JP3984452B2 - Video data distribution system, video data reception / playback device, computer program, and content illegal distribution prevention method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a moving image data distribution system equipped with means for preventing or deterring unauthorized copying of digital content on the user side when distributing digital content over a network.
[0002]
[Prior art]
Technology that distributes digital content such as audio data and video data through the Internet is in the practical use as streaming technology. However, digital data such as illegal copying is not subject to quality degradation no matter how many times it is replicated. How to prevent the act of infringing on the copyright of content is a big problem for service providers.
[0003]
The streaming distribution technique is a technique that performs content distribution from the distribution server and content reproduction on the user side so as not to be interrupted almost in real time with respect to contents such as video and audio requested by the user. For the user, there is an advantage that all data can be reproduced without downloading, and the content can be reproduced from the middle.
[0004]
Using digital watermarking technology that embeds copyright information etc. in digital content data in order to deter unauthorized copying against the problem of how to prevent the act of infringing the copyright of digital content This is one way. For example, there is Digimarc, US Pat. No. 5,636,292 as a technique for embedding a digital watermark by calculating data values for the hue, brightness, etc. of a pixel.
[0005]
As another technique for embedding a digital watermark, there is a technique for embedding watermark information in the frequency domain of the original image. These are Onishi, Oka, and Matsui "Signing method for images using PN series" 1997, Proceedings of the Symposium on Cryptography and Information Security, SCIS97-26B, Nakamura, Ogawa, and Takashima "Frequencies for copyright protection of digital images "Digital Watermarking in the Domain" 1997, Proceedings of Symposium on Cryptography and Information Security, SCIS97-26A, Ishizuka, Sakai, Sakurai, "Security and Reliability of Digital Watermarking Technology Using Digital Watermarking Technology Using Wavelet Transform Experimental Considerations ”1997, familiar with SCIS97-26D, Proceedings of the Symposium on Cryptography and Information Security.
[0006]
The above is a technique for embedding a watermark in a still image. As an electronic watermark embedding technique suitable for moving image data, a method for embedding watermark information in a motion vector is disclosed in, for example, Japanese Patent Laid-Open No. 2000-165248. .
[0007]
As another means, there is a method in which a data header describing data attributes such as data recording prohibition information is added to data and distributed. The recording device refers to the data header and prohibits the recording operation if there is data recording prohibition information.
[0008]
[Problems to be solved by the invention]
However, although the digital watermark technology can prevent unauthorized copying of digital content, it cannot completely prevent unauthorized distribution of digital content. Also, the method of recording permission / non-permission of recording of digital content in the header portion of the content data and controlling the operation at the time of playback has a weak point that the data header portion is easily distinguished from the content data portion and easily tampered with. .
[0009]
Therefore, the present invention provides a moving image distribution system that prevents illegal leakage of digital contents by using a dedicated client device equipped with a digital watermark technique and a mechanism that allows the server side to know that the digital content has been copied on the client side. This is the issue.
[0010]
[Means for Solving the Problems]
A first invention for solving the problem is a moving image data distribution system including a moving image distribution server that distributes moving image data through a network and a client terminal connected to the network that receives and reproduces the moving image data. AndThe client terminal receives streaming data for receiving and playing moving image data, streaming recording means for recording and recording moving image data, and detects watermark data that means that copying of moving image data is prohibited by detecting an electronic watermark embedded in the moving image data. And a watermark detecting means for stopping the recording operation of the moving image data by the streaming recording means, and a watermark inserting means for inserting a digital watermark into the received moving image data. A special message protocol is defined between the client terminal and the client terminal, when recording the video data, sends a recording notification message including the recording date and time and the identification information of the client terminal to the video distribution server. The video distribution server sends the message By keeping an information management means for recording managing the contents when digits, and summarized in that you can manage the server-side that an attempt was made to record the moving image data on the client side.
[0011]
In the method of recording prohibition attribute information in the fixed header part area in the content data and controlling the copy of the content, there is a drawback that a malicious person knows the mechanism and is easily falsified, The moving image data distribution system of the first invention eliminates such drawbacks.
[0012]
The watermark detection means interrupts the request and reception of the next frame data while checking the presence or absence of digital watermark insertion for the first few frames received, detects the presence and content of the digital watermark, and detects the moving image data. When the watermark data indicating that the copy is prohibited is detected, the recording operation of the moving image data by the streaming recording unit is stopped. Otherwise, the request and reception of the frame data are resumed while the recording operation is enabled. You may comprise as follows.
