JPH10304206A - Image coding/decoding system and image coding and decoding device for the system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image coding/decoding system in which the security of image data is improved while keeping the service performance for image data distribution. SOLUTION: A scrambling quantization table 8 different from a quantization table 4 used for coding is described onto a header 16 of coded data 15 that are generated by image coding and the resulting coded data 15 are distributed to an opposite party. A copy 4a of the quantization table 4 in use is stored in an IC card 22 and the card is mailed to the opposite party. In the case of reproducing by the opposite party, the opposite party does not use the scrambling quantization table 8 but read the true quantization table 4a from the IC card 22 and decodes the coded data by using the table 4a. Since a party not receiving the IC card 22 decodes the coded data 15 by using the scrambling quantization table 8 included in the coded data 15, the party cannot normally reproduce the image. However, even in this case, a degree of scattering of the scrambling quantization table 8 is designed properly to allow even the party to grasp an outline of the image.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image encoding / decoding system for securing image data.

[0002]

2. Description of the Related Art In an image encoding method represented by JPEG or the like, encoding processing is conventionally performed according to the flow shown in FIG. That is, after transforming an input image into data of another dimension by image transform 1 such as DCT (discrete cosine transform), quantization 2 is performed, and finally, the quantized data is subjected to variable length coding such as Huffman coding. Apply 3.

The coded data 5 comprises a header 6 and a coded bit stream 7. As shown in the figure, the header 6 of the encoded data 5 includes the value of the quantization table 4 used for the encoding process.

FIG. 2 shows a conventional image decoding system.

In the decoding process, a header analysis 11 of input coded data is performed, and then a variable length decoding 12 is performed.
Is performed, inverse quantization 13 is performed using the quantization table 4 obtained by the header analysis 11, and finally inverse conversion 14 is performed to reproduce and output normal image data.

In order to improve security,
Data such as images may be encrypted. In this case, as shown in FIG. 3, encryption 15 is generally performed on the entire data.

[0007]

In the image encoding / decoding system shown in FIGS. 1 and 2, since no security is applied to the image, it is possible to use software having a decoding function of the same system. , Images can be played. Therefore, there is a problem that redistribution of an image by an unauthorized person cannot be prevented.

The use of the encryption system shown in FIG. 3 improves security. However, since the image data is completely concealed by the encryption, the image cannot be reproduced without the same method of decryption software. Therefore, there is a problem of lack of serviceability.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an image encoding / decoding system capable of improving security while maintaining serviceability in image data distribution.

[0010]

According to the image encoding / decoding method of the present invention, an apparatus for transmitting an image includes an image encoding means for encoding image data using a predetermined key, and an image encoding means. Data generating means for adding a disturbance key different from the key used by the encoding means to output data of the image encoding means to generate encoded data to be transmitted, and a key used by the image encoding means. Key storage means for storing the same true key in a predetermined key transmission medium. Further, the device on the receiving side of the encoded data decodes the encoded data received from the transmitting side device by using the key from the key acquiring unit for acquiring the key from the key transmission medium and the key from the key acquiring unit. Image decoding means for reproducing data.

According to the method of the present invention, the same true key as the key used in image encoding is transmitted to the receiving side via the key transmission medium, so that the receiving side transmits the true key from the medium. Once obtained, the encoded data can be decoded using this to obtain normal image data. On the other hand, an unauthorized person to whom the key transmission medium is not supplied has to perform decoding using the disturbance key added to the encoded data, and thus cannot obtain normal image data.

As the key transmission medium, a transportable data storage such as an IC card, a disk, or a non-volatile memory can be used, and it may be distributed to the receiving side. Alternatively, the true key may be distributed to the recipient using a communication network as a key transmission medium and in a manner or route that is as secure as possible and different from the encoded data.

As a key, a quantization table used for quantization at the time of encoding and inverse quantization at the time of decoding can be used, but is not limited to this. In short, data, tables, parameters, or files that are commonly used in image encoding and decoding and cannot be decoded normally without them, and can be kept secret from a third party What is necessary is just such.

However, when a quantization table is used as a key, by setting the degree of disturbance of the disturbance quantization table to an appropriate level, general image reproducing software or the like can be used without a true quantization table. , The outline of the image can be seen. This method is effective, for example, when it is desired to show a brief outline of an image in order to stimulate purchase intention. Note that the image encoding device and the decoding device of the present invention can be typically implemented by a computer,
The program for that can be installed or loaded into a computer through various media such as a disk storage, a semiconductor memory, and a communication line.

