Patent Publication Number: US-2006001899-A1

Title: Method and apparatus for image processing

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
      This Nonprovisional application claims priority under 35 U.S.C. $119(a) on Patent Application No. 2004-171775 filed in Japan on Jun. 9, 2004, the entire contents of which are hereby incorporated by reference.  
     BACKGROUND OF THE INVENTION  
      1. Field of the Invention  
      The present invention relates to a method and an apparatus for image processing to provide a user with security environments pertinent to the user.  
      2. Description of Related Art  
      An image processing apparatus is known having an electronic filing function for reading an image data by optically scanning an original, temporarily saving the image data in a recording medium, and reading again the image data of the original from the recording medium a number of times which is equal to a desired number of copies for printing out the image data on sheets of copy paper (For example, see Japanese Patent Laid-Open No. 06-178041).  
      It is common for such conventional image processing apparatuses with the electronic filing function to have a file allocation table (FAT) arranged for determining the location of storage on the recording medium where any image data is to be saved or identifying the location of storage from which desired image is read out. FAT assigns each image data to be saved on the recording medium with its data number and its reference value is specified by the data number to allocate the image data at its storage location on the recording medium.  
      FAT is updated whenever the action of printing out each desired image data has been completed. When FAT is deleted or updated, its assigning image data can not be read out from the recording medium by the action of the image data processing apparatus. Accordingly, the use of FAT allows any data to be protected from false access thus ensuring the security of image data.  
      However, as relevant technologies for the data processing have been advanced and spread out, they may permit any false third party to remove the recording medium (for example, a hard disk drive) from the image processing apparatus where image data remain saved but not perfectly erased with the deletion or updating of FAT and thus illegally read any desired image data from the recording medium.  
      Some modifications are proposed for protecting the image data from unauthorized leakage or use.  
      The modifications include an image processing apparatus (disclosed in Japanese Patent Laid-Open Publication No. 07-28365) where the protection is based on identification of each individual user, another image processing apparatus (disclosed in Japanese Patent Laid-Open Publication 2000-187419) where each image data to be read is accompanied with its pertinent information which is traceable, a further image processing apparatus (disclosed in Japanese Patent Laid-Open Publication No. 01-256068) where each image data is encrypted before saved on a recording medium, and a still further image processing apparatus (disclosed in Japanese Patent Laid-Open Publication No. 09-223061) where each image data saved on a recording medium is automatically erased upon its necessity being canceled. The modifications are capable of inhibiting unauthorized leakage or use of image data stored on the image processing apparatus.  
      However, those modifications may fail to protect the image data from being leaked or illegally used because they need initial setting of their actions which is a troublesome task and has to be conducted without errors by every user controlling the printer driver or operating panel of the image processing apparatus.  
      Also, since the processes of the conventional image processing apparatuses are analogous, they allow some of the image data at no secrecy to be encrypted or each of the image data to be systematically erased and will thus consume more time resulting in the slowdown.  
     BRIEF SUMMARY OF THE INVENTION  
      The present invention has been developed in view of the above aspects and its object is to provide a method and an apparatus for image processing where the process involves receiving an image data and one or more reference data to be cited for processing the image data, examining the level of secrecy of the image data from the reference data, determining an process to be carried out from a result of the examination, and carrying out the determined process, so that the security environment depending on the conditions of use can be established without declining the efficiency of the process.  
      An image processing method according to the present invention is characterized by the steps of receiving image data and reference data for processing the image data, judging a level of secrecy of the image data to be processed, on the basis of the received reference data, determining a process to be executed on the basis of a result of the judgment, and executing the process.  
      In the present invention, the method comprises the steps of receiving an image data and one or more reference data to be cited for processing the image data, examining the level of secrecy of the image data from the reference data, determining an process to be executed from a result of the examination, and executing the determined process. As a result, the process is varied between the high level of secrecy and the low level of secrecy. Accordingly, the secrecy of the image data can be protected without declining the processing efficiency.  
      An image processing apparatus according to the present invention is characterized by comprising means for receiving image data and reference data for processing the image data, means for judging a level of secrecy of the image data to be processed, on the basis of the received reference data, means for determining a process to be executed on the basis of a result of the judgment, and means for executing the process.  