[0013]
Moving image data distribution system of the first inventionThe advantage is that even if the content data can be duplicated and recorded, the original data is always processed in some way, so that the quality deteriorates and the source of the duplicated client terminal or the content data is added to the content data. It can be recorded.
[0016]
  Also,The moving image distribution server, which is the content data supply side, can manage where and when the content data was recorded and duplicated by recording and managing the recording notification message.
[0018]
  further,According to such a video data distribution system, not only can the video data recorded on the client side be managed on the server side, but also the client that has recorded and copied the watermark data when content data is illegally distributed. By including the terminal identification information, the source can be identified.
[0019]
The first to solve the problem2The invention of the1Video data distribution system of the present inventionIt is the moving image data receiving / reproducing apparatus which works as a client terminal which comprises.
[0020]
A third invention for solving the problem is a computer program that causes a computer to operate as the moving image data reception / playback device of the second invention by being incorporated in the computer..
[0022]
  Solve the problemFirst4The present invention is a content illegal distribution prevention method in a video data distribution system comprising a video distribution server that distributes video data through a network, and a client terminal connected to the network that receives and reproduces the video data,In the video distribution server, at least the first few frames of the video content to be distributed, control information on whether or not to allow recording recording on the client terminal side for each frame or under what conditions recording information is invisible watermarking Prepare video data embedded in the content data as information,
The client terminal extracts the presence / absence and contents of digital watermark insertion from the received stream data, controls the recording / recording function of the stream data according to the presence / absence of the digital watermark and the extracted contents, and records and records the video content on the client terminal side In this case, a recording notification that can specify the recorded client terminal, recording date and time, recording condition or recording state is transmitted from the client terminal to the video distribution server, and this information is recorded and managed on the server side.
On the client terminal side, the invisible digital watermark that can specify the recorded client terminal, the recording date and time, or the visible digital watermark is inserted into the recording record data,The content illegal distribution prevention method is characterized in that the fact that content data is copied on the server side can be managed and the source of the leakage can be specified when the content is illegally distributed.
[0023]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, a moving image data distribution system 1 (hereinafter referred to as system 1) according to an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a diagram for explaining the overall configuration of the system 1. Reference numeral 10 denotes a moving image distribution server that performs streaming distribution. Reference numeral 20 denotes a client terminal used by the user. Reference numeral 9 denotes a network such as the Internet that connects the moving image distribution server 10 and the client client terminal 200. The moving image distribution server 10 includes streaming distribution means 11 that transmits moving image data 19 as streaming data while synchronizing with the client terminal 20. Information management means 13 for processing a recording notification message transmitted from the client terminal and a management database 14 for collecting and managing the contents of the recording notification message are provided. The network I / O unit 114 converts the streaming data sent from the streaming delivery unit 11 into a packet flowing through the network 9, and a data format that can be handled by the streaming delivery unit 11 or the information management unit 13 for the packet arriving from the network 9. A physical and logical interface device for converting to
[0024]
FIG. 2 is a block diagram showing the configuration of the client terminal 20. The client terminal 20 includes a network I / O unit 214 that is a physical and logical interface device that handles packets flowing through the network 9, a streaming playback unit 21 that receives and plays back streaming data, and a streaming recording unit 23 that records moving image data. , A watermark detection unit 22 for detecting a digital watermark in the moving image data, and a watermark insertion unit 24 for inserting a digital watermark when recording. Data processed by the streaming playback means 21 is expanded on the VRAM 216 and displayed on the monitor 217. The streaming recording unit 23 has a unique identification number for each client terminal. This identification number is also recorded in the management database 14 of the moving image distribution server 10.
[0025]
Prior to the description of the system 1, the streaming distribution and streaming data playback method will be described. A protocol at the application layer level is defined between the streaming delivery means 11 and the streaming playback means 21, and (1) a connection request from the streaming playback means 21 to the streaming delivery means 11, and (2) a streaming data delivery request. , (3) Streaming data transmission and reception, (4) Termination notification, and (5) Connection release messages are exchanged to deliver and receive one piece of content data. FIG. 3 is a diagram showing the above steps (2) and (3). The terminal 20 makes a streaming distribution request to the moving image distribution server 10. On the other hand, the moving image distribution server 10 divides the streaming data on the time axis and distributes the divided streaming data. The data received at the terminal 20 may arrive before or after the order of transmission at the video distribution server 10 moves around the network. The streaming reproduction means 21 of the data terminal 20 reconstructs the received data in the order of distribution from the server 10 and reproduces it.
