Patent Publication Number: US-2006002564-A1

Title: Information processing system, information processing apparatus, information processing method, recording medium and program

Description:
BACKGROUND OF THE INVENTION  
      1. Field of the Invention  
      The present invention relates to an information processing system, an information processing apparatus, an information processing method, a recording medium and a program which are suitable for secured transmission and reception of confidential electronic files.  
      2. Description of the Related Art  
      Recently, electronic delivery in which an electronic file having documents and/or images filed in an electronic form is stored in a recording medium, such as a magnetic disk, and mailed or delivered to the destination of delivery. When so-called confidential information is to be delivered in such electronic delivery, a security measure to guarantee a high-level confidentiality should be taken.  
      For instance, a method of enhancing the security in transmitting and receiving an electronic file is disclosed in Unexamined Japanese Patent Application KOKAI Publication No. 2000-123479. According to the method, when a user records an electronic file on an optical disk medium, the unique ID of an optical disk drive unit of an authorized or legitimate user is recorded together with the electronic file. When a user extracts an electronic file recorded on an optical disk medium, on the other hand, the recorded ID is compared with the unique ID of the optical disk drive unit the user is currently using. When both IDs match with each other, a program for extracting the electronic file recorded on the optical disk medium is invoked. Accordingly, the user can prevent illegitimate use of the recording medium even if a third party finds out a password or the like.  
      However, a user who records an electronic file on a recording medium should make the recording beforehand using an exclusive drive unit and deliver the recording medium. A user who extracts an electronic file from a delivered recording medium should have a dedicated security program installed in a computer beforehand. When a user who wants to extract an electronic file from the delivered recording medium using a plurality of computers, a dedicated security program should be installed in all the computers to be used beforehand. When a user who wants to extract an electronic file using a plurality of computers, located at different sites (e.g., in an office and the destination of a business trip), a dedicated security program should be installed in the computers at the different sites. This enforces users to prepare for desired actions previously, which requires a lot of work and is very troublesome, not to mention the cost required.  
      Another method of enhancing the security is disclosed in Unexamined Japanese Patent Application KOKAI Publication No. 2003-233949. According to the method, an optical disk medium has a read-only area and a writable area. Data reading from this optical disk medium is allowed only when unique information stored in the read-only area of the optical disk medium is valid.  
      As the validity is determined based on the unique information stored in the recording medium, however, the security cannot be guaranteed when the unique information is read illegitimately. The security cannot be guaranteed when the user has lost the recording medium itself.  
      It is apparent that the prior arts are not adequate to secure the confidentiality of an electronic file to be stored in a recording medium by a user.  
     SUMMARY OF THE INVENTION  
      The present invention has been devised in consideration of the situations, and aims at providing an information processing system, an information processing apparatus, an information processing method, a recording medium and a program which are suitable for secured transmission and reception of confidential electronic files.  
      To achieve the object, an information processing system according to the first aspect of the invention comprises: 
          a first information processing apparatus including 
            a key generation section which generates a set of a private key and a public key,     a private-key storage section which stores the private key in a first key recording medium,     a public-key storage section which stores the public key in a second key recording medium or a recording medium,     a private-key acquisition section which acquires the private key to be stored in the first key recording medium,     a common-key decryption section which decrypting an encrypted common key with the private key, and     an electronic-file decryption section which decrypts an encrypted electronic file with the common key decrypted by the common-key decryption section; and    
            a second information processing apparatus including 
            a common-key generation section which generates a common key for encrypting an electronic file,     an electronic-file encryption section which encrypts the electronic file using the common key,     an electronic-file storage section stores the electronic file, encrypted by the electronic-file encryption section, in the recording medium,     a public-key acquisition section which acquires the public key stored in the second key recording medium or the recording medium,     a common-key encryption section which encrypts the common key with the public key, and     a common-key storage section which stores the common key, encrypted by the common-key encryption section, in the recording medium.    
               

      An information processing apparatus according to the second aspect of the invention comprises: 
          a key generation section which generates a set of a private key and a public key;     a private-key storage section which stores the private key in a first key recording medium;     a public-key storage section which stores the public key in a second key recording medium or a recording medium; a private-key acquisition section which acquires the private key to be stored in the first key recording medium;     a common-key decryption section which decrypts an encrypted common key with the private key; and     an electronic-file decryption section which decrypts an encrypted electronic file with the common key decrypted by the common-key decryption section.        

      The information processing apparatus can further comprise: 
          an electronic-file information storage section which stores information indicating a confidential level of an electronic file; and     a pattern determination section which selects one procedure from predetermined plural key generating procedures based on information to be stored in the electronic-file information storing section, and     wherein the public-key storage section stores the public key, generated by the key generation section, in the second key recording medium or the recording medium based on the one procedure selected by the pattern determination section.        

      The information processing apparatus can further comprise: 
          an electronic-file-store information storage section which stores information on a user who receives the recording medium; and     a pattern determination section which selects one procedure from predetermined plural key generating procedures based on information to be stored in the electronic-file-store information storage section, and     wherein the public-key storage section stores the public key, generated by the key generation section, in the second key recording medium or the recording medium based on the one procedure selected by the pattern determination section. The electronic-file encryption section can determine from which one of the second key recording medium and the recording medium an encrypted common key is to be acquired, and acquire the encrypted common key from the second key recording medium or the recording medium based on a result of determination.        

      The key generation means can extract information unique to the recording medium, and generate a set of a private key and a public key based on the unique information.  
      The key generation means can generate a set of a private key and a public key based on information on the user who receives the recording medium or a date.  
      An information processing apparatus according to the third aspect of the invention comprises: 
          a common-key generation section which generates a common key;     an electronic-file encryption section which encrypts the electronic file with the common key;     an electronic-file storage section which stores the electronic file, encrypted by the electronic-file encryption section, in a recording medium;     a public-key acquisition section which acquires the public key stored in a second key recording medium or the recording medium;     a common-key encryption section which encrypts a common key, which is used in encryption in the electronic-file encryption section, with the public key; and     a common-key storage section which stores the common key, encrypted by the common-key encryption section, in the recording medium.        

      The information processing apparatus can further comprise: 
          a pattern determination section which determines which procedure in predetermined plural key generating procedures is used, and     wherein the public-key acquisition section acquires a public key according to a predetermined procedure determined by the pattern determination section, and     the common-key generation section generates a common key according to the predetermined procedure determined by the pattern determination section.        