      The image processing apparatus is arranged for receiving an image data and one or more reference data to be cited for processing the image data, examining the level of secrecy of the image data from the reference data, determining an process to be executed from a result of the examination, and executing the determined process. As a result, the process is varied between the high level of secrecy and the low level of secrecy. Accordingly, the secrecy of the image data can be protected without declining the processing efficiency.  
      An image processing apparatus according to the present invention is characterized by comprising means for receiving image data and reference data for processing the image data, means for judging the level of secrecy of the image data on the basis of the received image data and reference data, means for determining a process to be executed on the basis of a result of the judgment, and means for executing the process.  
      The image processing apparatus is arranged for receiving an image data and one or more reference data to be cited for processing the image data, examining the level of secrecy of the image data from a combination of the image data and the reference data, determining an process to be executed from a result of the examination, and executing the determined process. As a result, the process is varied between the high level of secrecy and the low level of secrecy. Accordingly, the secrecy of the image data can be protected without declining the processing efficiency.  
      The image processing apparatus according to the present invention is characterized in that the reference data indicates whether or not image data is encrypted.  
      Since the reference data indicates whether the image data is encrypted or not, the level of secrecy is judged to be high when the image data is encrypted and thus the process can be executed so as to protect the secrecy. When the image data is not encrypted, the process can be conducted with no protection of the secrecy.  
      The image processing apparatus according to the present invention is characterized by comprising means for combining the received image data with prescribed image data, and wherein the reference data indicates whether or not the image data is to be combined with the prescribed image data.  
      Since the reference data indicates whether or not the image data is combined with the additional image data, the level of secrecy is judged to be high when the image data is accompanied with a specific marking such as “confidential” or “important”, or a specific tint block pattern and the process can be executed so as to protect the secrecy. When the additional image data is not combined, the process can be conducted with no protection of the secrecy.  
      The image processing apparatus according to the present invention is characterized in that the reference data indicates information data about a user.  
      Since the reference data is a data about the user, the level of secrecy of the image data received from certain users is judged to be high and the process can be executed so as to protect the secrecy. The image data from other users can thus be protected with no level of secrecy.  
      The image processing apparatus according to the present invention is characterized in that, the invalidation process is executed on the image data, when it is judged that the level of secrecy of the image data is high.  
      Since the image data is invalidated when it is judged that the level of secrecy of the image data is high, it can be protected from being illegally accessed by and leaked to any dishonest third party.  
      The image processing apparatus according to the present invention is characterized in that, the encryption process is executed on the image data, when it is judged that the level of secrecy of the image data is high.  
      Since the image data is encrypted when it is judged that the level of secrecy of the image data is high, it can be protected from being decoded and read by any dishonest third party even after successfully intercepted.  
      The image processing apparatus according to the present invention is characterized by comprising means for receiving user data, and means for identifying a user from the received user data, wherein the process is paused until the user is identified, when it is judged that the level of secrecy of the image data is high.  
      Since the process is paused before the user is identified when it has been judged that the level of secrecy of the image data is high, the image data can be protected from being illegally accessed by and leaked to any dishonest third party.  
      As featured, the present invention involves receiving an image data and its reference data to be cited for processing the image data, examining the level of secrecy of the image data from the reference data, determining an process to be executed from a result of the examination, and executing out the determined process. As a result, the process is varied between the high level of secrecy and the low level of secrecy. Accordingly, the secrecy of the image data can be protected without declining the processing efficiency.  
      As featured, the present invention involves examining the level of secrecy of the image data to be processed from a combination of the image data and its reference data, determining an process to be executed from a result of the examination, and executing the determined process. As a result, the process is varied between the high level of secrecy and the low level of secrecy. Accordingly, the secrecy of the image data can be protected without declining the processing efficiency.  
      The present invention is featured in that the reference data indicates whether the image data is encrypted or not. Accordingly, when the image data is encrypted, it is judged to be high in the level of secrecy and can thus be processed so as to protect the secrecy. When the image data is not encrypted, it is judged to be low in the level of secrecy and can thus be processed with no protection of the secrecy. In other words, the secrecy remains protected without declining the efficiency of the process.  