[0026]
In describing the moving image data distribution system 1 of the present invention, the following description will be focused on the processing operation of the client terminal 20.
[0027]
FIG. 5 is a flowchart illustrating a recording procedure for recording streaming data on the terminal side. Hereinafter, the flow of processing in the terminal 20 will be described with reference to FIG. When the system user requests streaming data from his / her client terminal 20 and performs recording / recording simultaneously with reception / reproduction, the following procedure is performed. First, the client terminal 20 is set in a recording state (S10), and identification information (device ID) of the streaming recording means 23, a recording state start date and time, and a data transmission request are transmitted to the moving image distribution server 10 (S12). The moving image distribution server 10 temporarily records the received device ID and recording state start date and time in a buffer area managed by the information management means 13 (this information will be managed when the reception (recording) end notification is received from the terminal 20 later. Are recorded within). Thereafter, the streaming delivery means 11 starts transmitting the designated streaming data 19. The streaming data is divided and the streaming data is transmitted to the client terminal 20.
[0028]
When the client terminal 20 receives the streaming data (S14), it stores the first several frames in the received streaming data as a temporary file A in the hard disk 215. The watermark detection means 22 is immediately activated to detect an invisible digital watermark in the saved file A (S16). While the presence / absence of the digital watermark is detected, the client terminal 20 does not send a message requesting the next data to the moving image distribution server 10, so that the streaming data is not transmitted from the server 10. Subsequent operations differ depending on the detection result of the watermark detection means 22. After the invisible digital watermark detection process is completed, the file A is unnecessary and is discarded.
[0029]
If no watermark is detected in the file A, a streaming data transmission request is sent to the moving image distribution server 10 to resume transmission / reception of subsequent streaming data. Thereafter, the received streaming data is written into the VRAM 216 and reproduced and displayed on the monitor 217. At the same time, the streaming recording unit 23 records the received streaming data on the hard disk 215 as the file B (S18). The streaming delivery unit 11 of the server 10 and the streaming reproduction unit 21 of the client terminal 20 transmit and receive moving image data for each short unit time while synchronizing. After completion of transmission / reception of all data, the watermark insertion means 24 inserts an invisible digital watermark into the file B (S20). Information to be embedded at this time is a device ID and a recording date and time. After the insertion of the watermark, the moving image distribution server 10 is notified of the end of recording of the streaming data (S24).
The monitor 217 displays that the recording of the streaming data has been completed normally (S26), and ends the one-time moving image content reproduction / recording process.
[0030]
The service provider of the moving image content can control whether or not the user is permitted to make a copy of the content data on the client terminal 20 by embedding an invisible watermark in the streaming data. The service provider specifies two ways of prohibiting recording of streaming data or permitting recording on the condition that visible watermark is inserted by embedding invisible watermark in the first few frames of streaming data. it can. Then, by distributing the content data embedded with the watermark, the operation on the client side is controlled. In this case, the information to be embedded as the invisible digital watermark may be anything as long as the streaming recording unit 23 of the client terminal 20 can distinguish the recording permission under the recording prohibition or visible watermark insertion conditions. The side needs to hold information as shown in FIG. 7 as a digital watermark detection file.
[0031]
If the watermark detection means 22 detects that an invisible watermark is present in the file A in step S16, the watermark detection means 22 extracts the invisible watermark and compares it with the watermark detection file to determine the content (S17). . If the existing watermark indicates that recording is prohibited, the file A is discarded and the recording process is displayed on the monitor 217 (S30). Then, a streaming data transmission request is sent to the moving image distribution server 10 to resume transmission / reception of subsequent streaming data. Thereafter, the received streaming data is reproduced and displayed on the monitor 217, but is not recorded on the hard disk 215 (S32). When the reception of all the streaming data is completed, the moving image distribution server 10 is notified of the end of the streaming data reception (S34). The reception end notification includes information indicating that the streaming data has not been recorded in the terminal 20.