      The common-key storage section can determine in which one of the second key recording medium and the recording medium the common key generated by the common-key generation section is to be stored, and store the common key in the second key recording medium or the recording medium based on a result of determination.  
      The common-key generation means can extract information unique to the recording medium, and generate a common key based on the unique information.  
      An information processing method according to the fourth aspect of the invention comprises: 
          a key generation step of generating a set of a private key and a public key;     a private-key storage step of storing the private key in a first key recording medium;     a public-key storage step of storing the public key in a second key recording medium or a recording medium;     a private-key acquisition step of acquiring the private key to be stored in the first key recording medium;     a common-key decryption step of decrypting an encrypted common key with the private key; and     an electronic-file decryption step of decrypting an encrypted electronic file with the common key decrypted at the common-key decryption step.        

      An information processing method according to the fifth aspect of the invention comprises: 
          a common-key generation step of generating a common key;     an electronic-file encryption step of encrypting the electronic file with the common key;     an electronic-file storage step of storing the electronic file, encrypted at the electronic-file encryption step, in a recording medium;     a public-key acquisition step of acquiring the public key stored in a second key recording medium or the recording medium;     a common-key encryption step of encrypting a common key, which is used in encryption at the electronic-file encryption step, with the public key; and     a common-key storage step of storing the common key, encrypted at the common-key encryption step, in the recording medium.        

      An information processing system according to the sixth aspect of the present invention comprises: 
          a first information processing apparatus including 
            key generation means for generating a set of a private key and a public key,     private-key storage means for storing said private key in a first key recording medium,     public-key storage means for storing said public key in a second key recording medium or a recording medium,     private-key acquisition means for acquiring said private key to be stored in said first key recording medium,     common-key decryption means for decrypting an encrypted common key with said private key, and     electronic-file decryption means for decrypting an encrypted electronic file with said decrypted common key; and    
            a second information processing apparatus including 
            common-key generation means for generating a common key for encrypting an electronic file,     electronic-file encryption means for encrypting said electronic file using said common key, electronic-file storage means for storing said electronic file, encrypted by said electronic-file encryption means, in said recording medium,     public-key acquisition means for acquiring said public key stored in said second key recording medium or said recording medium,     common-key encryption means for encrypting said common key with said public key, and     common-key storage means for storing said common key, encrypted by said common-key encryption means, in said recording medium.    
               

      An information processing apparatus according to the seventh aspect of the present invention comprises: 
          key generation means for generating a set of a private key and a public key;     private-key storage means for storing said private key in a first key recording medium;     public-key storage means for storing said public key in a second key recording medium or a recording medium;     private-key acquisition means for acquiring said private key to be stored in said first key recording medium;     common-key decryption means for decrypting an encrypted common key with said private key; and     electronic-file decryption means for decrypting an encrypted electronic file with said common key decrypted by said common-key decryption means.        

      An information processing apparatus according to eighth aspect of the present invention comprises: 
          common-key generation means for generating a common key;     electronic-file encryption means for encrypting said electronic file with said common key;     electronic-file storage means for storing said electronic file, encrypted by said electronic-file encryption means, in a recording medium;     public-key acquisition means for acquiring said public key stored in a second key recording medium or said recording medium;     common-key encryption means for encrypting a common key, which is used in encryption in said electronic-file encryption means, with said public key; and     common-key storage means for storing said common key, encrypted by said common-key encryption means, in said recording medium.        

      A computer readable recording medium according to the ninth aspect of the invention has: 
          a writable area for storing an electronic file; and     a read-only area where a program for generating a private key, a public key and a common key is stored,     the program allowing a computer to function as:     key generation means for generating a set of a private key and a public key;     private-key storage means for storing the private key in a first key recording medium;     public-key storage means for storing the public key in a second key recording medium or a recording medium;     private-key acquisition means for acquiring the private key to be stored in the first key recording medium;     common-key decryption means for decrypting an encrypted common key with the private key acquired by the private-key acquisition means;     electronic-file decryption means for decrypting an encrypted electronic file with the common key decrypted by the common-key decryption means;     common-key generation means for generating a common key; electronic-file encryption means for encrypting the electronic file with the common key;     electronic-file storage means for storing the electronic file, encrypted by the electronic-file encryption means, in a recording medium;     public-key acquisition means for acquiring the public key stored in a second key recording medium or the recording medium;     common-key encryption means for encrypting a common key, which is used in encryption in the electronic-file encryption means, with the public key acquired by public-key acquisition means; and     common-key storage means for storing the common key, encrypted by the common-key encryption means, in the recording medium.        

      A program according to the tenth aspect of the invention allows a computer to function as: 
          key generation means for generating a set of a private key and a public key;     private-key storage means for storing the private key in a first key recording medium;     public-key storage means for storing the public key in a second key recording medium or a recording medium;     private-key acquisition means for acquiring the private key to be stored in the first key recording medium;     common-key decryption means for decrypting an encrypted common key with the private key;     electronic-file decryption means for decrypting an encrypted electronic file with the common key decrypted by the common-key decryption means;     common-key generation means for generating a common key;     electronic-file encryption means for encrypting an electronic file, which should keep confidentiality, with the common key;     electronic-file storage means for storing the electronic file, encrypted by the electronic-file encryption means, in a recording medium;     public-key acquisition means for acquiring the public key stored in a second key recording medium or the recording medium;     common-key encryption means for encrypting a common key, which is used in encryption in the electronic-file encryption means, with the public key acquired by the public-key acquisition means; and     common-key storage means for storing the common key, encrypted by the common-key encryption means, in the recording medium.       

