Patent Publication Number: US-2009235363-A1

Title: Image formation device and license management system

Description:
This application is based on the application No. 2008-063824 filed in Japan, the contents of which are hereby incorporated by reference. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to an image formation device for enabling an optional function that is invalid in an initial state with the entry of a license code, and a license management system including this image formation device. 
     2. Description of the Background Art 
     Conventionally known image formation devices include what are called complex devices or MFPs (multifunction peripherals). These types of devices have several functions as a copier, a scanner, a fax machine, a network printer, a box and the like. Especially in recent years, there is a trend toward an increasing number of functions to be implemented in image formation devices in response to user&#39;s needs. Under these circumstances, a user does not always require all functions implemented in the image formation device for daily doings. Hence, several function implemented in the conventionally used image formation device are divided into standard functions that are set to be effectively available in initial states, and optional functions that are set to be invalid in initial states. When a user wishes to use an optional function, the user purchases a license code, enters this license code into the image formation device to enable the optional function, thereby making this optional function usable in the image formation device. 
     In this case, according to a publicly known technique, device identification information unique to an image formation device is incorporated into a license granted to the user. So the granted license enables an optional function only in a device that is given device identification information coinciding with that of the granted license. This technique is disclosed for example in Japanese Patent Application Laid-Open No. 2004-213469. 
     According to the technique disclosed in this publication, once a license is granted, an optional function of an image formation device may be enabled many times using the granted license. This results in difficulty in managing a license actually used. These days a license management server installed in a manufacturer or a distributor remotely monitors the usage of a license at an image formation device installed in a user&#39;s office environment. Especially in this case, if a user repeatedly uses a license once granted, the license management server cannot know the proper usage of a license. 
     SUMMARY OF THE INVENTION 
     First, the present invention is intended for an image formation device. 
     According to one aspect of this invention, the image formation device enables an optional function that is invalid in an initial state with the entry of a license code. The image formation device comprises: a storage part for storing specific information unique to the image formation device; an input part for receiving a license code input thereto that is generated based on the specific information; an authentication part for authenticating the license code received through the input part using the specific information stored in the storage part; a function enabling part for enabling an optional function when the authentication part recognizes the license code as a proper license code; and a function disabling part for disabling the optional function that has been enabled by the function enabling part and changing said specific information stored in said storage part. 
     According to this aspect, the image formation device authenticates a license code using specific information of its own. The image formation device enables an optional function when this license code is recognized as a license code properly issued for the image formation device itself. Thus, the optional function cannot be enabled with the entry of a license code issued for another device. Further, disabling an optional function causes the image formation device to change specific information that is used to authenticate a license code for enabling the optional function. Thus, the optional function cannot be enabled again using a license code that was granted before this optional function is disabled. This prevents the optional function from being enabled repeatedly using a license once granted. 
     Second, the present invention is intended for a license management system. 
     According to one aspect of this invention, the license management system comprises an image formation device and a license management server connected through a network to the image formation device. The image formation device enables an optional function that is invalid in an initial state with the entry of a license code. The license management server issues a license and transmits a license code to the image formation device, while managing the usage of a license relating to the optional function. The image formation device includes: a storage part for storing specific information unique to the image formation device; an input part for receiving a license code input thereto through the network; an authentication part for authenticating the license code received through the input part using the specific information stored in the storage part; a function enabling part for enabling an optional function when the authentication part recognizes the license code as a proper license code; and a function disabling part for disabling the optional function that has been enabled by the function enabling part. The license management server includes: a license management database for storing the usage of a license; a specific information retrieval part for retrieving the specific information stored in the storage part from the image formation device through the network; a code generation part for generating a license code used to enable an optional function based on the specific information retrieved by the specific information retrieval part; a transmission part for transmitting the license code generated by the code generation part to the image formation device; and a license management part being caused by the transmission of the license code to update the license management database. The function disabling part changes said specific information stored said storage part after disabling said optional function. 
     According to this aspect, the image formation device authenticates the license code generated by the license management server using specific information of its own. The image formation device enables an optional function when this license code is recognized as a license code properly issued for the image formation device itself. Thus, the optional function cannot be enabled with the entry of a license code issued for another device. Further, disabling an optional function causes the image formation device to change specific information that is used to authenticate a license code for enabling the optional function. Thus, the optional function cannot be enabled again using a license code that was granted before this optional function is disabled. This prevents the optional function from being enabled repeatedly using a license once granted. Further, the license management server is allowed to precisely manage the usage of a license at all times. 
     According to another aspect of this invention, the license management system comprises: an image formation device including a storage part for storing specific information unique to the image formation device, and enabling an optional function that is invalid in an initial state with the entry of a license code; a license management server issuing a license code corresponding to the optional function of the image formation device, and managing the usage of a license at the image formation device; and an information processing device so connected to the image formation device and the license management server as to realize data communication with the image formation device and the license management server. For enabling the optional function of the image formation device, the information processing device retrieves the specific information from the image formation device, and transmits a request for issue of a license code together with the specific information to the license management server. The license management server generates the license code for enabling the optional function of the image formation device based on the specific information, and transmits the license code to the information processing device. The information processing device outputs the license code received from the license management server and a function enabling command to the image formation device. The image formation device authenticates the license code received from the information processing device using the specific information stored in the storage part, and enables the optional function when the license code is recognized as a proper code. For disabling the optional function of the image formation device, the information processing device transmits a request for issue of a disabling code together with the specific information to the license management server. The license management server generates the disabling code based on the specific information, and transmits the disabling code for disabling the optional function of the image formation device to the information processing device. The information processing device outputs the disabling code received from the license management server and a function disabling command to the image formation device. The image formation device authenticates the disabling code received from the information processing device using the specific information stored in the storage part, disables the optional function when the disabling code is recognized a proper code, and changes the specific information stored in the storage part to information different from previous information. 
     According to this aspect, the image formation device authenticates the license code generated by the license management server using specific information of its own. The image formation device enables an optional function when this license code is recognized as a license code properly issued for the image formation device itself. Thus, the optional function cannot be enabled with the entry of a license code issued for another device. Further, disabling an optional function causes the image formation device to change specific information that is used to authenticate a license code for enabling the optional function. Thus, the optional function cannot be enabled again using a license code that was granted before this optional function is disabled. This prevents the optional function from being enabled repeatedly using a license once granted. Further, the license management server is allowed to precisely manage the usage of a license at all times. Still further, the information processing device is operated to enable or disable an optional function at the image formation device, resulting in enhanced operability. 
     Thus, according to the present invention, the image formation device is capable of preventing an optional function from being enabled many times using a license once granted. Further, in the license management system, the license management server is allowed to precisely manage the usage of a license at all times. 
