through the communication network, or the communication network may be connected from one to the other. May be transmitted via the Internet. After the use condition information is first shared between the server device 0200 and the terminal device 0210, the use condition information is updated on each device based on the same content execution information. Be managed. Therefore, the updated usage condition information is not transmitted / received between the server device 0200 and the terminal device 0210, and the server device-side usage condition information management unit 0201 and the terminal device 201 are not transmitted / received. It is shared by the device side use condition information management unit 0 2 1 1. In other words, it can be said that the usage condition information is synchronized without using communication. The use condition information is also used for generating a common key, as described later.

“Content execution information” is information relating to the execution of content executed by the terminal device. As described above, content execution information is required to execute content on a terminal device. The terminal device can execute the content based on the content execution information within the “permitted range of content execution” indicated by the usage condition information. Specifically, the content execution information may include a content ID of a specific content, an execution file of the content associated with the content ID, and the like. The content ID may be managed in a server device and a terminal device to be described later by a table configured to be associated with information on what content should be used to update the usage condition information. .

FIG. 3 is a diagram illustrating an example in which the usage condition information is similarly updated in each of the server device and the terminal device based on the content execution information. In this example, the usage condition information is converted into a point, and the content execution information includes a content ID associated with a point required to execute the content. Figure A is included in the content execution information. This is an example of a table configured by associating a content ID to be executed with a point required for executing the content specified by the content ID. As shown in FIG. A, the content ID “001” of the movie A is managed in association with the point “3 points” required for executing the content of the movie A. In addition, the content ID “002” of document B is managed in association with a point “2 points” required for executing the content of the document. Also, the content ID “003” of the content of the sport C is managed in association with the point “1 point” required for executing the content of the sport C. In this case, based on the content ID included in the content execution information, a point required for executing the content in the server device and a terminal device described later is specified.

Figure B shows that the usage condition information “100 points” first shared by the server device and the terminal device is necessary for the execution of specific content because they are registered in the server device and the terminal device. An example is shown in which the same update is performed based on the number of points. As described above, the content execution information includes the content ID. Therefore, if the server device and the terminal device acquire the same content execution information, etc., the same "point required for content execution" can be specified in both devices based on the table shown in Fig. A. Can be done. Then, based on the specified “points required for executing the content”, the server device and the terminal device can update the usage condition information points and can share the updated usage condition information points. For example, based on the content execution information including the content ID “001” of movie A, three points are required to execute the content of movie A, and the server device and the terminal The point of the usage condition information of the device is updated from the first shared point of 100 to 97 points (update point A;). Furthermore, based on the content execution information including the content ID “002” of documentary B. In this case, the number of bytes required to execute the contents of the document is 2 points, and the usage condition information of the super-unit and the terminal device is from the updated 97 points mentioned above. The content is updated to 95 points (updated point B) _{t In addition} , if the content execution information including the content ID “003” of sports C is included, the sports content is executed. The required point is one point, and the usage condition information of the server device and the terminal device is updated from 95 points after the above-mentioned update to 94 points (update) Point C).

The “server device-side common key generation unit 0202” generates a common key based on the use condition information. For example, as shown in the figure, a common key is generated based on the usage condition information A managed by the server-side usage condition information management unit 0201. After the usage rule information A is updated to the usage rule information B in the server side usage rule information management unit 0201, a common key is generated based on the updated usage rule information B. In this case, the common key generated based on usage condition information A is different from the common key generated based on usage condition information B. In other words, if the usage condition information is different, the generated common key is also different. Specifically, the generation of the common key based on the usage condition information can be realized by calculating using a function with a numerical value or the like indicated by the usage condition information as an initial value. That is, the calculation result is used as a common key. This common key is a key for encrypting and decrypting information in the common key cryptography. As described above, in the public key scheme, the public key used for information encryption must be transmitted and received between the information transmitting side and the information receiving side. Therefore, the public key is used as a key to secure the secret for decryption. The key may be compromised. On the other hand, in the present invention, the common key is generated based on the use condition information shared by the server device and the terminal device described later and updated with the same content. Therefore, the common key can be transferred between the server and the terminal. The common key can be shared without transmitting and receiving to and from the device, and there is no risk of unauthorized decryption unlike the public key method. Further, the invention of the present application uses the usage condition information originally used for allowing the execution of the content also for generating the common key, so that the information necessary only for generating the common key is transmitted to the server device and the terminal. There is no need to send and receive between devices. That is, the amount of information transmitted and received between the server device and the terminal device can be reduced. Note that “the server device and the terminal device share a common key” does not only mean that the server device and the terminal device hold the same common key when they are the same. In the present invention, “a server device and a terminal device share a common key” means that information encrypted by one device is replaced by a key corresponding to the key used for encryption by the other device. In decryption

• Includes cases where it can be cut.