    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
      These objects and other objects and advantages of the present invention will become more apparent upon reading of the following detailed description and the accompanying drawings in which:  
       FIG. 1  is a diagram showing the configuration of an information processing system according to one embodiment of the invention;  
       FIG. 2  is a diagram showing an example of the structure of a CD-R;  
       FIG. 3  is a diagram showing an example of the configuration of a receiver PC (Personal computer);  
       FIG. 4  is a diagram showing an example of information to be contained in delivery data information  441 ;  
       FIG. 5  is a diagram showing an example of information to be contained in supplier information  442 ;  
       FIG. 6  is a diagram showing an example of the functional structures of a PC which is used by a receiver;  
       FIG. 7  is a diagram showing an example of the configuration of a PC which is used by a supplier;  
       FIG. 8  is a diagram showing an example of the functional structures of a PC which is used by the supplier;  
       FIG. 9  is a flowchart illustrating a transmission/reception routine;  
       FIG. 10  is a flowchart illustrating a pattern determination routine;  
       FIG. 11  is a diagram illustrating an information management routine for a pattern  1 ;  
       FIG. 12  is a flowchart illustrating a key generation routine for the pattern  1 ;  
       FIG. 13  is a flowchart illustrating an encryption routine for the pattern  1 ;  
       FIG. 14  is a flowchart illustrating a decryption routine for the pattern  1 ;  
       FIG. 15  is a diagram illustrating an information management routine for a pattern  2 ;  
       FIG. 16  is a flowchart illustrating a key generation routine for the pattern  2 ;  
       FIG. 17  is a diagram illustrating an information management routine for a pattern  3 ;  
       FIG. 18  is a flowchart illustrating a key generation routine for the pattern  3 ;  
       FIG. 19  is a flowchart illustrating an encryption routine for the pattern  3 ,  
       FIG. 20  is a flowchart illustrating a decryption routine for the pattern  3 ;  
       FIG. 21  is a diagram showing an example of the configuration of a PC which is used by a supplier; and  
       FIG. 22  is a flowchart illustrating procedures for determining a pattern in the encryption routine. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
      An information processing system, an information processor, a information processing method, a recording medium and a program according to the present invention will now be explained with reference to the accompanying drawings. The following descriptions of embodiments of the present invention will be given of a case of electronic delivery, as an example, where delivery data which should be kept confidential is stored in a recording medium, and mailed or delivered to a delivery destination. The descriptions of embodiments of the present invention will be also given of a case, as an example, where an encryption procedure (the key generation process, encryption process, and decryption process to be discussed later) which depends on the usage pattern of the delivery data is determined, and electronic delivery is carried out in accordance with the determined encryption procedure.  
     First Embodiment  
       FIG. 1  is a diagram illustrating the embodiment which delivers delivery data using the information processing system of the present invention.  
      First, a supplier  3  receives a recording medium CD-R (Compact Disc-Rewritable)  2  which stores delivery data, and a USB memory  4  which stores a public key  6 , from a receiver  1 .  
      Next, the supplier  3  supplies the receiver  1  with delivery data which is encrypted with a common key  7 , and a CD-R  2  which stores a common key  8  encrypted with the public key  6 .  
      The receiver  1  then decrypts the encrypted common key  8  with a private key  5 , and the encrypted delivery data with the decrypted common key  7 .  
      That is, the receiver  1  can receive delivery data from the supplier  3  while keeping the confidentiality of delivery data.  
       FIG. 2  is a diagram illustrating an example of the structure of the CD-R  2  as the recording medium. As illustrated in  FIG. 2 , the CD-R  2  has a read-only area (ROM (Read Only Memory) section)  21 , and a writable area (RAM (Random Access Memory) section)  22 . The ROM section  21  stores a security program such as a key generation program to execute later-described key generation or the like, and a control program to perform control on browsing, referencing, copying of delivery data, and the like. The key generation program is read from the CD-R  2  prior to the reading of the control program. A hybrid type CD-R is available as such a CD-R  2 .  
      The CD-R  2  is used as the recording medium in the embodiment, but other recording media like a DVD-R (Digital Versatile Disk-Recordable) may be used as well.  
      In the information processing system, the USB (Universal Serial Bus) memory  4 , a different recording medium from the CD-R  2 , is used together with the CD-R  2 . As will be described later, the USB memory  4  stores the private key  5  or the public key  6 . The reason why the private key is stored in the USB memory  4 , different from the CD-R  2 , is to make the content of delivery data (confidential information), stored in the CD-R  2 , viewless without the private key  5  or the public key  6 , stored in the USB  4 , even if the CD-R  2  is lost.  
      Although the USB memory  4  is used in the embodiment, another flush memory having substantively the same function as that of the USB memory  4  may be used.  
      In the information processing system of the present invention, as will be described later, the key generation program to be discussed later, the public key  6 , and the private key  5  are stored in the CD-R  2  and the USB memory  4 , received by the supplier  3  illustrated in  FIG. 1 . The supplier  3  stores delivery data encrypted with the common key  7  in the received CD-R  2 , and encrypts the common key  7  with the public key  6 . Accordingly, delivery data encrypted with the common key  7 , and the common key  8  encrypted with the public key  6  are stored in the CD-R  2  delivered to the receiver  1 . As the receiver  1  decrypts the encrypted common key  8  with the private key  5  stored in the USB memory  4 , and decrypts the encrypted delivery data with the decrypted common key  7 , the receiver  1  can view the contents of delivery data (confidential information).  
      As illustrated in  FIG. 1 , the receiver  1  has a PC  11 , etc. The PC  11  can run the program stored in the CD-R  2 . The PC  11  can store the private key  5 , etc, in the USB memory  4 , and can use the stored private key  5  or the like. The PC  11  comprises, for example, an ordinary personal computer.  
       FIG. 3  is a diagram illustrating the configuration of the PC  11  owned by the receiver  1 .  
      As illustrated in  FIG. 3 , the PC  11  of the receiver  1  includes a control section  41 , an input section  42 , a display section  43 , a memory section  44 , interfaces  45  and  47 , an optical disk section  46 , and a USB section  48 .  
      The control section  41  includes, for instance, a CPU (Central Processing Unit), and controls the entire PC  11 . The PC  11  executes various processes by, for instance, running a program stored in the memory section  44 . The details of the processes of the control section  41  will be described later.  
      The input section  42  includes input media, such as a keyboard, a mouse, and a pointing device, and notifies various information inputted by a person in charge of the receiver  1  to the control section  41 .  
      The display section  43  includes a display device, such as a LCD (Liquid Crystal Display), or a PDP (Plasma Display Panel), and displays various information inputted from the control section  41 .  
