Abstract:
A digital signing method in a digital signing apparatus that provides a digital signature to electronic data, including: inputting data to be signed with the digital signature; presenting attribute information of one or more signature keys; displaying said attribute information of said one or more signature keys presented to a user; creating signature data by using said inputted data and a signature key corresponding to said attribute information of signature key selected by said user from said attribute information of said one or more signature keys displayed; and saving signature data created or a signature file created based on said signature data in a storage unit.

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to digital signing method, digital signing apparatus, portable information processing apparatus, digital signing system, and recording medium carrying a digital signing program and signature data creation program. 
     In recent years, methods and apparatuses are disclosed for providing digital signature to digital data, especially the data electronically digitalized by reading paper document by a scanner, or the like (Patent Reference 1, for example). 
     Patent Reference 1 uses an IC card for the device that carry out the encrypting processing used for creating digital signature data, wherein this reference allows plural persons to provide respective digital signatures on a single document by repeatedly using the same means, in other words, by using respective IC cards. 
     In Patent Reference 1, it is assumed thereby that each IC card carries the key for only one digital signature. 
     (Patent Reference 1) Japanese Laid Open Patent Application 2003-318885 official gazette 
     SUMMARY OF THE INVENTION 
     However, in actual civil life, there arise often the cases in which a single person carries plural seals and use the seals according to the purposes or according to the situations. For example, there can be a case in which a person uses a private seal in ordinary situations but uses a special seal authenticating the power of the person in the case of making a seal on a contract document on behalf of a company. 
     The same situation occurs also in the use of digital signatures. 
     For example, there can be a situation in which a person having a public qualification of doctor signs his or her private mails electronically by using a personal signature key given to individuals while the same person uses a signature key given to the public qualification of doctor when signing in electronic care records. Only with the use of the signature key issued for the public qualification of doctor, the electronic care record bears the authority of doctor, while in the case the doctor has signed with his or her private signature key, the electronic care record is void for the authority of public qualification of doctor. 
     Similarly, a clerk of a government office has to use a private digital signature for private purposes and an official digital signature for official purposes. 
     Recently, there is a movement of submitting “E-document Bill” to the Diet and the needs for the technology enabling flexible use of digital signature is increasing. 
     The present invention has been made in view of the foregoing situations and circumstances and has its object of enabling a single user to use plural digital signature keys flexibly according to the purposes. 
     More specifically, the present invention provides a digital signing method in a digital signing apparatus that provides a digital signature to electronic data, comprising: 
     a signature object data inputting step for inputting data to be signed with digital signature; 
     a signature key presentation requesting step for requesting presentation of attribute information of one or more signature keys; 
     a signature key displaying step for displaying said attribute information of said one or more signature keys presented in the signature key presentation requesting step to a user; 
     signature data creation requesting step requesting creation of signature data by using: said electronic data inputted in said signature object data inputting step; and a signature key corresponding to said attribute information of said signature key selected by said user from said attribute information of said one or more signature keys displayed in said signature key displaying step; and 
     a signature data saving step for saving signature data created in response to said request in said signature data creation requesting step or a signature file created based on said signature data in a storage unit. 
     According to the present invention, it becomes possible for a single user to use plural digital signature keys according to the purposes and circumstances, by providing a digital signing method carried out on a digital signing apparatus that provides a digital signature to electronic data, such that the digital signing method includes: a signature object data inputting step for inputting data to be signed with digital signature; a signature key presentation requesting step for requesting presentation of attribute information of one or more signature keys; a signature key displaying step for displaying said attribute information of one or more signature keys presented in the signature key presentation requesting step to a user; signature data creation requesting step requesting creation of signature data by using: said electronic data inputted in said signature object data inputting step; and a signature key corresponding to said attribute information of said signature key selected by said user from the attribute information of the one or more signature keys displayed in said signature key displaying step; and a signature data saving step for saving signature data created in response to said request in said signature data creation requesting step or a signature file created based on said signature data in a storage unit. 
     Here, it should be noted that the foregoing attribute information of signature key corresponds for example to the profile information of signature key attached to the signature key, as will be described later in the embodiments of the present invention. 
     Further, the present invention provides a digital signing apparatus, portable information processing apparatus, a digital signing system, a digital signing program, a signature data creation program, and also a recording medium storing such digital signing program or signature data creation program. 
     According to the present invention, it becomes possible for a single user to use plural digital signature keys appropriately according to the purposes or circumstances. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a diagram showing the hardware construction of an exemplar digital signing system; 
         FIG. 2  is a first function diagram of the digital signing system; 
         FIG. 3  is a second functional diagram of the digital signing system; 
         FIG. 4  is a first diagram showing an interior construction of a signature data creation part; 
         FIG. 5  is a second diagram showing the interior construction of the signature data creation part; 
         FIG. 6  is a first sequence diagram of a digital signature processing; 
         FIG. 7  is a first diagram showing a signature key listing display screen; 
         FIG. 8  is a second sequence diagram of the digital signature processing; 
         FIG. 9  is a third sequence diagram of the digital signature processing; 
         FIG. 10  is a diagram showing an example of an IC card insertion requesting display screen; 
         FIG. 11  is a second diagram showing the signature key listing display screen; and 
         FIG. 12  is a diagram showing an example of signature key list displayed on the display part. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Hereinafter, an embodiment of the present invention will be explained with reference to the drawings. 