As described above, the server device side use condition information management unit 0201 and the terminal device side use condition information management unit 0221 share the use condition information first. Accordingly, the common key generated by the server-side common key generation unit 0 202 based on the use condition information and the terminal-side common key generation unit 0 2 12 of the terminal device 0 210 described later correspond to each other. I do. In other words, the server device 0200 and the terminal device 0210 can share a common key. Further, as described above, the usage condition information is updated and managed based on the content execution information. Then, as described above, the updated usage condition information is also used by the server-side usage condition information management unit 0 201 of the server device 200 and the terminal-side usage condition information of the terminal device 210. Shared by the management unit 0 2 1 1. Therefore, the common key generated by the server-side common key generation unit 0 202 and the terminal-device-side common key generation unit 0 212 based on the updated usage condition information correspond to each other. That is, the server device 0200 and the terminal device 0210 can also share a common key generated based on the updated usage condition information. At this time, a common key generated based on the pre-update usage condition information and a post-update None of the generated common keys are transmitted and received between the server device 0200 and the terminal device 0210.

The “encryption unit 0203” encrypts the content execution information using the common key generated by the common key generation unit 0202. The content execution information to be encrypted by the encryption unit 0 203 is specified based on a content execution information distribution request, which is a request for distribution of the content execution information transmitted from the terminal device, as described later. It can be acquired.

As described above, according to the present invention, a common key can be shared without transmitting and receiving between the server device 0200 and the terminal device 0210, so that information can be shared using the common key. It can be safely shared. The information to be securely shared may be “other common key” or the “information for generating another common key”. The advantage of using a common key that can be shared without transmitting / receiving between the server device 0200 and the terminal device 0210 and further encrypting other common keys, etc. It is as follows.

A problem arises when the encrypted content can be decrypted only with a common key that can be shared only between the server device 0200 and the specific terminal device 0210. The problem is that the server device 200 needs to encrypt and transmit the content to each of the terminal devices using a specific common key. When the number of terminal devices reaches tens of thousands or hundreds of thousands, the burden becomes a serious problem.

On the other hand, if a server device and a plurality of terminal devices can share a key (another common key), the content encrypted with the key (another common key) can be transmitted and received between the terminal devices. it can. In this case, the load on the server device 200 is reduced.

Therefore, the “other common key” that is common between the server device 0200 and the plurality of terminal devices 0210 is referred to as the server device 0200 and the terminal device 0210. The advantage is that it can be safely shared between

As in the prior art of Patent Document 1, when transmitting and receiving a common key after encrypting it with a public key, the public key must be transmitted from the information receiving side to the transmitting side in advance. Therefore, there is a risk that the public key serves as a clue and the secret key is illegally decrypted and obtained. On the other hand, a common key, such as a common key in the information management system of the present invention, which can be shared without transmitting and receiving between the server device and the terminal device, does not have the risk of unauthorized decryption as in the prior art. Therefore, in the information management system of the present invention, if a common key that can be shared without being transmitted and received between the server device and the terminal device is used, the other common key or the generation information of the other common key is illegal. Acquisition can be made more difficult.

The “transmission unit 0 204” transmits the encrypted content execution information encrypted by the encryption unit 0 203.

(Terminal device)

`` Terminal device 0 2 1 0 '' is composed of a receiving unit 0 2 13, a terminal device side usage condition information management unit 0 2 1 1, a terminal device side common key generation unit 0 2 1 2, and a decryption unit 0 2 1 4. Having.

