JP4332076B2 - Image recording apparatus and image reproducing apparatus - Google Patents

Description

  The present invention relates to an image recording apparatus such as a digital camera including a photoelectric conversion element and an image reproducing apparatus that displays an image according to image data, and in particular, an image recording apparatus that prevents a captured image from being seen by others, The present invention relates to a digital camera and an image playback device.

  A digital camera, which is one of image recording devices, includes a photoelectric conversion element such as a CCD, and generates image data corresponding to image light incident thereon, so that an image is viewed unlike a conventional film camera. Therefore, it is not necessary to develop the film. That is, in the case of a digital camera, the captured image can be viewed immediately.

  Since the film camera cannot confirm whether or not a desired image has been taken until the film is developed, the photographer is anxious. For example, when shooting a subject for which it is difficult to determine the exposure conditions, or when shooting under conditions where the amount of light is small, there is anxiety about not being able to shoot with proper exposure and anxiety of camera shake. There are many other reasons why a desired image cannot be obtained, such as subject blur, flare, and ghost.

  On the other hand, if it is a digital camera that can immediately confirm the captured image, it can be confirmed whether or not the image has been captured with proper exposure. If the desired image has not been captured, it can be recaptured. For this reason, digital cameras are becoming mainstream as imaging devices instead of film cameras.

  However, being able to see the captured image immediately is convenient for the photographer, but also causes a problem that the photographed image can be easily seen by others.

In other words, in the case of a film camera, an image cannot be viewed unless the film is developed, and it takes time and money to develop the film. It is unlikely that an image can be seen in a user's eye unless the person knows in advance.
On the other hand, in the case of a digital camera, since an image can be viewed without requiring time and money, there is a risk that an image of interest will be viewed by a person who does not know what is being photographed.

  In this way, in the case of a digital camera, if the camera is lost or stolen, there is a risk that the image will be stolen by a third party, and even if the camera itself is not stolen, There is a risk that an image will be stolen by stealing the eyes of the owner.

  As a conventional technique for solving such a problem, there is a “digital camera” disclosed in Patent Document 1 and a “digital camera” disclosed in Patent Document 2.

  The invention disclosed in Patent Document 1 is a digital camera in which an image recording memory in the digital camera is protected by a password so that an image cannot be seen by others.

The invention disclosed in Patent Document 2 is a digital camera that encrypts image data using an encryption key created by a computer terminal.
JP 2000-125237 A JP 2000-299847 A

  However, since the invention disclosed in Patent Document 1 forces the user to input a password every time an image is viewed, it is difficult for the owner to use.

  The invention disclosed in Patent Document 2 has a problem in terms of protection of confidentiality because confidentiality is not considered in the delivery of the encryption key itself.

The present invention has been made in view of such problems, the user of without sacrificing convenience, and various image recording instrumentation 置及 beauty having a function of protecting the confidentiality of image data while corresponding to the operating mode An object is to provide an image reproducing apparatus.

In order to achieve the above object, according to a first aspect of the present invention, there is provided an image recording apparatus for recording image data, a means for generating key data for encrypting the image data, and notification from an external apparatus. A public key storage means for storing a public key of a public key cryptosystem, an encryption means for encrypting image data with the key data, and encrypting the key data with the public key, encrypted image data , A recording means for associating and recording the public key and key data encrypted with the public key on the information recording medium; and means for adding header information to the encrypted image data . A plurality of public keys respectively corresponding to a plurality of external devices can be stored, the encryption means encrypts key data with each of the plurality of public keys stored in the public key storage means, and the recording means Image data When a plurality of public keys, and records on the information recording medium in association with the key data encrypted with a plurality of public keys each, the encrypted key data in each of the plurality of public keys and a plurality key A key table is recorded, and the key table provides an image recording apparatus that is included in header information . In this way, the key used for encrypting the image data can be recorded together with the encrypted image data by encrypting the key for encrypting the image data with the public key of the public key encryption method. Is maintained, and as a result, the confidentiality of the image data is maintained. In this way, it becomes possible to reproduce an image with a plurality of reproducing apparatuses having a secret key corresponding to the public key, and the convenience for the user is not impaired. In this way, even if the photographer cannot see the image data itself, the image data can be specified by the additional information, so that the photographer can easily select a transmission image. In this way, the image data and the key can be handled together, and the image data can be kept secret without impairing convenience.