[0015]

Embodiments of the present invention will be described below with reference to the accompanying drawings.

FIG. 4 shows an embodiment of the transmitting apparatus according to the present invention.

An image coding device 201 provided on the transmission side
In the same manner as in the conventional example shown in FIG. 1, an input image is subjected to image transformation 1 such as DCT using a predetermined quantization table 4 to be transformed into data of another dimension, and then quantization 2 is performed. Next, variable length coding 3 such as Huffman coding is performed. Then, a header 16 is added to the coded bit stream 7 obtained by the variable length coding 3 so that the final coded data 1
5 is generated. At this time, the apparatus 201 describes, in the header 16 of the encoded data 15, a quantization table 8 for disturbance that is different from the quantization table 4 actually used and that is separately prepared. Then, for the quantization table 4 actually used, a copy (hereinafter, referred to as a “true quantization table”) 4a is stored in an appropriate storage. This true quantization table 4a is used as a key for correctly decrypting an image by an authorized person or the like who can receive services.
It is distributed by a different route from the encoded data 15. For example, the encoded data 15 is distributed online through a network, while the true quantization table 4a is distributed by a highly reliable offline delivery means (for example, mail).

The image conversion 1, the quantization 2, the variable-length coding 3, and the generation of the coded data 15 can be performed by dedicated hardware. Will be implemented.

FIG. 5 shows an embodiment of the receiving apparatus according to the present invention.

An image decoding device 202 provided on the receiving side
Performs a header analysis 11, a variable length decoding 12, an inverse quantization 13 and an inverse transform 14 on the input encoded data 15 in the same manner as in the conventional example shown in FIG. However, this device 202
The switching 10 can selectively use the disturbance quantization table 8 extracted from the header 16 by the header analysis 11 from the header 16 and the true quantization table 4a distributed by another route in the inverse quantization 13. It has become. That is, in the switching 10, the true quantization table 4a
Is supplied, the true quantization table 4a is selected, and if the true quantization table 4a is not supplied, the disturbance quantization table 8 obtained by the header analysis 11 is selected.

When the true quantization table 4a is supplied to the device 202, a correct image can be reproduced. on the other hand,
If the true quantization table 4a is not supplied to the apparatus 202, or if the apparatus 202 is not used and general image reproducing software or the like having no function of the switching 10 is used, the quantization table 8 for disturbance is used. , The inverse quantization 13 is performed, so that only the disturbed image can be reproduced.

It should be noted that header analysis 11, variable length decoding 1
2, inverse quantization 13, inverse transformation 14, and switching 10
Can be implemented in dedicated hardware, but is typically implemented by execution of a computer program.

Hereinafter, the above embodiment will be described more specifically.

FIG. 6 shows the configuration of the image encoding device 201 in more detail.

The image encoding device 201 performs the encoding processes 1, 2, and 3 as described above, and also performs the writing process 21 to obtain the true quantization table 4.
a is recorded on the IC card 22. Further, the quantization table 8 for disturbance is generated by the table generation process 23, and the encoded data 15 is generated by the encoded data generation process 24.
The quantization table 8 for disturbance is recorded in the header 16 of.

FIG. 7 shows the structure of the image decoding apparatus in more detail.

[0027] The image decoding device 202 is provided with the IC card 22.
Is set, the table reading process 31
As a result, the true quantization table 4 is output from the IC card 22.
Read a. And the switching process 10
The true quantization table 4a is automatically selected and passed to the inverse quantization process 13. On the other hand, if the IC card 22 is not set, the switching process 10 selects the disturbance quantization table 8 from the header analysis process 11 and passes it to the inverse quantization process 13.

According to the above embodiment, the security can be improved without greatly impairing the serviceability of image distribution. Further, by designing the quantization table 8 for disturbance, the degree and mode of disturbing the image can be freely set. For example, the outline of the image may be grasped by appropriate disturbance. As a result, it is possible to obtain an effect such as stimulating purchase will.

The present invention can be implemented not only in the above embodiment but also in various other forms. For example, the security key is not limited to an IC card, but may be recorded and distributed by another means.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating an outline of a conventional image encoding method.

FIG. 2 is a block diagram schematically showing a conventional image decoding method.