     It is therefore an object of the present invention to provide an image formation device capable of preventing an optional function from being enabled many times using a license once granted, and a license management system in which a license management server is allowed to precisely manage the usage of a license at all times. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic diagram showing the configuration of a license management system as an example of the present invention; 
         FIG. 2  is a block diagram showing an exemplary internal structure of a license management server; 
         FIG. 3  is a block diagram showing an exemplary internal structure of an information processing device; 
         FIG. 4  is a block diagram showing an exemplary internal structure of an image formation device; 
         FIG. 5  is a flow diagram showing exemplary procedures and operations for enabling an optional function that is invalid in the image formation device; 
         FIG. 6  shows an exemplary configuration of a license management database; 
         FIG. 7  shows an example of a license certificate provided from an administrator to a user; 
         FIG. 8  is a flow diagram showing an exemplary process sequence at the information processing device and the license management server for entering license information into the information processing device; 
         FIG. 9  shows an example of license information stored in a storage part of the information processing device; 
         FIG. 10  is a flow diagram showing an exemplary process sequence at the information processing device and the image formation device for entering device registration information into the information processing device; 
         FIG. 11  shows an example of the device registration information stored in the storage part of the information processing device; 
         FIGS. 12 and 13  are flow diagrams showing an exemplary process sequence at the information processing device, the license management server and the image formation device for enabling an optional function of the image formation device; 
         FIGS. 14 to 16  are flow diagrams showing an exemplary process sequence at the information processing device, the license management server and the image formation device for disabling an optional function of the image formation device; and 
         FIG. 17  is a flow diagram showing an exemplary transfer process of a license. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     A preferred embodiment of the present invention is described in detail below with reference to figures. In the description given below, those elements which are shared in common through the description are represented by the same reference numerals, and these elements are not discussed repeatedly for the same description. 
       FIG. 1  is a schematic diagram showing the configuration of a license management system  1  according to the present preferred embodiment. The license management system  1  comprises a license management server  40  installed in a management center  2  such as a manufacturer or a distributor of image formation devices  10 , a plurality of image formation devices  10  (including  10 A and  10 B) installed in a user&#39;s office environment  3 , and an information processing device  50  installed in the user&#39;s office environment  3 . The configuration of the license management system  1  is such that the license management server  40  of the management office  2  manages the usage of licenses at the image formation devices  10  in the user&#39;s office environment  3 . The license management server  40  includes a storage part  41  such as a hard disk. A license management database  42  for storing and managing license codes issued by an administrator  6  is built in the storage part  41 . In  FIG. 1 , several image formation devices  10  are shown to be installed in the office environment  3 , whereas one image formation device  10  may be installed. 
     The image formation device  10  has several functions as a copier, a network printer, a scanner, a fax machine and the like, and is what is called a complex device or an MFP. In the image formation device  10 , at least a predetermined function of a plurality of functions is a standard function that is set to be effectively available in an initial state, and the remaining function is an optional function that is set to be invalid in an initial state. In the present preferred embodiment, at least one optional function is implemented in the image formation device  10 . When a user  5  wishes to use an optional function, the user  5  follows procedures and performs operations discussed later to enter a license code granted from the license management server  40  into the image formation device  10 , thereby making this optional function valid and usable in the image formation device  10 . 
     As shown in  FIG. 1 , each of the image formation devices  10  including  10 A and  10 B is connected to a network  7  such as a LAN, and is so configured as to realize data communication with the information processing device  50  connected to the network  7 . Each of the image formation devices  10  including  10 A and  10 B includes therein a storage part for storing specific information  21  unique to the image formation device  10  discussed later. In the example shown in  FIG. 1 , “AAA” is stored as the specific information  21  in the image formation device  10 A, and “BBB” is stored in the image formation device  10 B. The specific information  21  is defined so that the specific information  21  is unique to each image formation device  10  at least in an environment where each image formation device  10  is connected to the network  7 . 
     The information processing device  50  is formed for example from a generally-used PC, and is connected through a communication network  4  such as the Internet or a telephone line to the license management server  40 . The information processing device  50  has a function management program installed in advance therein. The information processing device  50  executes the function management program to conduct data communication for obtaining a license code from the license management server  40  through the communication network  4 , and to conduct control for enabling or disabling an optional function of the image formation device  10  connected to the network  7 . 
     As discussed, in the present preferred embodiment, the license management server  40  conducts data communication with the image formation devices  10  indirectly through the information processing device  50  and not directly with the image formation devices  10 , thereby managing the usage of licenses at the image formation devices  10 . 
       FIG. 2  is a block diagram showing the internal structure of the license management server  40 . The license management server  40  has a hardware configuration formed from a CPU  43 , a ROM  47 , a RAM  48  and a communication interface  49  as well as the above-discussed storage part  41  that are connected to each other through a bus line. The license management server  40  may have a display device, a keyboard and the like. The storage part  41  has a license management program  43   a  stored therein as well as the license management database  42 . The CPU  43  reads the license management program  43   a  from the storage part  41  and executes the same, so that the CPU  43  becomes operative to function as a license registration part  44 , a license management part  45  and a code generation part  46 . 
     The license registration part  44  enters a newly issued license into the license management database  42 . The license management part  45  suitably updates the license management database  42  to always keep the usage of a license in the license management database  42  up to date. The license management part  45  causes the license management database  42  to precisely reflect the usage of a license at the user&#39;s office environment  3  for example by data communication with the information processing device  50 . The code generation part  46  generates a license code for enabling an optional function of the image formation device  10 , or a disabling code for disabling an optional function of the image formation device  10  again after this optional function is enabled. The code generation part  46  includes a code encryption part  46   a . A code to be generated at the code generation part  46  is encrypted at the code encryption part  46   a . The code encryption part  46   a  encrypts a license code for enabling an optional function and a disabling code for disabling an optional function using the specific information  21  of the image formation device  10  as a key. 
     The ROM  47  and the RAM  48  store control parameters and the like used by the CPU  43 . The communication interface  49  conducts data transmission to and from the information processing device  50  through the communication network  4 . The communication interface  49  is operative to function as an input part for receiving various types of information and requests from the information processing device  50 , and an output part for outputting codes and various types of information to the information processing device  50 . 
       FIG. 3  is a block diagram showing the internal structure of the information processing device  50 . The information processing device  50  has a hardware configuration formed from a CPU  51 , a storage part  54  such as a hard disk, a display device  61 , a keyboard  62 , a ROM  63 , a RAM  64  and a communication interface  65  that are connected to each other through a bus line. The storage part  54  has a function management program  55 , license information  56  and device registration information  57  stored therein. The CPU  51  reads the function management program  55  from the storage part  54  and executes the same, so that the CPU  51  becomes operative to function as a function management part  52  and a command output part  53 . 
     The function management part  52  conducts data communication with the license management server  40  to enter the license information  56  into the storage part  54 , while conducting data communication with the image formation device  10  connected to the network  7  to obtain various types of information from the image formation device  10 , thereby entering the device registration information  57  into the storage part  54  in association with the license information  56 . The function management part  52  requests the license management server  40  to issue a license code and a disabling code in response to instructions from the user  5  given through the keyboard  62  and the like, and obtains these codes in encrypted form from the license management server  40 . 
