JP2004139605A - Method for distributing digital contents - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a contents distribution technology that takes into consideration illegal copy prevention. <P>SOLUTION: Digital contents are loaded to an information terminal such as a PC 4, and ID information inherent to a viewer or user of the PC 4 is then embedded in the contents. The ID information is embedded at a prescribed position of the contents. Otherwise, the ID information may be embedded over the entire contents in the form of a spatial frequency. The contents with the ID embedded therein can be hereafter used by the terminal. <P>COPYRIGHT: (C)2004,JPO

Description

The present invention relates to a content distribution method using a method of embedding identification information (ID) in digital content and reading this information.

Since the Information Super Highway concept was proposed in the United States in 1991, the distribution of information via networks, such as the Internet, is forming a new social infrastructure. In this new network society, interest in transaction security has been growing, especially in fields such as electronic commerce, and research on cryptography and authentication that is difficult to break has been actively conducted.

However, on the other hand, in the distribution of digital content (hereinafter, simply referred to as "content") such as still images, moving images, and music, the principle of "free (free)" information disclosure on the Internet is the principle. For this reason, even valuable content such as works of cultural value can be easily copied and redistributed without permission at present. The charging of the use of content on the Internet, the prevention of piracy and alteration, and the protection of rights in copyrighted works are issues that need attention and solutions. These are extremely important issues in the healthy mutual development of a networked society and culture in the future.

Against this background, there is a need for a general-purpose method to track illegally copied digital content.

An object of the present invention is to provide a method of embedding and distributing identification information (ID) applicable to existing content.

Another object of the present invention is to provide a content distribution method by an ID embedding method that can embed an ID even in a content that does not play a role in the content and that does not have a comment area.

Another object of the present invention is to provide a content distribution method based on an ID embedding method that can suppress a significant decrease in content quality due to embedding of an ID.

Another object of the present invention is to provide a content distribution method using an ID embedding method that can easily detect an embedded ID.

Another object of the present invention is to provide a content distribution method using an ID reading method for easily detecting an ID embedded in content and interpreting the ID information.

A method according to an embodiment of the present invention comprises the steps of loading the content into an information terminal utilizing the content, wherein the content terminal is associated with the information terminal or its user at a predetermined location in a perceivable portion of the loaded content. Embedding ID information. (The content may be any collection of digital data or may be in the form of an array of data values. The perceivable part is the content, not the reserved or commented areas that do not play a role in the content. Includes data that plays a role in.)

Content is first loaded on the information terminal. Subsequently, the ID information is embedded in a predetermined position of the content. The user who created the illegal copy of the content is specified by the ID information embedded in the content. Since the ID information is embedded at a predetermined position, it is not necessary to search for a character string. Since there is no need to prepare special data blocks in advance, this method can be applied to existing content. Content is distributed using the above-described modes.

In another aspect of the present invention, ID information is embedded in the form of spatial frequency information throughout the content loaded on the information terminal. “Spatial frequency information” is information related to spatial frequency in some way. In this aspect, for example, ID information is converted into spatial frequency information by inverse orthogonal transform, and this is reflected in the content data. The inverse orthogonal transform may be an inverse fast Fourier transform (IFFT), an inverse discrete cosine transform (IDCT), or the like. This method can also be applied to existing content.

According to the ID reading procedure of the present invention, first, content is obtained, for example, via a network, and ID information is read from a predetermined position of the content. This ID information is uniquely associated with the information terminal or its user. In another aspect, spatial frequency information is extracted from the acquired content and subjected to orthogonal transform. Through this conversion, the ID information embedded in the content is restored. The orthogonal transform may be a fast Fourier transform (FFT), a discrete cosine transform (DCT), or the like. Distribute the content using the above method.

As shown in FIG. 1, the present invention can be applied to a network system including a server 2 and a client-side device connected to a network 9. In the figure, PCs 4 and 8 as information terminals and a personal digital assistance (PDA) 6 are included as devices on the client side.

The content is supplied from the server 2 to the client device, and the ID is embedded on the client side. Here, as an example, it is assumed that the PC 4 has an ID embedding function.

FIG. 2 is a flowchart showing the operation when the PC 4 receives the content. The PC 4 first downloads the content from the server 2 via the network 9 (S0). At this time, a program for decoding (decoding) or decrypting the content is also downloaded from the server. The program may be included in the downloaded viewer or browser, which returns the encrypted content to a usable form. User ID information unique to the PC 4 or its user is embedded in the viewer. The ID is embedded in the content when decoding the content with this viewer (S2). After embedding the ID, use such as displaying the content on a screen or copying the content is permitted.