[0032]
When the watermark detection means 22 extracts the invisible digital watermark and collates it with the digital watermark detection file to determine the content (S17), if the designation of permitting the upper recording of visible watermark insertion is specified, the streaming data Subsequent transmission / reception of streaming data is resumed by making a transmission request to the moving image distribution server 10. Thereafter, the received streaming data is reproduced and displayed on the monitor 217 and simultaneously recorded on the hard disk 215 as a file B (S19). Thereafter, the watermark insertion means 24 is activated to insert a visible digital watermark into the file B (S21). . At this time, the visible watermark to be inserted uses a bit pattern held in the client terminal 20 in advance. After completion of visible watermark insertion, a recording end notification is transmitted to the moving image distribution server 10 (S24). The server 10 includes information indicating whether the invisible watermark is inserted and recorded on the terminal 20 side, and information temporarily stored in the buffer before transmitting the content data (device ID). , Transmission request date and time) is added to the management database 14 as one record. The monitor 217 displays that the recording of the streaming data has been completed normally (S26), and ends the one-time moving image content reproduction / recording process.
[0033]
FIG. 6 illustrates the management information recorded in the management database 14. Data shown in FIG. 6 is recorded for each content provided by the server 10. One row (device ID, date / time, recording state) in FIG. 6 is one record added by one reception of content data. Therefore, the service provider can know which content, when and how the copy was performed by referring to the database 14.
[0034]
In the present invention, it is necessary to embed an electronic watermark in streaming data. The technique for this is described below.
[0035]
A visible digital watermark gives a change that can be clearly perceived from the original image by a process such as combining the original image with a bit pattern representing a specific character, character string, or mark. For example, when a bit pattern representing a specific character, character string, or mark is defined as a binary bit pattern, only the luminance of a pixel having a value of 1 (or 0) is changed to 0 (or 1). If the value of the image data is left as it is, the visible watermark is inserted into the original image data.
[0036]
As a method for embedding an invisible digital watermark in a still image, a method is known in which an image is frequency-converted and digital watermark data is embedded in a frequency spectrum. Such a technique is specifically described in “Digital Watermarking and Content Protection” by Otsuka Ono.
[0037]
One specific example. The original still image is converted into frequency components using DCT (Discrete Cosine Transform) and converted into n high frequency components f (1), f (2), f (3),. The watermark information is embedded. In the embedding method, when the information Bit used as watermark information is 0, the quantized value is an even number, and when Bit is 1, the quantized value is an odd number. As a result, a total of n-bit watermark information is embedded in 1-bit units for n high-frequency component values.
[0038]
The watermark is detected by the following method. First, it is converted into frequency components using DCT, then quantized, and watermark information is detected from the place where watermark embedding is performed. In the detection method, watermark embedding is 0 when the quantized value is an even number, and 1 is embedded when the value is an odd number, so that watermark information can be detected.
[0039]
The watermark is embedded in a high-frequency region with relatively high redundancy, and only the least significant bit of the quantized value has an effect. Therefore, the effect of returning to the original image is small. In addition, in the above method, only one block that performs DCT conversion of 8 pixels × 8 pixels in the original image is affected by the watermark insertion, so that it cannot be actually detected that the watermark is inserted. For still images with a large number of pixels, multiple blocks to embed watermarks can be provided to increase the amount of watermark insertion information, or to increase the tolerance of embedded watermarks by providing redundancy to the watermark information to be inserted. Is possible.
[0040]
In order to apply this method to moving image data, as described with reference to the flowchart of FIG. 5, the above-described embedding process may be performed on the first few frames of the stream data. Since moving image data has a small number of pixels in one frame, it should be avoided to provide a plurality of DCT conversion processing blocks for embedding a watermark. Instead, if a plurality of frames are used, the amount of information and redundancy of the inserted watermark can be increased. .
[0041]
FIG. 4 is a conceptual diagram when a device ID and time are embedded in several frames of moving image data by the above method. The same device ID and date are repeatedly inserted over several frames, and the insertion information has redundancy. In the present invention, in both cases where the invisible digital watermark is inserted in advance on the server 10 side and is embedded on the terminal 20 side in step S20 in FIG. . This is because it is easy to detect the invisible digital watermark.
