JP2006129063A - Contents reproducing method, reproduction program and reproducing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for switching channels at a high speed at the time of performing online contents distribution. <P>SOLUTION: A contents reproduction program is used to execute the step of receiving a reproduction start request by a user and transmitting to an authentication application user authentication and a confirmation request for a viewing consent condition. Further, the contents reproduction program is used to execute the step of reading a decryption key stored beforehand in a cache of its own node and starting to reproduce encrypted contents without waiting for the arrival of a response message from the authentication application. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method for decrypting and reproducing encrypted content distributed from a content providing system to a viewing terminal (node) via a network.

  Conventionally, a VOD (Video On Demand) system that provides video content such as a movie in response to a user's request has been provided. In recent years, the above video content has been distributed via a network in order to apply higher resolution digital data. Development of a VOD system for distribution is being actively carried out.

  In a VOD system on a network, video content encryption is required as an essential condition in order to prevent illegal copying of content data. Conventionally, many proposals have been made regarding an encrypted distribution system in which a content provider encrypts and distributes content in response to a user request (for example, Patent Documents 1 and 2).

In addition, the VOD system is required to be able to flexibly specify permission conditions such as a viewing period and the number of times of viewing. There are two methods for controlling the license conditions: a method managed on the server side and a method managed on the client side.
JP 2002-261743 A JP 2003-8563 A

  However, the conventional encrypted distribution system has several problems.

  In the case where the permission conditions for content are controlled on the server side, the same conditions can be managed flexibly and strictly, but access to the server occurs each time content data is played back. There is a problem that a delay occurs in time. In particular, in the case of a broadcast-type service in which an arbitrary channel is selected from a plurality of broadcasting channels (programs) and the program is viewed from the middle, such as terrestrial television broadcasting that is widely spread now, The delay in the response time until the start of reproduction causes a reduction in service, such as stressing the user.

  On the other hand, in the case where the license condition is controlled on the client side, although the delay until playback is minimized, the viewing period expires by hacking the license condition itself, for example, by rewinding the calendar or timer of the client device. However, there are problems such as performing reproduction and enabling a reproduction operation more than the reproducible number of times by backing up the license condition management data file.

  SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a method capable of safely and reliably managing access conditions and switching a plurality of channels at a high speed in order to solve the above-described problems of the prior art.

  A first aspect of the present invention is a content reproduction program for decrypting and reproducing encrypted content streamed from a content providing system via a network, and viewing desired encrypted content from the content providing system in advance on a computer A license storage step of storing the license to be stored in a cache file of the own node together with a decryption key necessary for decrypting the encrypted content and an identifier unique to the encrypted content, and when the reproduction request for the encrypted content is generated, At the same time as requesting acquisition of permission conditions from the content providing system, a decryption key acquiring step for acquiring a decryption key of the encrypted content from the cache file, and before receiving a permission response from the content providing system, the decryption key is used. Encryption And decoding and reproducing initiating a decoding and reproduction of the content, to the content playback program to be run.

  That is, in the first invention, the license storage means acquires a license of the content to be viewed in advance from the content providing system, and stores it as a license file in the cache of its own node together with the identifier unique to the encrypted content and its decryption key, When the decryption key acquisition unit sends a request for permission to distribute the encrypted content when a request for reproducing the encrypted content is generated, the decryption key acquisition unit supports the identifier of the encrypted content stored in advance from the cache file of the local node. The decryption / playback unit is configured to start decryption / playback of the encrypted content before receiving a permission response from the content providing system using the decryption key. On the other hand, it takes authentication until delivery of the desired content is started. Between it can be omitted, and come out the effect of eliminating the frustrating due to the delay of the Licensed response time of the order to watch.

  According to a second aspect of the present invention, in the decryption and playback step, the permission condition of the encrypted content that has started playback is acquired from the content providing system, and when the permission condition is not playable, the encrypted content is played back. The content reproduction program according to the first aspect of the invention is characterized by including a step of stopping.

  That is, according to the second invention, a license response is received from the content providing system for the encrypted content that has been decrypted and reproduced based on the license information in the cache file of the own node (client) that has been acquired and stored in advance. By providing a mechanism to stop playback of the encrypted content when the license condition is not playable when the license is received, for example, to prevent unauthorized use due to overuse, expiration, etc. Can do.