FIG. 3 shows a configuration of the PC 4 related to embedding an ID. In the following examples, content is considered an image. First, the user requests a content manager or a provider (not shown) operating the server 2 to distribute the content. After authenticating the user, the content manager sends the content and the viewer 12 to the PC 4 via the network as shown in FIG. These are received by the communication unit 10 of the PC 4.

The viewer 12 received in the PC 4 is used to decode and display the received content. As shown in FIG. 3, the content is input to the viewer 12. The viewer 12 includes an image decoding unit 14 that decodes an image compressed or encrypted by the content manager before transmission to the PC 4, an ID holding unit 16 storing an ID, and an ID holding unit 16. An ID embedding unit 18 for reading out the ID and embedding the ID in the decoded image is provided. The image decoding unit 14 has a built-in decoding algorithm. When transmitting the viewer 12, the content manager stores and provides an ID unique to the user who has requested the content in the ID holding unit 16. The viewer 12 can be provided as a plug-in type device for an existing browser on the Internet, for example.

In order to prevent the image before the ID embedding from being read and used, for example, the memory area of the PC 4 for storing the image without the ID embedded is protected by the ID embedding unit 18 and the content without the ID is read. Is prevented. When a read access occurs to a memory area in which content having no ID is stored, for example, the system is configured to be interrupted or reset. When the embedding of the ID is completed, this protection is removed, and free use of the image is permitted.

(3) As shown in FIG. 3, the image containing the ID is sent to the display control unit 20. The image is now converted to a display format for display 24. The storage device control unit 22 writes data to a storage device 26 such as a hard disk unit, and stores a decoded image in the storage device 26.

FIG. 4 shows an internal configuration of the ID embedding unit 18 of FIG. 3 according to one embodiment of the present invention. The ID embedding unit 18 includes an ID reading unit 30 that reads an ID from the ID holding unit 16, a decoded image reading unit 32 that reads a decoded image, a predetermined position of a data line of the decoded image, for example, There is a combining unit 34 for embedding the ID at the center, at the end, or the like. If the ID is n bits and the luminance of each pixel is represented by multi-scale, for example, the synthesizing unit 34 replaces the least significant bit (LBS) of the luminance with each bit of the ID in order from the first pixel to n pixels. To go.

In the actual operation, first, the user of the PC 4 requests the server 2 of the content manager to distribute a certain content. After the content is encrypted on the server 2 side, it is sent to the PC 4 via the network together with the viewer 12. The communication unit 10 of the PC 4 receives the transmitted content, and this is passed to the viewer 12, which is also received from the network. In the viewer 12, the image decoding unit 14 decodes the content and passes it to the ID embedding unit 18. The ID reading unit 30 of the ID embedding unit 18 reads the ID from the ID holding unit 16 and supplies the ID to the synthesizing unit 34. The decoded image is read by the decoded image reading unit 32 and passed to the synthesizing unit 34. After receiving the ID and the decoded image, the combining unit 34 embeds the ID in the image by replacing the LSB of the luminance according to the method described above. The image with the ID is displayed on the display 24. In addition, it may be sent to the storage device 26. Thereafter, if unauthorized modification or duplication is performed on the image with the ID stored in the storage device 26, the modified or duplicated copy is embedded in the image stored in the storage device 26. ID information that has been assigned.

FIG. 5 shows another configuration of the ID embedding unit 18 according to another embodiment of the present invention. 4, the same reference numerals are given to the members equivalent to those in FIG. 4, and the description is omitted. The configuration of FIG. 5 includes an IFFT unit 40 that performs an inverse fast Fourier transform (IFFT) on a signal representing an ID, and a combining unit 42 that combines the converted ID (ie, the output of the IFFT unit 40) with a decoded image. including.

In this embodiment, the ID information is represented as a signal in the frequency domain. When embedding such an ID, inverse orthogonal transform is performed on the frequency signal indicating the ID information, and a bit pattern is formed in the content area. This bit pattern is embedded in the digital content. In this specification, the term “content area” refers to an area representing data included in digital content, and the “frequency domain” refers to a mapping area obtained by performing orthogonal transformation on the content area. When the content is a two-dimensional image (to be exemplified later), the content region becomes a two-dimensional spatial region, and the corresponding frequency region becomes a two-dimensional spatial frequency region. When the content is audio, the content domain is, for example, a time domain, and the frequency domain is, for example, a one-dimensional frequency domain.

