Abstract:
An imaging apparatus includes an image data generating unit, an authentication data generating unit, a receiving unit and an authentication unit. The image data generating unit generates first image data. The authentication data generating unit generates first authentication data from the first image data. The receiving unit receives second image data and second authentication data from an external device, wherein both the second image data and the second authentication data are generated by a second imaging apparatus, and the second authentication data is generated from the second image data. The authentication unit has (a) a first authentication mode where the authentication unit authenticates, using the first authentication data, whether the first image data has been altered, and (b) a second authentication mode where the authentication unit authenticates, using the second authentication data, whether the second image data has been altered.

Description:
FIELD OF THE INVENTION 
   The present invention relates to an apparatus having a function of authenticating if image data has not been altered. 
   BACKGROUND OF THE INVENTION 
   Some imaging apparatuses such as a digital camera and the like have a function of generating authentication data, which is used to authenticate if image data has not been altered, together with that image data. 
   However, in a conventional imaging apparatus with that function, it cannot be authenticated if image data generated by the self apparatus or the other apparatus has not been altered, unless a special apparatus is prepared. 
   The present invention has been made in consideration of the above problem, and has as its object to authenticate if image data generated by the self apparatus or the other apparatus has not been altered, without preparing for any special apparatus. 
   SUMMARY OF THE INVENTION 
   In order to achieve the above object, for example, an imaging apparatus of the present invention comprises the following arrangement. 
   That is, an imaging apparatus having a function of authenticating if image data generated by a self apparatus has not been altered, and a function of authenticating if image data generated by the other apparatus has not been altered. 
   In order to achieve the above object, for example, an imaging apparatus of the present invention comprises the following arrangement. 
   That is, an imaging apparatus having a first mode of generating image data, and generating authentication data used to authenticate if the image data has not been altered, and a second mode of authenticating if the image data has not been altered, using the authentication data. 
   Other features and advantages of the present invention will be apparent from the following description taken in conjunction with the accompanying drawings, in which like reference characters designate the same or similar parts throughout the figures thereof. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention. 
       FIG. 1  is a block diagram showing the arrangement of an imaging apparatus according to an embodiment of the present invention; 
       FIG. 2  shows an example of an image file with authentication data; 
       FIG. 3  is a flow chart showing the processing sequence executed in a photographing mode with an authentication function; 
       FIG. 4  is a flow chart showing the processing sequence for generating authentication data; and 
       FIG. 5  is a flow chart showing the processing sequence executed in an authentication mode. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
   Preferred embodiments of the present invention will now be described in detail in accordance with the accompanying drawings. 
   The arrangement of an imaging apparatus  10  according to an embodiment of the present invention will be described first with reference to the block diagram of  FIG. 1 . An imaging apparatus  10  need only be an apparatus which has a function of generating digital image data of an object and its additional data. Therefore, the imaging apparatus  10  can be any of a digital still camera, digital video camera, and scanner. 
   The imaging apparatus  10  comprises an image generator  101 , storage interface  102 , digital interface  103 , console  104 , display  105 , and controller  106 , as shown in  FIG. 1 . 
   The image generator  101  has a function of generating digital image data of an object and its additional data. 
   The storage interface  102  has a function of writing an image file in a storage medium  1021  as a removable storage medium, and a function of reading an image file from the storage medium  1021 . Note that the storage medium  1021  can store not only image files generated by the imaging apparatus  10  but also those generated by apparatuses other than the imaging apparatus  10 . 
   The digital interface  103  can digitally communicate with an external apparatus  1031 . The digital interface  103  has a function of writing an image file held by the storage medium  1021  in the external apparatus  1031 , and a function of reading an image file held by the external apparatus  1031  from it. The image file read from the external apparatus  1031  is written in the storage medium  1021 . 
   The console  104  is means for accepting user&#39;s instructions, and has a shutter button used to instruct generation of image data, a mode select button used to switch the operation mode of the imaging apparatus  10  to a predetermined mode, and the like. 
   The display  105  displays thumbnail data of image data generated by the image generator  101 , or that in an image file read out from the storage medium  1021  or external apparatus  1031 . 