In any of the above configurations of the first aspect of the present invention, a means for determining whether or not to encrypt image data according to an input operation from the user, and a thumbnail when encrypting the image data It is preferable to have means for converting the resolution of the data so that the resolution is lowered and means for adding the thumbnail data with the converted resolution to the encrypted image data. In this way, when the image data is encrypted, the resolution of the thumbnail data can be converted to such an extent that only the photographer can guess the contents, so that the photographer can easily select the transmission image. It becomes like this.
Or means for encrypting the thumbnail data with key data different from the image data, and means for adding the encrypted thumbnail data to the encrypted image data. The encryption means corresponds to the image data. It is preferable that the key data to be encrypted is encrypted with the public key and the key data corresponding to the thumbnail data is not encrypted with the public key. In this way, only a specific user can browse image data, and other users can browse only thumbnail data. As a result, the degree of freedom in using the captured image data is increased and the convenience for the user is improved. In this case, it is more preferable that the key data for encrypting the thumbnail data is generated in the apparatus based on the information unique to the apparatus. In this way, a key to encrypt the thumbnail data can be generated in a fixed manner, so that a specific administrator (device manufacturer or police organization) can check the thumbnail data, and even if the image is used for a crime, The administrator can confirm the contents.

  In any of the above-described configurations of the first aspect of the present invention, the image processing apparatus includes a display unit that displays an image corresponding to the image data. When the image data is encrypted, the image data before encryption is volatile. When the image is stored on the memory and displayed, it is preferably displayed on a display unit that displays an image corresponding to the image data before encryption stored in the volatile memory. In this way, the user can easily check the image data immediately after shooting.

  In any of the above-described configurations of the first aspect of the present invention, the digital camera preferably photoelectrically converts image light from a subject and performs image processing to generate image data.

In order to achieve the above object, the present invention provides, as a second aspect, means for generating a public encryption key type key pair and means for outputting a public key that is one of the key pairs to the image recording apparatus. A means for obtaining encrypted image data recorded in the image recording apparatus, and a key encrypted with each of a plurality of public keys and a plurality of public keys included in header information added to the image data Means for obtaining a key table with data, key data decrypting means for decrypting the encrypted key data with a secret key which is the other of the key pair, and means for decrypting the image data with the decrypted key data When, using a key table included in the header information of the image data, and means for searching for key data corresponding to the public key, which is one of the key pair, the key data decoding means, the retrieved key pair corresponding to the public key on the other hand is a The data is intended to provide an image reproducing apparatus characterized by decrypting the private key is the other key pair. In this way, it is possible to reproduce the image data only with the image reproducing apparatus in which the captured image data is concealed and the public key is registered, without requiring a special effort.

The present invention can provide an image recording instrumentation 置及 beauty image reproducing device provided with a function of protecting the confidentiality of image data while coping with no, and various operation mode damaging the convenience of the user.

A preferred embodiment of the present invention will be described. FIG. 1 shows a configuration of a digital camera device according to the present embodiment. The digital camera device 1 includes a system control unit 2, an imaging unit 3, an image processing unit 4, a display control unit 5, an LCD 6, a recording media interface unit 7, a hard key interface unit 9, and a communication interface unit 10.
The system control unit 2 includes a CPU, a flash memory, an SDRAM, a timer, and the like, and controls the operation of the entire digital camera device 1. The imaging unit 3 is composed of optical system components (lens and lens driving motor), CCD, CCD driving circuit, A / D converter, etc., and converts image light into an electrical signal, which is further A / D converted. To generate digital data. The image processing unit 4 is composed of an image processing DSP (digital signal processor) for performing image compression / decompression, a RAM, and the like. The image processing unit 4 performs various image processing on the digital data generated by the imaging unit 3 and performs imaging. The driving timing of the CCD of the unit 3 is controlled, and the lens driving motor is controlled to perform zooming, focusing, exposure adjustment, and the like. The display control unit 5 includes a D / A converter, an on-screen display controller, and the like, performs image processing for causing the LCD 6 to display the image signal processed by the image processing unit 4, and provides a user interface. Various graphic images are generated and displayed on the LCD 6. The LCD 6 displays images and graphics for user interface. The recording media interface unit 7 includes a memory card controller and the like, and reads and writes data from and to the attached recording media 8. The hard key interface 9 is composed of a sub CPU and the like, and detects the state of a user interface such as an input key and a dial (not shown) (whether the key is pressed or where the dial is located), or the main CPU. Main power control to the (CPU in the system control unit 2) is performed. The communication interface unit 10 includes a communication card controller and the like, and performs data communication by connecting various communication modules.