FIG. 6 shows an example in which ID information is represented as a signal in the frequency domain. A two-dimensional image is used as an example of the content. A rectangle 52 represents a two-dimensional spatial frequency domain corresponding to the two-dimensional spatial domain. Arrows 54a and 54b indicate the x and y directions of the spatial region, respectively, and arrows 56a and 56b indicate the direction in which the frequency increases in the frequency regions corresponding to the x and y directions of the aural region, respectively. In this frequency domain, signals indicating ID information of three users A, B, and C are plotted at (xa, ya), (xb, yb), and (xc, yc), respectively. For example, in the case of the user A, the frequency signal has a sharp peak around (xa, ya). The steep peak may have a finite width or a delta function. Thus, the user ID information is represented by one point in the two-dimensional frequency domain.

FIG. 7 shows a state where the ID information of the user A is converted into an actual bit pattern in the spatial domain by the IFFT unit 40. The value of the pixel of the bit pattern in FIG. 7 is “1” in the hatched portion and “0” in the other portions. In this example, since the frequency signal indicating the ID information of the user A is substantially at the center of the spectrum region in both the x and y directions (FIG. 6), the spatial frequencies of the hatched portion and other portions in FIG. The values are almost equal in the directions. In the case of the user B, the frequency signal indicating the ID information has a higher frequency in both directions, so that the bit pattern formed in the hatched portion and the other portion becomes thin (not shown).

FIG. 8 is a diagram for explaining a method of embedding a bit pattern including ID information into a decoded image (digital content) as shown in FIG. In this example, the luminance of the pixel of the decoded image is represented by 8-bit binary data. The ID information is embedded in the decoded image by replacing the LSB of the luminance of the decoded image with the value of the corresponding pixel in the bit pattern including the ID information. Therefore, in this example, if a certain pixel exists in the hatched portion of FIG. 7 in the decoded image, its LSB is replaced with “1”, and if it exists in other portions, it is replaced with “0”. The 7 bits other than the LSB of the pixel luminance are left as the original data of the decoded image. As described above, according to this embodiment, the ID can be embedded in the entire image or a part having a certain spread therein. This method is effective as a countermeasure against cutting off part of the content. This is because, by properly taking the above-mentioned spread portion in which the ID is to be embedded, even if that portion is cut off, it is possible to practically impair the usability of the content. A specific embodiment has been described for embedding ID information of the present invention. Various modification techniques are conceivable for these embodiments. Hereinafter, some of them are shown.

First, in the above-described embodiment, the content is distributed via the network. However, the content may be stored in a storage medium such as a CD-ROM or a flexible disk, distributed, and loaded on a PC. The embodiment described above is also applicable to the case where such another method is used for distributing the content.

Second, in the above-described embodiment, a still image is considered as an example of digital content, but the method of the present invention can be applied to other types of digital content such as a moving image (eg, video) and audio. In the case of a moving image, the ID information may be divided into a plurality of parts, and different parts may be embedded in different image frames. In the case of audio content, the image decoding unit 14 in FIG. 3 may be changed to an audio decoding unit, the display control unit 20 may be changed to an audio output control unit, and the display 24 may be changed to a speaker. Since the audio is one-dimensional data unlike the image, the IFFT may be one-dimensional. In the case of an image, ID information is inserted in bits relating to luminance, but in the case of audio, it may be inserted in an LSB of frequency data.

Third, the place where the ID is inserted need not be limited to the LSB of the content. Any bit of the quantized data may be placed in a range that does not significantly affect the quality of the perceived content. In addition, it is also possible to adopt a method of intentionally embedding the watermark as a visible watermark.

Fourth, in the above-described embodiment, the ID is inserted in the lower bit regardless of the upper bit. However, an offset may be added to the lower bit so that the entire data including the upper bit includes the ID.

FIG. 13 is an example of a 3 × 3 pixel area in content such as an image, and the luminance of each pixel is “10, 8, 0...”. FIG. 14 shows the luminance of the same 3 × 3 pixel area, but here, the luminance is represented by a remainder system of three. Due to this remainder system, for example, the value corresponding to the pixel of luminance “10” is “1”. FIG. 15 shows a sample data pattern generated by the above-described method and representing ID information, which should be embedded in the 3 × 3 pixel area of FIG. This ID pattern is also represented by a remainder system of three. In this example, the user wants to put “0” in the first row, “1” in the second row, and “2” in the third row. FIG. 16 shows a state in which an offset of -1, 0 or 1 is added to the luminance of each pixel in the 3 × 3 pixel area shown in FIG. 14 in order to obtain each pixel value in the 3 × 3 pixel area shown in FIG. Is shown. In practice, any one of the offsets -1, 0, and 1 is added to each pixel according to the calculation shown in FIG. 16, and the ID information is embedded in the 3 × 3 pixel area of the image shown in FIG. That is, in this method, since an offset is added to the entire luminance data, the entire data including the upper bits includes the ID.