     Embodiment 1 
       FIG. 1  is a hardware construction diagram showing an example of digital signing system. 
     As shown in  FIG. 1 , the digital signing system includes a digital multifunction apparatus  1  and an IC card  2 , wherein the digital multifunction apparatus  1  includes: an operation panel  11 , an image scanner  12 , an IC card read/write unit  13 , a CPU  14 , a hard disk drive  15 , a ROM  16 , a RAM  17 , a media drive  18  and a network adapter  19 , while the IC card  2  includes a CPU  41 , a RAM  42  and a flash ROM  43 . 
     The operation panel  11  accepts input operation from the operator and carries out display to the operator. On the other hand, the image scanner  12  reads a paper document and creates an electrons document. Further, the IC card read/write unit  13  reads data from the IC card  2  and writs data to the IC card  2 . The IC card  2  may be an ordinary IC card used for recording information or data or a multiple application IC card. 
     The CPU  14  controls the digital multifunction apparatus  1  according to a program (digital signing program) stored in the RAM  17 . The hard disk drive  15  stores the program (digital signing program), signature files, signature data, and the like. The ROM  16  stores data, and the like. The RAM  17  reads out the program (digital signing program) at the time of activation of the digital multifunction apparatus  1  from the hard disk drive  15  and holds the program thus read out, or stores the object data to which the digital signature is to be made. Further, the RAM  17  is used for storing message digests. 
     The media drive  18  is used for reading and writing from and to a recording medium such as floppy-disk (trade mark), CD-R disk, or the like. The program (digital signing program) of the digital multifunction apparatus  1  may be stored in the hard disk drive  15  from the beginning, or it may be installed in the hard disk drive  15  from the recording medium via the media drive  18 . The network adapter  19  connects the digital multifunction apparatus  1  to a network. Further, the program (digital signing program) of the digital multifunction apparatus  1  may be downloaded from network through the network adapter  19  and stored in the hard disk drive  15  subsequently. 
     Similarly, the CPU  41  controls the IC card  2  according to the program (signature data creation program) included in the signature data creation part  25  held in the RAM  42  as will be describe later and/or the program corresponding to the signing application included in the signature data creation part  25 . Further, the flash ROM  43  stores signature keys, the program (signature data creation program), and the like. 
     For example, when the IC card  2  has received a command from the digital multifunction apparatus  1  via the IC card read/write unit  13 , the RAM  42  reads out the program (signature data creation program) from the flash ROM  43  and holds the program thus read out therein. 
     The functional construction of an exemplar digital signing system is shown in  FIG. 2 , wherein it should be noted that  FIG. 2  is a first functional diagram of the digital signing system. 
     As shown in  FIG. 2 , the digital signing system includes: an object data input part  21 ; an interface part  22 , a file after-processing part  23 ; a signature file creation managing part  24 ; and a signature data creation part  25 . In  FIG. 2 , the arrows of unbroken line represent movement of main data while the arrows of broken line represent delivery of parameters and instructions. 
     It should be noted that all of the object data input part  21 , the interface part  22 , the file after-processing part  23 , the signature file creation managing part  24  and the signature data creation part  25 , shown in  FIG. 2  may be included in the digital multifunction apparatus  1 , or alternatively, it is possible to construct such that only the signature data creation part  25  is included in the IC card  2 . 
     The interface part  22  may receive the instruction for digital signature from the user, or display the available digital signature key to the user, or receive the selection result of the digital signature key from the user. For example, the operation panel  11  of  FIG. 1  corresponds to the interface part  22 . 
     It should be noted that the object data input part  21  is used for inputting the object data to be provided with the digital signature. This data will be called hereinafter as signature object data. For example, in the case of inputting a paper document after transformation to electronic data, the image scanner  12  of  FIG. 1  corresponds to the object data input part  21 . Further, in the case of inputting the document held (or saved) in the hard disk drive  15 , or the like, of the digital multifunction apparatus  1  already in the form of electronic document, or in the case of reading out the electronic document from the hard disk drive  15 , or the like, or in the case of inputting the document stored in an electronic document storage server, or the like, connected to the digital multifunction apparatus  1  via a network, it is the process of acquiring, via the network, the electronic document from the electronic document storage server, or the like, that corresponds to object data input part  21 . 
     The signature file creation managing part  24  is a managing part that manages the processing related to digital signature creation. For example, the signature file creation managing part  24  performs various functions such as: inquiring the candidacy of possible signature key to the electrons signature data creation part  25 ; urges the user for selection of key via the interface part  22 ; asks the digital signature data creation part  25  for creation of the digital signature data; and creates the digital signature file of file form based on the created digital signature data. 
     The signature data creation part  25  is a creation part that crates the signature data (the signature object data subjected to encrypting processing with the digital signature key). The plural signature keys are held in the signature data creation part  25 . In the case of using the IC card  2 , for example, the card application stored in the IC card  2  corresponds to the signature data creation part  25 . Conversely speaking, the card application corresponding to the signature data creation part  25  is stored in the IC card  2 . 