      The memory section  44  comprises a semiconductor memory, a magnetic disk, or the like, and records various information and programs. The memory section  44  stores delivery data information  441 , supplier information  442 , etc.  
      The delivery data information  441  contains confidential information on delivery goods which is delivered by the supplier  3 .  
       FIG. 4  is a diagram illustrating an example of information contained in the delivery data information  441 . As illustrated in this figure, the delivery data information  441  includes the name of the supplier  3 , the name of the delivery goods, a delivery date, a delivery condition, and a confidential level. The confidential level is a parameter which represents the degree of the confidentiality.  
      The supplier information  442  contains information on the supplier  3 .  
       FIG. 5  is a diagram illustrating an example of information contained in the supplier information  442 . As illustrated in this figure, the supplier information  442  includes the name of the supplier  3 , a new flag (a flag which represents whether or not the supplier is a newly registered one), the size, the contact address and the name of the person in charge of the supplier  3 .  
      The interface  45  is an interactive communication interface with an optical disk drive, and connected to the optical disk section  46 . The interface  47  is an interactive communication interface with a USB, and connected to the USB section  48 .  
      An example of the functional structure of the control section  41  of the PC  11 , which is owned by the receiver  1 , will be illustrated in  FIG. 6 . As illustrated in this figure, the PC  11  includes an encryption procedure determining section  51 , a public key/private key generating section  52 , a private key acquiring section  53 , a decryption section  54 , and a public key/private key storing section  55 .  
      The encryption procedure determining section  51  comprises the control section  41 , etc., and controls the process regarding the determination of the encryption procedure (the procedure for the key generation routine, encryption routine, and decryption routine). To be more precise, the encryption procedure determining section  51  selects a predetermined encryption procedure from encryption procedures of patterns  1  to  3  to be discussed later, based on the delivery data information  441  stored in the memory section  44 . For instance, when the key generation programs are installed on the PC  11  of the receiver  1  and a PC  31  of the supplier  3 , the encryption procedure determining section  51  determines the pattern  3  as the encryption procedure.  
      The public key/private key generating section  52  comprises the control section  41 , and activates the key generation program stored in the CD-R  2  and generates a set of the private key  5  and the public key  6  in the key generation process to be discussed later.  
      The private key acquiring section  53  comprises the control section  41 , and acquires the private key  5 , stored in the USB memory  4 , in the decryption process to be discussed later.  
      The decryption section  54  comprises the control section  41 , and, decrypts the encrypted common key  8  with the private key  5  acquired by the private key acquiring section  53 , in the later described decryption process. The decryption section  54  decrypts encrypted delivery data with the decrypted common key  7  in the description process to be discussed later.  
      The public key/private key storing section  55  comprises the control unit  41 , etc, and stores the private key  5 , generated by the public key/private key generating section  52 , in the first USB memory  4  inserted into the USB section  48 , The public key/private key storing section  55  also stores the public key  6 , generated by the public key/private key generating section  52 , in the second USB memory  4  inserted into the USB section  48 .  
      The supplier  3  has the PC  31 , etc. The PC  31  is a computer which can activate the program stored in the CD-R  2 . The PC  31  stores the encrypted common key  8 , etc. in the USB memory  4 . The PC  31  takes out the public key  6 , etc, stored in the CD-R  2  or the USB memory  4 , and executes the later described encryption process or the like. For instance, the PC  31  comprises a general personal computer.  
       FIG. 7  is a diagram illustrating the configuration of the PC  31  owned by the supplier  3 . As illustrated in  FIG. 7 , the PC  31  includes a control section  61 , an input section  62 , a display section  63 , a memory section  64 , interfaces  65 ,  67 , an optical disk section  66 , and a USB section  68 .  
      The control section  61  includes, for instance, a CPU, and controls the entire PC  31  of the supplier  3 . The PC  31  executes various processes by, for instance, running a program stored in the memory section  64 .  
      The input section  62  includes input media such as a keyboard, a mouse, and a pointing device, and notifies various information inputted by a person in charge of the supplier  3  to the control section  61 .  
      The display section  63  includes a display device, such as a LCD, or a PDP, and displays various information input from the control section  61 .  
      The memory section  64  comprises a semiconductor memory, a magnetic disk, or the like, and records various information and programs.  
      The interface  65  is an interactive communication interface with an optical disk drive which can perform the reading from and the writing to the CD-R  2 , and connected to the optical disk section  66 . The interface  67  is an interactive communication interface with a USB, and connected to the USB section  68 .  
      An example of the functional structure of the control section  61  of the PC  31 , which is owned by the supplier  3 , is illustrated in  FIG. 8 . As illustrated in this figure, the PC  31  includes a common key generating section  71 , a public key acquiring section  72 , an encryption section  73 , and an encrypted data storing section  74 .  
      The common key generating section  71  comprises the control section  61 , and generates the common key  7  based on, for instance, information unique to the CD-R  2  (for instance, a product code).  
      The public key acquiring section  72  comprises the control section  61 , etc., and acquires the public key  6  stored in the CD-R 2  or the USB memory  4 .  
      The encryption section  73  comprises the control section  61 , and, encrypts delivery data with the common key  7 , generated by the common key generating section  71 . The encryption section  73  encrypts the common key  7  with the public key  6 , acquired by the public key acquiring section  72 .  
      The encrypted data storing section  74  comprises the control section  61 , etc., and stores the common key  8 , encrypted by the encryption section  73 , in the RAM section  22  of the CD-R  2  inserted into the optical disk section  66 . The encrypted data storing section  74  stores delivery data, encrypted by the encryption section  73 , into the RAM section  22  of the CD-R  2  inserted into the optical disk section  66 .  
      Next, the information processing method using the information processing system will be explained. According to the information processing method of the present invention, when the supplier  3  electronically delivers delivery data to the receiver  1 , the supplier  3  first receives the CD-R  2  and the USB memory  4 , which have undergone the key generation process to be discussed later, from the receiver  1 . Next, the supplier  3  executes the encryption process to be discussed later, and delivers the CD-R  2  and the USB memory  4  to the receiver  1 . The receiver  1  then decrypts delivery data, stored in the delivered CD-R  2 , through the decryption process to be discussed later. The information processing method will be explained in detail below.  
      In the transmitting and receiving routine according to the information processing method of the present invention, one encryption procedure is selected from a plurality of predetermined encryption procedures. In the embodiment, there are encryption procedures for pattern  1 , pattern  2 , and pattern  3 . The PCs  11  and  31  execute the key generation routine, the encryption routine, and the decryption routine in accordance with the selected encryption procedure.  