     The command output part  53  generates a function enabling command or a function disabling command regarding a particular one of the plurality of image formation devices  10  connected to the network  7 , and outputs the generated command to the particular image formation device  10 . A command given from the command output part  53  contains an encrypted code that the function management part  52  received from the license management server  40 . The image formation device  10  that has received this command enables or disables an optional function based on the command and the encrypted code. 
     The display device  61  of the information processing device  50  presents various types of information to the user  5 , and is formed for example from a liquid crystal display device and the like. The keyboard  62  is a manipulated input part operable by the user  5  that may also include a mouse and the like. The ROM  63  and the RAM  64  store control parameters and the like used by the CPU  51 . The communication interface  65  conducts data transmission to and from the license management server  40  through the communication network  4 , while conducting data transmission to and from the image formation device  10  through the network  7 . The communication interface  65  is operative to function as an input part for receiving various types of information and codes from the license management server  40  and the image formation device  10 , and an output part for outputting various types of requests and commands to the license management server  40  and the image formation device  10 . 
       FIG. 4  is a block diagram showing the internal structure of the image formation devices  10 . In  FIG. 4 , the structure of the image formation device  10 A is shown as a representative structure. The other image formation devices  10  connected to the network  7  have the same structure as that of the image formation device  10 A, with only the exception of the substance of the specific information  21 . As shown in  FIG. 4 , the image formation device  10  includes a CPU  11  for executing a certain program to control the image formation device  10  in its entirety, a storage part  20  formed from a hard disk, a memory and the like, an operation panel  24  for allowing the user  5  to operate the image formation device  10 , a ROM  27 , a RAM  28 , an original transport section  31 , a scanner section  32 , a sheet feed section  33 , a printer section  34 , and a communication interface  29 . 
     The CPU  11  executes a certain program for enabling or disabling an optional function, so that the CPU  11  becomes operative to function as a command analysis part  12 , a device information output part  13 , a code authentication part  14 , a function enabling part  16  and a function disabling part  17 . The storage part  20  stores the specific information  21  uniquely defined for the image formation device  10 . In  FIG. 4 , “AAA” is stored as the specific information  21 . The specific information  21  may be rewritten by the CPU  11 . The specific information  21  may alternatively be stored in the RAM  28 . 
     Upon receipt of a command given from the information processing device  50  through the communication interface  29 , the command analysis part  12  is brought into operation to analyze this command. When this command requests information relating to the image formation device  10 , the command analysis part  12  brings the device information output part  13  into operation. When this command gives instructions to enable or disable an optional function, the command analysis part  12  brings the code authentication part  14  into operation, and gives an encrypted code that has been received together with the command to the code authentication part  14 . 
     The device information output part  13  is brought into operation under instructions from the command analysis part  12 , and outputs various types of information relating to the image formation device  10  to which the device information output part  13  belongs. Especially when the information processing device  50  requests specific information of the image formation device  10 , the device information output part  13  reads the specific information  21  from the storage part  20 , and outputs the specific information  21  thereby read. 
     The code authentication part  14  authenticates an encrypted code. The code authentication part  14  reads the specific information  21  stored in the storage part  20 , and authenticates a received license code or a disabling code using this specific information  21 . The code authentication part  14  has a decryption part  15 , and decrypts an encrypted code based on the specific information  21 . When the received code is successfully decrypted, the code authentication part  14  recognizes that this code is a proper code. By way of example, the code authentication part  14  decrypts a code that has been decrypted using the specific information  21  as a key. When a resultant decrypted code contains particular information such as a certain bit sequence, the code authentication part  14  recognizes the decrypted code as a proper code. When the resultant decrypted code does not contain particular information, the authentication part  14  does not recognize the decrypted code as a proper code. When the authentication part  14  recognizes the decrypted code as a proper code, the authentication part  14  brings either the function enabling part  16  or the function disabling part  17  into operation. Namely, when the code authentication part  14  authenticates a license code for enabling an optional function, the code authentication part  14  brings the function enabling part  16  into operation after code authentication. When the code authentication part  14  authenticates a disabling code for disabling an optional function, the code authentication part  14  brings the function disabling part  17  into operation after code authentication. 
     The function enabling part  16  enables a designated optional function of a plurality of functions of the image formation device  10  based on a function enabling code. By way of example, the function enabling part  16  enables an optional function that is invalid in an initial state, thereby making this optional function effectively available in the image formation device  10 . As a result, the user  5  is allowed to use this optional function. 
     The function disabling part  17  disables an optional function that is effectively available in the image formation device  10  based on a function disabling code. By way of example, the function disabling part  17  disables an optional function that is effectively available in the image formation device  10 , thereby making this optional function invalid again in the image formation device  10 . As a result, the user  5  is prevented from using this optional function. The function disabling part  17  has a specific information rewriting part  18 . The specific information rewriting part  18  rewrites the specific information  21  stored in the storage part  20  to change the specific information  21  uniquely defined for the image formation device  10 . Disabling an optional function by the function disabling part  17  causes the specific information rewriting part  18  to change the specific information  21 . In this case, the specific information rewriting part  18  rewrites the specific information  21  so as to make the new specific information  21  still unique to the image formation device  10  at least in an environment where the image formation device  10  is connected to the network  7 . 
     The operation panel  24  is operated by the user  5  when the user  5  uses the image formation device  10 . The operation panel  24  has a display part  26  formed from a liquid crystal display and the like for presenting various types of information to the user  5 , and an operation part  25  formed from a touch panel arranged on the front side of the display part  26  and a plurality of operation buttons arranged around the display part  26 . The user  5  operates the operation part  25  with reference to a screen displayed on the display part  26 , so that the user  5  selects a function to be used from a plurality of functions of the image formation device  10 , and makes various settings and inputs relating to the function thereby selected. 
     The ROM  27  and the RAM  28  store control parameters and the like used by the CPU  11 . The communication interface  29  conducts data transmission to and from the information processing device  50  through the network  7 . The communication interface  29  is operative to function as an input part for receiving various types of information from the information processing device  50  to enter the received information into the CPU  11 , and an output part for outputting various types of information given from the CPU  11  to the information processing device  50 . 
     The original transport section  31  receives originals placed therein when functions such as a copier, a scanner, a fax machine are used. The original transport section  31  automatically transmits originals one by one to the scanner section  32 , by which the scanner section  32  optically reads characters, symbols, images and the like recorded on originals. When the image formation device  10  forms images to generate printed outputs, the sheet feed section  33  automatically feeds sheets one by one that are media on which images are to be formed to the printer section  34 . The printer section  34  is brought into operation to execute jobs relating to functions such as a copier, a network printer, a fax machine and the like, and forms images on sheets fed from the sheet feed section  33  to produce printed outputs. The sections  31 ,  32 ,  33  and  34  perform the above-discussed operations when the functions are made valid in the image formation device  10 . When the functions are invalid, the sections  31 ,  32 ,  33  and  34  do not perform the above-discussed operations. 