     The file after-processing part  23  is a processing part for processing the digital signature file created in the digital signature file creation managing part  24 . For example, the file after-processing part  23  saves the digital signature file in a recording medium such as the hard disk drive  15  of the digital multifunction apparatus  1 , or transfers the same to the file control server, or the like, connected to the digital multifunction apparatus  1  via the network and requests saving. 
     With the functional construction of the digital multifunction apparatus  1  shown in  FIG. 2 , the data input via the object data input part  21  is forwarded to the signature data creation part  25  via the signature file creation managing part  24 . However, in the case of doing digital signature it is generally practiced to use a method in which encrypting processing is performed after transforming the signature object data to small size data called message digest (MD) by applying thereto a one-way function (hash function, for example). 
     Therefore, it is also possible to include an object data preprocessing part  26  that implements the one-way function in the functional construction of the digital multifunction apparatus  1 . 
     Another example of the functional construction of the digital signing system is shown in  FIG. 3 , wherein  FIG. 3  is a second functional diagram of the digital signing system. 
     As shown in  FIG. 3 , the digital signing system includes the object data input part  21 , the interface part  22 , the file after-processing part  23 , the signature file creation managing part  24 , the signature data creation part  25 , and the object data preprocessing part  26 . Similarly to  FIG. 2 , the arrows of unbroken line of  FIG. 3  represent movement of main data while the arrows of broken line represent delivery of parameters and instructions. 
     It should be noted that all of the object data input part  21 , the interface part  22 , the file after-processing part  23 , the signature file creation managing part  24  and the signature data creation part  25 , shown in  FIG. 2  may be included in the digital multifunction apparatus  1 , or alternatively, it is possible to construct such that only the signature data creation part  25  is included in the IC card  2 . 
     As mentioned above, the object data preprocessing part  26  implements the one-way function and transforms the signature object data into small size data called the message digest. 
     Hereinafter, for the sake of simplicity of explanation, the digital signing system will be explained for the case in which the system has the functional construction of object data preprocessing part  26  as shown in  FIG. 3 . However, this does not limit the scope of the present invention. 
       FIG. 4  shows an example of interior construction of the signature data creation part  25 , and thus,  FIG. 4  is a first diagram showing the interior construction of the signature data creation part. 
     As a method of realizing the signature data creation part  25  shown in  FIG. 2  or  FIG. 3 , there is a method of constructing the signature data creation part  25  by a single object (single card application in the case of constructing the signature data creation part  25  with card application). 
     When constructing the signature data creation part  25  with single object (or single card application) like this, the object (or card application) has plural signature key sets as the data and a signature implementation method implementing the encrypting processing by the specified key and a signature key list presentation method presenting the profile information of possible signature keys in the form of list as the method (or function), as shown in  FIG. 4 . Here, the signature key set means a data set that includes the secret key used for encrypting processing of the digital signature and the profile information with regard to the secret key (information such as “key for the general manager” or “key for private”) as the elements thereof. 
     By constructing the signature data creation part  25  as shown in  FIG. 4 , it becomes possible to present the profile information of possible plural signature keys as per request. 
     Another example of the internal construction of the signature data creation part  25  is shown in  FIG. 5 , and thus,  FIG. 5  is a second diagram showing the interior construction of the signature data creation part. 
       FIG. 4  shows an example in which the signature data creation part  25  is formed with a single object (or card application) having plural signature key sets. It should be noted that the construction of  FIG. 4  can be realized by using an ordinary IC card of non-multiple application type IC card. On the other hand, it is possible to construct the signature data creation part  25  with plural objects (or card applications) having one or more signature key sets as shown in  FIG. 5 . In the case of realizing the construction shown in  FIG. 5  with an IC card, it is necessary to use a multiple application IC card, not an ordinary IC card. 
     In the case of constructing the signature data creation part  25  with plural objects (or card applications), each of the objects (or card applications) has one or more signature key sets as the data and a signature implementation method for implementing the encrypting processing by the specified key and a signature key profile information presentation method for presenting the profile information of possible signature keys as the method (or function), as shown in  FIG. 5 . 
     In the case of using the construction shown in  FIG. 5 , the signature file creation managing part  24  may know the available object (or card application) of the signature data creation part  25 , on the basis of the setting file, or the like, set up in the signature file creation managing part  24 . Alternatively, it is possible to implement an object (or card application) that presents an available object (or card application) in the signature data creation part  25  and know the available object (or card application) of the signature data creation part  25  via the object (or card application). 
     The signature file creation managing part  24  can use the method of an object (or card application) by knowing the object (or card application) of available signature data creation part  25 . There may be one such available object (or card application) of the signature data creation part  25  or there may be plural such available objects. In the case there is on object (or card application) in the signature data creation part  25  available by the signature file creation managing part  24  and in the case that object (or card application) has only one set of signature key, there is no need for the user to designate the signature key. 
     By constructing the signature data creation part  25  as shown in  FIG. 5 , too, it becomes possible to present the profile information of plural possible signature keys according to request, for example. 
     An example of digital signature processing is shown in  FIG. 6 , and thus,  FIG. 6  forms a first sequence diagram of digital signature processing. 
