JP2001078014A - Function addition method for digital camera, and recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize a function addition method for digital camera which can select whether or not a user is informed of that authentication data are added to a photographed picture. SOLUTION: A program which is recorded in an external recording, medium and pads picture alteration detection data into picture data is transmitted to a digital camera 1 from a personal computer 20 through an interface 17 and is installed in a flash memory 16 of the digital camera 1. At the time of installation of the program, the user can select whether it is installed so that the program name can be displayed or cannot be displayed. If the program is so installed that the program name cannot be displayed, the program name is not displayed in the set mode and cannot be deleted. Therefore, it is possible that the user is not informed whether alteration of a photographed picture can be detected or not when an owner of the digital camera 1 is different from the user.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for adding a function of detecting falsification of image data and recording authentication data for signature by an image data creator to image data recorded by a photographed digital camera. It is.

[0002]

2. Description of the Related Art Conventionally, when a photograph is taken, a camera is used in which light taken in from a lens is irradiated onto a film and a chemical reaction occurs to record an image. With the above camera, a photograph can be printed by developing the film and printing it on photographic paper. Since the reaction of silver chloride is generally used as the above chemical reaction, a photograph taken by such a camera is called a silver halide photograph.

On the other hand, in recent years, digital cameras that convert light into an electric signal by an optical sensor such as a CCD, convert the light into a digital signal, and then record the digital signal on a recording medium such as a flash memory have become widespread. With a digital camera,
Images can be easily stored and various processes can be easily performed by an individual using a processing device such as a personal computer, and a photograph can be printed without developing the film by outputting it with a printer. 2. Description of the Related Art Improvements in the printing quality of printers have made it possible to print high-quality photographs that are almost indistinguishable from silver halide photographs.

[0004]

However, when a photograph taken by a digital camera is used as an important proof photograph, such as when the photograph is to be used for a proof photograph such as non-life insurance, the image photographed by the digital camera becomes a personal computer. Etc., which makes it easier to process without leaving any trace of processing compared to silver halide photographs, making it difficult to discriminate even if a fraudulently tampered photograph is used. And there is a problem that it can be abused.

[0005] In addition, even in the case of a digital camera in which authentication data capable of detecting falsification of image data is added to the image data and recorded, if the user knows that the authentication data will be recorded, a normal operation is performed. When photographing with a digital camera, the photographer's consciousness may change, resulting in different photographing results. SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a digital camera function adding method capable of selecting whether to notify a user of adding authentication data to a captured image.

[0006]

According to the digital camera function adding method according to claim 1 of the present invention or a computer readable recording medium according to claim 7, a program for embedding authentication data in image data is stored in a digital camera. And a procedure for selecting whether or not the fact that the program for embedding the authentication data is installed can be displayed on the display unit of the digital camera. For this reason, if the owner of the digital camera and the photographer are different and you do not want to be notified whether or not to embed the authentication data, it is impossible to display that the program for embedding the authentication data is installed, It can be used as a normal digital camera for the person. If the photographer wants to be notified that a program for embedding authentication data is installed, the photographer can select to display the program. Authentication data includes image tampering detection data,
Electronic signature data or the like can be used.

According to the digital camera function adding method of the second aspect of the present invention, it is determined at the time of introduction of the program whether or not it is possible to display that the program for embedding authentication data is installed.

According to the digital camera function adding method according to the third aspect of the present invention or the computer-readable recording medium according to the eighth aspect, image data photographed by the digital camera is compressed and recorded. Therefore, the number of recorded images can be increased. As a compression method, it is possible to use a compression method, such as JPEG, which makes it difficult to determine image degradation with the naked eye.

According to the digital camera function adding method according to the fourth aspect of the present invention or a computer-readable recording medium according to the ninth aspect, a procedure for introducing a program for encrypting authentication data into the digital camera is included. Therefore, it is possible to prevent the authentication data from being rewritten according to the change of the image data.

According to the digital camera function adding method of the present invention or the computer-readable recording medium of the present invention, image tampering detection data is used as authentication data. As the image alteration detection data,
A hash value calculated by a hash function can be used for the entire image data.

According to the digital camera function adding method of the present invention or the computer-readable recording medium of the present invention, digital signature data for authenticating an image creator is used as authentication data.

[0012]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 2 is a block diagram for explaining the digital camera 1 according to the embodiment of the present invention. Control unit 11, condenser lens 12, CCD as optical sensor
(Charge Coupled Device) 13, A / D converter 14,
RAM (Random Access Memory) 15, flash memory 16 as an image recording medium for recording image data, interface 17 for inputting / outputting the contents of flash memory 16 to an external processing device such as personal computer 20, and displaying images Liquid crystal display (LCD) 19
Etc. The control unit 11 includes a CPU, a ROM in which programs for performing various controls of the digital camera 1 are recorded, and an input / output unit. The flash memory 16 may be built in the digital camera 1, may be a memory card detachable from the digital camera 1, or may include both of them.