     Next, it is discussed how to enable an optional function of the image formation device  10  in the license management system  1  with the configuration discussed above.  FIG. 5  is a flow diagram showing procedures and operations for enabling an optional function that is invalid in the image formation device  10 . First, the user  5  of the image formation device  10  follows a procedure for purchasing a certain license (process P 10 ). By way of example, the user  5  informs the administrator  6  of an optional function the user  5  wishes to purchase, and the number of image formation devices  10  at which the optional function is intended to be used. Then the user  5  pays some fee to complete the procedure for purchasing the license. When the purchasing procedure is successfully completed, the administrator  6  issues a license code corresponding to the optional function targeted for the purchase. The license code issued at this time is used to enable an optional function that is shared by the plurality of the image formation devices  10 . 
     The administrator  6  enters license information containing the issued license code into the license management server  40  (process P 11 ). At this time, in the CPU  43  of the license management server  40 , the license registration part  44  is brought into operation to enter new license information given from the administrator  6  into the license management database  42 .  FIG. 6  shows an exemplary configuration of the license management database  42 . The license management database  42  contains a license code  42   a  issued by the administrator  6 , a product code  42   b  corresponding to an optional function targeted for purchase, the number of purchased licenses  42   c , the number of used licenses  42   d , and the number of unused licenses  42   e  that are recorded therein. The number of purchased licenses  42   c  corresponds to the number of image formation devices  10  at which a purchased optional function is intended to be used. The number of used licenses  42   d  is part of the number of purchased licenses  42   c , and corresponds to the number of image formation devices  10  at which the optional function has already been enabled using the license indicated by the number  42   d . The number of unused licenses  42   e  is part of the number of purchased licenses  42   c , and corresponds to the number of remaining licenses that have not been used for enabling the optional function. In  FIG. 6 , license information L 1  is assigned a license code “1234-5678-9012-3456-7890” that enables an optional function represented by a product code “LK101.” The license information L 1  contains the number of purchased licenses  42   c  which is “10,” the number of used licenses  42   d  which is “0,” and the number of unused licenses  42   e  which is “10.” The number of used licenses  42   d  is “0” at the time of its entry when the license information L 1  is entered in process P 11 , so the number of purchased licenses  42   c  and the number of unused licenses  42   e  are the same. In the present preferred embodiment, both the number of used licenses  42   d  and the number of unused licenses  42   e  are shown to be recorded in the license management database  42 . However, if one of the number of used licenses  42   d  and the number of unused licenses  42   e  is recorded, the other one may be obtained by subtracting the recorded number from the number of purchased licenses  42   c . Accordingly, both of these numbers are not always required to be recorded. 
     Following the process discussed above, the entry of license information into the license management server  40  is completed. Next, the administrator  6  provides the user  5  with the license information containing the issued license code (process P 12 ). By way of example, the license information is provided from the administrator  6  to the user  5  in the form of a license certificate  9  shown in  FIG. 7 . The license certificate  9  includes a purchased license code, a product code corresponding to an optional function targeted for purchase, and the number of purchased licenses. Thus the user  5  is allowed to know the license code and the like by receiving the license information provided from the administrator  6 . The transfer of the license certificate  9  is not the only way of provision of license information. License information may be provided in any way such as e-mail system. 
     When the user  5  receives the license information, the user  5  operates the information processing device  50  to enter the license information into the information processing device  50  (process P 13 ). At this time, the user  5  inputs the license information to the information processing device  50  based on the license information described in the license certificate  9 . The information processing device  50  conducts data communication with the license management server  40  in order to check whether or not the received license information conforms to license information recorded in the license management server  40 . The information processing device  50  enters the received license information into the storage part  54  only when this license information conforms to the license information recorded in the license management server  40 . 
       FIG. 8  is a flow diagram showing an exemplary process sequence at the information processing device  50  and the license management server  40  for entering license information into the information processing device  50 . In the information processing device  50 , the CPU  51  executes the function management program  55  to start this process sequence, and the function management part  52  is brought into operation in the CPU  51 . The user  5  inputs a license code and a product code to the information processing device  50  based on the information in the license certificate  9  (step S 100 ). When the input of the license code and the product code by the user  5  is completed, the information processing device  50  transmits the received license code and the product code to the license management server  40  (step S 101 ). 
     In the license management server  40 , upon receipt of the license code and the product code from the information processing device  50  (step S 102 ), the license management part  45  is brought into operation in the CPU  43  to check whether or not a combination of the received license code and the product code can be found in the license management database  42  (step S 103 ). By way of example, when the received license code is “1234-5678-9012-3456-7890” and the product code is “LK101”, the combination thereof conforms to the license information L 1  shown in  FIG. 6 . In this case, a check result is OK. In contrast, when a combination of the received license code and the product code cannot be found in the license management database  42 , a check result is NG. 
     The license management server  40  evaluates a check result (step S 104 ). When the check result is OK, the license management server  40  reads the number of unused licenses  42   e  of the corresponding license information L 1  from the license management database  42  (step S 105 ), and transmits the number of unused licenses to the information processing device  50  (step S 106 ). 
     Upon receipt of the number of unused licenses from the license management server  40  (step S 107 ), the information processing device  50  is allowed to know that the check result obtained in the license management server  40  is OK. Then, the information processing device  50  stores the license code and the product code input in step S 100 , and the number of unused licenses received from the license management server  40  into the storage part  54 , thereby entering the license information  56  into the storage part  54  (step S 108 ).  FIG. 9  shows an example of the license information  56  thereby stored in the storage part  54  of the information processing device  50 . The license information  56  contains a license code  56   a , a product code  56   b  corresponding to an optional function, and the number of unused licenses  56   c . The license code  56   a , the product code  56   b  and the number of unused licenses  56   c  coincide with those of the license information L 1  recorded in the license management database  42 , by which consistency is maintained between the information held in the information processing device  50  and the information held in the license management database  42 . When the license information  56  is successfully entered into the information processing device  50  in this way, this process for the entry is completed. 
     When the check result obtained in the license management server  40  is NG, on the other hand, the license management server  40  generates an error message (step S 109 ), and transmits this error message to the information processing device  50  (step S 110 ). 
     Upon receipt of the error message from the license management server  40  (step S 111 ), the information processing device  50  is allowed to know that the check result obtained in the license management server  40  is NG. In this case, the information processing device  50  displays an error message urging the user  5  to re-enter the license code and the product code, and completes the process (step S 112 ). 