       FIG. 6  shows an example in which the user selects one signature key from the two signature keys stored in the IC card  2  for an electronic document created by scanning a paper document with the image scanner  12  by using the operation panel  11 , or the like and saves the electronic document in the hard disk drive  15  inside the digital multifunction apparatus  1  with the digital signature. Hereinafter, explanation will be made for the case in which the two signature keys have the profile information in the form of the name of the keys (“key for general manager” and “key for private”, for example). Further, in  FIG. 6 , it is assumed that the signature data creation part  25  shown in  FIG. 3  is implemented in the IC card  2  and that the object data input part  21 , the interface part  22 , the file after-processing part  23 , the signature file creation managing part  24  and the object data preprocessing part  26  are implemented in the digital multifunction apparatus  1 . 
     First, the user carries the IC card  2  and the paper document to be scanned to the digital multifunction apparatus  1 , inserts the IC card  2  into the IC card read/write unit  13 . 
     Next, the user sets the paper document on the image scanner  12 , and switches the digital multifunction apparatus  1  to scanner mode by using the operation panel  11 . Further, the user designates “scan with digital signature option” and starts scanning (sequence SQ 1  of  FIG. 6 ). For the operation panel  11 , it is possible to use a liquid crystal display having touch function, for example. 
     When data input is instructed by the user, the interface part  22  informs to the object data input part  21  that data input was instructed by the user (sequence SQ 2  of  FIG. 6 ). 
     The object data input part  21  creates, when it is informed from the interface part  22  that data input was instructed by the user, the signature object data by reading the paper document set by the user (sequence SQ 3  of  FIG. 6 ), and delivers the same to the signature file creation managing part  24  (sequence SQ 4  of  FIG. 6 ). 
     The signature file creation managing part  24  expands the signature object data delivered from the object data input part  21  on the RAM  17  and instructs pre-processing to the object data preprocessing part  26  (Sequence SQ 5  of  FIG. 6 ). 
     The object data preprocessing part  26  applies the one-way function to the signature object data instructed by the signature file creation managing part  24  for the processing (sequence SQ 6  of  FIG. 6 ) and creates a message digest of the signature object data. Further, the object data preprocessing part  26  expands the message digest on the RAM  17  and returns the message digest to the signature file creation managing part  24  (sequence SQ 7  of  FIG. 6 ). 
     On the other hand, the signature file creation managing part  24  delivers a signature key listing request for calling the signature key list presentation method of the object (or card application) inside the IC card  2  or the signature key profile information presentation method of one or more objects (or card application) within the IC card  2  via the IC card read/write unit  13  (sequence SQ 8  of  FIG. 6 ). 
     In the case the IC card  2  is a multiple application IC card, the signature file creation managing part  24  may deliver the signature key listing request to the signature data creation part  25  by including the application identifier for distinguishing the available object (or card application) in the multiple application IC card, in the signature key listing request. 
     In the case the IC card  2  has the construction shown in  FIG. 4 , the signature data creation part  25  executes, upon reception of the signature key listing request from the signature file creation managing part  24 , the signature key list presentation method of the corresponding object (or card application) (sequence SQ 9  of  FIG. 6 ) and collects the profile information from the signature key set of the corresponding object (or card application). Further, the signature data creation part  25  presents the profile information thus collected to the signature file creation managing part  24  as signature key list (sequence SQ 10  of  FIG. 6 ). 
     On the other hand, in the case the IC card  2  has the construction shown in  FIG. 5 , the signature data creation part  25  executes, upon reception of the signature key listing request from the signature file creation managing part  24 , the signature key profile information presentation method of corresponding plural objects (or card applications) (sequence SQ 9  of  FIG. 6 ), and collects the profile information from the plural corresponding objects (or card applications). Further, the signature data creation part  25  presents the profile information thus collected to the signature file creation managing part  24  as the signature key list (sequence SQ 10  of  FIG. 6 ). In the description hereinafter, it is assumed that the signature data creation part  25  executes, in response to the request from the signature file creation managing part  24 , the signature key profile information presentation method of plural objects (or card applications), collects the profile information from the plural objects (or card applications), and presents the profile information thus collected to the signature file creation managing part  24  as the signature key list, for the sake of simplification of explanation. 
     It should be noted that the signature data creation part  25  may present the profile information to the signature file creation managing part  24  by including an identifier of the key (such as key number). 
     Upon receipt of presentation of the signature key list from the signature data creation part  25 , the signature file creation managing part  24  asks for selection of the signature key to the interface part  22  (sequence SQl 1  of  FIG. 6 ). 
     Upon receipt of the selection request of signature key from the signature file creation managing part  24 , the interface part  22  creates a signature key list display screen  31  as shown in  FIG. 7  and displays the same on the operation panel  11  (sequence SQ 12  of  FIG. 6 ).  FIG. 7  is a first diagram showing the signature key list display screen. 
     As shown in  FIG. 7 , the signature key list display screen  31  displays a list of the signature keys available for digital signature. In addition to the list of the signature keys, it is also possible to display the name and authority or title of the user as a part of the profile information. As mentioned above, the profile information is displayed on the screen by being provided to the interface part  22  via the signature file creation managing part  24  as a return value of the signature key list presentation method. 
     The user refers to the signature key list display screen  31  such as the one shown in  FIG. 7  and selects an appropriate signature key (sequence SQ 13  of  FIG. 6 ). Thereby, the user selects, for example, the key for private use for the case of providing a digital signature to a private document and selects the key of general manager when to provide a digital signature to the document with the power of general manager. 