FIG. 3 is a block diagram showing a conventional encryption process.

FIG. 4 is a block diagram schematically showing an embodiment of a transmitting device according to the present invention.

FIG. 5 is a block diagram schematically showing an embodiment of a receiving-side device according to the present invention.

FIG. 6 is a block diagram illustrating details of an image encoding device on a transmission side.

FIG. 7 is a block diagram illustrating details of an image decoding device on the receiving side.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Image conversion process 2 Quantization process 3 Variable length encoding process 4 Quantization table 4a True quantization table 8 Disturbance quantization table 10 Switching process 11 Header analysis process 12 Variable length decoding process 13 Inverse quantization process 14 Inverse Conversion process 15 Encoded data 16 Header 21 Table writing process 22 IC card 23 Table generation process 24 Encoded data generation process 31 Table reading process 201 Image encoding device 202 Image decoding device

──────────────────────────────────────────────────続 き Continued on front page (51) Int.Cl. ⁶ Identification code FI H04N 7/167 H04N 7/167 Z

Claims (10)

[Claims] 1. A method in which a transmitting device encodes and transmits image data and a receiving device receives and decodes the encoded image data, wherein the transmitting device sets a predetermined key. Image encoding means for encoding image data using the image encoding means, and a disturbing key different from the key used by the image encoding means is added to the output data of the image encoding means and transmitted to the receiving side device. Coded data generating means for generating coded data to be generated, and key storing means for storing the same true key as the key used by the image coding means in a predetermined key transmission medium, wherein the receiving side device has A key acquisition unit that acquires a key from the key transmission medium; and an image decoding unit that decodes the encoded data received from the transmission side device using the key from the key acquisition unit to reproduce the image data. Image encoding / decoding method is characterized in that a means. 2. The method according to claim 1, wherein the image encoding unit includes a quantization unit that quantizes the image data using a predetermined quantization table as the predetermined key. An image encoding / decoding method, wherein the image decoding means has an inverse quantization means for inversely quantizing the image data using a quantization table as a key from the key acquisition means. 3. The method according to claim 1, wherein said receiving apparatus further comprises key extracting means for extracting said disturbing key from said encoded data, and said image decoding means comprises: An image encoding / decoding method characterized by selectively using a key from the key acquisition unit and the disturbance key from the key extraction unit. 4. The method according to claim 3, wherein said image decoding means uses a key from said key obtaining means when a key from said key obtaining means is supplied, and said key obtaining means Wherein the disturbing key from the key extracting means is used when no key is supplied from the image encoding / decoding system. 5. The image encoding / decoding method according to claim 1, wherein the key transmission medium is a transportable data storage. 6. The method according to claim 1, wherein the disturbing key decodes the encoded data using the disturbing key, so that the outline of the original image data can be grasped. An image encoding / decoding method characterized in that image data that has been disturbed to a certain extent can be reproduced. 7. An image encoding device that encodes image data using a predetermined key in an apparatus that encodes image data, and a disturbing key different from the key used by the image encoding device. Encoded data generation means for generating encoded data by adding to output data of the encoding means; and key storage means for storing the same true key as the key used by the image encoding means in a predetermined key transmission medium An image encoding device comprising: 8. An apparatus for decoding original image data from encoded data including an internal key and encoded image data, wherein the key acquiring means acquires an external key from a predetermined key transmission medium; An image in which the encoded data is decoded by selectively using any of a key extracting unit for extracting an internal key from the encoded data and an external key from the key acquiring unit and an internal key from the key extracting unit. An image decoding device, comprising: decoding means. 9. An image encoding unit that encodes image data using a predetermined key, and a disturbance key different from the key used by the image encoding unit is added to output data of the image encoding unit. An image encoding apparatus comprising: encoded data generating means for generating encoded data; and key storage means for storing the same true key as the key used by the image encoding means in a predetermined key transmission medium. As a computer-readable recording medium carrying a program for causing a computer to function. 10. An apparatus for decoding original image data from encoded data including an internal key and encoded image data, wherein the key acquiring means acquires an external key from a predetermined key transmission medium; An image in which the encoded data is decoded by selectively using one of a key extraction unit for extracting an internal key from the encoded data, an external key from the key acquisition unit, and an internal key from the key extraction unit. A computer-readable recording medium carrying a program for causing a computer to function as an image decoding device including a decoding unit.