  In a third aspect of the invention, the decryption / reproduction step includes a step of erasing a decryption key necessary for decrypting the encrypted content from the cache file when the permission condition acquired from the content providing system is not reproducible. The present invention relates to the content reproduction program according to the first or second invention.

  That is, according to the third aspect of the invention, a license response is received from the content providing system for the encrypted content that has been decrypted and reproduced based on the license information in the cache file of the own node (client) that has been acquired and stored in advance. When the license condition is not reproducible at the stage of receiving the decryption key, the decryption key cannot be used by deleting the decryption key necessary for decrypting the encrypted content from the cache file of the local node. The reproduction of the content that has already been started to be reproduced is immediately interrupted, and unauthorized use due to an excess of the number of usable times or an expiration can be prevented.

  According to a fourth aspect of the present invention, in the decryption / playback step, when the permission condition acquired from the content providing system is not playable, a viewing contract update is performed to acquire a new permission condition necessary for playback of the encrypted content that has been stopped playing. The content reproduction program according to any one of the first to third inventions, further comprising a step of displaying the menu screen of the first node on the display of the own node.

  That is, according to the fourth invention, regarding the encrypted content whose reproduction has been stopped, since the menu screen for viewing contract update is presented on the display of the own node after the stop, the user is permitted to resume the content reproduction. The conditions can be acquired, the number of times that the service can be used and the expiration can be recovered, and the convenience of continuous use is given to the user who has forgotten these restrictions.

  According to the present invention, the license storage means acquires the license of the content to be viewed in advance from the content providing system, stores it in the cache of its own node as a license file together with the identifier unique to the encrypted content and the decryption key thereof, The acquisition unit transmits a request for permission to distribute the encrypted content, and at the same time acquires a decryption key corresponding to the identifier of the encrypted content stored in advance from the cache file of the own node. Before receiving a permission response from the content providing system using the key, the decryption reproduction of the encrypted content is started, so that the distribution of the desired content to the user is started. The time required for authentication can be saved, and access for viewing The effect of eliminating the frustrating due to the delay of between comes out.

  In addition, for the encrypted content that has been decrypted and played back based on the license information in the cache file of its own node that has been acquired and saved in advance, the license condition is played back when the license response is received from the content providing system. By providing a mechanism for stopping reproduction of the encrypted content when it is not possible, for example, unauthorized use due to exceeding the number of usable times or expiring can be prevented.

  In addition, for the encrypted content that has been decrypted and played back based on the license information in the cache file of its own node that has been acquired and saved in advance, the license condition is played back when the license response is received from the content providing system. If it is not possible, the decryption key required for decrypting the encrypted content is deleted from the cache file of its own node, so the decryption key cannot be used, and playback of the content that has already started playback is not possible. It is interrupted immediately, and unauthorized use due to exceeding the number of usable times or expiring can be prevented.

  Furthermore, for encrypted content that has been stopped from playback, the menu screen for updating the viewing contract is displayed on the display of the local node after the stop, so the user can acquire permission conditions for restarting content playback and can be used. Recovery for the number of times and expiration is possible, and the convenience of continuous use is given to users who have forgotten these restrictions.

  As described above, according to the content reproduction program of the present invention, when online content distribution is performed, channel switching can be performed at high speed while strictly operating viewing access conditions.

  The content reproduction system of the present invention is used in a video content distribution system such as VOD (Video on Demand) in a network environment such as the Internet or a CATV (Cable TV) network, and enables high-speed channel switching. .

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 shows a basic configuration of a content reproduction system according to an embodiment of the present invention. This content reproduction system includes a content providing system 2 that distributes content such as broadcast programs and videos via a network 6 and a client 1 (node) that receives and views the content.

  The content distribution system 2 on the content distribution side stores information necessary for the user to view the content, such as the contract content ID (Identity: identifier), permission conditions (reproduction deadline, number of times, etc.) and encryption key. A license server 3 having a license file 300 and a license application 30 in which a license application 30 for distributing a license to the client 1 in response to a user's request and registration of a newly created license, a user ID (Identity), a password, a license condition, etc. An authentication server 4 including an authentication DB (database) 400 in which user personal information and contract information are registered, an authentication application 40 in which user personal information and contract information are registered and authenticated, and encrypted content Stored encrypted content DB 500 For example, the creation of the encrypted content, registration, and a distributing performs content application 50 is built-in content server 5 which encrypted content according to a user request from the client 1.