     Following the process discussed above, the entry of license information into the information processing device  50  (process P 13 ) shown in  FIG. 5  is completed. The user  5  continues to operate the information processing device  50  to register the image formation device  10  with the information processing device  50  (process P 14 ). Namely, the user  5  operates the information processing device  50 , so that the information processing device  50  obtains necessary information from each of the plurality of image formation devices  10  connected to the network  7  in the office environment  3 . The information processing device  50  stores the information thereby obtained as device registration information  57  into the storage part  54 . 
       FIG. 10  is a flow diagram showing an exemplary process sequence at the information processing device  50  and the image formation device  10  for entering the device registration information  57  into the information processing device  50 . In the information processing device  50 , the CPU  51  also executes the function management program  55  to start this process sequence, and the function management part  52  is brought into operation in the CPU  51 . After the start of the process sequence, the information processing device  50  reads the license information  56  stored in the storage part  54 , and causes license codes contained in the license information  56  to be displayed in list form on the display device  61  (step S 121 ). Then, the user  5  operates the keyboard  62  and the like to select a license code corresponding to an optional function that the user  5  wishes to enable from the license codes displayed in list form on the display device  61  (step S 122 ). 
     After the user  5  selects a license code, the information processing device  50  sends retrieval information out to the network  7  in order to retrieve the image formation device  10  connected to the network  7  (step S 123 ). By way of example, this retrieval information is broadcast to all devices connected to the network  7 . In the image formation device  10 , upon receipt of this retrieval information (step S 124 ), the device information output part  13  is brought into operation in the CPU  11  to generate response information responsive to the retrieval information. Thereafter the image formation device  10  transmits the response information to the information processing device  50  (step S 125 ). This response information contains information identifying the image formation device  10  and the like as well as the device address (IP address) or MAC address of the image formation device  10 . All of the devices connected to the network  7  transmit such response information. Thus, the information processing device  50  receives not only the response information independently transmitted from each of the plurality of image formation devices  10  including  10 A and  10 B, but also the response information transmitted from other devices such as PCs connected to the network  7 , if any. The response information transmitted from the image formation device  10  differs from the response information transmitted from a device that is not the image formation device  10 . 
     Upon receipt of the response information through the network  7  (step S 126 ), the information processing device  50  determines from the information contained in the received response information whether or not the received response information has been given from the image formation device  10 . The information processing device  50  holds only the response information given from the image formation device  10 , thereby extracting all of the image formation devices  10  connected to the network  7  (step S 127 ). In the present preferred embodiment, the response information given from the image formation devices including  10 A and  10 B are held to thereby extract the image formation devices including  10 A and  10 B. 
     Thereafter the information processing device  50  transmits a request for specific information through the network  7  in order to obtain the specific information  21  uniquely defined for each of the image formation devices including  10 A and  10 B (step S 128 ). By way of example, this request for specific information is multicast to the plurality of image formation devices including  10 A and  10 B connected to the network  7 . In the image formation device  10 , upon receipt of this request for specific information (step S 129 ), the device information output part  13  is brought into operation again in the CPU  11 . The device information output part  13  reads the specific information  21  stored in the storage part  20  (step S 130 ), and transmits the specific information  21  thereby read to the information processing device  50  (step S 131 ). All of the image formation devices  10  connected to the network  7  transmit the specific information  21 . Thus, each of the plurality of image formation devices including  10 A and  10 B independently transmits the specific information  21  to the information processing device  50 . 
     Upon receipt of the specific information  21  from each of the image formation devices  10  through the network  7  (step S 132 ), the information processing device  50  associates the device address, the MAC address and the specific information  21  of each of the image formation devices  10 . Then, the information processing device  50  stores these pieces of information as the device registration information  57  into the storage part  54  (step S 133 ). The device registration information  57  thereby stored is associated with the license code selected in step S 122 .  FIG. 11  shows an example of the device registration information  57  thereby stored in the storage part  54  of the information processing device  50 . The device registration information  57  contains a device address  57   a , a MAC address  57   b , specific information  57   c  and an encrypted code  57   d . The information entered by the process discussed above are the device address  57   a , the MAC address  57   b  and the specific information  57   c . The encrypted code  57   d  remains blank. With reference to  FIG. 11 , first registration information D 1  of the device registration information  57  relates to the image formation device  10 A (see  FIG. 1 ), and second registration information D 2  relates to the image formation device  10 B. When the device registration information  57  is successfully entered in this way, this process for the entry is completed. 
     Following the process discussed above, the registration of the image formation device  10  with the information processing device  50  shown in  FIG. 5  (process P 14 ) is completed. The user  5  continues to operate the information processing device  50  to proceed to the process for enabling an optional function at the image formation device  10  (process P 15 ). In this process, the user  5  operates the information processing device  50 , so that the information processing device  50  transmits a request for issue of license together with the specific information  21  of the image formation device  10  to the license management server  40 , and receives an encrypted license that has been encrypted using the specific information  21  from the license management server  40 . Then, the information processing device  50  provides the image formation device  10  with this encrypted license code together with a function enabling command. The image formation device  10  authenticates the encrypted license code using the specific information  21  of its own. When the encrypted license code is recognized as a proper code, the image formation device  10  enables an optional function designated by the function enabling command. 
       FIGS. 12 and 13  are flow diagrams showing an exemplary process sequence at the information processing device  50 , the license management server  50  and the image formation device  10  for enabling an optional function of the image formation device  10 . In the information processing device  50 , the CPU  51  also executes the function management program  55  to start this process sequence. After the start of the process sequence, the function management part  52  is brought into operation in the CPU  51  of the information processing device  50  to read the license information  56  from the storage part  54 . Thereafter license codes contained in the license information  56  are displayed in list form on the display device  61  (step S 141 ). The user  5  operates the keyboard  62  and the like to select a license code corresponding to an optional function that the user  5  wishes to enable from the license codes displayed in list form on the display device  61  (step S 142 ). 
     The information processing device  50  reads the device registration information  57  from the storage part  54  that is associated with the license code selected by the user  5 , and causes the image formation devices  10  contained in the device registration information  57  to be displayed in list form on the display device  61  (step S 143 ). The user  5  operates the keyboard  62  and the like to designate the image formation device  10  at which the user  5  wishes to enable the optional function from the image formation devices  10  displayed in list form on the display device  61  (step S 144 ). At this time, two or more of the image formation devices  10  may be designated. For the simplification of the discussion given below, however, only the image formation device  10 A is designated as an example. 
     When the image formation device  10 A designated by the user  5  is selected, the image processing device  50  reads the specific information  57   c  corresponding to the image formation device  10 A from the device registration information  57  (step S 145 ). This specific information  57   c  coincides with the specific information  21  unique to the image formation device  10 A. Thereafter the image processing device  50  transmits a request for issue of license together with the specific information  21  of the selected image formation device  10 A to the license management server  40  (step S 146 ). This request for issue of license contains information specifying the license code. 
