JP2004228866A - Communication terminal with digital camera, image authentication system using it, and image authentication method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a communication terminal with a digital camera which enables a third person to guarantee the presence / absence of an alteration to photographed digital images, an image authentication system using it, and an image authentication method. <P>SOLUTION: The communication terminal with the digital camera is provided with an optical system (S110) for forming the optical image of a subject, a conversion means (S115) for converting the formed optical image of the object into a digital image, a first generation means (S120) for generating first authentication information for discriminating the presence / absence of an alteration to the digital image on the basis of the digital image converted in the conversion means, a transmission means (S135) for transmitting the first authentication information to an authentication server, and an output means (S145) for outputting the digital image. A user can access only the digital image after the first authentication information is generated. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a communication terminal with a digital camera, an image authentication system using the same, and an image authentication method.
[0002]
[Prior art]
In recent years, mobile phones having a digital camera function have become widespread. For this reason, when it becomes necessary to take a proof photograph suddenly for some reason, it is expected that the chance of using a digital camera provided in a mobile phone for the photographing will increase. For example, if you take a picture of the scene to make a proof picture when claiming non-life insurance when a traffic accident occurs, if you have a mobile phone with a digital camera function, take a picture of the place with the digital camera That can be expected. However, there is a problem that a digital image recorded by a digital camera is easy to process and may be falsified and abused.
[0003]
2. Description of the Related Art Conventionally, there has been known a digital camera that outputs a digital image capable of detecting whether or not tampering has been performed (for example, Patent Document 1). According to the digital camera of Patent Literature 1, feature data (first authentication information) is generated from image data (digital image), and the generated feature data is embedded in the image data. It can be determined whether or not tampering has been performed.
[0004]
[Patent Document 1]
JP 2001-78070 A
[0005]
[Problems to be solved by the invention]
However, according to the conventional digital camera, although tampering after the feature data is embedded in the digital image can be determined, tampering by the photographer before embedding the feature data cannot be determined. If the digital image is altered by the photographer before embedding the feature data, the feature data generated based on the altered digital image will be embedded in the altered digital image. In this case, if tampering is not performed thereafter, it is only determined that there is no tampering in the determination using the embedded feature data. Therefore, a digital image that has been falsified by the photographer is treated as valid evidence.
[0006]
SUMMARY OF THE INVENTION The present invention has been made in view of the above-described problems, and has been made in consideration of a communication terminal with a digital camera capable of guaranteeing whether a captured digital image has been tampered with by a third party, an image authentication system using the same, and an image authentication method. The purpose is to provide.
[0007]
[Means for Solving the Problems]
In order to achieve the above object, a communication terminal with a digital camera according to the present invention comprises: an optical system that forms an optical image of a subject; a conversion unit that converts the formed optical image of the subject into a digital image; First generating means for generating first authentication information for determining whether the digital image has been tampered with, based on the digital image converted in step 1, transmitting means for transmitting the first authentication information to the authentication server, Output means for outputting, wherein the user can access only the digital image after the first authentication information is generated. According to this communication terminal with a digital camera, the user cannot access the digital image before the first authentication information is generated by the generation means. Therefore, the digital image before the first authentication information is generated cannot be altered even by the photographer himself. Since the generated first authentication information is transmitted to the authentication server, tampering after the digital image can be accessed is based on the first authentication information transmitted to the authentication server and the falsified digital image. It can be determined by comparing the authentication information generated with the authentication information. Therefore, even if the tampering has been performed by the photographer himself, it can be determined. If the authentication server is installed in a third-party authentication organization, if the authentication information generated based on the digital image is transmitted to the authentication organization, the third-party can assure whether the captured digital image has been tampered with. In addition, since the communication terminal with the digital camera according to the present invention transmits the first authentication information instead of transmitting the digital image itself to the authentication server, the transmission load and the storage load of the authentication server can be reduced.
[0008]
Further, the communication terminal with a digital camera according to the present invention further comprises transmission instruction means for instructing whether or not to transmit the first authentication information, wherein the transmission means is instructed to transmit by the transmission instruction means. Only the first authentication information is transmitted. According to the communication terminal with a digital camera, the user can instruct whether to transmit the first authentication information.