  On the other hand, in order to view the content contracted with the content providing side, the client 1 (node) used by the user acquires the license acquired by the user from the license server 3 in advance and stores the license cache file 100 in the cache memory of the own node. The license storage means 11 for downloading and saving as, the personal information user authentication means 12 for inquiring permission conditions for reproducing the distributed encrypted content, and the encrypted content from the license cache file 100 previously stored in its own node A content reproduction program 10 comprising a decryption key acquisition means 13 for extracting a decryption key to be decrypted and a decryption reproduction means 14 is incorporated.

  Here, as the client 1 (node) used by the user who views the content, for example, a personal computer, a set top box, a mobile phone, a PDA (Personal Digital Assistance: personal portable information terminal), or the like can be considered.

  Note that the client 1, the license server 3, the authentication server 4, and the content server 5 that are nodes connected to each other in the network 6 have a content reproduction program 10, a license application 30, an authentication application 40, and a content application 50, respectively. Each function is realized by executing a program built in advance on the computer.

  These programs and applications are recorded on a computer-readable recording medium such as a flexible disk, a compact disk, and a ROM (Read Only Memory), and are not particularly shown in the figure, but are built-in or externally connected. It may be in an executable state by being set in a medium reading device and installed.

  The operation of each program and application will be described below.

  When a viewing request is made by the user, the content reproduction program 10 transmits a user authentication and permission condition acquisition request to the authentication application 40 via the network 6. Upon receiving the user authentication and permission condition acquisition request, the authentication application 40 accesses the authentication database 400, confirms whether the received authentication request is valid, and transmits the permission condition to the content reproduction program 10.

  On the other hand, the content reproduction program 10 acquires the decryption key corresponding to the encrypted content requested for viewing from the license cache file 100 without waiting for the permission condition to be transmitted from the authentication application 40, and further, the network. 6, the content application 50 is requested to distribute encrypted content. In response to this, the content application 50 retrieves the encrypted content from the encrypted content DB 500 and distributes it to the content reproduction program 10.

  Then, the content reproduction program 10 uses the decryption key acquired from the license cache file 100 to start decryption and reproduction of the distributed encrypted content. If the permission condition received from the authentication application 40 is “unplayable” after the start of playback, the decryption playback of the encrypted content is stopped and playback stored in the license cache file 100 is performed. 2 is deleted, and a viewing contract screen 111 as shown in FIG. 2 is displayed to prompt the viewing user to input contract renewal. The user updates the contract on the viewing contract screen 111.

  FIG. 2 is a configuration diagram showing the relationship between the viewing contract screen and the license file in the viewer terminal according to the embodiment of the present invention. In the content reproduction program 10, the viewing contract screen 111 is displayed on the display 110 of the client 1 before starting the viewing service or when the viewing contract is to be updated, and setting of whether or not the program (channel) that the user wants to subscribe to can be viewed. I do. For example, in the viewing contract screen 111, the user selects “view” or “not view” for each program (channel 1, 2, etc.).

  When the program that the user wants to subscribe to is confirmed on the viewing contract screen 111, the content reproduction program 10 requests the license application 30 for a license corresponding to the encrypted content of the program that the user wants to subscribe to. The license application 30 extracts a license corresponding to the requested encrypted content from the license file 300 and transmits it to the content reproduction program 10. The content reproduction program 10 downloads the received license to the license cache file 100.

  Here, the configuration of the database of each server in the content providing system 2 referred to with the content reproduction program 10 of the client 1 will be described below with reference to FIGS.

  FIG. 3 shows a data configuration example of a license file according to the embodiment of the present invention. The license file 300 includes a plurality of records including items of “encrypted content ID”, “transaction ID”, “permission condition (number of times, time limit)”, and “encryption key”.

  The “encrypted content ID” is an identifier unique to the encrypted content, and the “transaction ID” is an identifier unique to the transaction (viewing contract transaction) at the time of issuing the license. Furthermore, as the “permission condition”, in this embodiment, the “number of times” at which the content can be reproduced and the “time limit for reproduction” are exemplified, but in addition, the number of times the content can be moved between clients, the content A content protection level that prescribes a level for protecting the content, a reproducible size that prescribes from the beginning of the encrypted content to a designated location, etc.