      Next, a routine of transmitting and receiving an electronic file with the confidentiality using the information processing system of the present invention will be explained with reference to the flowchart of  FIG. 9 .  
      First, the encryption procedure determining section  51  which is achieved by the control section  41  selects one of the patterns from the procedures of patterns  1  to  3 , based on the delivery data information  441  (step S 1 ).  
      In the pattern  1 , the supplier  3  receives the CD-R  2  which stores the key generation program in the ROM section  21 , and the USB memory  4  which stores the public key  6 , from the receiver  1 . The supplier  3  stores delivery data for which a predetermined encryption process is performed in the RAM section  22  of the CD-R  2 .  
      According to the pattern  1 , the first USB memory  4  stores the private key  5 , and the second USB memory  4  stores the public key  6 . The pattern  1  has the higher confidentiality in comparison with the patterns  2  and  3 .  
      In the pattern  2 , the difference from the pattern  1  is that the public key  6  is stored in the RAM section  22  of the CD-R  2 . The user&#39;s processing operation is easier than that of the pattern  1 .  
      In the pattern  3 , the ROM section  21  of the CD-R  2  does not store the key generation program, In this case, the key generation program is installed in the PC  11  of the receiver  1  and the PC  31  of the supplier  3 .  
       FIG. 10  is a flowchart for explaining the pattern selecting process in the step S 1 .  
      First, the control section  41  determines whether or not the security is the primary concern (step S 5 ). In the embodiment, the control section  41  performs the determination based on the confidential level contained in the delivery data information  441 .  
      In a case where the security is the primary concern (step S 5 ; YES), the control section  41  selects the pattern  1  (step S 6 ). For instance, two stage levels regarding the confidential level are set beforehand by the person of the receiver  1  in charge. If a high confidential level is set, the control section  41  selects the pattern  1 .  
      In a case where the user-friendliness for the process of the user is emphasized in addition to the security (step S 5 ; NO), the control section  41  determines whether or not the key generation program is installed on both of the PC  11  of the receiver  1  and the PC  31  of the supplier  3 . In the embodiment, the control section  41  performs the determination based on the new flag contained in supplier information  442 . For instance, two kinds of information for the new flag are set beforehand by the person in charge of the receiver  1 .  
      In a case where information indicating that the key generation program has not yet been installed on the PC  31  used by the supplier  3  is set in the new flag (step S 7 ; YES), the control section  41  selects the pattern  2 . In contrast, in a case where information indicating the installation of the key generation program on the PC  31  used by the supplier  3  is set in the new flag (step S 7 ; NO), the control section  41  selects the pattern  3 .  
      When the patterns of the encryption procedure are selected, the public key/private key generating section  52  achieved by the control section  41  executes the key generation process of the selected pattern (step S 2 ). The key generation process will be described later.  
      When the key generation process is executed, the CD-R  2  and the USB memory  4  for which the key generation process is performed are sent to the supplier  3  from the receiver  1 . The person in charge of the supplier  3  received the CD-R  2  and the USB memory  4  for which the key generation process is performed. The control section  61  of the PC  31  of the supplier  3  executes the encryption process of the selected pattern for the confidential electronic file (step S 3 ). The encrypted electronic file is stored in the RAM section  22  of the CD-R  2 . The details of the encryption process will be explained later.  
      When the encryption process is executed, the CD-R  2  and the USB memory  4  which have undergone the encryption process are sent to the receiver  1  from the supplier  3 .  
      The person in charge of the receiver  1  receives the CD-R  2  and the USB memory  4  which have undergone the encryption process. The control section  41  of the PC  11  of the receiver  1  executes the decryption process of the selected pattern (step S 4 ). The details of the decryption process will be explained later.  
      Accordingly, the person in charge of the receiver  1  can safely receives confidential delivery data.  
      Next, the key generation routine, the encryption routine, and the decryption routine for the each determined pattern will now be explained.  
      &lt;Pattern  1 &gt; 
       FIG. 11  is a diagram illustrating the outline of the key generation routine, encryption routine, and decryption routine for the pattern  1 .  
      In the pattern  1 , the PC  11  of the receiver  1  generates the private key  5  and the public key  6  by the key generation process to be discussed later. The PC  11  of the receiver  1  stores the private key  5  in the first USB memory  4 , and also stores the public key  6  in the second USB memory  4 . The second USB memory  4  and the CD-R  2  for storing delivery data to be delivered are sent to the supplier  3 .  
      In the pattern  1 , the key generation program is stored in the ROM section  21  of the CD-R  2  to be sent. As mentioned above, the ROM section  21  of the CD-R  2  stores the program which executes the reference, the copying, etc. of delivery data.  
      Next, the PC  31  of the supplier  3  generates the common key  7  with the public key  6  by the key generation program. The PC  31  of the supplier  3  encrypts the electronic file  9  with the common key  7  through the encryption routine to be discussed later, thereby generating the encrypted electronic file  10 . The PC  31  of the supplier  3  encrypts the common key  7  with the public key  6 , thereby generating the encrypted common key  8 . The supplier  3  saves the encrypted electronic file  10  and the encrypted common key  8  in the CD-R  2  and sends the CD-R  2  to the receiver  1 .  
      The PC  11  of the receiver  1  decrypts the encrypted common key  8  with the private key  5 , by the decryption routine to be discussed later, thereby generating the decrypted common key  7 . The PC  11  of the receiver  1  decrypts the encrypted electronic file  10  with the common key  7 , thereby obtaining the decrypted electronic file  9 .  
      Next, the details of the key generation routine, encryption routine, and decryption routine for the pattern  1  will now be explained.  
      (Key Generation Routine)  
      The key generation routine is a process which generates the set of the private key  5  and the public key  6 , and stores the generated private key  5  and public key  6  in the USB memories  4 . The key generation routine for the pattern  1  will now be explained with reference to the flowchart of  FIG. 12 .  
      When the CD-R  2  is inserted into the optical disk section  46  of the PC  11  by the person in charge of the receiver  1 , the control section  41  of the PC  11  activates the key generation program stored in the CD-R  2  (step S 11 ).  
      When the key generation program is activated, the public key/private key generating section  52  generates the set of private key  5  and the public key  6  in accordance with the key generation program (step S 12 ). The generated keys may be used only for the current delivery, or may be used within the term of validity determined by the receiver  1  beforehand.  