The “receiving unit 0 2 1 3” receives the encrypted content execution information. The “terminal-side use condition information management unit 0 2 1 1” manages the use condition information based on the content execution information. The content execution information is obtained by using a common key generated by a terminal-side common key generation unit 0 2 12 described later. The encrypted content execution information received by the reception unit 0 2 13 is decrypted by a decoding process described later. Are decrypted by the converting unit 0 2 1 4. In addition, the use condition information has the same content in the server device use condition information management unit 0201 and the terminal device use condition management unit 0221, that is, it is shared. Is assumed. Further, as described above, the method for sharing the usage condition information first does not matter. Thus, the same usage condition information as the server device Since the usage condition information updated based on the same content execution information is managed on the basis of the above, the transmission and reception of the updated usage condition information is not performed directly between the server device and the terminal device. Can be shared at

The “terminal device side common key generation unit 0 2 1 2” generates a common key based on the usage condition information managed by the terminal device side usage condition information management unit 0 2 1 1. For example, as shown in the figure, the common key is generated based on the use condition information A managed by the terminal device side use condition information management unit 0 211. After the usage condition information A is updated to the usage condition information B based on the content execution information by the terminal device side usage condition information management unit 0 2 1 1, a common key is generated based on the usage condition information B. I do. In this case, the common key generated based on the use condition information A is different from the common key generated based on the use condition information B. That is, if the use condition information is different, the generated common key is also different Then, as described above, the usage condition information managed by the terminal device side usage condition information management unit is shared between the server device 0200 and the terminal device 0210. The common key generated by the common key generation unit 0 2 1 2 corresponds to the common key generated by the server-side common key generation unit 0 2 0 2, and the server device 0 2 0 0 and the terminal The devices 0 210 can share a common key.

The “decryption unit 0 2 1 4” uses the common key generated by the terminal-side common key generation unit 0 2 12 to encrypt the encrypted content execution information received by the reception unit 0 2 13. Decrypt and obtain content execution information. As described above, the content execution information is information related to content execution, and may include a content ID, a content execution file associated with the content ID, and the like. Therefore, by decoding the content execution information, the terminal device can execute the content specified by the content ID. Further, as described above, the content execution information includes a common key other than the common key generated based on the use condition information or generation information (key generation information) of the other common key. In some cases, the content is encrypted with the other common key. In this case, the encrypted content execution information is decrypted with the common key generated by the terminal-side common key generation unit 0 2 12 to obtain the other common key and the like, and the encrypted content execution information is encrypted with the other common key. The content can be decrypted (see Fig. 6).

(Processing flow)

FIG. 4 is a diagram showing an example of the processing flow of the present embodiment. An example of the processing flow of the present embodiment will be described with reference to FIG. The processing shown in the figure can be executed by a program to be executed by a computer (terminal device or the like), and this program must be recorded on a recording medium readable by the computer (terminal device). Can be.

Usage condition information, which is information relating to one or more of the number of times the content is used, the expiration date, the usage period, and the content ID, which are allowed in the terminal device in association with the terminal device. A common key is generated based on the managed key (server device-side common key generation step S0401). The content execution information is encrypted by using the common key generated in step 0401 (content execution information encryption step S0402). Further, the encrypted content execution information encrypted in step 0402 is transmitted to the terminal device (encrypted content execution information transmission step S0403). Further, the use condition information managed by the server device is managed based on the content execution information that has been encrypted in step 0401 (use condition information management step S04). 0 4). Further, it receives the encrypted content execution information transmitted in step 0403 (encrypted content execution information receiving step S0405). So Next, a common key is generated based on the usage condition information managed by the terminal device (terminal device side common key generation step S0406). Further, the encrypted content execution information received in step 0405 is decrypted using the common key generated in step 0406 to obtain content execution information (content execution information decryption). Conversion step S 0 4 0 7). Finally, the use condition information managed by the terminal device is managed based on the content execution information obtained by decoding in the step S 407 (the terminal device side use condition information management step S 0 4 0 8).

As described above, the content execution information to be encrypted by the encryption unit 0203 is specified based on the content execution information distribution request that is a request for distribution of the content execution information transmitted from the terminal device. Can be. For example, as shown in FIG. 5, a content execution information delivery request receiving unit 0505 is further provided in the server device 0500, and the content execution information delivery unit is provided in the terminal device 0510. A request input section 0 5 15 and a content execution information distribution request transmission section 0 5 16 are further provided. The content execution information distribution request input unit 0 5 15 transmits the content execution information distribution request input from the content execution information distribution request transmission unit 0 5 16, and the content execution information distribution request reception unit Receive with 0 5 0 5. As described above, the server device 0500 receives the content execution information distribution request transmitted from the terminal device 0510, and identifies the content execution information based on the content execution information distribution request. can do. Industrial applicability

As described above, by using the present invention, a common key (or key generation information) is not transmitted and received between the server device and the terminal device, and the common key is exchanged between the two devices. And easily share a common key shared between both devices. You can change it.