  In the record of the embodiment, “encrypted content ID” C12345 is related to “transaction ID” 001, “usable condition” is “use number of times” is 3 times, and “use time limit” is December 1, 2004. It is shown that the “encryption key” xyz123 is assigned under the above.

  FIG. 4 shows a data configuration example of the authentication database according to the embodiment of the present invention. The authentication DB 400 includes a plurality of records including items of “user name”, “user ID”, “password”, and “permission conditions (encrypted content ID, number of times, time limit, playability)”. The “user name”, “user ID”, and “password” are unique information that identifies the registered user. The “encrypted content ID”, “number of times”, and “expiration date” in the “permission condition” are the same as those in the license file 300. The “reproducibility” is an item determined based on the reproducible “number of times” and the usage “expiration date”, and is expressed as “possible” or “impossible”.

  In the first record of the embodiment, as the “permission condition” of the user A, regarding “content ID” C12345, the “number of times” is three times and the “expiration date” is limited to “reproduction availability” on December 1, 2004. Indicates that it is judged possible.

  Further, when a license acquisition request is made, the encrypted content ID and permission conditions of the corresponding license are registered in the authentication DB. If there is an authentication request and playback is possible, the permission conditions are updated (for example, if the limit on the number of playbacks is 3 times, it is reduced to 2 times). As a result of updating the permission condition, when the number of times of reproduction becomes zero, the reproduction permission is changed to the reproduction impossible (this is used at the time of the next authentication request).

  FIG. 5 shows a data configuration example of the encrypted content database according to the embodiment of the present invention. The encrypted content DB 500 includes a plurality of records including items of “encrypted content ID” and “file name”. “File name” in the embodiment indicates that encrypted content corresponding to the program “channel 1” selected by the user is stored in the viewing contract screen 111 of the client 1 in FIG.

  For example, each channel corresponds to a plurality of encrypted contents such as news from 7 o'clock and entertainment program from 8 o'clock.

  FIG. 6 shows a conceptual diagram of content encryption according to the embodiment of the present invention. FIG. 6 shows an example of the data structure of how the encrypted content is stored in the database. Using the encryption key in the license file 300, the plaintext content before encryption is encrypted by the content application 50 and stored in the encrypted content DB 500. The plaintext content has a structure in which a plurality of TS (Transport Stream) packets are continuous. At the time of encryption, the whole or a part of the content can be encrypted by designating the encryption rate in units of TS packets in consideration of the processing performance of the receiving terminal. The embodiment shows a case where 50% of the plaintext content is encrypted, and an example in which one TS packet is encrypted is shown.

  FIG. 7 shows the data structure of a TS packet when transmitting encrypted content according to the embodiment of the present invention. 1) shows the data structure of the TS packet, 2) shows the plaintext TS packet, and 3) shows the data structure of the encrypted TS packet. The header portion is scrambled control bits for identifying plaintext / ciphertext (for example, plaintext is represented as 00 and ciphertext is represented as 01), and the data storage portion is composed of plaintext data or encrypted data.

  Next, the processing flow of the content reproduction program 10 from the reception of the encrypted content of the present invention to the decryption reproduction will be described below with reference to FIGS.

  FIG. 8 shows an encrypted content request flow according to the embodiment of the present invention. A main thread that performs main control of the content reproduction application 10 will be described. In response to a request for reproducing encrypted content from the user, the main thread first initializes the reproducible flag in the permission condition data storage area to 0 (provisional reproduction) in step S11. Next, in step S12, a permission condition acquisition thread 1 and an encrypted content decryption playback thread 2 are generated.

  Note that a thread is a function that allows programs to be processed in parallel within the same process, and makes it possible to share resources such as memory within the same process.

  In step S12, after the thread is generated, the main thread ends the encrypted content reproduction request process, and waits for an event from the user.

  FIG. 9 shows a processing flow for obtaining the permission condition according to the embodiment of the present invention. It is a figure explaining the thread | sled 1 for permission conditions acquisition. When a thread is generated by the main thread, the permission condition acquisition thread 1 first transmits a user authentication and permission condition acquisition request to the authentication application 40 of the authentication server 4 via the network 6 in step S21. The permission condition acquisition thread 1 waits for reception until a permission condition from the authentication application 40 is transmitted.