[0042]
In the watermark detection process, only these few frames and only a specific DCT processing block among them are subjected to DCT conversion, so that the load on the terminal 20 (reproducing apparatus) is not so large. Also, since the watermark is inserted on the terminal 20 side (S20 and S21 in FIG. 5) after all the streaming data is received, that is, after the reproduction is completed, it is not necessary to worry about the time required for the watermark insertion. Therefore, the streaming reproduction means 21, the watermark detection means 22, the streaming recording means 23, and the watermark insertion means 24 can be realized by software processing.
[0043]
The moving image data distribution system 1 that is the optimal embodiment of the present invention has been described above in detail. Next, a moving image data distribution system 2 as another embodiment will be described.
[0044]
FIG. 8 is a block diagram showing the overall configuration of a moving image data distribution system 2 (hereinafter, system 2) according to another embodiment of the present invention. The system 2 has a configuration in which the moving image distribution server 10B and the client terminal 20 are connected via the network 9. The moving image distribution server 10B is configured by removing the information management means 13 and the management database 14 from the moving image distribution server 10. The client terminal 20 is the same as that used in the system 1.
[0045]
The operation of the system 2 is basically the same as that of the system 1. However, even if the content data is recorded and recorded at the client terminal 20, the only difference is that the moving image distribution server 10B does not receive and record and manage the recording / recording message.
[0046]
Since the system 2 does not manage when and where the content data is replicated on the server side, the management level is lower than that of the system 1 in terms of monitoring the content replication status, but the content data with the digital watermark inserted is distributed. Thus, whether or not copying on the client side can be controlled, and when content data is copied on the client side, a visible or invisible watermark is always inserted. Therefore, as the watermark information to be inserted, the device ID of the client terminal and the copy By including the date and time, illegal distribution of the content data can be suppressed, and the outflow source can be specified even when it is illegally leaked.
[0047]
The method for embedding an invisible digital watermark in the moving image data and the detection method described here are not limited to the methods given as an example. Any method may be used as long as a watermark image is embedded in the frequency spectrum after converting the frame image of several frames from the head of the moving image data into the frequency domain.
[0048]
【The invention's effect】
The present invention has been described in detail with two embodiments. According to the second embodiment (system 2), when content data is recorded and copied on the terminal device side, an invisible or visible digital watermark is inserted into the content data, so that the content provider has the same quality as the original. This prevents the content from being distributed, and embeds information identifying the copied device in the watermark, so that it is possible to identify the outflow source when the copied data is illegally distributed.
[0049]
Further, according to the first embodiment (system 1), when content data is recorded and copied on the terminal device side, an invisible or visible digital watermark is inserted, and the fact is recorded and managed on the server side. Therefore, the content provider can prevent the same quality content as the original from being distributed. In addition, by embedding information that identifies the copied device in the watermark, it is possible to specify the source of the leaked data when it was illegally distributed, and the information managed on the server side when specifying this source As a result, it is possible to obtain the support of the video content data.
[0050]
In any of the embodiments, since a method of embedding control information such as copy permission / non-permission as invisible watermark information in streaming data is employed, compared with a method of recording control information in a header portion in streaming data, Tampering is difficult, and there is a remarkable effect that unauthorized copying becomes more difficult.
[Brief description of the drawings]
FIG. 1 is a configuration diagram of a moving image data distribution system 1 according to an embodiment of the present invention.
FIG. 2 is a block diagram illustrating the configuration of a client terminal 20;
FIG. 3 is an explanatory diagram of a streaming data distribution principle.
FIG. 4 is a diagram for explaining a digital watermark insertion principle;
FIG. 5 is a diagram illustrating a moving image content data recording procedure.
FIG. 6 is a recording example of a management database 14;
FIG. 7 is an example of a digital watermark detection file referred to by the watermark detection means 22;
FIG. 8 is a configuration diagram of a moving image data distribution system 2 according to an embodiment of the present invention.