[0009]
Further, the communication terminal with a digital camera according to the present invention further comprises an embedding means for embedding the first authentication information as a digital watermark in the digital image, and the output means outputs the digital image in which the first authentication information is embedded. Features. According to the communication terminal with a digital camera, tampering after embedding the first authentication information can be determined as tampering based only on the digital image, and the load on the authentication server can be reduced.
[0010]
Further, the transmitting means of the communication terminal with the digital camera according to the present invention transmits a camera ID capable of uniquely identifying the communication terminal with the digital camera to the authentication server in association with the first authentication information, and the output means outputs the camera ID. It is characterized in that it is output in association with a digital image. According to this communication terminal with a digital camera, the reliability of determination of the presence or absence of tampering can be improved by transmitting and outputting the camera ID.
[0011]
To achieve the above object, an image authentication system according to the present invention is a communication terminal with a digital camera according to claim 1, an authentication server and an image authentication system using the authentication terminal, wherein the authentication server has a digital camera. Receiving means for receiving the first authentication information from the communication terminal; storage means for storing the received first authentication information; verification request receiving means for receiving the second authentication information from the authentication terminal; A verification result returning means for performing verification based on the authentication information and the second authentication information received from the authentication terminal and returning a verification result, wherein the authentication terminal includes an input means for inputting a digital image, and an input digital image. A second generation unit that generates the second authentication information from the authentication server; a verification request transmission unit that transmits the generated second authentication information to the authentication server; Characterized in that it comprises discriminating means for discriminating tampering of a digital image, a based on the results. According to this image authentication system, by installing the authentication server in an authentication institution as a third party, the third party can assure whether or not the captured digital image has been tampered with.
[0012]
Further, the storage unit of the image authentication system according to the present invention stores the first authentication information in association with the reception, and the verification result returning unit stores the first authentication information matching the second authentication information received from the authentication terminal. When stored in the first authentication information, the reception time stored in association with the first authentication information is returned in association with the collation result. According to this image authentication system, it is possible to know the approximate time when the digital image was taken, and the validity of the digital image as evidence is improved.
[0013]
Each function of the plurality of means provided in the present invention is realized by a hardware resource whose function is specified by the configuration itself, a hardware resource whose function is specified by a program, or a combination thereof. The functions of the plurality of means are not limited to those realized by hardware resources which are physically independent of each other.
Further, the present invention can be specified not only as an invention of an apparatus, but also as an invention of a program, an invention of a recording medium on which the program is recorded, and an invention of a method.
[0014]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described based on examples.
FIG. 2 is a schematic diagram showing the configuration of the image authentication system 1 according to one embodiment of the present invention. The image authentication system 1 includes a mobile phone 2 as a communication terminal with a digital camera, an authentication server 3, and an authentication terminal 4. As shown, the mobile phone 2 is connected to a mobile phone network M via a base station L. The mobile phone network M is connected to a communication network N such as the Internet, and the authentication server 3 and the authentication terminal 4 are connected to the communication network N. Thereby, the mobile phone 2, the authentication server 3, and the authentication terminal 4 are communicably connected. The authentication server 3 is installed in, for example, a certification organization as a third party, and the authentication terminal 4 is installed in, for example, an insurance company.
[0015]
FIG. 3 is a block diagram illustrating a configuration of the mobile phone 2.
The wireless communication unit 25 as a transmission unit and an output unit includes a modulation / demodulation circuit, an antenna for performing wireless communication with the base station L, and the like. The wireless communication unit 25 receives various digital signals such as audio data by demodulating a signal received by an antenna, and modulates various digital signals such as audio data, a digital image, first authentication information, and a camera ID. To transmit from the antenna.
[0016]
The audio input / output unit 22 includes a D / A converter, an A / D converter, a speaker, a microphone, and the like. The audio input / output unit 22 converts the audio data input from the wireless communication unit 25 into an analog signal using a D / A converter and sounds it through a speaker, and converts the analog signal input from the microphone into a digital signal using an A / D converter. And outputs the result to the wireless communication unit 25.
[0017]
The optical system 11 includes a lens, a diaphragm, and the like housed in a housing. The optical system 11 forms an optical image of a subject on a light receiving surface of the image sensor 12.