The digital camera 1 of the present embodiment transmits a program recorded on an external recording medium (for example, a magnetic disk or a CD-ROM) from the personal computer 20 to the digital camera 1 via the interface 17. Can be installed (installed) in the flash memory 16 of the digital camera 1. A program for introducing the program is also recorded on an external recording medium, and is executed by the personal computer 20, whereby the program is installed. The program installed in the digital camera 1 can be executed by the control unit 11 of the digital camera 1. The program may be installed in a digital camera 1 by recording the program in a removable memory card and transmitting the program to a flash memory 16 built in the digital camera 1.

In the present embodiment, a program (hereinafter referred to as a watermark program) including a procedure for generating image falsification detection data as authentication data in image data, and for embedding the image data in the image data by a digital watermarking method by generating feature data from the image data is used. Introduce to the camera. When photographing is performed by the digital camera 1, the above-described program is executed, and image data is recorded in the flash memory 16. When installing the program, the user can select whether to install the program name so that it can be displayed or not. The installation of the program may be performed by the owner himself after purchasing the digital camera 1, or may be sold with the program installed.

The user inputs settings to the input keys provided on the digital camera 1 to set a photographing mode for photographing with the digital camera, a reproduction mode for displaying already photographed images, and various settings for operation of the digital camera. Modes can be switched. In the setting mode, a program name indicating the type of the installed program can be displayed on the LCD 19. Also,
The program name can be selected by operating the input key to delete the program.

If the program name is installed so that the program name cannot be displayed at the time of installation, the program name is not displayed in the setting mode and cannot be deleted. Therefore, in a case where the owner of the digital camera 1 is different from the photographer and the user does not want to inform the photographer whether or not tampering of the photographed image can be detected, the photographer can use the digital camera 1 as a normal digital camera. it can.

FIG. 1 is a flowchart showing a process in which a digital camera 1 in which a watermark program is installed performs photographing. When the user presses the shutter of the digital camera 1, the light condensed by the condenser lens 12 is input to the CCD 13 and converted into an electric signal in step S101. The aperture and shutter speed of the condenser lens 12, that is, the accumulation time of the CCD 13 are controlled by the control unit 11.
Automatically or by user instructions. As the CCD 13, for example, R (Red), G (Gre
By using the CCD 13 in which a plurality of pixels having primary color filters of en) and B (Blue) are arranged in a matrix, a color image can be taken. C (Cya
n), a CCD having complementary color filters of M (Magenta), Y (Yellow), and G (Green) may be used.

In step S102, the electric signal output from the CCD 13 is converted into a digital signal by the A / D converter 14. In step S103, the electric signal is converted into a digital signal.
Digital data output from DMA for high speed
(Direct Memory Access) and directly specifies the address of the RAM 15 without the intervention of the control unit 11 and is recorded. RA
DRAM with self-refresh function as M15
Can be used.

In step S104, various image corrections such as white balance adjustment, interpolation processing, and color correction are performed on the data recorded in the RAM 15. Here, other image processing such as enlargement / reduction of an image may be performed.

In steps S105 to S110, steps S104 and S104 are performed to increase the number of images to be recorded on the image recording medium.
Data corrected by JPEG (Joint Photographic E
xperts Group) to generate small-capacity image data. The JPEG compression is performed by the control unit 11 using software, and a dedicated circuit can be used for speeding up.

The procedure of JPEG compression will be described below. In step S105, first, the image data is set to 8 × 8 pixels by 1
Divide into multiple blocks as a unit. For example, 640
80 × 60 = 48 for image data of × 480 pixels
It is divided into 00 blocks, and the processing is performed in block units.

Next, the relative relationship (spatial frequency) between the densities of the pixels is checked for each block of B1 to B480, and the DC
Each block is divided into a low-frequency term DCT0 to a high-frequency term DCT63 by a T (spread cosine transform) method. DCT0 to DCT63 are 8-bit values. FIG. 3 shows the DCT 63 of the high frequency term in hexadecimal. Then, quantization is performed using a predetermined quantization table so that many of the high-frequency terms become zero, and the compression ratio becomes high when Huffman coding is performed in a later process.

