JP3521723B2 - Digital camera and image authentication system using the same - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a digital camera that records captured images as digital data.

[0002]

2. Description of the Related Art Conventionally, when taking a picture, a camera has been used which records an image by irradiating a film with light taken in from a lens and causing a chemical reaction. With the above cameras, photographs 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 salt photograph.

On the other hand, in recent years, a digital camera is widely used, which converts light into an electric signal by an optical sensor such as CCD, converts the light into a digital signal, and then records it in a recording medium such as a flash memory. With a digital camera,
Images can be saved and various processing can be easily done by individuals using a personal computer, etc., and by printing with a printer, photographs can be printed without developing the film. Improvements in the print 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 a certification photograph for property insurance, the image photographed by the digital camera can be easily processed by a personal computer or the like. Since it can be processed without leaving a trace of processing as compared with silver salt photographs, it is difficult to determine even if an illegally processed so-called tampered photograph is used, and it may be misused. There is a problem that there is.

Therefore, it is an object of the present invention to provide a digital camera which outputs image data capable of confirming whether or not the image data at the time of photographing is changed, and an image authentication system using the same.

[0006]

According to the digital camera of the present invention, an optical sensor having a plurality of pixels, means for converting the output of the optical sensor into image data composed of digital signals, In a digital camera having a compression means for irreversibly compressing image data and a recording medium for recording the irreversibly compressed image data, either a checksum, a CRC or a one-way hash function is used as tampering detection data from the irreversibly compressed image data. And a means for encrypting any of the alteration detection data, and a means for integrally recording the lossy compressed image data and the encrypted alteration detection data on a recording medium. . Therefore, if the image data recorded on the recording medium at the time of shooting is changed by even one bit after being output from the digital camera, the image data and the tampering detection data are inconsistent, and the image data is changed after shooting. It can be judged that it was done. Further, if the image data and the tampering detection data are consistent with each other, it can be determined that the image remains as it was at the time of shooting. As a method for generating the tampering detection data, a method for obtaining a checksum of the image data or a CRC (Cyclic Redundanc) is used.
y check) or one-way hash function
function) can be used.

Further, since the tampering detection data is encrypted, the image data may be changed to another image data for which the same tampering detection data can be obtained, or the tampering detection data may be changed in accordance with the change of the image data. Can be prevented from being rewritten.

According to the digital camera of the second aspect of the present invention, since the recording medium is detachable, the recording medium can be used as an output means from the digital camera. In addition, when inputting image data by directly reading the recording medium removed from the digital camera with a personal computer, etc., in order to output as image data that can be judged whether it has been changed from the time of shooting, image data and tampering detection It is necessary that the usage data and the recording data are recorded integrally on the recording medium.

According to the image authentication system of the third aspect of the present invention, a means for inputting the integrally recorded lossy compressed image data and the encrypted alteration detection data, and the lossy compressed image. And a means for collating the data with any of the decrypted and encrypted alteration detection data, it is possible to determine whether or not the input image data is changed after being recorded by the digital camera.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described in detail below with reference to the drawings.

FIG. 2 shows a digital camera 1 according to an embodiment of the present invention.
It is a block diagram for explaining. Control device 11, condenser lens 12, CCD (Charge Coupl) as an optical sensor
ed Device) 13, A / D converter 14, RAM (Random
Access memory) 15, a flash memory 16 as an image recording medium for recording image data, an interface 17 for outputting the contents of the flash memory 16 to an external personal computer 20, and the like. Control device 11
Includes a CPU, a ROM in which a program for performing various controls of the digital camera 1 is recorded, and an input / output unit.

FIG. 1 is a flow chart showing a process of photographing by the digital camera 1. When the user presses the shutter of the digital camera 1, step S10
Then, the light condensed by the condenser lens 12 is input to the CCD 13 and converted into an electric signal. The aperture of the condenser lens 12 and the shutter speed, that is, the accumulation time of the CCD 13 are controlled automatically by the control device 11 or by user's instruction. As the CCD 13, for example, as shown in FIG. 3, a CCD 13 in which a plurality of pixels having R (Red), G (Green), and B (Blue) primary color filters are arranged in a matrix is used to capture a color image. be able to. C (Cyan), M (Magenta),
C with Y (Yellow) and G (Green) complementary color filters
Sometimes a CD is used.