The image sensor 12 as a conversion unit is an area image sensor including a photoelectric conversion element discretely arranged in a two-dimensional space and a charge transfer element such as a CCD (Charge Coupled Device). The image sensor 12 is driven by a sensor controller 16. The image sensor 12 accumulates charges obtained by photoelectric conversion for each photoelectric conversion element for a certain period of time, and outputs an analog signal corresponding to the amount of light received for each photoelectric conversion element. Four complementary color filters of C (Cyan), M (Magenta), Y (Yellow) and G (Green) or primary color filters of R (Red), G (Green) and B (Blue) are provided on the light receiving surface. Thus, a color image can be formed.
[0018]
An A / D converter (ADC) 13 as a conversion unit quantizes an analog signal output from the image sensor 12 and converts the analog signal into a digital signal. Specifically, for example, the ADC 13 performs a process of reducing noise included in the analog signal, a process of adjusting a level of the analog signal by adjusting a gain, a quantization process, and the like.
The image forming unit 14 as a conversion unit performs image forming processing, white balance correction, γ correction, color space conversion, and the like on the digital signal output from the ADC 13, and performs R, G, and B gradation values for each pixel. And a digital image representing gradation values of Y, Cb, and Cr. Here, the image forming process means that a digital image having three gradation values of RGB or YCbCr is obtained for each pixel by interpolating pixels consisting of density information of one color with density information of different colors of neighboring pixels. This is the output process.
[0019]
The compression / decompression unit 15 compresses or decompresses a digital image. More specifically, the digital image is compressed at a predetermined compression rate by performing series conversion and entropy coding of the digital image, and the digital image is expanded by performing the inverse transform thereof. More specifically, digital image data is compressed using, for example, discrete cosine transform (DCT), quantization, wavelet transform, run-length coding, Huffman coding, or the like. Among these, the compression / decompression unit 15 of the present embodiment performs compression using DCT, quantization, and Huffman coding. When DCT and quantization are performed, some information is discarded. Therefore, if the first authentication information is embedded in a digital image before compression, the first authentication information cannot be restored when decompressed. For this reason, the compression / decompression unit 15 outputs the digital image after the DCT and the quantization and a part of the information is discarded to the authentication information generation process 52 described later, and the authentication information embedding process 51 described later. When the digital image in which the first authentication information is embedded is output from the device, Huffman encoding, which is the remaining compression processing, is performed on the output digital image.
[0020]
The operation unit 18 as transmission instruction means includes a plurality of number switches for inputting telephone numbers and the like, a transmission switch for instructing transmission, a response switch for instructing a response, and an instruction for converting an optical image into a digital image. , And various push button switches such as a switch for selecting various menus displayed on the LCD 26.
[0021]
The LCD 26 functions as an electronic viewfinder in the shooting mode. The display controller 23 includes a frame buffer for storing data to be displayed on the LCD 26, and a display circuit for driving the LCD 26 based on the data stored in the frame buffer.
The CPU 17 controls the entire mobile phone 2 by executing a computer program stored in the ROM 19. The CPU 17 also functions as a first generation unit and an embedding unit by executing a computer program stored in the ROM 19. The ROM 19 is a memory in which computer programs and data necessary for the operation of the CPU 17 and an ID (camera ID) capable of uniquely identifying the mobile phone 2 are stored in advance. The work memory 20 is a memory for temporarily storing various programs, data, and the like. The flash memory 27 is a nonvolatile memory for storing a compressed digital image.
[0022]
FIG. 4 is a block diagram illustrating a hardware configuration of the authentication server 3. The authentication server 3 includes a CPU 30, a ROM 31, a RAM 32, and a storage unit 34 as a storage unit, and a communication unit 33 as a reception unit, a collation request reception unit, and a collation result return unit. I have. The CPU 30 executes a computer program stored in the ROM 31 or the storage unit 34 to control the entire authentication server 3. The CPU 30 also functions as a verification result returning unit by executing a computer program. Further, the CPU 30 causes the authentication server 3 to function as a database by executing the database management program. The ROM 31 is a memory in which programs and data necessary for the operation of the CPU 30 are stored in advance. The RAM 32 is a memory that temporarily stores various programs, data, and the like. The storage unit 34 is configured by a hard disk or the like, and stores data such as an operating system (OS), various computer programs, first authentication information, a camera ID, and reception time. The communication unit 33 is configured to be connectable to the communication network N by a modem, a network interface card, or the like.