Also, even if the encrypted content execution information is illegally acquired by another terminal device that is not the original transmission destination, the other terminal device cannot generate a common key. This is because, in order to generate a common key, it is necessary to obtain usage condition information possessed by the terminal device that should originally receive the encrypted content execution information.

In this regard, there is a possibility that the usage condition information is illegally acquired depending on the method of sharing the usage condition information between the terminal device and the server device first. However, as described above, the usage condition information is first shared by the server device and the terminal device, and then updated by each device based on the content execution information. Then, the updated usage condition information is not transmitted and received between the server device and the terminal device.

Therefore, after the use condition information is updated, the updated use condition information is directly obtained from the terminal device illegally, or the first use condition information and all the content execution information used for the update are illegally obtained. Otherwise, the secret key cannot be obtained fraudulently. In the latter case, it is hard to imagine it because a person trying to use the common key illegally must constantly monitor the transmission and reception of information between a specific terminal device and a server device. Therefore, if the present invention is used, the common key can be safely shared between the server device and the terminal device.

In addition, if a common key that can be safely shared between the server device and the terminal device is used as in the present invention, illegal acquisition of another common key or generation information of the common key can be compared with the conventional technology. It can be more difficult to send and receive data between the server device and the terminal device. It is generally said that the public key system shown in the above-mentioned prior art has high security. However, the public key for encryption transmitted and received between the information sending side and the receiving side uses the private key for decryption. May provide clues to decryption and may not provide sufficient security.

Since the invention of the present application originally uses the usage condition information used for executing the content to generate the common key, information necessary only for generating the common key is transmitted between the server device and the terminal device. There is no transmission or reception.

Claims

The scope of the claims

1. In association with the terminal device, execute the usage condition information, which is information on one or more of the number of usages of the content allowed, the usage period, the usage period, and the content ID, to the terminal device. A server device usage condition information management unit that manages based on content execution information that is information related to the execution of the content to be executed;

A server-side common key generation unit that generates a common key based on the usage condition information managed by the server-side usage condition information management unit;

An encryption unit that encrypts the content execution information using a common key generated by the common key generation unit;

A transmission unit for transmitting the encrypted content execution information encrypted by the encryption unit to the terminal device;

A server device having

A receiving unit that receives the encrypted content execution information,

A terminal device side use condition information management unit that manages the use condition information based on the content execution information,

A terminal-side common key generation unit that generates a common key based on the usage condition information managed by the terminal device-side usage condition information management unit;

A decryption unit that decrypts the encrypted content execution information received by the receiving unit by using the common key generated by the terminal-side common key generation unit and acquires the content execution information;

A terminal device having

An information management system comprising

The use condition information of the server-side use condition information management unit and the use condition information of the terminal device-side use condition information management unit are synchronized without communication. Information management system.

2. The server device further comprises:

A content execution information distribution request receiving unit that receives a content execution information distribution request that is the content execution information distribution request;

The terminal device further comprises:

A content execution information distribution request input unit for inputting the content execution information distribution request;

2. The information management system according to claim 1, comprising: a content execution information distribution request transmitting unit that transmits the content execution information distribution request.

3. The content is encrypted with an encryption key,

The content execution information includes key generation information that is information for generating a decryption key for decrypting the encryption key in the terminal device.

3. The content execution device according to claim 1 or 2.

4. The server device according to claim 1.

5. The terminal device according to claim 1.

6. An information management method in an information management system including a server device and a terminal device,

Usage condition information, which is information relating to any one or more of the number of times of use of content, the expiration date, the usage period, and the content ID, which are allowed for the terminal device in association with the terminal device, A server-side common key generation step for generating a common key based on what is managed by the device; and

A content execution information encryption step of encrypting the content execution information using a common key generated in the server-side common key generation step;

The encrypted content encrypted in the content execution information encryption step. Transmitting encrypted content execution information to the terminal device,

Based on the Konten' the content execution information as a target of encryption in execution information encrypting step, and the usage condition information management step of managing the usage condition information managed by the server device _Λ

An encrypted content execution information receiving step of receiving the encrypted content execution information transmitted in the encrypted content execution information transmitting step; and a use condition information managed by a terminal device. A terminal-side common key generation step of generating a common key based on the

Using the common key generated in the terminal-side common key generation step, decrypting the encrypted content execution information received in the encrypted content execution information receiving step to obtain content execution information Execution information decoding step;

A terminal device side use condition information management step of managing the use condition information managed by the terminal device based on the content execution information decoded and acquired in the content execution information decoding step; ,

Information management method.