In step S106, the DCT 63, which is the highest frequency component in each block, is examined in order from the top block of the DCT-converted image data in order to determine the position where feature data is to be embedded in a later process. . Then, blocks whose DCT value is other than 0 and 1 are stored as embedded blocks. In the example shown in FIG. 3, B3, B4, B5, and B6 are selected and stored as embedded blocks. In this embodiment, since a 128-bit hash value is used, 1
28 blocks are selected. 128 embedded blocks
If the number of embedded blocks is less than the number of embedded blocks, when the number of missing embedded blocks matches the unexamined block, all remaining blocks are regarded as embedded blocks. Then, all the least significant bits of the DCT 63 of the embedded block are replaced with 0. Thereby, for example, the DCT 63 of the block B4 is F
Although rewritten from F to FE, small fluctuations at high frequencies are barely detectable to the naked eye, and image distortion is minimized.

In step S107, step S106
The control unit 11 generates feature data based on the image data partially rewritten in. As the feature data, for example, hash values calculated by various one-way hash functions can be used. In addition to a hash value, a known method such as a checksum or a CRC method that can detect whether or not data has been changed from the original can be applied to the present invention. By using these methods, different feature data can be assigned to each image data, and it is almost impossible to reproduce the original image data from the feature data. In this embodiment, a 128-bit hash value is calculated as the feature data. For example, an MD5, SHA or RIPEMD hash function can be used.

In step S108, the control unit 11 encrypts the characteristic data such as the hash value so that the characteristic data is not easily analyzed or rewritten to obtain encrypted data. As an encryption method, a known method such as the RAS method using a public key and a secret key can be used. The encrypted data encrypted with the secret key can be decrypted using the public key paired with the secret key. The secret key is recorded in the digital camera 1 as a file with a hidden attribute. The secret key must not be known to others, and in this embodiment, the user does not need to know the secret key. In general, it is very difficult to find a corresponding private key from a public key. As a result, it is possible to prevent the image data from being changed to another image data that can obtain the same feature data, and from being rewritten in accordance with the change in the image data.

In step S109, the encrypted data obtained by encrypting the hash value is written one bit at a time to the least significant bit of the DCT 63 of the selected embedded block, thereby minimizing the deterioration of the image and reducing the characteristic data to the image data. Embed in In the case of a color image, JPEG image data is Y (luminance), U, V (hue).
, But the encrypted feature data is embedded in the Y component.

In step S110, the data in which the encrypted data is embedded is subjected to Huffman encoding to compress the data. In Huffman coding, the reversibility of data is satisfied, and there is no loss of data before and after processing. The compression ratio can be changed by changing the degree of quantization by the quantization table in S105.

In step S111, the image data compressed in step S110 is recorded as a JPEG file 30 in the flash memory 16 as an image recording medium. The flash memory 16 is a rewritable recording medium capable of storing recorded contents without power supply, and is built in the digital camera 1 or is detachably attached to the digital camera 1. Generally JPEG file 3
0 is composed of a header section 31 including information such as a data length and a compression ratio and an image data section 32 as shown in FIG.
In the case of the JPEG file 30 recorded by the digital camera 1, information such as a photographing date and photographing conditions is also included in the header section 3.
1 may be recorded. In this embodiment, the public key 33 corresponding to the secret key used for encryption is further added to the header section 31 and recorded.

If the setting is made so that the watermark program is not executed in the setting mode, the data that has been DCT-transformed and quantized in step S105 is compressed by Huffman coding in step S110 according to the same procedure as ordinary JPEG compression. Is done.

In the above example, the feature data is embedded in a process in the middle of the JPEG compression. , The feature data may be embedded by the same process as in steps S106 to S109, and Huffman encoding may be performed again.

The digital camera 1 as described above, a computer such as a personal computer 20 having means for inputting image data output from the digital camera 1, and whether or not the image data recorded by the digital camera 1 has been changed The image tampering detection system is configured by a detection program installed in the personal computer 20 or the like to determine the falsification.

The process of detecting image tampering by the image tampering detection system of this embodiment will be described with reference to the flowchart shown in FIG. In step S201, image data is read from the digital camera into the personal computer 20 by the detection program. As means for reading image data into the personal computer 20, the personal computer 20 is connected to the interface 17 of the digital camera 1 via a serial cable 18 or the like,
When the EG file is transferred to the personal computer 20, or when the flash memory 16 is detachably formatted in a format compatible with the personal computer 20, the JPEG file recorded on the flash memory 16 via the adapter is used. It is also possible to read 30 directly by the personal computer 20.

In step S202, the above step S
In the same procedure as when the block in which the feature data is embedded is selected in 106, a block in which the feature data is to be embedded is selected, and 128-bit encrypted data is extracted.

In step S203, all 0s are written into the bits where the encrypted data is embedded, and the original image data before the encrypted data is embedded is generated. In step S204, 1 is performed in the same procedure as in step S106.
Calculate a 28-bit hash value.