     When a signature key is selected by the user, the interface part  22  delivers the profile name of the key and/or the identifier of the key selected by the user to the signature file creation managing part  24  (sequence SQ 14  of  FIG. 6 ). 
     Upon reception of the profile name of the key and/or the identifier of the key selected by the user from the interface part  22 , the signature file creation managing part  24  delivers a signature data creation request that calls the signature implementation method of the object (or card application) inside the IC card  2  to the signature data creation part  25  via the IC card read/write unit  13  while using the profile name and/or the identifier of the key and further the corresponding Message digest held on the RAM 17  as a parameter (sequence SQ 15  of  FIG. 6 ). 
     Upon reception of the signature data creation request from the signature file creation managing part  24 , the signature data creation part  25  executes the signature implementation method of the corresponding object (or card application) on the basis of the parameter (sequence SQ 16  of  FIG. 6 ) and returns the signature data to the signature file creation managing part  24  as the result of execution (sequence SQ 17  of  FIG. 6 ). For example, the signature implementation method encrypts the message digest according to the RSA 1024-bit method, or the like, while using the signature key, which is distinguished by the profile name and/or the identifier of the key provided as the parameter. 
     Upon reception of the signature data form the signature data creation part  25 , the signature file creation managing part  24  files the signature data and creates a signature file (sequence SQ 18  of  FIG. 6 ) and delivers the request of post-processing including the signature file, to the file after-processing part  23  (sequence SQ 19  of  FIG. 6 ). 
     Upon reception of the request of post-processing from the signature file creation managing part  24 , the file after-processing part  23  stores the signature file included in the request of the post-processing in a specified location of the hard disk drive  15  (sequence SQ 20  of  FIG. 6 ) and notifies the result of the post-processing (completion of saving, for example) to the signature file creation managing part  24  (sequence SQ 21  of  FIG. 6 ). Here, it should be noted that the specified location of the hard disk drive  15  means for example a private folder of the user who had carried out the scanning. 
     Upon reception of the notification of result from the file after-processing part  23 , the signature file creation managing part  24  notifies the result to the interface part  22  (sequence SQ 22  of  FIG. 6 ). 
     Further, upon reception of the notification of result from the signature file creation part  24 , the interface part  22  displays the result on the operation panel  11  (sequence SQ 23  of  FIG. 6 ). 
     By carrying out the processing shown in  FIG. 6 , it becomes possible for a single user to use plural digital signature keys in digital signature according to the purposes and situations. 
     Although the user has to make decision whether or not to provide digital signature to the data at the time the user inputs data in the example of  FIG. 6 , it is also possible to configure such that the user can decide whether or not to provide the digital signature to the data after inputting the data and the electronic data has been created in the digital multifunction apparatus  1 . Further, in the case the scanning is conducted after the user has selected not to provide digital signature, the process sequences SQ 5 -SQ 18  of  FIG. 6  can be omitted from the process sequence. 
     Further, while explanation has been made in  FIG. 6  that the signature file creation managing part  24  delivers the signature key listing request for calling the signature key list presentation method or the signature key profile information presentation method to the signature data creation part  25  in the sequence SQ 8 , it is also possible to implement such that the signature file creation managing part  24  delivers the signature key listing request for calling the signature key list presentation method always to the signature data creation part  25  and the signature data creation part  25  calls a dummy signature key list presentation method in the case the signature data creation part  25  has the construction shown in  FIG. 5 . Thereby, the dummy signature key list presentation method calls the signature key profile information presentation method of one or plural objects (or card applications). With this implementation, there is no need in the signature file creation managing part  24  to worry about whether the signature data creation part  25  has the construction shown in  FIG. 4  or the construction shown in  FIG. 5 . This applies also to the embodiments to be explained below. 
     Hereinafter, embodiments different from Embodiment 1 will be explained. 
     Embodiment 2 
     As shown in  FIG. 6  Embodiment 1 has been implemented such that the signature file creation managing part  24  requests presentation of the signature key list (and/or list of the profile information) to the signature data creation part  25  and the received signature key list (and/or the list of the profile information) is shown to the user via the interface part  22  for selection, after that the data input has occurred, while it is also possible that the data input is conducted after the signature file creation managing part  24  has displayed the signature key list (and/or list of the profile information) to the user via the interface part  22  in response, for example to the request from the user. 
     Another example of the digital signature processing is shown in  FIG. 8 , and thus,  FIG. 8  is a second sequence diagram of digital signature processing. 
     First, the user carries the IC card  2  and the paper document to be scanned to the digital multifunction apparatus  1 , inserts the IC card  2  into the IC card read/write unit  13 . 
     Next, the user touches a signature key listing request button, or the like, of the operation panel  11  and requests display of the signature key list (sequence SQ 30  of  FIG. 8 ). 
     Upon request of the user for display of the signature key list, the interface part  22  notifies to the signature file creation managing part  24  that display of the signature key list is requested by the user (sequence SQ 31  of  FIG. 8 ). 
     Upon reception of notification from the interface part  22  that display of the signature key list was requested by the user, the signature file creation managing part  24  delivers a signature key listing request for calling the signature key list presentation method or the signature key profile information presentation method of the object (or card application) inside the IC card  2  to the signature data creation part  25  via the IC card read/write unit  13  (sequence SQ 32  of  FIG. 8 ). 