     In the license management server  40 , upon receipt of the request for issue of license from the information processing device  50  (step S 147 ), the license management part  45  of the CPU  43  is brought into operation to search the license management database  42  (step S 148 ). Namely, the license management part  45  searches the license management database  42  to check whether or not the license code specified by the request for issue of license is recorded therein. If this license code is recorded in the license management database  42 , the license management part  45  performs a check to see that the number of unused licenses  42   e  (see  FIG. 6 ) is 1 or more. If the number of unused licenses  42   e  is 1 or more, a result obtained in step S 149  is OK. Then the license management part  45  updates the license management database  42  (step S 150 ). Namely, the license management part  45  increases the number of used licenses  42   d  by 1 and decreases the number of unused licenses  42   e  by 1, thereby updating the license management database  42 . When requests for issue of license regarding N (N is 2 or more) image formation devices are concurrently made, the license management part  45  performs checks (step S 148 ) to see that the number of unused licenses  42   e  is N or more. If a result of checks is OK, the license management part  45  increases the number of used licenses  42   d  by N and decreases the number of unused licenses  42   e  by N to update the license management database  42  (step S 150 ). 
     Thereafter the code generation part  46  is brought into operation in the CPU  43  of the license management server  40 . The code generation part  46  reads the license code specified by the request for issue of license from the license management database  42 , and encrypts this license code using the specific information  21  as a key that has been received together with the request for issue of license (step S 151 ). The license code thereby becomes an encrypted license code that is encrypted using the specific information  21  (such as “AAA”, for example) as a key. This is an exemplary license code that is generated based on the specific information  21 . The code generation part  46  transmits the license code thereby encrypted to the information processing device  50  (step S 152 ), and the information processing device  50  receives the encrypted license code (step S 153 ). 
     As a result of the checks at the license management server  40  (step S 148 ), the license code specified by the request for issue of license may not be recorded in the license management database  42 , or the number of unused licenses  42   e  may not be enough. In either case, a result obtained in step S 149  is NG. Then, the license management part  45  generates an error message (step S 154 ). This error message is transmitted from the license management server  40  (step S 155 ), and is received by the information processing device  50  (step S 156 ). 
     Referring next to the flow diagram shown in  FIG. 13 , when the information processing device  50  receives the encrypted license code from the license management server  40 , the information processing device  50  incorporates the received encrypted license code into the device registration information  57  (step S 160 ). Namely, in the device registration information  57  shown in  FIG. 11 , this encrypted license code fills in a blank for the encrypted code  57   d  of the registration information D 1  corresponding to the image formation device  10 A. Thereafter the command output part  53  is brought into operation in the CPU  51  of the information processing device  50 . The command output part  53  generates a function enabling command for the image formation device  10 A designated in step S 144  (step S 161 ), and transmits this function enabling command and the encrypted license code obtained from the license management server  40  to the image formation device  10 A (step S 162 ). 
     In the image formation device  10 A, upon receipt of the function enabling command and the encrypted license code from the information processing device  50  (step S 163 ), the command analysis part  12  conducts command analysis (step S 164 ). When the command analysis part  12  determines that the received command is a function enabling command, the command analysis part  12  specifies the optional function to be enabled using information contained in the command. Then, the command analysis part  12  gives the encrypted license code that has been received together with the function enabling command to the code authentication part  14 , by which the decryption part  15  of the code authentication part  14  is brought into operation. The decryption part  15  reads the specific information  21  from the storage part  20 , and decrypts the encrypted license code using this specific information  21  as a key (step S 165 ). That is, the encrypted license code is decrypted using the specific information  21  (such as “AAA”) as a key. As discussed above, the decrypted license code contains particular information when the decryption is successfully completed. The code authentication part  14  determines whether or not the decrypted license code is a proper code based on the presence or absence of such particular information (step S 166 ). 
     A result obtained in step S 167  is OK when the decrypted license code is recognized as a proper code. Then the function enabling part  16  is brought into operation in the CPU  11 . The function enabling part  16  enables the optional function designated by the function enabling command, thereby making this optional function usable in the image formation device  10 A (step S 168 ). As a result, this optional function is effectively available in the image formation device  10 A to complete the process for enabling the optional function. 
     When the decrypted license code is not recognized as a proper code, on the other hand, a result obtained in step S 167  is NG. Then the code authentication part  14  generates an error message (step S 169 ). This error message is transmitted from the image formation device  10 A (step S 170 ), and is received by the information processing device  50  (step S 171 ). 
     When the information processing device  50  receives the error message from the license management server  40  (step S 156 ), or from the image formation device  10 A, the information processing device  50  causes the received error message to be displayed on the display device  61  (step S 172 ). The information processing device  50  thereby informs the user  5  of the fact that the optional function has not successfully been enabled, and completes the process. When the user  5  tries to enable the optional function again, process steps starting from step S 141  are repeated. 
     Following the process discussed above, an optional function is enabled in the image formation device  10 A (process P 15 ). In this process, the license management server  40  encrypts a license code using the specific information  21  uniquely defined for the image formation device  10 A, thereby generating an encrypted license code applicable only to the image formation device  10 A as discussed above. The image formation device  10 A receives the encrypted license code input thereto, and decrypts this encrypted license code using the specific information  21  of its own, thereby determining whether or not the decrypted license code is a proper code. The image formation device  10 A enables an optional function only when the decrypted license code is a proper code. Thus, a license code issued by the license management server  40  is not applied to other image formation devices such as the image formation device  10 B, thereby allowing the license management server  40  to precisely manage the usage of a license. 
     In the present preferred embodiment, the image formation device  10 A receives both a function enabling command and an encrypted license code. The image formation  10 A may receive only an encrypted license code. In this case, the image formation device  10 A first decrypts the encrypted license code to authenticate the decrypted license code. When the decrypted license code is recognized as a proper code, an optional function to be enabled is specified by the decrypted license code. Then, the function enabling part  16  enables the specified optional function. 
     Discussed next is the process of disabling an optional function in a condition where this optional function is effectively available in the image formation device  10 . In this disabling process, the user  5  operates the information processing device  50 , so that the information processing device  50  transmits a request for issue of a disabling code together with the specific information  21  of the image formation device  10  to the license management server  40 , and obtains the disabling code that has been encrypted using the specific information  21  from the license management server  40 . Then, the information processing device  50  provides the image formation device  10  with this encrypted disabling code together with a function disabling command. The image formation device  10  authenticates the encrypted disabling code using the specific information  21  of its own. When the encrypted disabling code is recognized as a proper code, the image formation device  10  disables an optional function designated by the function disabling command. Disabling the optional function causes the image formation device  10  to change the specific information  21  of its own to information different from previous information. 
       FIGS. 14 to 16  are flow diagrams showing an exemplary process sequence at the information processing device  50 , the license management server  40  and the image formation device  10  for disabling an optional function of the image formation device  10 . In the information processing device  50 , the CPU  51  also executes the function management program  55  to start this process sequence. After the start of the process sequence, the function management part  52  is brought into operation in the CPU  51  of the information processing device  50  to read the license information  56  stored in the storage part  54 . License codes contained in the license information  56  are displayed in list form on the display device  61  (step S 200 ). The user  5  operates the keyboard  62  and the like to select a license code corresponding to an optional function that the user  5  wishes to disable from the license codes displayed in list form on the display device  61  (step S 201 ). 