  Next, when permission conditions are received in step S22, whether permission is permitted is determined in step S23. If the permission condition is “reproducible” in step S23, the reproducibility flag in the permission condition data storage area is set to 1 (reproducible) in step S24. If the permission condition is “unreproducible”, the reproducibility flag in the permission condition data storage area is set to 2 (reproducible) in step S25, and the permission condition acquisition thread 1 ends.

  FIG. 10 shows a decryption / reproduction flow of the encrypted content according to the embodiment of the present invention. It is a figure explaining the thread | sled 2 for encryption content decoding reproduction | regeneration. First, in step S31, the encrypted content decryption / playback thread 2 requests the content application 50 of the content server 5 to distribute encrypted content via the network 6. In step S32, a decryption key corresponding to the encrypted content to be reproduced is acquired from the license cache file 100 stored in advance in the local node. Furthermore, in step S33, the reproducible flag in the permission condition data storage area is referred to.

  Next, in step S34, the presence / absence of a reproducible flag is determined. When the content of the reproducible flag is 0 (provisional reproduction) or 1 (reproducible), the reception of encrypted content is awaited. Then, reception processing is performed in step S35, and reception of stream data for one frame is determined in step S36. When data for one screen of the encrypted content is accumulated, in step S37, the distributed encrypted content is decrypted using the decryption key acquired from the license cache file 100, and sequentially decrypted in step S38. Displayed content on the screen.

  If it is determined in step S39 that the encrypted content to be distributed is not yet terminated, the process returns to the reproducibility flag acquisition process in the permission condition data storage area, and the processing is repeated until the encrypted content terminates in step S35 and subsequent steps. repeat.

  On the other hand, if the reproducible flag is 2 (reproducible) in step S34, the decryption / reproduction of the encrypted content is stopped and the corresponding decryption key in the license cache file 100 is deleted in step S40. The viewing contract screen 111 of FIG. 2 is displayed and the process ends.

  The embodiments of the present invention described above are as shown in the following supplementary notes.

(Supplementary Note 1) A content playback program for decrypting and playing back encrypted content streamed from a content providing system via a network,
On the computer,
A license storage step of acquiring a license for viewing desired encrypted content from the content providing system in advance, and storing it in a cache file of the own node together with a decryption key necessary for decrypting the encrypted content and an identifier unique to the encrypted content When,
A decryption key obtaining step of requesting the content providing system to obtain permission conditions at the time of occurrence of a reproduction request for the encrypted content, and simultaneously obtaining a decryption key of the encrypted content from the cache file;
A decryption / reproduction step of starting decryption / reproduction of the encrypted content using the decryption key before receiving a permission response from the content providing system;
Content playback program that executes

  (Additional remark 2) The said decoding reproduction | regeneration step acquires the permission conditions of the said encrypted content which started reproduction | regeneration from the said content provision system, and when the permission conditions cannot be reproduced | regenerated, the reproduction | regeneration of the said encrypted content is stopped. The content reproduction program according to supplementary note 1, comprising a step.

  (Additional remark 3) The said decoding reproduction | regeneration step includes the step which erase | eliminates the decoding key required for the decoding of encryption content from the said cache file, when the said permission conditions acquired from the said content provision system are improper reproduction | regeneration. The content reproduction program according to supplementary note 1 or supplementary note 2, which is characterized.

  (Supplementary Note 4) In the decryption and playback step, when the permission condition acquired from the content providing system is not playable, a viewing contract update menu for acquiring a new permission condition necessary for playback of the encrypted content whose playback has been stopped The content reproduction program according to any one of supplementary notes 1 to 3, further comprising a step of displaying a screen on a display of the own node.