According to this method, as in the case where the ID is embedded in the lower bits, it is possible to avoid a state in which the ID is directly visible in the lower bits of the data, and thus the security is improved. It is also advantageous that data such as "2" as well as "0" and "1" can be embedded. Although a coset of 3 has been considered here, this may be another number. Also, any other mathematical, Boolean, or cryptographic method may be employed.

Fifth, in the above-described embodiment, the combining unit 34 (FIG. 4) embeds an ID at a predetermined position such as the head of a data string. However, the predetermined position may be a position in the content data in which the influence of a slight shift given to the data value is difficult to recognize. In that case, the quality of the content (the quality of still images, moving images, sound, text, etc.) is not significantly affected.

Sixth, in the embodiment shown in FIG. 3, the image decoding unit 14 and the ID embedding unit 18 have different configurations. These configurations may be integrated, and the ID may be embedded simultaneously with the restoration of the image.

{Seventhly, in the embodiment shown in FIG. 3, a program for decryption and / or decoding is installed in a viewer or a browser. However, this program may take any form as long as it can restore the content to a format that is easy for the user to use.

Eighth, the ID information of one user is represented by one point in the frequency domain (FIG. 6), but this may be another method. For example, the ID information of one user may be represented by a set of a plurality of discrete points, a two-dimensional area, or the like.

Ninth, as shown by the two straight lines 100 and 102 in FIG. 9, the reference information may be included in a frequency domain expression as shown in FIG. Since the position of the reference information is fixed and known in the frequency domain, the reference information can be used when reading the ID information from the content. With the help of the reference information, even if the content is deformed, for example, rotated or enlarged, the position of the ID can be specified with higher accuracy, and the user represented by the ID can be identified.
The above is the method of embedding the ID information. Next, a method of reading the embedded ID information will be described.

と き When content is illegally copied or modified (hereinafter referred to as fraud), we want to identify the fraudster. This is made possible by reading the ID information embedded in the content. A device that reads out the ID (hereinafter referred to as a “detection device”) may exist in any part of the network, and for example, a proxy server or the like may include the detection device.

FIG. 10 is a flowchart showing the operation of the detection device. The detecting device loads the content from the storage device or the storage medium (S10), and reads the ID information embedded therein (S12). If any wrongdoing is found, take appropriate action, such as notifying the content owner to the content manager.

FIG. 11 shows an embodiment of a detection device for reading out ID information embedded in content. The detecting device 60 (which may be included in the PC) includes a communication unit 62 for acquiring the content from the network, an ID reading unit 64 for reading the ID from the acquired content, and a display 68 for displaying the read ID. It has a display control unit 66 for controlling.

In this embodiment, the ID reading unit 64 extracts a predetermined position in the acquired data string of the content, for example, the LSB at the head of the data string, and reconstructs the ID. As a result of the extraction, if ID information that can significantly identify the user does not appear, it is determined that the content is the original, that is, the content in which the ID information of the user is not embedded. On the other hand, if the content in which the ID of a certain user is embedded is found on the network, there is a possibility that the user identified by the ID information has illegally distributed the content. In this way, the wrongdoing is tracked based on the ID.

FIG. 12 shows another ID reading unit according to another embodiment of the present invention. The ID reading unit operates to read an ID embedded as spatial frequency information in the content. The ID reading unit 64 extracts an LSB of the acquired content data to form a bit pattern and an LSB extraction unit 72. The ID reading unit 64 performs a fast Fourier transform (FFT) on the bit pattern formed based on the extracted LSB. ) Is performed.

動作 The operation by this configuration is equivalent to tracing FIGS. 6 to 8 in reverse. First, an LSB representing the embedded ID information is extracted (FIG. 8). Subsequently, a bit pattern formed by the LSB in the content is detected (FIG. 7). Thereafter, the FFT unit 74 calculates a spatial frequency in each of the x and y directions from the bit pattern. In the case of the bit pattern in FIG. 7, the ID of the user A in FIG. 6 is found as a result of the FFT calculation. Thus, the fraudster is identified as the user A.

According to this method, it is also advantageous that it is not necessary to compare the suspicious content with the original content in order to detect the ID.