     The information processing device  50  reads the device registration information  57  from the storage part  54  that is associated with the license code selected by the user  5 , and causes the image formation devices  10  contained in the device registration information  57  to be displayed in list form on the display device  61  (step S 202 ). At this time, only the image formation devices  10  given encrypted license codes that fill columns for the encrypted code  57   d  of the device registration information  57  are extracted and displayed in list form. As a result, the image formation devices  10  at which the optional function selected by the user  5  is effectively available are displayed in list form on the display device  61 . Then, the user  5  operates the keyboard  62  and the like to designate the image formation device  10  at which the user  5  wishes to disable the optional function from the image formation devices  10  displayed in list form on the display device  61  (step S 203 ). At this time, two or more of the image formation devices  10  may be designated. For the simplification of the discussion given below, however, only the image formation device  10 A is designated as an example. 
     When the image formation device  10 A designated by the user  5  is selected, the image processing device  50  reads the specific information  57   c  of the image formation device  10 A contained in the device registration information  57  (step S 204 ). This specific information  57   c  coincides with the specific information  21  of the image formation device  10 A stored therein. Thereafter the image processing device  50  transmits a request for issue of a disabling code together with the specific information  21  of the selected image formation device  10 A to the license management server  40  (step S 205 ). This request for issue of a disabling code contains information specifying the license code corresponding to the optional function to be disabled. 
     In the license management server  40 , upon receipt of the request for issue of a disabling code from the information processing device  50  (step S 206 ), the license management part  45  of the CPU  43  is brought into operation to search the license management database  42  (step S 207 ). Namely, the license management part  45  searches the license management database  42  to check whether or not the license code specified by the request for issue of a disabling code is recorded therein. If this license code is recorded in the license management database  42 , the license management part  45  performs a check to see that the number of used licenses  42   d  (see  FIG. 6 ) is 1 or more. If the number of used licenses  42   d  is 1 or more, a result obtained in step S 208  is OK. Thereafter the code generation part  46  is brought into operation in the CPU  43  of the license management server  40 . The code generation part  46  generates a disabling code for disabling an optional function corresponding to the specified license code, and encrypts this disabling code using the specific information  21  as a key that has been received together with the request for issue of a disabling code (step S 210 ). The disabling code thereby becomes an encrypted code that is encrypted using the specific information  21  (such as “AAA”, for example) as a key. The code generation part  46  transmits the disabling code thereby encrypted to the information processing device  50  (step S 211 ), and the information processing device  50  receives the encrypted disabling code (step S 212 ). 
     As a result of the checks at the license management server  40  (step S 207 ), the license code specified by the request for issue of a disabling code may not be recorded in the license management database  42 , or the number of issued licenses  42   d  may be zero. In either case, a result obtained in step S 208  is NG, and the license management part  45  generates an error message (step S 213 ). This error message is transmitted from the license management server  40  (step S 214 ), and is received by the information processing device  50  (step S 215 ). 
     Referring next to the flow diagram shown in  FIG. 15 , when the information processing device  50  receives the encrypted disabling code from the license management server  40 , the information processing device  50  deletes the encrypted license code of the image formation device  10 A contained in the device registration information  57  (step S 220 ). As a result, in the device registration information  57  shown in  FIG. 11 , a column for the encrypted code  57   d  of the registration information D 1  corresponding to the image formation device  10 A returns to a blank column. Thereafter the command output part  53  is brought into operation in the CPU  51  of the information processing device  50 . The command output part  53  generates a function disabling command for the image formation device  10 A (step S 221 ). This function disabling command designates the optional function to be disabled. The information processing device  50  transmits this function disabling command and the encrypted disabling code obtained from the license management server  40  to the image formation device  10 A (step S 222 ). 
     In the image formation device  10 A, upon receipt of the function disabling command and the encrypted disabling command from the information processing device  50  (step S 223 ), the command analysis part  12  conducts command analysis (step S 224 ). When the command analysis part  12  determines that the received command is a function disabling command, the command analysis part  12  specifies the optional function to be disabled using information contained in the command. Then, the command analysis part  12  gives the encrypted disabling code that has been received together with the function disabling command to the code authentication part  14 , by which the decryption part  15  of the code authentication part  14  is brought into operation. The decryption part  15  reads the specific information  21  from the storage part  20 , and decrypts the encrypted disabling code using this specific information  21  as a key (step S 225 ). That is, the encrypted disabling code is decrypted using the specific information  21  (such as “AAA”) as a key. As discussed above, the decrypted disabling code contains particular information when the decryption is successfully completed. The code authentication part  14  determines whether or not the decrypted disabling code is a proper code based on the presence or absence of such particular information (step S 226 ). 
     A result obtained in step S 227  is OK when the decrypted disabling code is recognized as a proper code. Then the function disabling part  17  is brought into operation in the CPU  11 . The function disabling part  17  disables the optional function designated by the function disabling command, thereby making this optional function unusable in the image formation device  10 A (step S 228 ). As a result, this optional function is unavailable in the image formation device  10 A, and cannot be used by the user  5  accordingly. 
     Thereafter the specific information rewriting part  18  is brought into operation in the function disabling part  17 . Disabling the optional function that has been valid causes the specific information rewiring part  18  to rewrite the specific information  21  stored in the storage part  20 , thereby changing the specific information of the image formation device  10 A (step S 229 ). As an example, the specific information  21  is changed from “AAA” to “ZZZ.” The specific information  21  after having been rewritten by the specific information rewriting part  18  is still unique to the image formation device  10 A, at least in an environment where the image formation device  10 A is connected to the network  7 . The specific information  21  may be defined in any manner. As an example, the device identification information of the image formation device  10 A such as MAC address or serial number, and temporal information such as year, month, day, time, minute and second at which the specific information  21  is generated are computed based on a certain rule. Resultant information obtained therefrom is applied as new specific information. The specific information rewriting part  18  thereby changes the specific information  21  stored in the storage part  20 , so that in the image formation device  10 A, the above-discussed optional function cannot be enabled again using an encrypted license code previously authenticated. 
     Thereafter the function disabling part  17  generates a code notifying the completion of disabling process (step S 230 ), and transmits this code to the information processing device  50  (step S 231 ). This code is received by the information processing device  50  (step S 232 ). 
     When the decrypted disabling code is not recognized as a proper code, on the other hand, a result obtained in step S 227  is NG. Then the code authentication part  14  generates an error message (step S 233 ). This error message is transmitted from the image formation device  10 A (step S 234 ), and is received by the information processing device  50  (step S 235 ). 