      The public key/private key generating section  52  generates the set of the private key  5  and the public key  6  based on unique information (for instance, the serial number) of the CD-R  2  which is inserted into the optical disk section  46 . When a different CD-R  2  is inserted into the optical disk section  46 , therefore, a different set of the private key  5  and the public key  6  is to be generated by the public key/private key generating section  52 .  
      The public key/private key generating section  52  can generate the set of the private key  5  and the public key  6  with information which contains the name of the person carrying out the key generation routine, date, etc. Accordingly, the security can be further enhanced.  
      When the private key  5  and the public key  6  are generated, the public key/private key storing section  55  requests the person in charge of the receiver  1  to insert the first USB memory  4  into the USE section  48  of the PC  11 . When the first USB memory  4  is inserted into the USB section  48 , the public key/private key storing section  55  stores the private key  5  in the first USB memory  4  (step S 13 ).  
      Next, the public key/private key storing section  55  requests the person in charge of the receiver  1  to insert the second USB memory  4  into the USB section  48 . When the second USB memory  4  is inserted into the USB section  48 , the public key/private key storing section  55  stores the public key  6  in the second USB memory  4  (step S 14 ), and terminates this routine.  
      While the public key/private key storing section  55  stores the private key  5  in the first USB memory  4  in the embodiment, it may store the private key  5  in a recording device included in the memory section  44  of the PC  11 . That is, the location where the private key  5  is stored is not limited to the recording medium such as a removable disk, but may be a recording device such as a hard disk built in a computer.  
      (Encryption Routine)  
      The encryption routine is a process which generates the common key  7 , and, encrypts delivery data with the common key  7  and encrypts the common key  7  used for the encryption of delivery data, with the public key  6 . The encryption routine for the pattern  1  will now be explained with reference to the flowchart of  FIG. 13 .  
      When the CD-R  2  is inserted into the optical disk section  66  of the PC  31  by the person in charge of the supplier  3 , the control section  61  of the PC  31  activates the key generation program stored in the CD-R  2  (step S 21 ).  
      When the key generation program is activated, the common key generating section  71  generates the common key  7  in accordance with the key generation program (step S 22 ).  
      The common key generating section  71  generates the common key  7  based on unique information of the CD-R  2  which is inserted into the optical disk section  66  (for instance, serial number). When a different CD-R  2  is inserted into the optical disk section  66 , therefore, a different common key  7  is generated by the common key generating section  71 .  
      When the common key  7  is generated, the encryption section  73  encrypts delivery data with the generated common key  7  (step S 23 ).  
      When delivery data is encrypted, the control section  61  stores encrypted delivery data in the RAM section  22  of the CD-R  2  (step S 24 ).  
      The public key acquiring section  72  requests the person in charge of the supplier  3  to insert the second USB memory  4  into the USB section  68  of the PC  31 . When the second USB memory  4  is inserted into the USB section  68 , the public key acquiring section  72  acquires the public key  6  stored in the second USB memory  4 . When the public key  72  acquires the public key  6 , the encryption section  73  encrypts the common key  7 , which is used for the encryption of delivery data, with the acquired public key  6  (step S 25 ).  
      When the common key  7  is encrypted, the encrypted data storing section  74  stores the encrypted common key  8  in the RAM section  22  of the CD-R  2  (step S 26 ), and terminated this routine.  
      (Decryption Routine)  
      The decryption routine is a process which decrypts the common key  8  encrypted by the private key  5 , and decrypts delivery data with the decrypted common key  7 . The decryption routine of the pattern  1  will now be explained with reference to the flowchart of  FIG. 14 .  
      When the CD-R  2  is inserted into the optical disk section  46  of the PC  11  by the person in charge of the receiver  1 , the control section  41  of the PC  11  activates the key generation program stored in the CD-R  2  (step S 31 ).  
      The private key acquiring section  53  requests the person in charge of the receiver  1  to insert the first USB memory  4  into the USB section  48  of the PC  11 . When the first USB memory  4  is inserted into the USB section  48 , the private key acquiring section  53  acquires the private key  5  stored in the first USB memory  4 .  
      When the private key acquiring section  53  acquires the private key  5 , the decryption section  54  decrypts the encrypted common key  8 , stored in the RAM section  22  of the CD-R  2 , with the acquired private key  5  (step S 32 ).  
      Subsequently, the decryption section  54  decrypts encrypted delivery data, stored in the RAM section  22  of the CD-R  2 , with the decrypted common key  7  (step S 33 ), and finishes the process.  
      As mentioned above, according to the pattern  1 , the key generation program is stored in the ROM section  21  of the CD-R  2  which is to be distributed. Accordingly, the installation of the security program, such as the key generation program, on the PC  11  or the PC  31  is not required.  
      When confidential encrypted delivery data is referred to at different locations, the contents of delivery data can be seen without installing the decryption program to all of the PCs  11  at plural different locations. This can ensure the secured management and storage of delivery data over a long term using the CD-R  2  as the recording medium.  
      Because the private key  5  is stored in the USB memory  4 , different from the CD-R  2 , the contents of delivery data (confidential information) stored in the CD-R  2  can be seen without the private key  5  in the USB memory  4  even if the CD-R  2  is lost. Accordingly, the security-based confidentiality can be enhanced.  
      The high confidentiality can be ensured by decrypting the common key  7  with the public key  6  and strictly administrating the private key  5 .  
      Although the control section  61  of the PC  31  of the supplier  3  stores the encrypted common key  8  in the RAM section  22  of the CD-R  2  in the embodiment, it may store that key  8  in the second USB memory  4 .  
      In this case, in the step S 26  of the encryption routine executed by the PC  31 , the encrypted data storing section  74  determines whether or not the second USB memory  4  is inserted into the USB section  68 . In a case where the second USB memory  4  is inserted into the USB section  68 , the control section  61  stores the encrypted common key  8  in the second USB memory  4 .  
      At the step S 32  of the decryption process executed by the PC  11 , the decryption section  54  determines whether or not the second USB memory  4  is inserted into the USB section  48 . In a case where the second USB memory  4  is inserted into the USB section  48 , the control section  41  decrypts the encrypted common key  8  stored in the second USB memory  4 .  
      &lt;Pattern  2 &gt; 
      Next, the key generation routine, encryption routine, and decryption routine for the pattern  2  will now be explained.  FIG. 15  is a diagram illustrating the key generation, encryption, and decryption routines for the pattern  2 . The pattern  2  differs from the pattern  1  in that the public key is stored in the RAM section  22  of the CD-R  2 .  
      (Key Generation Routine)  
      The key generation routine for the pattern  2  will now be explained with reference to the flowchart of  FIG. 16 .  