(Supplementary Note 5) A content reproduction method for decrypting and reproducing encrypted content streamed from a content providing system via a network,
A license storage step of acquiring a license for viewing desired encrypted content from the content providing system in advance, and storing it in a cache file of the own node together with a decryption key necessary for decrypting the encrypted content and an identifier unique to the encrypted content When,
A decryption key obtaining step of requesting the content providing system to obtain permission conditions at the time of occurrence of a reproduction request for the encrypted content, and simultaneously obtaining a decryption key of the encrypted content from the cache file;
A decryption / reproduction step of starting decryption / reproduction of the encrypted content using the decryption key before receiving a permission response from the content providing system;
A content reproduction method characterized by comprising:

(Supplementary Note 6) A content playback apparatus for decrypting and playing back encrypted content streamed from a content providing system via a network,
License storage means for acquiring a license for viewing desired encrypted content from the content providing system in advance and storing it in a cache file of the own node together with a decryption key necessary for decrypting the encrypted content and an identifier unique to the encrypted content When,
A decryption key acquisition means for requesting the content providing system to acquire a permission condition at the same time when the reproduction request for the encrypted content occurs, and for acquiring a decryption key of the encrypted content from the cache file;
Decryption and reproduction means for starting decryption and reproduction of encrypted content using the decryption key before receiving a permission response from the content providing system;
A content playback apparatus comprising:

It is a figure which shows the basic composition of the content reproduction system which becomes embodiment of this invention. It is a block diagram showing the relationship between the viewing contract screen and the license file in the viewer terminal according to the embodiment of the present invention. It is a figure which shows the data structural example of the license file which becomes embodiment of this invention. It is a figure which shows the example of a data structure of the authentication database which becomes embodiment of this invention. It is a figure which shows the example of a data structure of the encryption content database which becomes embodiment of this invention. It is a conceptual diagram of the content encryption which becomes embodiment of this invention. It is a figure which shows the data structure of TS packet at the time of transmitting the encrypted content which becomes embodiment of this invention. It is a figure which shows the request | requirement flow of the encryption content which becomes embodiment of this invention. It is a figure which shows the processing flow which acquires the permission conditions used as embodiment of this invention. It is a figure which shows the decoding reproduction | regeneration flow of the encryption content which becomes embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Client 2 Content provision system 3 License server 4 Authentication server 5 Content server 6 Network 10 Content reproduction program 11 License storage means 12 User authentication means 13 Decryption key acquisition means 14 Decryption reproduction means 30 License application 40 Authentication application 50 Content application 100 License cache File 300 License file 400 Authentication DB (database)
500 Encrypted content DB (database)

Claims (5)

A content playback program that decrypts and plays back encrypted content streamed from a content providing system via a network,
On the computer,
A license storage step of acquiring a license for viewing desired encrypted content from the content providing system in advance, and storing it in a cache file of the own node together with a decryption key necessary for decrypting the encrypted content and an identifier unique to the encrypted content When,
A decryption key obtaining step of requesting the content providing system to obtain permission conditions at the time of occurrence of a reproduction request for the encrypted content, and simultaneously obtaining a decryption key of the encrypted content from the cache file;
A decryption / reproduction step of starting decryption / reproduction of the encrypted content using the decryption key before receiving a permission response from the content providing system;
Content playback program that executes   The decryption and playback step includes a step of acquiring permission conditions for the encrypted content that has started playback from the content providing system, and stopping the playback of the encrypted content when the permission conditions are not playable. The content reproduction program according to claim 1.   The decrypting / reproducing step includes a step of erasing a decryption key necessary for decrypting the encrypted content from the cache file when the permission condition acquired from the content providing system is not reproducible. The content reproduction program according to claim 1 or 2.   The decryption and playback step displays a menu screen for updating a viewing contract for acquiring new permission conditions necessary for playback of the encrypted content whose playback has been stopped when the permission conditions acquired from the content providing system are not playable. The content reproduction program according to claim 1, further comprising a step of displaying on the display. A content playback method for decrypting and playing back encrypted content streamed from a content providing system via a network,
A license storage step of acquiring a license for viewing desired encrypted content from the content providing system in advance, and storing it in a cache file of the own node together with a decryption key necessary for decrypting the encrypted content and an identifier unique to the encrypted content When,
A decryption key obtaining step of requesting the content providing system to obtain permission conditions at the time of occurrence of a reproduction request for the encrypted content, and simultaneously obtaining a decryption key of the encrypted content from the cache file;
A decryption / reproduction step of starting decryption / reproduction of the encrypted content using the decryption key before receiving a permission response from the content providing system;
A content reproduction method characterized by comprising:

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