      The present invention is featured in that the reference data indicates whether or not the image data is combined with an additional image data. Accordingly, the level of secrecy is judged to be high when the image data is accompanied with a specific marking such as “confidential” or “important”, or a tint block pattern and the process can be selected so as to protect the secrecy. When the additional image data is not combined, the action can be conducted with no protection of the secrecy. Therefore, the secrecy remains protected without declining the efficiency of the process.  
      The present invention is featured in that the reference data is a data about the user. Accordingly, when the level of secrecy of the image data received from certain user is judged to be high, the process can be selected so as to protect the secrecy. The image data from other users can thus be protected with no level of secrecy. In other words, the secrecy remains protected without declining the efficiency of the process.  
      The present invention is featured in that, when it is judged that the level of secrecy of the image data is high, the image data is invalidated. Accordingly, the image data can be protected from being illegally accessed by and leaked to any dishonest third party.  
      The present invention is featured in that, when it is judged that the level of secrecy of the image data is high, the image data is encrypted. Accordingly, the image data can be protected from being decoded and read by any dishonest third party even after successfully intercepted.  
      The present invention is featured in that, when it is judged that the level of secrecy of the image data is high, the action can be paused before the user is identified. Accordingly, the image data can be protected from being illegally accessed by and leaked to any dishonest third party.  
      The above and further objects and features of the invention will more fully be apparent from the following detailed description with accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS  
       FIG. 1  is a block diagram of the entire arrangement of an image processing system according to the present embodiment;  
       FIG. 2  is a schematic view showing an example of the print setting screen generated by the printer driver installed in the data processing terminal;  
       FIG. 3  is a schematic view showing an example of the option setting screen;  
       FIG. 4  is a concept view showing the detail of the print job generated by the printer driver;  
       FIG. 5  is a block diagram showing the internal structure of the image forming apparatus;  
       FIGS. 6A  to  6 E are diagrams showing an example of the security level calculating table stored in the management section;  
       FIG. 7  is a flowchart explaining the steps of a process to be executed by the image forming apparatus;  
       FIGS. 8A and 8B  are explanatory diagrams explaining examples for calculating the security levels;  
       FIG. 9  is a diagram showing a list of the processes to be executed depends on the calculated security levels;  
       FIG. 10  is a flowchart explaining the steps of a process to be executed by the image forming apparatus; and  
       FIGS. 11A and 11B  are explanatory diagrams explaining examples for calculating the security levels. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION  
      The present invention will be described in more detail referring to the accompanying drawings.  
      Embodiment 1  
       FIG. 1  is a block diagram of the entire arrangement of an image processing system according to the present embodiment. Denoted by  100  is an image forming apparatus which has a scanner function of reading the image of an original, a copy function of reproducing the image on a sheet of, e.g., paper or OHP film, and a print function of printing the image on the sheet according to a given printing job. The image forming apparatus  100  is connected by a communications network N to a group of data processing terminals  200  such as personal computers or work stations. The data processing terminal  200  has an application program installed for producing texts and graphics and a driver program (printer driver) installed for operating the image forming apparatus  100  over the communications network N. This allows the printer driver when read out and actuated to provide the image forming apparatus  100  with a printing job for printing down texts and graphics.  
      The data processing terminals  200  are accompanied with user identification peripherals  201  for identifying their users from the user authentication information including the name, the status, and the department of the users. For example, the user identification peripheral  201  incorporates a reader for reading the user authentication information, described above, from an IC card which is assigned to the individual user. The user authentication information received by the user identification peripheral  201  is used as one of the data attached to the printing job.  
      In this embodiment, the image forming apparatus  100  analyzes the printing job received over the communications network N to judge the level of secrecy of an image data to be handled and then executes the printing job according to the judgment.  
       FIG. 2  is a schematic view showing an example of the print setting screen generated by the printer driver installed in the data processing terminal  200 . The print setting screen  20  shown in  FIG. 2  displays, at least, a printer selecting dialog box  21  for selecting a printer (the image forming apparatus) suited for carrying out the desired printing job, a print range specifying dialog box  22  for specifying the range of printing, and a prints number specifying dialog box  23  for determining the number of prints. The printer selecting dialog box  21  indicates the name of a printer selected by the user, the operation data of the selected printer, and the user authentication information entered by the user operating the user identification peripheral  201 .  