In step S11, the electric signal output from the CCD 13 is converted into a digital signal by the A / D converter 14, and in step S12 the digital data output from the A / D converter 14 is DMA ( Dire
It is recorded by directly specifying the address of the RAM 15 by the ct Memory Access) without going through the control device 11. RAM1
As 5, a DRAM having a self-refresh function can be used.

In step S13, various image corrections such as white balance adjustment, interpolation processing, and color correction are performed on the data recorded in the RAM 15.

In step S14, the data corrected in step S13 in order to increase the number of recordings on the image recording medium is processed by JPEG (Joint Photographic Experts Group).
The image data is compressed by a method such as the above to generate a small amount of image data. JPEG has about 1 of 256 gradations for each color of R, G and B.
It is an irreversible image compression method that can handle 6.7 million-color images, and the storage image quality can be adjusted by changing the compression rate. JPEG compression is
In addition to the software operation by the control device 11, a dedicated circuit can be used for speeding up.

In step S15, the tampering detection data is generated by the control device 11 based on the image data generated in step S14. A checksum, for example, can be used as the tampering detection data. Here, it is assumed that the binary representation of the image data 32 is shown in FIG. As shown in FIG. 4A, the control device 11 calculates a total value of 8 bits without carry in the horizontal direction of the image data, and when it is used as a checksum 33, the image data 32 is changed. If
Checksum 3 and total value obtained from image data 32
Since 3 is inconsistent, it is possible to determine whether the image data 32 has been changed by collating the image data 32 with the checksum 33. In this case, if 2 bits are changed in one row, it cannot be detected that the change has been made. Therefore, as shown in FIG.
For bits, the checksum 33 in which the total value is calculated in each column may be further used.

In addition to the checksum, a known method for error detection used in data communication, which can detect whether the data has been changed from the original, such as a CRC method and a one-way hash function, is provided. It can be applied to the invention. By using these methods,
Different tampering detection data can be assigned to each image data, and it is very difficult to reproduce the original image data from the tampering detection data, and it can be said that there is no practical problem.

In step S16, the tampering detection data such as the checksum 33 is encrypted by the control device 11 into the encrypted data 34 so as not to be analyzed or easily rewritten. As an encryption method, a known method such as an RAS method using a public key and a secret key can be used. Encrypted data 34 encrypted with a private key
Can be decrypted using the public key paired with the private key. The private key is stored in the digital camera 1 and should not be known to others. Also, the user does not need to know the private key. However, it is very difficult to obtain the private key from the public key. As a result, it is possible to prevent the image data 32 from being changed to another image data that can obtain the same checksum 33 and the checksum 33 from being rewritten in accordance with the change of the image data 32.

In step S17, the image data 32 and the encrypted data 34 are integrally 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 that can retain the contents that have been recorded without continuing to energize, and is built in the digital camera 1 or detachably attached to the digital camera 1. J
As shown in FIG. 5, the PEG file 30 generally includes a header section 31 containing information such as data length and compression rate, and image data 32. In the case of the JPEG file 30 recorded by the digital camera 1, information such as shooting date and shooting conditions such as shutter speed can also be recorded in the header section 31. In this embodiment, the encrypted data 34 is further added to the header part 31 and recorded.

The flash memory 16 is the digital camera 1.
If the JPEG file 30 does not include the tampering detection data such as the encrypted data 34, it is stored in the flash memory 16 if it cannot be removed. 20
Alteration detection data is generated at the stage of outputting to
It is also possible to add and output to the header part 31 of the G file 30. If you can transfer images from the personal computer 20 to the digital camera 1, JPE
It is necessary to distinguish the header portion 31 of the G file 30 and the like so that the alteration detection data is not added when the G file 30 is transferred to the personal computer 20 again.

On the other hand, if the flash memory 16 is detachable from the digital camera 1 and its contents can be read by a personal computer or the like, or if the digital camera 1 itself has a function of correcting an image, image data In order to integrally output the tampering detection data and the tampering detection data, it is necessary that the tampering detection data be simultaneously recorded when the image data is recorded in the flash memory 16.

To determine whether or not the digital camera 1 as described above, the personal computer 20 having means for inputting the image data output from the digital camera 1, and the image data recorded by the digital camera 1 have been changed. An image authentication system is configured by the authentication program installed in a computer such as the personal computer 20.