[0023]
FIG. 5 is a block diagram illustrating a hardware configuration of the authentication terminal 4. The authentication terminal 4 includes a CPU 40, a ROM 41, a RAM 42, a communication unit 47 as an input unit and a verification request transmission unit, a storage unit 45, an operation unit 43, and a display unit 44, which are interconnected by a bus 48. The CPU 40 executes a computer program stored in the ROM 41 or the storage unit 45 to control the entire authentication terminal 4. The CPU 40 also functions as a second generation unit and a determination unit by executing a computer program. The operation unit 43 includes a mouse, a keyboard, and the like, and is used for selecting a digital image that requires the authentication server 3 to perform verification. The display unit 44 is composed of a CRT, an LCD (Liquid Crystal Display), or the like, and displays a screen for selecting a digital image, a screen for notifying the result of determining whether there is tampering, and the like.
[0024]
These programs and various data may be input by downloading from a predetermined server via a network, or may be input by reading from a computer-readable storage medium such as a removable memory (not shown).
FIG. 6 is a data flow diagram in the mobile phone 2.
The authentication information generation process 52 is a process of generating first authentication information for determining whether the digital image has been tampered with based on the digital image. When the digital image [0] that has been subjected to DCT conversion and quantization is output from the compression / decompression unit 15, the authentication information generation process 52 performs first authentication based on the output digital image [0]. Information is generated, and the digital image [1] after the generation of the first authentication information and the generated first authentication information are output to the authentication information embedding process 51. Further, the generated first authentication information is output to the authentication information transmission process 55. The authentication information generation process 52 specifically calculates a hash value of the digital image using a hash function such as MD5, SHA, and RIPEMD, and uses the calculated hash value as first authentication information. Thereby, the first authentication information is generated. By using the hash function, different first authentication information can be generated for each digital image. In the present embodiment, the first authentication information is generated by a hash function. However, any method other than the hash function, such as a checksum or a CRC method, may be used as long as it can detect whether or not the digital image has been changed from the original. May be used.
[0025]
The authentication information embedding process 51 is a process of embedding the first authentication information as a digital watermark in a digital image. When the digital image [1] and the first authentication information are output from the authentication information generation process 52, the authentication information embedding process 51 embeds the first authentication information in the digital image [1] and performs the first authentication. The digital image [2] in which the information is embedded is output to the compression / expansion unit 15. The output digital image [2] is subjected to Huffman encoding, which is the remaining processing for compression, in the compression / decompression unit 15, and the compressed digital image [2] is output to the file management process 53. The embedding of the first authentication information is specifically performed by, for example, a patchwork method. The patchwork method is a method of embedding information by causing a statistical bias in a digital image. When there are a subset A = {a1, a2,..., An} and a subset B = {b1, b2,. A digital image has a property that an expected value Y of a difference between pixel values represented by the following equation is substantially zero.
Y = Σ (ai−bi) / N
According to this property, when “X” is added to each pixel value of the subset A and “X” is subtracted from each pixel value of the subset B, the expected value Y becomes substantially “2X”. Conversely, when "X" is subtracted from each pixel value of subset A and "X" is added to each pixel value of subset B, expected value Y becomes substantially "-2X". Accordingly, a certain positive / negative threshold value is set, and it can be determined that “1” is embedded when the expected value Y is larger than the positive threshold value, and “0” is embedded when the expected value Y is smaller than the negative threshold value. It can be determined that it has not been done. Thereby, information of one bit can be embedded. Therefore, assuming that a 128-bit hash value is generated, the first authentication information can be embedded as a digital watermark by dividing the digital image into 256 subsets. In order to extract embedded information, information for specifying a subset divided at the time of embedding is required. It is known to use a white noise mask as a method of dividing the pixels constituting the digital image into subsets on the embedding side and a method of uniquely specifying the divided subset on the extraction side. In the authentication information embedding process 51, specifically, for example, a white noise mask used by the authentication terminal 4 to specify the subset is stored in the ROM in advance, and the digital image is divided into subsets using the stored white noise mask. . When a white noise mask is used, the number of elements of a subset is substantially uniform, does not overlap each other, and pixels constituting one subset can be selected from the entire digital image in a well-balanced manner. When the digital watermark is embedded, tampering after embedding the first authentication information can be determined based only on the digital image. Therefore, the load on the authentication server 3 can be reduced.