     Referring next to the flow diagram shown in  FIG. 16 , upon receipt of the code notifying the completion of disabling process from the image formation device  10 A, the information processing device  50  incorporates this code into the device registration information  57  (step S 240 ). By way of example, this code is incorporated into a column for the encrypted code  57   d  of the device registration information  57 . As a result, the information processing device  50  is allowed to determine whether or not the optional function is valid or invalid in each of the image formation devices  10  contained in the device registration information  57  by referring to the device registration information  57 . Thereafter the information processing device  50  transmits the code notifying the completion of disabling process to the license management server  40  (step S 241 ). Upon receipt of the code notifying the completion of disabling process from the information processing device  50  (step S 242 ), the license management server  40  updates the license management database  42  (step S 243 ). Namely, in the license information L 1  shown in  FIG. 6 , the number of used licenses  42   d  is decreased by 1 and the number of unused licenses  42   e  is increased by 1, thereby updating the license management database  42 . As a result, a license corresponding to the disabled optional function is stored as an unused license in the license management database  42 . 
     When the information processing device  50  receives the error message from the license management server  40  (step S 215 ), or from the image formation device  10 A (step S 235 ), the information processing device  50  causes the received error message to be displayed on the display device  61  (step S 245 ). The information processing device  50  thereby informs the user  5  of the fact that the optional function has not successfully been disabled, and completes the process. When the user  5  tries to disable the optional function again, process steps starting from step S 200  are repeated. 
     Following the process discussed above, an optional function is disabled in the image formation device  10 A. In this process, the license management server  40  encrypts a disabling code using the specific information  21  uniquely defined for the image formation device  10 A, thereby generating an encrypted disabling code applicable only to the image formation device  10 A as discussed above. The image formation device  10 A receives the encrypted disabling code input thereto, and decrypts this encrypted disabling code using the specific information  21  of its own, thereby determining whether or not the decrypted disabling code is a proper code. The image formation device  10 A disables an optional function only when the decrypted disabling code is a proper code. Thus, a disabling code issued by the license management server  40  is not applied to other image formation devices such as the image formation device  10 B, thereby allowing the license management server  40  to precisely manage the usage of a license. 
     In the present preferred embodiment, the disabling process of an optional function causes the specific information  21  stored in the storage part  20  of the image formation device  10  and uniquely defined for the image formation device  10  to be changed to information different from previous information. When the same optional function is to be enabled again in the image formation device  10 , a license code encrypted by using the specific information  21  as changed should be given from the license management server  40 . This prevents an encrypted license code once issued from being used repeatedly in the office environment  3  of the user  5 . As a result, the license management server  40  is allowed to precisely manage the usage of a license at all times. 
     Discussed next is the transfer of a license. As discussed above, when an optional function is disabled in a condition where this optional function is effectively available in the image formation device  10 , the license management server  40  regards a license corresponding to the disabled optional function as an unused license. As an example, after an optional function is disabled in the image formation device  10 A, a license corresponding to the disabled optional function may be used in the different image formation device  10 B to enable this optional function. In this case, the license is transferred between the image formation devices  10 . 
       FIG. 17  is a flow diagram showing the transfer process of a license. For the transfer of a license, the user  5  first operates the information processing device  50  to conduct the function disabling process (process P 20 ). This function disabling process (process P 20 ) follows the same steps discussed in detail above with reference to the flow diagrams of  FIGS. 14 to 16 . This function disabling process generates an unused license, and the license management server  40  allows this license corresponding to a disabled optional function to be given to a different image formation device. 
     Thereafter, the necessity of transfer of the unused license is established (process P 21 ). As an example, confirmation massage is displayed on the display device  61  of the information processing device  50  to determine whether or not the license should be transferred, thereby establishing the necessity of transfer. When the user  5  gives instruction to transfer the license, function enabling process is conducted in which the license is transferred to a different image formation device to enable the optional function in this image formation device (process P 22 ). This function enabling process (process P 22 ) is the same as the function enabling process shown in  FIG. 5  (process P 15 ), and follows the same steps discussed in detail above with reference to the flow diagrams of  FIGS. 12 and 13 . This function enabling process causes the unused license to be applied to the different image formation device  10  designated by the user  5  at which the optional function is to be enabled. 
     Following the process discussed above, a license is freely transferred between the plurality of image formation devices  10  installed in the office environment  3 . Thus, within the number of licenses already purchased and without the need of purchasing an additional license, the user  5  is allowed to suitably change the image formation device  10  at which an optional function is to be effectively available. As a result, the user  5  is allowed to efficiently use a license. 
     As discussed above, the image formation device  10  of the present preferred embodiment includes the specific information  21  stored in the storage part  20  that is uniquely defined for the image formation device  10 . The image formation device  10  receives a license code input thereto that is generated based on this specific information  21  by the license management server  40 , and authenticates the received license code using the specific information  21  in the storage part  20 . When the received license code is recognized as a proper license code as a result of authentication, the image formation device  10  enables a designated optional function. The image formation device  10  also disables an optional function that has been enabled by a license code. Disabling the optional function causes the image formation device  10  to change the specific information  21  stored in the storage part  20  to information different from previous information. Thus, after disabling the optional function, the image formation device  10  does not recognize a license code input thereto as a proper license code that had been granted before the optional function is disabled. As a result, the optional function is prevented from being enabled twice using the same license code. 
     In order to disable an optional function, the image formation device  10  receives a disabling code input thereto that is generated based on the specific information  21  by the license management server  40 , and authenticates the received disabling code using the specific information  21  in the storage part  20 . When the received disabling code is recognized as a disabling proper code as a result of authentication, the image formation device  10  disables a designated optional function. In order to enable or disable an optional function in the image formation device  10 , the image formation device  10  should receive a code that is issued each time the optional function is enabled or disabled. After the specific information  21  is changed, a code that is generated based on the previous information fails to enable or disable the optional function. This means enabling or disabling an optional function in the image formation device  10  always requires the issue of a code by the license management server  40 . As a result, the license management server  40  is allowed to precisely manage the usage of a license at all times. 
     Modifications 
     In the preferred embodiment discussed above, data communication between the image formation device  10  and the license management server  40  is realized through the information processing device  50 . Namely, in the preferred embodiment discussed above, the license management server  40  conducts data communication with the image formation devices  10  indirectly through the information processing device  50  and not directly with the image formation devices  10 , thereby managing the usage of licenses at the image formation devices  10 . Alternatively, the license management server  40  may conduct data communication directly with the image formation devices  10  without involving the information processing device  50 . In this case, the function of the information processing device  50  as discussed above may be provided in the license management server  40 , or in the image formation device  10 . When the function of the information processing device  50  is to be provided in the image formation device  10 , any one of the plurality of image formation devices  10  installed in the office environment  3  may have the function of the information processing device  50 . 
     While the invention has been shown and described in detail, the foregoing description is in all aspects illustrative and not restrictive. It is therefore understood that numerous modifications and variations can be devised without departing from the scope of the invention.