      Also, the print setting screen  20  displays at the lower right an execution button  24  for determining the printing job from the setting data entered in the print setting screen  20  and transferring it to the selected printer (for example, the image forming apparatus  100 ) selected at the printer select dialog box  21  and a cancel button  25  for canceling the printing job and returning to the previous application for displaying the print setting screen  20 . In addition, an option button  26  is provided at the lower left of the print setting screen  20  for setting any option.  
       FIG. 3  is a schematic view showing an example of the option setting screen. When the option button  26  on the print setting screen  20  is switched on, the option setting screen  30  appears for selecting any optional action of the printing. The option setting screen  30  displays an option setting dialog box  31  for determining yes or no of draft printing, background printing, and encrypted data transmission, a hold print setting dialog box  32  for determining items of the hold printing, and an additional image setting dialog box  33  for determining items of the additional image printing. Provided beneath the additional image setting dialog box  33  are an execution button  34  and a cancel button  35 . When the execution button  34  is switched on, a printing job specified by the settings entered in the setting dialog boxes  31  to  33  is produced. When the cancel button  35  is switched on, the settings on the option setting screen  30  are canceled and the screen returns back to the print setting screen  20 .  
      The option setting dialog box  31  includes check blanks for draft printing, background printing, and encrypted data transmission. When the check blanks are clicked, their corresponding action is carried out.  
      The hold print setting dialog box  32  is provided for setting the timing of starting the printing action. When a check blank for “general print” is clicked, its data of the printing job is transferred to the image forming apparatus  100 . Upon receiving the printing job, the image forming apparatus  100  starts the process of general print. When a check blank for “hold after print” is clicked, its data of the printing job is transferred to the image forming apparatus  100 . Upon receiving the printing job, the image forming apparatus  100  starts the action of printing and then saves the image data in an HDD  112  (See  FIG. 5 ). When a check blank for “hold not print” is clicked, its data of the printing job is transferred to the image forming apparatus  100 . Upon receiving the printing job, the image forming apparatus  100  remains not conducting the action of printing but starts the printing action only when a predetermined password is entered.  
      The additional image setting dialog box  33  is provided for selectively determining an extra image data to be added to the image data produced by the user. When check blanks are clicked, their corresponding options are added to the image data. For example, when one of the check blanks at the uppermost is clicked for “confidential” or “important”, its corresponding watermark can be printed down as an additional image data. When one of the check blanks at the middle is clicked for tint block “A” or “B”, its corresponding marking can be printed down. When one of the check blanks at the lowermost is clicked for “section code” or “bar code”, its corresponding code can be printed down.  
       FIG. 4  is a concept view showing the detail of the print job generated by the printer driver. The printing job determined by the print driver consists mainly of a printing data and its attribute data including the user authentication information, the document information, the hold print information, and the additional image information. The user authentication information is entered from the user identification peripheral  201  and may contain the name, status, and section of the user. The document information indicates a type of document as is specified with a flag. For example, “01” of the flag denotes that the document is of a confidential mode while “02” represents a sample mode. The hold print information is also flagged as specified by the settings in the hold print setting dialog box  32  on the option setting screen  30 . More particularly, when the hold print information is flagged at “01”, the general printing is executed. When “02”, the holding is carried out after the printing. When “03”, the holding only is carried out with no action of the printing. The additional image information indicates with a flag a type of the additional image data attached to the image data at the image forming apparatus  100 . For example, when the flag is “01”, the additional image is a watermark of “confidential”. When the flag is “03”, the tint block of B pattern is printed down as an additional image. The other types of the additional image information are similarly indicated by the flag. The printing data is written in the page description language (PDL). When the encrypted data transmission is selected on the option setting screen  30 , the printing data is encrypted and can be decoded at the image forming apparatus  100 .  
       FIG. 5  is a block diagram showing the internal structure of the image forming apparatus  100 . The image forming apparatus  100  includes a CPU  101 . In action, the CPU  101  operates a control program stored in and read from a ROM  103  for actuating a group of hardware components connected over a bus  102  as the image processing apparatus of the present invention.  
      A management section  104  comprises a set of non-volatile, rewritable memories for storage of various data about the action of the hardware components as well as the conditions of the apparatus and is arranged to periodically monitor the action of the hardware components and update the data stored in the memories. The management section  104  also includes a security level calculating table  104   a  for calculating the security level of each image to be released corresponding to the printing job. The security level calculating table  104   a  will be described later in more detail.  