     In the case the IC card  2  has the construction shown in  FIG. 4 , the signature data creation part  25  executes, in response to reception of the signature key listing request from the signature file creation managing part  24 , the signature key list presentation method of the corresponding object (or card application) (sequence SQ 33  of  FIG. 8 ), and collects the profile information from the signature key set of the corresponding object (or card application). Further, the signature data creation part  25  presents the signature key list the profile information thus collected to the signature file creation managing part  24  (sequence SQ 34  of  FIG. 8 ). 
     On the other hand, in the case the IC card  2  has the construction shown in  FIG. 5 , the signature data creation part  25  executes, upon reception of the signature key listing request from the signature file creation managing part  24 , the signature key profile information presentation method of corresponding plural objects (or card applications) (sequence SQ 33  of  FIG. 8 ), and collects the profile information of the corresponding plural objects (or card applications). Further, the signature data creation part  25  presents the profile information thus collected to the signature file creation managing part  24  as the signature key list (sequence SQ 34  of  FIG. 8 ). 
     Upon reception of the presentation of the signature key list from the signature data creation part  25 , the signature file creation managing part  24  requests selection of the signature key to the interface part  22  (sequence SQ 35  of  FIG. 8 ). 
     Upon reception of the selection request from the signature key more signature file creation managing part  24 , the interface part  22  crates the signature key list display screen  31  shown in  FIG. 7  and displays the same on the operation panel  11  (sequence SQ 36  of  FIG. 8 ). 
     Thereby, the user refers to the signature key list display screen  31  shown in  FIG. 7  and selects an appropriate signature key (sequence SQ 37  of  FIG. 8 ). 
     Upon selection of the signature key by the user, the interface part  22  delivers the profile name of the key selected by the user and/or the identifier of the key to the signature file creation managing part  24  (sequence SQ 38  of  FIG. 8 ). 
     On the other hand, the user sets the paper document on the image scanner  12  after selection of the signature key and switches the digital multifunction apparatus  1  to the scanner mode by using the operation panel  11 , for example. Further, the user selects “scan with digital signature option” and starts scanning (sequence SQ 39  of  FIG. 8 ). 
     Upon instruction of data input by the user, the interface part  22  notifies to the object data input part  21  that the data input has been instructed by the user (sequence SQ 40  of  FIG. 8 ). 
     Upon reception of notification that data input has been instructed by the user from the interface part  22 , the object data input part  21  reads the paper document set by the user and creates the signature object (sequence SQ 41  of  FIG. 8 ). Further, the object data input part  21  delivers the same to the signature file creation managing part  24  (sequence SQ 42  of  FIG. 8 ). 
     The signature file creation managing part  24  expands the signature object data delivered from the object data input part  21  on the RAM  17  and instructs pre-processing to the object data preprocessing part  26  (sequence SQ 43  of  FIG. 8 ). 
     The object data preprocessing part  26  applies a one-way function the signature object data instructed for processing by the signature file creation managing part  24  (sequence SQ 44  of  FIG. 8 ), and creates a message digest of that signature object data. Further, the object data preprocessing part  26  expands the message digest on the RAM  17  and returns the message digest to the signature file creation managing part  24  (sequence SQ 45  of  FIG. 8 ). 
     In the sequence SQ 38 , the signature file creation managing part  24  delivers a signature data creation request, which calls the signature implementation method of the object (or card application) inside the IC card  2  to the signature data creation part  25  via the IC card read/write unit  13  while using the profile name of the key and/or the identifier of the key specified by the user from the interface part  22  and the corresponding message digest held on the on RAM  17  as the parameters (sequence SQ 46  of  FIG. 8 ). 
     Upon reception of the signature data creation request from the signature file creation managing part  24 , the signature data creation part  25  executes the signature implementation method of the corresponding object (or card application) on the basis of the parameter (sequence SQ 47  of  FIG. 8 ), and returns the signature data to the signature file creation managing part  24  as the result of execution (sequence SQ 48  of  FIG. 8 ). 
     Upon reception of the signature data from the signature data creation part  25 , the signature file creation managing part  24  files the signature data and thus creates the signature file (sequence SQ 49  of  FIG. 8 ). Further, the signature file creation managing part  24  delivers the request of the post-processing including the signature file, for example, to the after-processing part  23  (sequence SQ 50  of  FIG. 8 ). 
     Upon reception of the request for post-processing from the signature file creation managing part  24 , the file after-processing part  23  saves the signature file included in the request of post-processing in a specified location of the hard disk drive  15  (sequence SQ 51  of  FIG. 8 ) and notifies the result of the post-processing (completion of saving, for example) to the signature file creation managing part  24  (sequence SQ 52  of  FIG. 8 ). 
     Upon reception of the notification of the result from the file after-processing part  23 , the signature file creation managing part  24  notifies the result to the interface part  22  (sequence SQ 53  of  FIG. 8 ). 
     Upon reception of the notification of the result from the signature file creation part  24 , the interface part  22  displays the result on the operation panel  11  (sequence SQ 54  of  FIG. 8 ). 
     According to the processing shown in FIG.  8 , too, it becomes possible for a single user to provide a digital signature by selectively using plural digital signature keys according to the purposes and situations. 