In step S205, step S202
Using the public key written in the header of the JPEG file, it is confirmed that the encrypted data extracted by the above is encrypted by the secret key, and at the same time, the encryption is decrypted. Thereby, a hash value before encryption is obtained.

In step S206, step S204
The hash value calculated in step S205 is compared with the hash value calculated in step S205, and if they match, it is determined that the image data has not been altered after being photographed by the digital camera 1 of the present embodiment, If they do not match, it is determined that the image data has been altered from the time of shooting. Also, in step S205, even if the encrypted data cannot be decrypted with the public key, it is considered that the image data was not captured by the digital camera 1 of the embodiment of the present invention or changed after the capture.

Therefore, when using the image tampering detection system according to the embodiment of the present invention, the submitter of the photograph is required to output a file containing the unmodified image data output from the digital camera 1 (in this embodiment, the JPEG file 30). ) Is recorded on a recording medium such as a floppy, or a flash memory 16 which is a removable recording medium removed from the digital camera 1 is submitted together with a printed photograph or at the request of the other party. The receiving side reads the received file using the detection program installed in the personal computer 20 and checks it, thereby confirming that the image data of the file has not been changed since the time when it was output from the digital camera 1. be able to.

Further, by providing the detection program with a function of displaying an image of image data such as the JPEG file 30, it is possible to confirm that the printed photo and the displayed image are the same.

In the above embodiment, JPEG-compressed data is recorded as image data on the image recording medium. However, the present invention is not limited to data compressed by another compression method, or uncompressed data recorded as image data. Can also be applied. Further, in the present embodiment, the feature data is encrypted and embedded in the image data portion of the JPEG file and recorded. However, according to the present invention, the feature data can be written in any position of the image data, such as writing in the header portion. Good.

Further, in this embodiment, the image falsification detection data which is destroyed by a slight change of the image data and can detect the falsification of the image is used as the authentication data.
Digital signature data that can authenticate the creator of the image data may be used. The electronic signature data can be embedded in the image data so that the data is not easily lost even if the image data is modified.

[Brief description of the drawings]

FIG. 1 is a flowchart illustrating a procedure for recording an image by a digital camera according to an embodiment of the present invention.

FIG. 2 is a block diagram illustrating a digital camera according to an embodiment of the present invention.

FIG. 3 is a schematic diagram for explaining a method for calculating feature data of image data according to an embodiment of the present invention.

FIG. 4 is a schematic diagram for explaining a structure of a JPEG file according to an embodiment of the present invention.

FIG. 5 is a flowchart illustrating a procedure for detecting tampering of image data according to the embodiment of the present invention.

[Explanation of symbols]

 Reference Signs List 1 digital camera 11 control unit 12 condenser lens 13 CCD (imaging unit) 14 A / D conversion unit 15 RAM 16 flash memory 17 interface 18 connection cable 19 liquid crystal display unit (LCD) 20 personal computer 30 JPEG file 31 header unit 32 image Data 33 public key

Continued on front page F-term (reference) AA14 AA36 BA06

Claims (11)

[Claims] 1. A method for adding a function to a digital camera that converts light from a shooting target into image data, comprising: introducing a program for embedding authentication data into the image data into the digital camera; Selecting whether or not to display on the display unit of the digital camera that a program for embedding is installed, on the display unit of the digital camera. 2. The method according to claim 1, wherein whether or not it is possible to display that the program for embedding the authentication data is installed is determined when the program is installed.
The method for adding functions of the digital camera described in the above. 3. The method according to claim 1, wherein the image data is compressed and recorded. 4. The digital camera function adding method according to claim 1, further comprising a step of introducing a program for encrypting the authentication data into the digital camera. 5. The digital camera according to claim 1, wherein the authentication data is image falsification detection data for determining whether there is tampering after image data generation. Method. 6. The authentication data according to claim 1, wherein the authentication data is electronic signature data for authenticating an image creator.
The method for adding functions of a digital camera according to any one of the above. 7. A program for adding a function to a digital camera for converting light from an object to be photographed into image data, wherein a program for embedding authentication data in the image data is introduced into the digital camera; A step of selecting whether or not it is possible to display on the display unit of the digital camera that the program for embedding is installed, on the display unit of the digital camera. 8. The recording medium according to claim 7, wherein the image data is compressed and recorded. 9. The recording medium according to claim 7, further comprising a step of introducing a program for encrypting the authentication data into the digital camera. 10. The computer-readable program according to claim 7, wherein the authentication data is image tampering detection data for determining whether there is tampering after image data generation. Recording medium on which is recorded. 11. The apparatus according to claim 7, wherein the authentication data is electronic signature data for authenticating an image creator.
10. A recording medium on which the computer-readable program according to any one of 9 is recorded.