  The recording medium 8 is constituted by a flash memory or the like, and is detachable from the recording medium interface unit 7. The recording medium 8 stores compressed or non-compressed image signals and various information related to images.

  The image playback device 11 is a device that displays an image corresponding to an image signal transferred from the connected digital camera device 1.

First, an operation similar to that of a conventional digital camera will be described.
The shooting operation will be described. Prior to shooting, the user operates an input key or dial (not shown) to determine a shooting operation mode (such as continuous shooting mode or normal shooting mode). The operation by the user is detected by the hard key interface unit 9, and the content of the operation is determined by the system control unit 2.

  The system control unit 2 causes the display control unit 5 to generate a guidance graphic according to the content of the operation by the user. The display control unit 5 displays this on the LCD 6 and prompts the user for the next input operation. When the operation mode is determined, the system control unit 2 sets processing parameters corresponding to the mode in the image processing unit 4.

  After the preparation for shooting is completed, the system control unit 2 drives the imaging unit 3 and the image processing unit 4. The imaging unit 3 starts an imaging operation for displaying a monitoring image prior to actual shooting in accordance with control from the image processing unit 4.

  Image data generated by imaging in the imaging unit 3 is continuously sent to the image display unit 4. The image processing unit 4 sends image data to the display control unit 5 after performing processing such as color space conversion, γ correction, and white balance adjustment.

  At this time, the image processing unit 4 simultaneously detects exposure and controls the imaging unit 3 to adjust the exposure.

  The display control unit 5 processes the image data, sends it to the LCD 6 for display, and presents the imaging state to the user.

  When the hard key interface unit 9 detects a half-pressed state of a release button (not shown), the system control unit 2 determines this. The system control unit 2 controls the image processing unit 4 and extracts an evaluation value for autofocus (AF) control from the monitoring image. Furthermore, the system control unit 2 controls the imaging unit 3 according to a predetermined algorithm to adjust the focus.

  When the hard key interface unit 9 detects that a zoom button (not shown) has been pressed, the system control unit 2 determines this. The system control unit 2 controls the imaging unit 3 to perform zoom operations (zoom in and zoom out) according to the input operation.

  When the hard key interface unit 9 detects that a release button (not shown) has been pressed, the system control unit 2 determines this. The system control unit 2 starts the shooting operation by controlling the image processing unit 4 according to the set shooting operation mode. The imaging unit 3 captures a predetermined image and sends it to the image processing unit 4 in accordance with control from the image processing unit 4. The image processing unit 4 performs image processing and compression processing according to the shooting operation mode. At this time, thumbnail image data is generated by generating and compressing reduced image data based on the image data.

  In the case of the normal shooting operation mode, when the imaging unit 3 captures an image for one frame, the process ends. In the continuous shooting mode, the system control unit 2 causes the imaging unit 3 to capture an image at a predetermined frame rate until notified from the hard key interface unit 9 that the release button has been released. A process of applying predetermined image processing to the image by the image processing unit 4 is repeatedly executed.

  The system control unit 2 reads the compressed image data and thumbnail data from the RAM of the image processing unit 4, adds header information, and then writes the compressed image data and thumbnail data to the recording medium 8 via the recording medium interface unit 7. Note that the header information here includes information indicating the selected shooting operation mode and information such as the shooting date and time.

  When writing image data to the recording medium 8, the system control unit 2 assigns a predetermined character string (for example, RIMG) + sequential number as a file name. The file name of the image data to be newly written to the recording medium is the maximum value +1 of the serial number of the file names of the already recorded image data. For example, if the image data already recorded on the recording medium 8 has the largest consecutive number in the file name is “RIMG343.jpg”, the system control unit 2 sets the file “RIMG344.jpg”. Write image data by name. If there is no image data in the recording medium 8, the system control unit 2 uses the RIMG001. The image data is written to the recording medium 8 with the serial number portion as “1” such as “jpg”.

  The system control unit 2 also updates the file management information in the recording medium 8 when writing the image data to the recording medium 8.