   The controller  106  controls various functions of the imaging apparatus  10 . The controller  106  has an authentication data generation unit  107 , image file generation unit  108 , image authentication unit  109 , and memory  110 , as shown in  FIG. 1 . 
   The authentication data generation unit  107  has a function of generating authentication data as data used to authenticate if image data has not been altered. 
   The image file generation unit  108  has a function of generating an image file with authentication data.  FIG. 2  shows an example of an image file with authentication data. As shown in  FIG. 2 , the image file with authentication data contains image data generated by the image generator  101 , additional data and authentication data of that image data, and ID data unique to the imaging apparatus  10 . In this embodiment, the authentication data and ID data are stored in a header field. Alternatively, these data may be stored in a data field or footer field in place of the header field. 
   The image authentication unit  109  has a function of authenticating if image data in an image file generated by the imaging apparatus  10  or the other imaging apparatus has not been altered. 
   The memory  110  stores common data and ID data. The common data and ID data in the memory  110  are important ones which are required upon generation of authentication data of image data. Especially, the common data must be securely managed so as not to externally leak. The common data in the memory  110  is common to a plurality of imaging apparatuses including the imaging apparatus  10 , and is the same data in all the imaging apparatuses. On the other hand, the ID data in the memory  110  is unique to one imaging apparatus, and is different for respective imaging apparatuses. 
   The processing sequence executed when the operation mode of the imaging apparatus  10  of this embodiment is a photographing mode with an authentication function will be described below with reference to the flow chart of  FIG. 3 . In the photographing mode with the authentication function, the imaging apparatus  10  can generate an image file with authentication data. 
   Step S 301 : When the user has pressed the shutter button of the console  104 , the image generator  101  generates digital image data of an object and its additional data. 
   Step S 302 : The authentication data generation unit  107  generates authentication data as data used to authenticate alteration of the image data generated by the image generator  101  using that image data. The method of generating this authentication data will be described later with reference to the flow chart of  FIG. 4 . 
   Step S 303 : The image file generation unit  108  generates an image file with authentication data, which contains the image data generated by the image generator  101 , the additional data and authentication data of that image data, and the ID data of the imaging apparatus  10 . Note that the additional data, ID data, and authentication data are stored in the header field of the image file, as shown in  FIG. 2 . 
   Step S 304 : The controller  106  determines a storage destination of the image file with authentication data, which is generated by the image file generation unit  108 . If the storage destination of the image file with authentication data is the storage medium  1021 , a process in step S 305  is executed; if it is the external apparatus  1031  such as a personal computer or the like, a process in step S 306  is executed. 
   Step S 305 : The controller  106  writes the image file with authentication data generated by the image file generation unit  108  in the storage medium  1021 . 
   Step S 306 : The controller  106  writes the image file with authentication data generated by the image file generation unit  108  in the external apparatus  1031 . 
   With the above processes, the imaging apparatus  10  can generate an image file with authentication data when the operation mode of the self apparatus is the photographing mode with the authentication function, and can store the generated image file in the storage medium  1021  or external apparatus  1031 . 
   The processing sequence for generating authentication data which is used to authenticate if image data generated by the image generator  101  has not been altered, on the basis of that image data, will be described below with reference to the flow chart of  FIG. 4 . 
   Step S 401 : The authentication data generation unit  107  generates key data by executing a first arithmetic process using the common data and ID data read out from the memory  110 . This embodiment adopts a method of generating key data using both the common data and ID data in place of generating key data using the ID data alone. With this method, it becomes difficult to analyze key data and to counterfeit authentication data, and the system security can be improved. 
   Step S 402 : The authentication data generation unit  107  generates a hash value (also called a message digest or digest data) of the image data generated by the image generator  101  from that image data. 
   Step S 403 : The authentication data generation unit  107  generates authentication data by executing a second arithmetic process using the key data obtained in step S 401  and the hash value obtained in step S 402 . Note that the second arithmetic process can exploit, e.g., an arithmetic operation based on a predetermined common key cipher system, an arithmetic operation based on a hash function with a key, and the like. 
   With the aforementioned processes, the imaging apparatus  10  can securely generate authentication data which is used to authenticate if image data generated by the image generator  101  has not been altered, on the basis of that image data. 