      An operating panel  105  comprises an operator including an array of hardware keys and a display including a liquid crystal display panel. It is arranged for switching the action of the hardware components, receiving commands of the user, including a startup of reading the original, and displaying various data to be viewed by the user.  
      An image reading section  106  comprises a light source for emitting a beam of light for scanning the original, an image sensor such as a CCD array, and an AD converter (not shown). In action, the image reading section  106  develops on the image sensor and converts an optical image of the original placed at the readout position into an analog electric signal-which is then converted into a digital signal by an AD converter. The image reading section  106  finally subjects the digital signal to correcting processes for eliminating unwanted artifacts derived from the optical characteristics of the light source during the scanning and the sensitivity inuniformity of the image sensor, hence forming the image data of a digital form.  
      An image forming section  107  comprises a charger for charging a photosensitive drum with a desired potential, a laser writer for emitting a laser beam to develop a static latent image of the image data on the photosensitive drum, a developer for feeding the latent image on the photosensitive drum with an amount of toner to have a toner image, and a transfer roll for transferring the toner image from the photosensitive drum to a sheet of paper (which all are not shown). In brief, the image of the original is printed down on a sheet of paper by an electronic photographic technology. Although the image forming section  107  is of an electronic photographic type using the laser writer the embodiment, it may be of any applicable type such as ink jet, thermal transfer, or sublimation type with equal success.  
      An image memory  108  is a semiconductor memory for temporarily saving an image data received from the image reading section  106 , an image data reconstructed according to the printing job received from a communications interface  109 , and an image data read out from an HDD  112 . In response to a command from the CPU  101 , the image data temporarily saved in the image memory  108  is transferred to a destination determined by the printing job. More specifically, when the printing down on a sheet of paper is commanded, the image data is received by the image forming section  107 . When the transfer is commanded, the image data is transmitted through the communications interface  109 . When the saving is commanded, the image data is received by the HDD  112 .  
      The communications interface  109  includes a network terminal circuit conforming to the standard of the communications network N and is arranged to receive the printing job from each of the data processing terminals  200  connected over the communications network N and supply the data processing terminals  200  with relevant data. In case that the image forming apparatus  100  is used as a network scanner, the image of an original produced by its image reading section  106  is transferred from the communications interface  109  to desired one of the data processing terminals  200 . The communications interface  109  controls the transmission and reception of various data.  
      An encrypting circuit  110  comprises an input buffer for receiving the data to be encrypted, an arithmetic operator for subjecting the data received at the input buffer to an arithmetic operation using a desired encryption algorithm, and an output buffer for holding a result of the arithmetic operation received from the arithmetic operation. The encryption algorithm may be of the advanced encryption standard (AES). In action, the data to be encrypted is received at the input buffer, subjected to the arithmetic operation, and then written in the output buffer after the end of the encryption. The data is then read out from the output buffer by the action of the CPU  101  in the image forming apparatus  100  before released from the encrypting circuit  110 .  
      A decrypting circuit  111  is substantially identical in the arrangement to the encrypting circuit  110  as comprising an input buffer for receiving the data to be decoded, an arithmetic operator for subjecting the data to an arithmetic operation using a desired decoding algorithm, and an output buffer for holding a result of the arithmetic operation. In action, the data to be decoded is received at the input buffer, subjected to the arithmetic operation, and then written in the output buffer after the end of the decoding process. The decoded data is then read out from the output buffer by the action of the CPU  101  in the image forming apparatus  100  before released from the decrypting circuit  111 .  
      The HDD  112  includes a magnetic recording medium of a disk shape where a part of its storage area acts as a data area for saving the image data. The image data can be read out from the data area of the HDD  112  when a command is received from the operating panel  105  or the data processing terminal  200  via the communications interface  109 . This allows the image data saved in the data area to be arbitrarily used for repeating the printing action even if the previous action of the printing fails to be completed or produces a less number of prints.  
      A user authentication device  113  is identical in the arrangement to the user identification peripheral  201  in the data processing terminal  200  and includes a reader for reading the authentication information of a user from the IC card assigned to the user. While the printing action is conducted by the image forming apparatus  100  using a copy function, it can be controlled as well as the requirements of the printing job at a desired level of the security determined by the authentication information of the user which is entered from the user authentication device  113 .  