Next, a reproduction operation similar to that of a conventional digital camera will be described.
When a command for reproducing (displaying) image data is input by a user operation, the hard key interface unit 9 detects this and puts it in the system control unit 2 for determination. The system control unit 2 reads the file management information in the recording medium 8 through the recording medium interface unit 7, and assigns frame numbers in ascending order of numbers to files according to the file name format ("RIMG" + serial number). Then, a frame number management table as shown in FIG. 2 is created. The system control unit 2 creates a frame number management table ignoring files that do not conform to the format.

  The frame number is a continuous number starting from 1. Thereafter, the file designation in the normal reproduction process is performed by the system control unit 2 referring to the frame number management table based on the frame number.

  The system control unit 2 reads the file with the largest frame number from the recording medium 8 via the recording medium interface unit 7 and writes it in the memory in the system control unit 2. The system control unit 2 analyzes the header information from the data on its own memory, extracts parameters necessary for decompressing the image data, and sets them in the image processing unit 4. Thereafter, the compressed image data on the memory provided in itself is transferred to the image processing unit 4.

The image processing unit 4 performs decompression processing on the compressed image data received from the system control unit 2 and stores the decompressed image data in a memory in the system control unit 2.
When the expansion of the image data is completed, the system control unit 2 sets a conversion magnification based on the memory address of the memory in the system control unit 2 and the image size in the display control unit 5.

  The display control unit 5 reads image data from a predetermined memory address of the memory in the system control unit 2, performs signal processing, and outputs the image data to the LCD 6 to display (reproduce) the image on the LCD 6.

Next, operations unique to the present invention will be described. FIG. 3 shows a flow of operations when generating a key of the digital camera device according to the present embodiment.
When the key generation process is selected and activated in the image playback device 11 (step S101), the control unit of the image playback device checks whether or not the digital camera device 1 is connected (step S102). When the digital camera device 1 is connected to the image reproduction device 11 (step S102 / Yes), the image processing device 11 generates a key pair based on a public encryption key such as RSA (step S104). When generating a key pair, the control unit of the image processing apparatus 11 generates a key pair using the date and time, display state, memory state, and the like at that time as a seed.
If the digital camera device 1 is not connected to the image playback device 11 (step S102 / No), the process is terminated.

  The image playback device 11 transfers the public key of the generated key pair to the digital camera device 1 and stores it in the flash memory in the system control unit 2 (step S105). The other key pair is stored in a storage device in the image reproduction device 11 (step S106).

Next, an operation at the time of shooting using an encryption key will be described. Hereinafter, photographing using the encryption key is also referred to as “secret photographing mode”. FIG. 4 shows a flow of operations in the secret shooting mode.
When the shooting mode is set by a user operation, the system control unit 2 determines whether or not the secret shooting mode is set (step S201). The setting of the secret shooting mode is performed by a user input operation using an input key (not shown), similarly to the setting of the general shooting operation mode.

  If the secret shooting mode is not set (step S201 / No), a normal shooting operation (shooting operation similar to a conventional digital camera) is performed (step S202). On the other hand, when the secret shooting mode is set (step S201 / Yes), the system control unit 2 checks whether or not the public key is registered in the memory in the system control unit 2 (step S203). If no public key is registered in the flash memory in the system control unit 2 (No in step S203), the system control unit 2 drives the display control unit 5 to display a warning message on the LCD 6 ( Step S204), the process shifts to a normal photographing operation (Step S202).

  When at least one public key is stored in the flash memory in the system control unit 2 (step S203 / Yes), the system control unit 2 generates a common key based on a common encryption key method such as AES (step S205). ). When generating the common key, the system control unit 2 uses the date and time at that time, the elapsed time since the digital camera device 1 was activated, various adjustment value data, and the like as a seed.

When the user performs a shooting operation in the secret shooting mode (step S206 / Yes), the system control unit 2 drives the imaging unit 3 and the image processing unit 4 to perform a shooting operation (step S208).
In addition, when the shooting operation is not performed by the user (step S206 / No) and the shooting end operation is performed (step S207 / Yes), the system control unit 2 ends the process.

  After the photographing operation, the system control unit 2 controls the image processing unit 4 to create display data at the time of reproduction from the imaged data after the image processing and store it in a predetermined area of the memory of the image processing unit 4 (Step S209).

  The system control unit 2 reads the compressed image data from the image processing unit 4, and encrypts the data using the common key generated in step S205 (step S210).