[0026]
The file management process 53 is a process for centrally managing writing and reading of a digital image to and from the flash memory 27. When the digital image [2] after compression is output from the compression / expansion unit 15, the file management process 53 stores the output digital image in the flash memory 27. At this time, the file management process 53 does not store the digital image [2] as it is, but stores the digital image [3] obtained by adding the photographing time and the camera ID to the digital image [2]. Thereby, the camera ID and the shooting time are associated with the digital image. Here, the time of photographing refers to the date and time when the digital image [2] was output to the file management process 53, and it is assumed that when the digital image [2] was output, the digital image [2] was acquired from a timing unit (not shown). It is preferable that the timekeeping unit periodically corrects the date and time via the wireless communication unit 25. Further, the file management process 53 provides the user with an interface for accessing the digital image [3] stored in the flash memory 27. For example, when the user selects digital image [3] from a predetermined menu and instructs display, or instructs transmission, the selected digital image [3] is stored in the flash memory 27 via the file management process 53. Read from. That is, the user can access the digital image only through the file management process 53. As is apparent from FIG. 6, the flash memory 27 stores the digital image [3] in which the first authentication information is generated and embedded. Therefore, the user cannot access the digital image [0] before the first authentication information is generated.
[0027]
The authentication information transmission process 55 is a process in which the generated first authentication information and the camera ID are associated with each other and transmitted to the authentication server 3 via the communication network N. The authentication information transmission process 55 stores the first authentication information and the camera ID in one message to be transmitted, and transmits the camera ID in association with the first authentication information.
The image output process 56 is a process of outputting a digital image. Specifically, the image output process 56 outputs the image by transmitting it to the authentication terminal 4 via the communication network N by the wireless communication unit 25, for example. When the mobile phone 2 includes a storage unit using a removable storage medium such as a removable memory, the digital image is output by writing to the storage medium, and the digital image is passed to the authentication terminal 4 via the storage medium. Good.
[0028]
FIG. 1 is a sequence diagram showing a flow of processing of the image authentication system 1.
In S105, the mobile phone 2 receives an instruction whether to transmit the first authentication information. Specifically, for example, a screen for selecting an instruction is displayed, and when either “transmit” or “do not transmit” is selected by the user, information corresponding to the selection is stored in a predetermined area of the work memory 20. Store. For example, when “transmit” is selected, information indicating transmission is stored. If it is possible to instruct whether or not to transmit the first authentication information, it is possible to prevent the unnecessary transmission of the first authentication information to the authentication server 3 for digital images that do not need to be verified.
[0029]
In S110, an optical image is formed on the image sensor 12 by the optical system 11.
In S115, the optical image is converted into a digital image. More specifically, the formed optical image is converted into an analog signal by the image sensor 12, and is subjected to predetermined processing by the ADC 13 to be converted into a digital signal representing the subject. Next, the image forming section 14 performs predetermined image processing on the converted digital signal. This converts the optical image into a digital image. Next, the compression / expansion unit 15 performs compression processing up to DCT and quantization on the converted digital image, and outputs the digital image in the middle of compression to the authentication information generation process 52.
[0030]
In S120, by executing the authentication information generation process 52, the first authentication information for determining whether the digital image has been tampered with is generated based on the digital image. The authentication information generation process 52 outputs the digital image and the first authentication information after generating the first authentication information to the authentication information embedding process 51, and outputs the first authentication information to the authentication information transmission process 55. .
[0031]
In S125, the first authentication information is embedded in the digital image by executing the authentication information embedding process 51. The digital image after the first generation information is embedded is subjected to the remaining compression processing by the compression / decompression unit 15, and then output to the file management process 53 and stored in the flash memory 27.
In S130, it is determined whether to transmit the first authentication information. If it is instructed to transmit in S105, the process proceeds to S135. If it is instructed not to transmit, the process proceeds to S145 without transmitting.
[0032]
In S135, the authentication information transmitting process 55 is executed, and the first authentication information and the camera ID are transmitted to the authentication server 3 in association with the first authentication information. In general, the possibility that the first authentication information matches in different digital images is sufficiently low, but the possibility of using the camera ID in addition to the first authentication information can be further reduced. As a result, it is possible to further reduce the possibility that a record registered for another digital image will be searched in a database search described later, and it is possible to improve the reliability of determining whether a digital image has been tampered with.