変 形 A number of modification techniques can be considered for the method of reading the ID information described above. The modification techniques of the ID embedding method already described in this specification have corresponding modification techniques of the ID reading method. For example, when an offset is added to the lower bits by the method described with reference to FIGS. 13 to 16, the ID can be read. When an ID is embedded in a predetermined position of the content (for example, a position where a shift of the data value does not have a perceptual effect), the ID reading that detects the same position in conformity with the ID embedding method. There is a way. In general, as long as the embedding device and the reading device adopt the same embedding / reading rule, reading of the ID is possible.

で は In the above embodiment, the detection device was connected to the network. However, if only the content stored on the storage medium is to be inspected, this device may be an offline stand-alone type.

{Furthermore, in the above-described embodiment, the embedding of the ID is performed by the information terminal using the content, that is, the user side. However, as will be apparent to those skilled in the art, the various methods described above for embedding ID information in content are similarly applied to content distribution designs in which ID embedding is performed on the content provider side. it can.

Of course, variations to the present invention will become apparent to those skilled in the art when viewing the present invention from various angles. Other embodiments are possible, as particular designs will occur depending on the particular application. Therefore, the scope of the present invention should not be limited by the embodiments described herein, but should be determined only by the appended claims.

1 is a diagram illustrating a network system to which a preferred embodiment of the present invention is applied. 9 is a flowchart showing an operation when a PC receives content with respect to embedding of an ID. FIG. 3 is a diagram showing a configuration related to embedding of an ID in a PC. FIG. 4 is an internal configuration diagram of an ID embedding unit of FIG. 3. FIG. 4 is a diagram illustrating another configuration of the ID embedding unit in FIG. 3. FIG. 5 is a diagram illustrating a relationship between ID and spatial frequency by using a spectral domain. FIG. 6 is a diagram showing a result of converting an ID of a certain user into an actual image data pattern by the IFFT unit of FIG. 5. FIG. 8 is a diagram illustrating a method of embedding the bit pattern of FIG. 7 in a decoded image. FIG. 7 is a diagram showing a state in which fixed reference information is superimposed on the spectrum region of FIG. 6. It is a flowchart which shows operation | movement of the inspection apparatus which reads the ID embedded in the content. FIG. 3 is a diagram illustrating a configuration of an ID reading unit in the detection device. FIG. 12 is a diagram illustrating another configuration of the ID reading unit in FIG. 11. It is a figure showing a 3x3 pixel area. FIG. 14 is a diagram showing the luminance of 3 × 3 pixels in FIG. 13 in a remainder system of 3; FIG. 14 is a diagram showing a data pattern to be embedded as an ID in a 3 × 3 area of FIG. 13. FIG. 16 is a diagram illustrating a state in which an offset 0 or ± 1 is added to the luminance of each pixel to obtain the state of FIG. 15 from the state of FIG. 14.

Explanation of reference numerals

DESCRIPTION OF SYMBOLS 10 Communication part 12 Viewer 14 Image decoding part 16 ID holding part 18 ID embedding part 20 Display control part 22 Storage device control part 24 Display 26 Storage device 30 ID reading part 32 Decoded image reading part 34 Synthesis part 40 IFFT part 42 Synthesis Unit 60 detection device 62 communication unit 64 ID reading unit 66 display control unit 68 display 72 LSB extraction unit 74 FFT unit

Claims (7)

Issuing a request for a certain digital content from the information terminal to the content manager in a manner that the information terminal or the user is specified;
Receiving in an encrypted form the content sent from the content manager in response to the request;
Receiving a program for decryption sent from the content manager in response to the request, in a form in which the information contains the ID information for identifying the information terminal or the user;
Processing the content using a received decryption program to generate the decrypted content with the ID information embedded in the content;
A digital content distribution method comprising: The step of processing comprises:
Decrypting the received content using the decryption program,
Embedding ID information in the decrypted content using the program for decryption,
The method of claim 1, comprising: The method of claim 1, further comprising preventing the decrypted content from being used before embedding the ID information therein. The method according to claim 1, further comprising, after embedding the ID information, permitting use of the digital content at the information terminal. The method according to claim 1, wherein the information terminal and the content manager are connected to a network, and the request, the digital content, and the program for decoding are transmitted via the network. Receiving a request issued from an information terminal for digital content possessed by a content manager in a form in which the request identifies the information terminal or a user thereof;
Sending the requested content to the information terminal in an encrypted form in response to the request;
Sending a program for decryption to the information terminal in response to the request, in a form in which it incorporates ID information identifying the information terminal or a user;
Wherein the program for decryption operates on the encrypted content so as to generate the decrypted content in a form in which the ID information is embedded in the content. Method. The method according to claim 6, wherein the information terminal and the content manager are connected to a network, and the request, the digital content, and the program for decoding are transmitted via the network.

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