  Further, the system control unit 2 reads the thumbnail data created by the image processing unit 4 from the image processing unit 4, and encrypts the data with the common key for thumbnails (step S211). Here, the thumbnail common key is key data unique to the camera generated using the serial number of the digital camera device 1 as a seed. The serial number is written in the flash memory of the system control unit 2 at the time of shipment.

  The system control unit 2 reads out the public key stored in the flash memory included in the system control unit 2 (step S212), sequentially encrypts the common key with the public key, and adds the public key to the header (step S213). , S214 / Yes). An example of the key table recorded in the header is shown in FIG.

  As shown in FIG. 5, the public key information generated and registered by the image playback device 11 and the common key encrypted with each key are added in a table. The system control unit 2 adds the thumbnail data and the created header information to the image data (step S214 / No), and then writes the image data in the recording medium 8 via the recording medium interface unit 7 (step S215).

  With the above processing, one photographing operation is completed, and a new common key is generated (step S205).

  The above processing is repeatedly executed until shooting is completed (until “Yes” in step S207).

  As shown in FIG. 6, after encrypting the main image data, the system control unit 2 controls the image processing unit 4 to perform processing for reducing the resolution of the thumbnail data before compression. You may make it read the data after compression (step S211 '). The processing for reducing the resolution here is performed by dividing the thumbnail image into minute blocks, calculating an average value for each block, and replacing the pixel data in the block with the average value data.

Next, an operation for reproducing (displaying) an image in the digital camera device 1 will be described. FIG. 7 shows a flow of operations at the time of image reproduction in the digital camera device 1.
The system control unit 2 reads an image file from the recording medium 8 in the same procedure as a conventional digital camera (step S301), and determines whether or not key data is included in the header (step S302). If no key data is included in the header (step S302 / No), the system control unit 2 performs a normal display operation (display operation similar to that of a conventional digital camera) (step S303).

  On the other hand, when at least one key data is included in the header (step S302 / Yes), the system control unit 2 searches a predetermined area in the memory of the image processing unit 4 and displays it corresponding to a frame to be played back. It is confirmed whether or not data exists (step S304). When there is display data corresponding to the frame to be reproduced (step S304 / Yes), the system control unit 2 transfers the data to the display control unit 5 and displays it on the LCD 6 (step S306). If there is no display data corresponding to the frame to be played back (No at Step S304), the system control unit 2 drives the display control unit 5 to display an unplayable warning message on the LCD 6 (Step S305).

  The system control unit 2 repeats the above process every time the user performs a frame advance operation (steps S307 / No, S308 / Yes), and if there is an input operation for ending the playback mode during that time, the process ends ( Step S307 / Yes).

  In addition, when a thumbnail having a reduced resolution is generated after the main image is compressed at the time of shooting, as shown in FIG. 8, when the image display data is not in the memory (No in step S304), the system control unit 2 Then, the thumbnail data is extracted from the image file, expanded to the image processing unit 4, the expanded data is transferred to the display control unit 5, and an image corresponding to this is displayed on the LCD 6 (step S305 ').

Next, an operation when reproducing image data (displaying an image) in the image reproducing apparatus 11 will be described. FIG. 9 shows the flow of this operation.
When the control unit reads the image file from the recording medium 8, it checks whether or not the key table as shown in FIG. 5 exists in the header (steps S401 and S402). (Step S402 / No), a normal reproduction operation (reproduction operation similar to a conventional digital camera) is performed (step S403).

  On the other hand, when the key table exists in the header of the image file (step S402 / Yes), the control unit reads the key pair generated by the image reproduction device 11 and stored in the memory (step S404). Further, a set of keys is read from the key table in the image file (step S405), and the information on these public keys is compared (step S406).

  If the public keys match (step S406 / Yes), the encrypted common key corresponding to the public key is decrypted with the secret key (step S409), and image data is further used using the decrypted key. Is decoded and reproduced (steps S410 and S411).

  If the public keys do not match (step S406 / No), it is checked whether another key exists in the header of the image file (step S407). If it exists (step S407 / Yes), the next key is checked. And the same processing is performed (step S405, step S406).

  If all the public keys do not match (step S407 / No), the image playback device 11 displays a warning that the image cannot be played back by the image playback device 11 (step S408), and the process ends.