As a means for inputting image data and tampering detection data to the personal computer 20, a serial cable 18 is used.
A method of transferring the JPEG file in the flash memory 16 to the personal computer 20 by connecting to the interface 17 of the digital camera 1 via the
In the case where the JPEG file 30 is removable and is formatted in a format compatible with the personal computer 20, the personal computer 20 can directly read the JPEG file 30 recorded in the flash memory 16 via the adapter.

When the encrypted data 34 in the header portion 31 of the JPEG file 30 is encrypted by the private key in the digital camera 1, the authentication program uses the public key to encrypt it by the private key. You can decrypt the code at the same time. By collating the decoded tampering detection data with the image data, it is possible to determine whether or not the image data has been changed since the time when the tampering detection data was generated. If the encrypted data 34 does not exist, the encrypted data 34
If the decrypted tampering detection data and the image data are inconsistent, the image data may not have been captured by the digital camera 1 of the embodiment of the present invention, or It is considered changed.

Therefore, when the image authentication system according to the embodiment of the present invention is used, the person who submits the photograph includes a file including the image data which is output from the digital camera 1 and is not changed (the JPEG file 30 in this embodiment). Is recorded on a recording medium such as a floppy disk, or a removable recording medium from which the flash memory 16 is removed from the digital camera 1 is submitted together with a printed photograph at the request of the other party. The receiving side reads the file received by using the authentication program installed in the personal computer 20 and examines it to confirm that the image data of the file has not been changed since the time when it was output from the digital camera 1. You can

By providing the authentication program with the function of displaying the image of the image data such as the JPEG file 30, it can be confirmed that the printed photograph and the displayed image are the same.

As described above with reference to the embodiments, by using the digital camera of the present invention and the image authentication system using the same, the photograph taken by the digital camera has not been changed since the time of photographing, and has not been tampered with. , You can confirm that it is the original one.

In the above embodiment, JPEG-compressed data is recorded as image data on the image recording medium, but the present invention can be compressed by other compression methods or uncompressed data can be recorded as image data. Can also be applied. Further, although the alteration detection data is recorded in the header portion of the JPEG file, the alteration detection data may be located at any position in the image data in the present invention. Regardless of whether the image data is uncompressed, reversibly compressed, or lossy compressed, the information of tampering detection data cannot be discriminated by the naked eye by the electronic watermark technology. Can be included in the image data.

Further, in this embodiment, the alteration detection data and the image data are integrally recorded as a JPEG file, but the alteration detection data may be recorded as a separate file and associated with the image data.

[Brief description of drawings]

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

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

FIG. 3 is a schematic diagram showing a CCD used in a digital camera according to an embodiment of the present invention.

FIG. 4 is a diagram illustrating a method of calculating a checksum of image data according to an embodiment of the present invention.

FIG. 5 is a diagram for explaining a method of recording image data and tampering detection data according to an embodiment of the present invention.

[Explanation of symbols]

1 digital camera 11 Control device 12 Condensing lens 13 CCD (optical sensor) 14 A / D converter 15 RAM 16 Flash memory (image recording medium) 17 Interface 18 connection cable 20 personal computers 30 JPEG files 31 Header 32 image data 33 Checksum (tampering detection data) 34 Encrypted data (tampering detection data)

─────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-10-164549 (JP, A) JP-A-11-98461 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) H04N 5/76-5/956

Claims (3)

(57) [Claims] 1. An optical sensor having a plurality of pixels, means for converting the output of the optical sensor into image data composed of digital signals, compression means for irreversibly compressing the image data, and recording irreversibly compressed image data. Recording medium,
A digital camera having: a means for generating either a checksum, a CRC, or a one-way hash function as tampering detection data from the lossy-compressed image data; and a means for encrypting any of the tampering detection data. A digital camera comprising: a unit configured to integrally record the lossy-compressed image data and the encrypted tampering detection data on the recording medium. 2. The recording medium is removable.
Digital camera described in. 3. An image authentication system using the digital camera according to claim 1, wherein the lossy compressed image data recorded integrally and the encrypted tampering detection data are recorded. An image authentication system comprising: a means for inputting any one of them; and a means for collating the lossy compressed image data with any one of the decrypted encrypted alteration detection data.