       FIGS. 6A  to  6 E are diagrams showing an example of the security level calculating table  104   a  stored in the management section  104 . In this embodiment, the level of the secrecy of each image to be released according to the printing job is calculated with the security level calculating table  104   a  shown in  FIGS. 6A  to  6 E.  FIG. 6A  indicates a list of reference numerals for the user authentication information. It is assumed in the list that Mr. Taro OO is ranked with  17  as a reference numeral for determining the level of the secrecy. Also, Mr. Jiro ((is ranked with  10  and Mr. Kenji XX is ranked with  5 . The reference numeral designated for ranking the user authentication information will be termed as score (A) hereinafter.  
      Similarly,  FIG. 6B  indicates a list of reference numerals for the document information where the document types of “confidential mode”, “sample mode”, and “other mode” are denoted by different reference numerals. The reference numeral designated for ranking the document information will be termed as score (B) hereinafter.  FIG. 6C  indicates a list of reference numerals for the hold print information where the selections of “general print”, “hold after print”, and “hold not print” are denoted by different reference numerals. The reference numeral designated for ranking the hold print information will be termed as score (C) hereinafter.  FIG. 6D  indicates a list of reference numerals for the additional image information where the additional images of “confidential”, “important”, “tint block A” and so on are denoted by different reference numerals. The reference numeral designated for ranking the additional image information will be termed as score (D) hereinafter.  FIG. 6E  indicates a list of reference numerals for determining whether or not the printing data is encrypted. In particular,  5  represents the data encrypted while  1  represents no encryption. The reference numeral designated will be termed as score (E) hereinafter.  
       FIG. 7  is a flowchart explaining the steps of a process to be executed by the image forming apparatus  100 . The CPU  101  in the image forming apparatus  100  monitors the communications interface  109  and judges whether a printing job is received or not (Step S 11 ). When the printing job is not received (No at S 11 ), the action stands by until the printing job is received. When the printing job is received (Yes at S 11 ), it is expanded to identify the printing data and its attribute data (Step S 12 ). When the printing data is encrypted, it is decoded by the decrypting circuit  111 .  
      This is followed by calculating a recommended value of the security from the attribute data (Step S 13 ). In this embodiment, the recommended value of the security is determined from the user authentication information and the document information. More specifically, the score (A) ranking the user authentication information and the score (B) ranking the document information are read out from the security level calculating table  104   a  and summed up to determine the recommended value of the security.  
      Then, the security level of an image to be printed according to the printing job is calculated (Step S 14 ). In this embodiment, the security level of the image to be printed is determined from a combination of the hold print information, the additional image information, and the encryption data. More specifically, the score (C) ranking the hold print information, the score (D) ranking the additional image information, and the score (E) ranking the encryption data are read out from the security level calculating table  104   a  and summed up to determine the security level.  
      The security level calculated at Step S 14  is then compared with the recommended value of the security calculated at Step S 13  for judging whether or not the security level is satisfied with the recommended value (Step S 15 ).  
      When the security level fails to conform to the recommended value (No at Step S 15 ), the holding action is carried out without executing the printing process regardless of the setting of the hold print information (Step S 16 ). More particularly, the printing data remains held in the HDD  112  until a correct password is entered from the operating panel  105 . It is then examined by the CPU  101  whether or not the password has been entered from the operating panel  105  (Step S 17 ). When the password is not entered (No at S 17 ), the operation stands by until the password is entered. When the password has been entered (Yes at S 17 ), the printing data is read out from the HDD  112  and subjected to the printing process (Step S 18 ). When it is judged that the security level is satisfied with the recommended value (Yes at S 15 ), the printing action is carried out according to the printing job (Step S 18 ).  
       FIGS. 8A and 8B  are explanatory diagrams explaining examples for calculating the security levels. In the printing job shown in  FIG. 8A , the user authentication information is specified by “Taro OO” and the document information is of “confidential mode”. As apparent from the security level calculating table  104   a  shown in  FIGS. 6A  to  6 E, the score (A) is  17  and the score (B) is  3 . Accordingly, the recommended value of the security is  20  for the printing job. Meanwhile, the printing job indicates that the hold print information is “general print” and the additional image information is of “confidential mode” while the printing data is encrypted. As the scores (C) to (E) are summed up, the security level is  11 . It is then apparent that the security level of the printing job shown in  FIG. 8A  fails to conform to the recommended value. As a result, the holding action is carried out without executing the printing process regardless of the setting of the hold print information because the security has to be maintained.  