[0033]
In S140, the authentication server 3 registers the received first authentication information and camera ID, and the reception time indicating the reception date and time as one record in the database. Here, the time of reception refers to the information indicating the date and time of reception in the present embodiment, but the time of reception may be information indicating only the date of reception or only the time of reception. May be information representing In the case of a date, the date may be a date or only a date, and these may be appropriately determined as necessary.
[0034]
In S145, the mobile phone 2 outputs to the authentication terminal 4 a digital image in which the first authentication information is embedded as a digital watermark and the camera ID and the time of shooting are added.
In S150, the authentication terminal 4 extracts the first authentication information from the digital image, and generates the second authentication information from the digital image from which the first authentication information has been extracted. The extraction of the first authentication information is performed by using the same white noise mask as in the authentication information embedding process 51. Specifically, the camera ID and the shooting time added first are taken out, and the digital image is returned to the state before the information was added. Next, after expanding the digital image, a subset is specified by a white noise mask, and the embedded bit information is determined. By repeating this for the bit length of the first authentication information, the first authentication information is specified. Next, the digital image is returned to the state before embedding by executing a process reverse to the authentication information embedding process 51. Thereby, the first authentication information is extracted. The second authentication information is generated by using the same hash function as the authentication information generation process 52 on the digital image from which the first authentication information has been extracted. Therefore, if the digital image has not been tampered with, the first authentication information and the second authentication information match.
[0035]
In S155, the first authentication information extracted in S150 and the generated second authentication information are compared, and if they match, information representing "match" is stored in a predetermined area of the RAM 42, and the process proceeds to S160. If they do not match, information indicating "does not match" is stored, and the flow advances to S175.
In S160, a request is made to the authentication server 3 for verification. Specifically, the request is made by transmitting the second authentication information and the camera ID to the authentication server 3.
[0036]
In S165, the authentication server 3 performs collation based on the second authentication information and the camera ID received from the authentication terminal 4, and the first authentication information and the camera ID registered in the database. Specifically, for example, the database is searched using the second authentication information and the camera ID received from the authentication terminal 4 as search conditions, and “1” is set if a record that matches both is searched, and “0” is set if not found. Make it the collation result.
[0037]
In S170, the collation result is returned to the authentication terminal 4. Specifically, either "0" or "1" is transmitted. When it is “1”, the reception time stored in the searched record is also transmitted.
In S175, the authentication terminal 4 receives the collation result and the reception time, and determines whether or not tampering has occurred. Details of the process of S175 will be described later.
[0038]
FIG. 7 is a flowchart showing the flow of the process of determining whether there is tampering in S175.
In S205, it is determined whether the information stored in the predetermined storage area of the RAM 42 indicates "match" or "not match". If it represents “match”, the process proceeds to S210, and if it represents “not match”, the process proceeds to S225.
[0039]
In S210, the value of the collation result is determined. If the collation result is "0", the process proceeds to S225, and if it is "1", the process proceeds to S215.
In S215, the time of reception and the time of shooting are compared. If the difference is equal to or greater than a preset threshold, the possibility that the digital image has been tampered with from the time specified at the time of shooting to the time specified at the time of reception cannot be denied, and the process proceeds to S225. If it is less than the threshold, the process proceeds to S220.
[0040]
In S220, it is determined that there is no tampering, and information indicating that there is no tampering is displayed on the display unit 44.
In S225, it is determined that there is tampering, and information indicating that there is a possibility of tampering is displayed on the display unit 44.
According to the image authentication system 1 according to the embodiment of the present invention described above, the user cannot access the digital image [0] before the first authentication information is generated in the authentication information generation process 52. Therefore, the digital image [0] before the first authentication information is generated cannot be altered even by the photographer himself. Since the generated first authentication information is transmitted to the authentication server 3, any tampering after the access to the digital image becomes possible, the first authentication information transmitted to the authentication server 3 and the falsified digital image Can be determined by collating with the second authentication information generated based on. Therefore, even if the tampering has been performed by the photographer himself, it can be determined. Since the authentication server 3 is installed in a third-party authentication organization, the authentication organization can guarantee the falsification of the captured digital image.
[0041]
In this embodiment, the case where the digital image is compressed has been described as an example. However, it is not always necessary to compress the digital image. If the compression is unnecessary, the first authentication information may be embedded without performing the compression process.