     Embodiment 3 
     Although explanation has been made in Embodiment 1 for the case that the user inserts the IC card  2  into the IC card read/write unit  13  first as shown in  FIG. 6 , it is also possible for the digital multifunction apparatus  1 , to determine whether or not the IC card  2  is inserted into the IC card read/write unit  13  in the stage in which scanning has been completed and the signature processing is going to be started (for example when the signature file creation managing part  24  is going to start the processing of sequence SQ 8  of  FIG. 6 ). Thus, when it is determined that the IC card is not inserted, the digital multifunction apparatus may display a request in the operation panel  11 , or the like, that that the IC card  2  is to be inserted into the IC card read/write unit  13  and urge the user to insert the IC card  2 . 
     Another example of digital signature processing is shown in  FIG. 9 , wherein it should be noted that  FIG. 9  is a third sequence diagram of digital signature processing. 
     First, the user brings the paper document to be scanned before the digital multifunction apparatus  1  and sets the paper document on the image scanner  12 . Further, the user switches the digital multifunction apparatus  1  to the scanner mode by using the operation panel  11 , and starts scanning by selecting “scan with digital signature” option (sequence SQ 60  of  FIG. 9 ). 
     When data input is instructed by the user, the interface part  22  notifies to the object data input part  21  that the data input has been instructed by the user (sequence SQ 61  of  FIG. 9 ). 
     Upon reception the notification from the interface part  22  that data input has been instructed by the user, the object data input part  21  reads the paper document set by the user and creates the signature object data (sequence SQ 62  of  FIG. 9 ) and delivers the same to the signature file creation managing part  24  (sequence SQ 63  of  FIG. 9 ). 
     The signature file creation managing part  24  expands the signature object data provided from the object data input part  21  on the RAM  17  and instructs the pre-processing to the object data preprocessing part  26  (sequence SQ 64  of  FIG. 9 ). 
     The object data preprocessing part  26  applies the one-way function to the signature object data, of which processing has been instructed by the signature file creation managing part  24  (sequence SQ 65  of  FIG. 9 ), creates the message digest of that signature object data, expands the same on the RAM  17 , and returns that message digest to the signature file creation managing part  24  (sequence SQ 66  of  FIG. 9 ). 
     Next, the signature file creation managing part  24  determines whether or not the IC card  2  is inserted to IC card read/write unit  13  (sequence SQ 67  of  FIG. 9 ). When it is determined that the IC card  2  is not inserted to the IC card read/write unit  13 , the signature file creation managing part  24  sends an insertion request of IC card to the interface part  22  (sequence SQ 68  of  FIG. 9 ). 
     Upon reception of the insertion request of IC card from the signature file creation managing part  24 , the interface part  22  creates an IC card insertion request display screen  32  as shown in  FIG. 10  and shows the same on the operation panel  11  (sequence SQ 69  of  FIG. 9 ).  FIG. 10  is a drawing showing an example of the IC card insertion request display screen. 
     As shown in  FIG. 10 , there is displayed, in the IC card insertion request display screen  32 , a request for insertion request of the IC card  2 . Thereby, the user refers to the IC card insertion request display screen  32  of  FIG. 10  and inserts the IC card  2  into IC card read/write unit  13 . 
     The signature file creation managing part  24  determines whether or not the IC card  2  is inserted into the IC card read/write unit  13  (sequence SQ 70  of  FIG. 9 ). 
     When it is determined that the IC card  2  is inserted into the IC card read/write unit  13 , the signature file creation managing part  24  delivers the signature key listing request, which calls the signature key list presentation method or the signature key profile information presentation method of the object (or card application) in the IC card  2 , to the signature data creation part  25  via the IC card read/write unit  13  (sequence SQ 71  of  FIG. 9 ). 
     When the signature file creation managing part  24  has determined that the IC card  2  is inserted to the IC card read/write unit  13  as a result of the determination in the sequence SQ 67  of  FIG. 9 , the processing from the sequence S 68  to the sequence S 70  may be omitted. 
     The processing from the sequence SQ 72  to the sequence SQ 86  of  FIG. 9  are made similarly to the processing from the sequence SQ 9  to the sequence SQ 23  of  FIG. 6 . 
     Embodiment 4 
     Although it has shown in Embodiment 1 that the signature file creation managing part  24  starts the processing of the sequence SQ 8  after receiving the message digest from the object data preprocessing part  26  in sequence SQ 7  as shown in  FIG. 6 , it is not always necessarily to carry out the processing with such an order. Thus, it is possible to configure such that the interface part  22  notifies to the signature file creation managing part  24  that the digital signature is to be provided at the same time as the sequence SQ 2  and carry out the processing from the sequence SQ 8  to the sequence SQ 14  for selection of the signature key, parallel with the sequence SQ 3 . Alternatively, it is possible to carry out the processing from the sequence SQ 8  to the sequence SQ 14  parallel with the processing from the sequence SQ 5  to the sequence SQ 7  for pre-processing. 
     Embodiment 5 
     Although it has been configured in Embodiment 1 that the interface part  22  creates the signature key list display screen  31  such that plural signature keys are arranged equally for urging the user for selection the signature key based on the returned value of the signature key list presentation method received through the signature file creation managing part  24  as shown in  FIG. 7 , it is possible to create the signature key list display screen  31  in which a default signature key is already selected as shown in  FIG. 11  and urge the user for selection of a signature key. 