   The processing sequence executed when the operation mode of the imaging apparatus  10  is an authentication mode will be described below with reference to the flow chart of  FIG. 5 . If the authentication mode is set, the imaging apparatus  10  can authenticate if image data generated by the imaging apparatus  10  or the other apparatus (including the external apparatus  1031 ) has not been altered. 
   Step S 501 : The controller  106  makes the user select one of image files stored in the storage medium  1021  or external apparatus  1031 . The user selects a desired image file by operating the console  104 . The storage interface  102  or digital interface  103  reads an image file of user&#39;s choice, and supplies the read image file to the image authentication unit  109 . 
   Step S 502 : The image authentication unit  109  checks if the image file selected by the user contains ID data. If the ID data is found, a process in step S 504  is executed; otherwise, a process in step S 503  is executed. 
   Step S 503 : In this case, the controller  106  displays, on the display  105 , a message or icon indicating that whether or not the image file has been altered cannot be authenticated, and advises the user accordingly. 
   Step S 504 : The image authentication unit  109  extracts ID data from the image file of user&#39;s choice. 
   Step S 505 : The image authentication unit  109  compares the ID data extracted in step S 504  with the ID data stored in the memory  110 . The ID data extracted in step S 504  is unique to an apparatus that generated the image file of user&#39;s choice. Therefore, if the two ID data match, it is determined that the image file of user&#39;s choice was generated by the imaging apparatus  10 . On the other hand, if the two ID data do not match, it is determined that the image file of user&#39;s choice was generated by an apparatus other than the imaging apparatus  10 . 
   Step S 506 : If the two ID data match, the controller  106  displays, on the display  105 , a message or icon indicating that the image file of user&#39;s choice was generated by the self apparatus, and advises the user accordingly. 
   Step S 507 : On the other hand, if the two ID data do not match, the controller  106  displays, on the display  105 , a message or icon indicating that the image file of user&#39;s choice was not generated by the self apparatus, and advises the user accordingly. 
   Step S 508 : The image authentication unit  109  generates key data by reading out the common data from the memory  110  and executing the first arithmetic process using the readout common data and the ID data obtained in step S 504 . This process is the same as that executed in step S 401  in  FIG. 4 . 
   Step S 509 : The image authentication unit  109  extracts image data from the image file of user&#39;s choice, and generates a hash value of the image data from the extracted image data. This process is the same as that executed in step S 402  in  FIG. 4 . 
   Step S 510 : The image authentication unit  109  generates authentication data by executing the second arithmetic process using the key data obtained in step S 508  and the hash value obtained in step S 509 . This process is the same as that executed in step S 403  in  FIG. 4 . 
   Step S 511 : The image authentication unit  109  compares the authentication data extracted from the image file of user&#39;s choice, and the authentication data obtained in step S 510  to authenticate whether or not the image data in that image file has been altered. 
   Step S 512 : If the two authentication data match, the image authentication unit  109  determines that the image data in the image file of user&#39;s choice has not been altered. In this case, the controller  106  displays, on the display  105 , a message or icon indicating that the image data has not been altered, and advises the user accordingly. 
   Step S 513 : If the two authentication data do not match, the image authentication unit  109  determines that the image data in the image file of user&#39;s choice has been altered. In this case, the controller  106  displays, on the display  105 , a message or icon indicating that the image data has been altered, and advises the user accordingly. 
   As described above, the imaging apparatus  10  according to this embodiment can authenticate whether or not image data generated by the self apparatus has been altered, and can also authenticate whether or not image data generated by the other apparatus has been altered. Therefore, the presence/absence of alteration can be easily authenticated without preparing for any special apparatus. 
   Also, the imaging apparatus  10  according to this embodiment can detect whether the image file of user&#39;s choice is generated by the self apparatus or the other apparatus, and can advise the user accordingly. 
   Note that the present invention can be practiced in various forms without departing from its principal feature. Therefore, the present invention should not be limited to the above embodiment. 
   According to the present invention, whether or not image data generated by the self apparatus the other apparatus has not been altered and whether or not image data generated by the other apparatus has not been altered can be authenticated. 
   As many apparently widely different embodiments of the present invention can be made without departing from the spirit and scope thereof, it is to be understood that the invention is not limited to the specific embodiments thereof except as defined in the claims.