[Brief description of the drawings]
FIG. 1 is a sequence diagram illustrating a flow of processing of an image authentication system.
FIG. 2 is a schematic diagram illustrating a configuration of an image authentication system.
FIG. 3 is a block diagram of a communication terminal with a digital camera.
FIG. 4 is a block diagram illustrating a hardware configuration of an authentication terminal.
FIG. 5 is a block diagram illustrating a hardware configuration of an authentication terminal.
FIG. 6 is a data flow diagram in a communication terminal with a digital camera.
FIG. 7 is a flowchart illustrating a flow of a process of determining whether there is tampering.
[Explanation of symbols]
1, image authentication system, 2 mobile phone (communication terminal with digital camera), 3 authentication server, 4 authentication terminal, 11 optical system, 12 image sensor (conversion unit), 14 image forming unit (conversion unit), 17 CPU ( One generation means, embedding means), 18 operation section (transmission instruction means), 25 wireless communication section (transmission means, output means), 30 CPU (collation result return means), 33 communication section (reception means, collation request reception means) , Collation result reply means), 34 storage unit (storage means), 40 CPU (second generation means, discrimination means), 47 communication unit (input means, collation request transmission means)

Claims (7)

An optical system that forms an optical image of the subject,
Conversion means for converting the optical image of the formed subject into a digital image,
First generating means for generating first authentication information for determining whether the digital image has been tampered with based on the digital image converted by the converting means,
Transmitting means for transmitting the first authentication information to the authentication server;
Output means for outputting a digital image;
A communication terminal with a digital camera, wherein the user can access only the digital image after the first authentication information is generated. Further comprising transmission instruction means for instructing whether to transmit the first authentication information,
2. The communication terminal with a digital camera according to claim 1, wherein the transmission unit transmits the first authentication information only when the transmission instruction unit instructs transmission. Further comprising an embedding means for embedding the first authentication information as a digital watermark in the digital image,
The communication terminal with a digital camera according to claim 1, wherein the output unit outputs a digital image in which the first authentication information is embedded. The transmitting means transmits a camera ID capable of uniquely identifying the communication terminal with the digital camera to the authentication server in association with the first authentication information,
The communication terminal with a digital camera according to claim 1, wherein the output unit outputs the camera ID in association with a digital image. An image authentication system using the communication terminal with a digital camera according to claim 1, an authentication server, and an authentication terminal,
The authentication server includes a receiving unit that receives the first authentication information from the communication terminal with the digital camera, a storage unit that stores the received first authentication information, and a verification request reception that receives the second authentication information from the authentication terminal. Means, and a collation result return means for performing collation based on the first authentication information stored in the storage means and the second authentication information received from the authentication terminal, and returning a collation result,
The authentication terminal includes an input unit that inputs a digital image, a second generation unit that generates second authentication information from the input digital image, and a verification request transmission unit that transmits the generated second authentication information to the authentication server. Determining means for determining whether or not the digital image has been tampered with based on the collation result received from the authentication server. The storage unit stores the first authentication information in association with the time of reception, and the verification result return unit stores the first authentication information that matches the second authentication information received from the authentication terminal in the storage unit. 6. The image authentication system according to claim 5, wherein the time of reception stored in association with the first authentication information is returned in association with the collation result. An image authentication method using a communication terminal with a digital camera, an authentication server and an authentication terminal,
In the communication terminal with a digital camera, a conversion step of converting an optical image of a subject into a digital image; A first generating step of generating, a transmitting step of transmitting the generated first authentication information to the authentication server, and an output step of outputting a digital image,
In the authentication server, a receiving step of receiving first authentication information from the communication terminal with a digital camera, and a storing step of storing the received first authentication information in a storage unit,
In the authentication terminal, an input step of inputting a digital image, a second generation step of generating second authentication information from the input digital image, and a verification request transmission step of transmitting the generated second authentication information to the authentication server. ,
In the authentication server, a verification request receiving step of receiving second authentication information from the authentication terminal, and performs verification based on the first authentication information stored in the storage unit and the second authentication information received from the authentication terminal, A verification result returning step of returning a verification result,
A determination step of determining whether the digital image has been tampered with, based on the verification result received from the authentication server,
Wherein the user is able to access only the digital image after the first authentication information is generated.

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