[Explanation of symbols]
9 Network
10 Video distribution server
10B video distribution server
11 Streaming delivery means
13 Information management means
14 Management database
19 Video content data
20 Client terminal
20B client terminal
21 Streaming playback means
22 Watermark detection means
23 Streaming recording means
24 Watermark insertion means
114 Network I / O
214 Network I / O section
215 hard disk
216 VRAM (video memo)
217 monitor

Claims (6)

A video delivery server with streaming delivery means for delivering video data over a network;
Streaming playback means for receiving and playing back moving picture data, streaming recording means for recording and recording moving picture data, and streaming when detecting watermark data that means that copying of moving picture data is prohibited by detecting an electronic watermark embedded in the moving picture data A watermark detecting means for stopping the recording operation of the moving picture data by the recording means, a client terminal connected to a network provided with a watermark inserting means for inserting a digital watermark into the received moving picture data;
A video data distribution system comprising:
A special message protocol is defined between the video distribution server and the client terminal. When the client terminal records video data, the video recording server records the date and time of recording and the identification of the client terminal. The video delivery server recorded the video data on the client side by providing an information management means for recording and managing the content when receiving the message. A video data distribution system characterized in that it can be managed on the server side . A video delivery server with streaming delivery means for delivering video data over a network;
Streaming playback means for receiving and playing back video data, streaming recording means for recording and recording video data, while checking the presence or absence of digital watermark insertion for the first few frames received, the request and reception of the next frame data is interrupted, The presence or absence of watermark insertion and the content thereof are detected, and when the watermark data meaning that the copying of the moving image data is prohibited is detected, the recording operation of the moving image data by the streaming recording means is stopped, and otherwise, the recording operation is possible A client terminal connected to a network comprising watermark detection means for resuming request and reception of frame data, and watermark insertion means for inserting a digital watermark into received video data;
A video data distribution system comprising:
A special message protocol is defined between the video distribution server and the client terminal. When the client terminal records video data, the video recording server records the date and time of recording and the identification of the client terminal. The video delivery server recorded the video data on the client side by providing an information management means for recording and managing the content when receiving the message. A video data distribution system characterized in that it can be managed on the server side . A video data receiving / reproducing device that connects to a network and receives video data from a server that transmits video data,
  When a streaming playback means for receiving and playing back video data, a streaming recording means for recording and recording video data, and a watermark data that means that copying of video data is prohibited by detecting an electronic watermark embedded in the video data A watermark detecting means for stopping the recording operation of the moving picture data by the streaming recording means, a watermark inserting means for inserting a digital watermark into the received moving picture data, and when recording the moving picture data, the recording is performed on the server of the moving picture data transmission source. A moving image data receiving / reproducing apparatus having a function of transmitting a recording notification message including a recording date and time and identification information of a client terminal. A video data reception / playback device that connects to a network and receives video data from a video data transmission source server,
Streaming playback means for receiving and playing moving image data, streaming recording means for recording and recording moving image data, and the next frame data request and reception are interrupted while checking for the presence of digital watermarking for the first few frames received. to detect the presence or absence and contents of that digital watermarking, when detecting the watermark data indicating the copy inhibition video data stops the recording operation of the moving image data by the streaming recording means, the recording operation is otherwise The watermark detection means for resuming the request and reception of frame data in a possible state, the watermark insertion means for inserting a digital watermark into the received video data, and when recording video data, the video data transmission source Recording notification message including the date and time of recording and the identification information of the client terminal on the server Video data receiving and reproducing device having a function of transmitting the over-di. A computer program for causing a computer to operate as the moving image data receiving / reproducing apparatus according to claim 3 or 4. A method for preventing illegal distribution of content in a video data distribution system comprising a video distribution server that distributes video data through a network and a client terminal connected to the network that receives and reproduces the video data,
  In the video distribution server, at least the first few frames of video content to be distributed, control information on whether or not to allow recording recording on the client terminal side for each frame or under what conditions recording information is invisible watermarking Prepare video data embedded in the content data as information,
  The client terminal extracts the presence / absence and contents of digital watermark insertion from the received stream data, controls the recording / recording function of the stream data according to the presence / absence of the digital watermark and the extracted contents, and records and records the moving picture content on the client terminal side. In this case, a recording notification that can specify the recorded client terminal, recording date and time, recording condition or recording state is transmitted from the client terminal to the video distribution server, and this information is recorded and managed on the server side.
  On the client terminal side, by inserting the invisible digital watermark that can identify the recorded client terminal, the recording date and time, or the visible digital watermark into the recording data,
A content illegal distribution prevention method characterized in that the fact that content data is replicated on the server side can be managed and the source of the leakage can be specified when the content is illegally distributed.

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