      When the CD-R  2  is inserted into the optical disk section  46  of the PC  11  by the person in charge of the receiver  1 , the control section  41  of the PC  11  activates the key generation program stored in the CD-R  2  (step S 41 ).  
      When the key generation program is activated, the public key/private key generating section  52  generates the set of private key  5  and the public key  6  in accordance with the key generation program (step S 42 ).  
      The public key/private key generating section  52  generates the set of the private key  5  and the public key  6  based on unique information (for instance, the serial number) of the CD-R  2  which is inserted into the optical disk section  46 . When a different CD-R  2  is inserted into the optical disk section  46 , therefore, a different set of the private key  5  and the public key  6  is generated by the public key/private key generating section  52 .  
      When the private key  5  and the public key  6  are generated, the public key/private key storing section  55  requests the person in charge of the receiver  1  to insert the USB memory  4  into the USB section  48  of the PC  11 . When the USB memory  4  is inserted into the USB section  48 , the public key/private key storing section  55  stores the private key  5  in the USB memory  4  (step S 43 ).  
      Next, the public key/private key storing section  55  stores the public key  6  in the RAM section  22  of the CD-R  2  (step S 44 ), and terminates this routine.  
      (Encryption Routine)  
      The encryption routine for the pattern  2  is basically same as that for the pattern  1 , except the procedure for acquiring the public key  6 . Therefore, the encryption routine for the pattern  2  will be explained with reference to the flowchart of  FIG. 13  which is used in the description of the encryption routine for the pattern  1 .  
      When the CD-R  2  is inserted into the optical disk section  66  of the PC  31  by the person in charge of the supplier  3 , the control section  61  activates the key generation program stored in the CD-R  2  (step S 21 ).  
      When the key generation program is activated, the common key generating section  71  generates the common key  7  in accordance with the key generation program (step S 22 ).  
      When the common key  7  is generated, the encryption section  73  encrypts delivery data with the generated common key  7  (step S 23 ).  
      When delivery data is encrypted, the control section  61  stores encrypted delivery data in the RAM section  22  of the CD-R  2  (step S 24 ).  
      The public key acquiring section  72  acquires the public key  6  stored in the second USB memory  4 . When the public key  72  acquires the public key  6 , the encryption section  73  encrypts the common key  7 , which is used for the encryption of delivery data, with the acquired public key  6  (step S 25 ).  
      When the common key  7  is encrypted, the encrypted data storing section  74  stores the encrypted common key  8  in the RAM section  22  of the CD-R  2  (step S 26 ), and terminates this routine.  
      (Decryption Routine)  
      The decryption routine for the pattern  2  is same as that for the pattern  1 . Accordingly, the decryption routine for the pattern  2  will be discussed referring to the flowchart of  FIG. 14  which is used in the description of the decryption routine for the pattern  1 .  
      When the CD-R  2  is inserted into the optical disk section  46  of the PC  11  by the person in charge of the receiver  1 , the control section  41  of the PC  11  activates the key generation program stored in the CD-R  2  (step S 31 ).  
      The private key acquiring section  53  requests the person in charge of the receiver  1  to insert the USB memory  4  into the USB section  48  of the PC  11 . When the USB memory  4  is inserted into the USB section  48 , the private key acquiring section  53  acquires the private key  5  stored in the USB memory  4 .  
      When the private key acquiring section  53  acquires the private key  5 , the decryption section  54  decrypts the encrypted common key  8 , stored in the RAM section  22  of the CD-R  2 , with the acquired private key  5  (step S 32 ).  
      Subsequently, the decryption section  54  decrypts encrypted delivery data, stored in the RAM section  22  of the CD-R  2 , with the decrypted common key  7  (step S 33 ), and terminates this routine.  
      As mentioned above, according to the pattern  2 , because the public key  6  is stored in the RAM section  22  of the CD-R  2 , the USB memory  4  is not required to store the public key  6 . That is, the operations of the key generation routine and the encryption routine become easier.  
      &lt;Pattern  3 &gt; 
      Next, the key generation routine, encryption routine, and decryption routine for the pattern  3  will now be described.  
       FIG. 17  is a diagram illustrating the key generation, encryption, and decryption processes of the pattern  3 .  
      The pattern  3  differs from the pattern  2  in that the key generation program is not stored in the ROM section  21  of the CD-R  2 .  
      (Key Generation Routine)  
      The key generation routine of the pattern  3  will now be discussed referring to the flowchart of  FIG. 18 .  
      When the instruction to activate the key generation program, preinstalled on the PC  11 , is entered through the input section  42  by the person in charge of the receiver  1 , the control section  41  of the PC  11  activates the key generation program (step S 51 ).  
      When the key generation program is activated, the public key/private key generating section  52  generates the set of private key  5  and the public key  6  in accordance with the key generation program (step S 52 ).  
      The public key/private key generating section  52  generates the set of the private key  5  and the public key  6  based on unique information (for instance, the serial number) of the CD-R  2  which is inserted into the optical disk section  46 . When a different CD-R  2  is inserted into the optical disk section  46 , therefore, a different set of the private key  5  and the public key  6  is generated by the public key/private key generating section  52 .  
      When the private key  5  and the public key  6  are generated, the public key/private key storing section  55  requests the person in charge of the receiver  1  to insert the USB memory  4  into the USB section  48  of the PC  11 . When the USB memory  4  is inserted into the USB section  48 , the public key/private key storing section  55  stores the private key  5  in the USB memory  4  (step S 53 ).  
      Next, the public key/private key storing section  55  stores the public key  6  in the RAM section  22  of the CD-R  2  (step S 54 ), and terminates this routine.  
      (Encryption Routine)  
      The encryption routine for the pattern  3  will now be described with reference to the flowchart of  FIG. 19 .  
      When the instruction to activate the key generation program, preinstalled on the PC  31 , is entered through the input section  62  by the person in charge of the supplier  3 , the control section  61  activates the key generation program (step S 61 ).  
      When the key generation program is activated, the common key generating section  71  generates the common key  7  in accordance with the key generation program (step S 62 ).  
      The common key generating section  71  generates the common key  7  based on unique information (for instance, the serial number) of the CD-R  2  which is inserted into the optical disk section  66 . When a different CD-R  2  is inserted into the optical disk section  66 , therefore, a different common key  7  is generated by the common key generating section  71 .  
      When the common key  7  is generated, the encryption section  73  encrypts delivery data with the generated common key  7  (step S 63 ).  
      When delivery data is encrypted, the control section  61  stores encrypted delivery data in the RAM section  22  of the CD-R  2  (step S 64 ).  
      The public key acquiring section  72  acquires the public key  6  stored in the RAM section  22  of the CD-R  2 . When the public key  72  acquires the public key  6 , the encryption section  73  encrypts the common key  7 , which is used to encrypt delivery data with the acquired public key  6  (step S 65 ).  