In addition, the said embodiment is an example of suitable implementation of this invention, and this invention is not limited to this. For example, in the above embodiment, an example in which RSA is used as the public key encryption method and AES is used as the common encryption key method is shown, but other encryption methods may be used.
In the above-described embodiment, an example in which the image reproduction device 11 confirms the key at the time of reproduction and decrypts the image data has been described. However, it is not always necessary to confirm the key at the time of reproduction. The key may be confirmed when data is transferred. Also, the decryption of the image data using the key can be performed in a batch rather than individually for each image data.
Furthermore, although the case where the image recording apparatus is a digital camera has been described in the above embodiment, any apparatus that records image data may be used, and the digital camera is not necessarily required.
As described above, the present invention can be variously modified.

It is a figure which shows the structure of the digital camera which implemented this invention suitably. It is a figure which shows the structural example of a frame number management table. It is a flowchart which shows the operation | movement flow at the time of key generation. It is a flowchart which shows the flow of operation | movement at the time of image data reproduction | regeneration. It is a figure which shows the structural example of the key table recorded in a header. It is a flowchart which shows the flow of operation | movement in secret imaging | photography mode. It is a flowchart which shows the flow of another operation | movement in secret imaging | photography mode. It is a figure which shows the flow of operation | movement at the time of the image reproduction by the image reproduction apparatus concerning this invention. It is a figure which shows the flow of another operation | movement of the image reproduction apparatus concerning this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Digital camera apparatus 2 System control part 3 Imaging part 4 Image processing part 5 Display control part 6 LCD
7 Recording Media Interface Unit 8 Recording Media 9 Hard Key Interface Unit 10 Communication Interface Unit 11 Image Playback Device

Claims (7)

An image recording apparatus for recording image data,
Means for generating key data for encrypting the image data;
Public key storage means for storing the public key of the public key cryptosystem notified from the external device;
Encrypting the image data with the key data, and encrypting the key data with the public key;
Recording means for associating the encrypted image data, the public key, and the key data encrypted with the public key onto an information recording medium ;
Means for adding header information to the encrypted image data ,
The public key storage means can store a plurality of public keys respectively corresponding to a plurality of external devices,
The encryption means encrypts the key data with each of the plurality of public keys stored in the public key storage means,
The recording means records the encrypted image data, the plurality of public keys, and key data encrypted with each of the plurality of public keys in association with the information recording medium, and Record a key table of public keys and key data encrypted with each of the plurality of keys,
The image recording apparatus , wherein the key table is included in the header information . Means for determining whether to encrypt the image data according to an input operation from a user;
Means for converting the resolution of thumbnail data so as to reduce the resolution when encrypting the image data;
2. The image recording apparatus according to claim 1 , further comprising means for adding thumbnail data with the resolution converted to the encrypted image data. Means for encrypting thumbnail data with key data different from the image data;
Means for adding the encrypted thumbnail data to the encrypted image data,
Said encryption means, the encrypting key data by the public key corresponding to the image data, the key data corresponding to the thumbnail data image recording according to claim 1, wherein the unencrypted by the public key apparatus. 4. The image recording apparatus according to claim 3, wherein key data for encrypting the thumbnail data is generated in the apparatus based on information unique to the apparatus. Having display means for displaying an image according to the image data;
When encrypting the image data, the image data before encryption is held on a volatile memory,
When displaying the image, the volatile one to be displayed on the display means to display the image corresponding to the unencrypted image data stored in the memory from claim 1, wherein 4 of 1 The image recording apparatus according to item. Photoelectrically converting an image light from a subject, an image recording apparatus according to any one of claims 1-5, characterized in that by carrying out image processing is a digital camera for generating the image data. Means for generating a public encryption key pair;
Means for outputting a public key which is one of the key pairs to an image recording device;
Means for obtaining encrypted image data recorded in the image recording device;
Means for obtaining a key table of a plurality of public keys and key data encrypted with each of the plurality of public keys included in the header information added to the image data;
Key data decrypting means for decrypting the encrypted key data with a secret key that is the other of the key pair;
Means for decrypting the image data with the decrypted key data;
Means for searching for key data corresponding to the public key which is one of the key pairs, using the key table included in the header information of the image data;
The image reproduction apparatus, wherein the key data decrypting means decrypts key data corresponding to a public key that is one of the searched key pairs with a secret key that is the other of the key pairs.

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