       FIG. 11  is a second diagram showing an example of the signature key list display screen, in which the key for private use is selected as the default signature key. 
     The default signature key can be implemented by setting a default flag to the profile information included in the signature key set, for example, such that the interface part  22 , checking the default flag, defines the signature key in which the default flag is set to the default signature key. Alternatively, it is possible to set an order of priority to the profile information included in the signature key set and cause the interface part  22  to check the order of priority and define the signature key of the highest order of priority as the default signature key. 
     Embodiment 6 
     While explanation has been made in Embodiment 1 for the case of using a liquid crystal display, or the like, for the operation panel  11 , there can be a case in which the display part can display only one or two lines depending on the type of the digital multifunction apparatus  1 . In the case the display part can make only a simple display, the interface part  22  does not create the signature key list display screen  31  shown in  FIG. 7  and displays the signature key list one line by one line in the display part as shown in  FIG. 12 . It should be noted that  FIG. 12  shows an example of the signature key list displayed on such a display part. As can be seen in  FIG. 12 , the display part displays one signature key (or single piece of profile information) in the signature key list (or the list of profile information). 
     Embodiment 7 
     While the user selected the signature key in Embodiment 1 by using the signature key list display screen  31  displayed by the interface part  22  in the operation panel  11  as shown in  FIG. 7 , it is also possible to configure that the user inputs profile information in the operation panel  11 , or the like, requests creation of the signature data. Thereby, it is possible to configure such that the signature file creation managing part  24 , upon acquisition of the profile information via the interface part  22 , delivers the signature data creation request, which calls the signature execution method of the object (or card application) inside the IC card  2  while using the profile information and the corresponding message digest held in the RAM  17  as parameter, to the signature data creation part  25  via the IC card read/write unit  13 . Upon reception of the signature data creation request from the signature file creation managing part  24 , the signature data creation part  25  executes the signature implementation method of the corresponding object based on the parameter. 
     Embodiment 8 
     In  FIG. 6  of Embodiment 1, the digital signature processing has been explained for the example in which a paper document is read from the image scanner  12 , while other inputting method can be used, provided that it is possible to develop the data to be provided with digital signature on the RAM  17 . For example, it is possible to read out the electronic document stored in the electronic document storage server, or the like, connected to the digital multifunction apparatus  1  via a network and expand the same on the RAM  17 . Alternatively, it is possible to read out the electronic document stored on the hard disk drive  15 , or the like, of the digital multifunction apparatus  1  and develop the same on the RAM  17 . In the case of reading out such stored electronic document, the user specifies the desired electronic document to be provided with the digital signature by using the operation panel  11 , or the like. 
     Embodiment 9 
     While explanation has been made in  FIG. 6  of Embodiment 1 that the signature file is saved in the hard disk drive  15  of the digital multifunction apparatus  1  in the post-processing conducted by the file after-processing part  23 , saving is not necessarily be done in the hard disk drive  15  of the digital multifunction apparatus  1 . 
     Thus, saving may be made in the recording medium inserted to the media drive  18  of the digital multifunction apparatus  1  or alternatively in a file control server, or the like, connected to the digital multifunction apparatus  1  via a network. 
     According to various embodiments explained heretofore, it becomes possible with the present invention that a single user can use plural digital signature keys according to the objects and situations. 
     Further, according to the present invention, it becomes possible to use plural digital signature keys with a single IC card. 
     Further, while explanation has been made on preferred embodiments of the present invention, the present invention is not limited to such specific embodiments and various modifications and variations are possible within the scope of the present invention. 
     For example, while explanation has been made for the case of using the digital multifunction apparatus  1  in the embodiment above, the present invention is not limited to such a digital multifunction apparatus  1  and it is possible to use a construction having an equivalent function such as a personal computer connected with a scanner apparatus and attached with the IC card  2 . 
     In any of the cases of using the digital multifunction apparatus  1  or personal computer, there is no need of implementing the signature data creation part  25  in the form of the IC card  2 . Thus, in place of the IC card  2 , it is possible to use a personal information processing apparatus of portable type having a CPU and memory (cellular phones, PDAs, and the like). 
     Further, it is also possible to implement the signature data creation part  25  on the digital multifunction apparatus  1  or personal computer, without separating from other functions. With such a construction, security of the signature key may become weaker as compared with the case of using the IC card  2 , or the like, the part corresponding to the IC card  2  and the IC card read/write unit  13  can be omitted, and the function can be implemented easily. 
     Also, while explanation has been made in the embodiment mentioned above that a signing application corresponding to the signature data creation part  25  is installed in the IC card  2 , it is possible to configure such that the digital multifunction apparatus  1  determines before the sequence SQ 8  of  FIG. 6  whether or not a signing application corresponding to the signature data creation part  25  is installed in the IC card  2 , and, if not, the digital multifunction apparatus  1  downloads the signing application from a server, or the like, that holds the signing application and install the same to the IC card  2 . 
     Further, the present invention is by no means limited to the embodiments described heretofore, but various variations and modifications may be made without departing from the scope of the invention. 
     The present invention is based on Japanese Priority Application 2004-227909 filed on Aug. 4, 2004, the entire contents of which are incorporated herein as reference.