      When the common key  7  is encrypted, the encrypted data storing section  74  stores the encrypted common key  8  in the RAM section  22  of the CD-R  2  (step S 66 ), and terminates this routine.  
      (Decryption Routine)  
      The decryption routine for the pattern  3  will now be described with reference to the flowchart of  FIG. 20 .  
      When the instruction to activate the key generation program, preinstalled on the PC  11 , is entered through the input section  42  by the person in charge of the receiver  1 , the control section  41  of the PC  11  activates the key generation program  1  (step S 71 ).  
      The private key acquiring section  53  requests the person in charge of the receiver  1  to insert the USB memory  4  into the USB section  48  of the PC  11 . When the USB memory  4  is inserted into the USB section  48 , the private key acquiring section  53  acquires the private key  5  stored in the USB memory  4 .  
      When the private key acquiring section  53  acquires the private key  5 , the decryption section  54  decrypts the encrypted common key  8 , stored in the RAM section  22  of the CD-R  2 , with the acquired private key  5  (step S 72 ).  
      Subsequently, the decryption section  54  decrypts encrypted delivery data, stored in the RAM section  22  of the CD-R  2 , with the decrypted common key  7  (step S 33 ), and terminates this routine.  
      In a case where the PC  11  used by the receiver  1  and the PC  31  used by the supplier  3  store the key generation program as described, it is unnecessary to store the key generation program in the ROM section  21  of the CD-R  2 . Accordingly, the pattern  3  is useful in this case.  
      As described above, according to the embodiment of the present invention, the key generation program can be stored in the ROM section  21  of the CD-R  2 . Therefore, the dedicated security program need not be installed on the PC  11  used by the receiver  1  and the PC  33  used by the supplier  3 .  
      The present invention is not limited to the above-described embodiment, and can be modified and adapted in various forms. Although the foregoing description of the embodiment of the present invention has been given, as an example, of a case where the encryption procedure determining section  51  selects one of the patterns from the pattern  1  to  3 , there may be only one pattern to avoid execution of the process of selecting the pattern. The number of patterns is not limited to three, and may be two, or four or greater.  
      The foregoing description of the embodiment of the present invention has been given, as an example, of a case where the optimal pattern is selected based on delivery data information  441  stored in the memory section  44 . The present invention, however, is not limited to that particular case, and the optimal pattern may be selected based on an arbitrary criterion.  
     Second Embodiment  
      Another embodiment to which the first embodiment has been adapted will be discussed below. According to the second embodiment, the supplier  3  automatically determines which one of predetermined encryption procedures (i.e., one of the patterns  1  to  3 ). Because the configurations of the PC  11  of the receiver  1  and the configurations of the PC  31  of the supplier  3  are substantially identical to those of the first embodiment, their descriptions will be omitted.  
      The control section  61  of the PC  31  of the supplier  3  according to the embodiment further comprises a pattern determining section  75  as shown in  FIG. 21 .  
      The pattern determining section  75 , which comprises the control section  61 , etc., determines whether the key generation program is stored in the recording medium  2  inserted in the optical disk section  66  or not. Based on the determination result, the pattern determining section  75  determines which one of the patterns  1  to  3  is to be selected. Further, the pattern determining section  75  input the determination result to the public key acquiring section  72 , and acquires a public key  6  from the USB memory  4  or the recording medium  2 .  
      (Key Generation Routine)  
      The encryption procedure determining section  51  of the PC  11  of the receiver  1  selects a pattern for the key generation routine  1  according to the above-described pattern selecting routine. Then, the public key/private key generating section  52  generates a set of the private key  5  and the public key  6  according to the key generation routine for the pattern selected by the encryption procedure determining section  51 . As the key generation routine for each pattern is the same as the one discussed above, its description will be omitted.  
      (Encryption Routine)  
      The encryption routine according to the embodiment will be discussed referring to the flowchart in  FIG. 21 .  
      When the CD-R  2  is inserted into the optical disk section  66  by a person in charge of the supplier  3 , the control section  61  of the PC  31  of the supplier  3  activates the key generation program when this program is on the CD-R  2  (step S 81 ; YES) (step S 82 ).  
      When the key generation program is not on the CD-R  2  (step S 81 ; NO), on the other hand, the control section  61  activates the key generation program prestored in the memory section  64  of the PC  31  (step S 86 ). In this case, the pattern determining section  75  determines that the encryption routine selected by the receiver  1  is the pattern  3 . Then, the control section  61  executes the key generation program for the pattern  3 .  
      As the control section  61  activates the key generation program at step S 82 , the pattern determining section  75  determines whether the second USB memory  4  is inserted in the USB section  68  or not (step S 83 ).  
      When the second USB memory  4  is inserted in the USB section  68  (step S 83 ; YES), the pattern determining section  75  determines that the encryption routine selected by the receiver  1  is the pattern  1 . Then, the control section  61  executes the encryption routine for the pattern  1  (step S 84 ). When the second USB memory  4  is not inserted in the USB section  68  (step S 83 ; NO), the pattern determining section  75  determines that the encryption routine selected by the receiver  1  is the pattern  2 . Then, the control section  61  executes the encryption routine for the pattern  2  (step S 85 ).  
      As the key generation routine for each pattern is the same as the one discussed above, its description will be omitted.  
      (Decryption Routine)  
      The decryption routine according to the embodiment is the same as the decryption routine for each pattern according to the first embodiment, its description will be omitted.  
      According to the embodiment, as apparent from the above, the supplier  3  can automatically recognize the pattern for a predetermined encryption routine selected by the receiver  1 .  
      As described above, the present invention can provide an information processing system, an information processing apparatus, an information processing method, a recording medium and a program which are suitable for secured transmission and reception of confidential electronic files.  
      Various embodiments and changes may be made thereunto without departing from the broad spirit and scope of the invention, The above-described embodiments are intended to illustrate the present invention, not to limit the scope of the present invention. The scope of the present invention is shown by the attached claims rather than the embodiments. Various modifications made within the meaning of an equivalent of the claims of the invention and within the claims are to be regarded to be in the scope of the present invention.  
      This application is based on Japanese Patent Application No. 2004-198604 filed on Jul. 5, 2004 and including specification, claims, drawings and summary. The disclosure of the above Japanese Patent Application is incorporated herein by reference in its entirety,