      In the printing job shown in  FIG. 8B , the user authentication information is specified by “Jiro ((” and the document information is of “other mode”. As apparent from the security level calculating table  104   a  shown in  FIGS. 6A  to  6 E, the score (A) is  10  and the score (B) is  1 . Accordingly, the recommended value of the security is  11  for the printing job shown in  FIG. 8B . Meanwhile, the printing job indicates that the hold print information is “general print” and the additional image information is “tint block pattern A” while the printing data is encrypted. As summed up, the security level is  14 . It is apparent that the security level of the printing job shown in  FIG. 8B  successfully conforms to the recommended value. As a result, the printing action is carried out according to the printing job.  
      In this embodiment, when the security level fails to conform to the recommended value, the printing job is held but not executed until a correct password is entered for maintaining the security. Since the image forming apparatus  100  enables to maintain the security with the use of the additional image information and the encryption of the printing data, it may optionally carry out its desired action regardless of the calculated security level not conforming to the recommended value.  
      Embodiment 2  
      The previous embodiment allows the printing action to be carried out depending on the result of the comparison between the calculated security level and the recommended value defined by the printing job. Alternatively, the actions to be carried out may be predetermined in relation to different security levels respectively. This allows the action to be executed corresponding to the security level calculated. The system and its image forming apparatus  100  in this embodiment are identical to those of Embodiment 1 and will be explained in no more detail.  
       FIG. 9  is a diagram showing a list of the processes to be executed depends on the calculated security levels. In this embodiment, the security level is calculated from all the data in each printing job. More particularly, the sum of the scores (A) to (E) shown in  FIGS. 6A  to  6 E is used for calculating the security level. The table shown in  FIG. 9  indicates that, when the security level is higher than  20  (referred to as level A), the image data in the printing data is encrypted and held but not subjected to the printing action and after the printing action, is invalidated. When the security level is between  15  and  20  (referred to as level B), the image data in the printing data is held but not subjected to the printing action and after the printing process, is invalidated. When the security level is between  10  and  15  (referred to as level C), the image data after the printing action is invalidated. When the security level is lower than  10  (referred to as level D), no security action is made.  
      The table is saved in the management section  104  of the image forming apparatus  100  and used for determining the process corresponding to the different security levels which are calculated from the security level calculating table  104   a.    
       FIG. 10  is a flowchart explaining the steps of a process to be executed by the image forming apparatus  100 . The CPU  101  in the image forming apparatus  100  monitors the communications interface  109  and judges whether a printing job is received or not (Step S 21 ). When the printing job is not received (No at S 21 ), the action stands by until the printing job is received. When the printing job is received (Yes at S 21 ), it is expanded to identify the printing data and its attribute data (Step S 22 ). When the printing data is encrypted, it is decoded by the decrypting circuit  111 .  
      This is followed by calculating the security level of an image to be printed according to the printing job (Step S 23 ). In this embodiment, the security level is determined from the user authentication information, the document information, the hold print information, the additional image information, and the encryption data.  
      It is then examined whether or not the security level is satisfied with the level A (Step S 24 ). When the security level satisfied with the level A (Yes at S 24 ), the image data in the printing data is transferred to the encrypting circuit  110  for encryption (Step S 25 ) and its encrypted form is saved in the HDD  112 . The printing action is held but not executed until a correct password is entered (Step S 26 ). It is then examined whether or not the password is entered from the operating panel  105  (Step S 27 ). When the password is not entered (No at S 27 ), the operation is held until the password is entered. When it is judged that the password is entered (Yes at S 27 ), the encrypted image data is read out from the HDD  112 , decoded by the decrypting circuit  111 , and transferred to the image forming section  107  where it is subjected to the printing action (Step S 28 ). When the printing action has been completed, the image data saved in the HDD  112  is invalidated (Step S 29 ). The invalidation of the image data may be conducted by writing one or more times a zeroes or random data over the image data which can thus be deleted and not reproduced.  
      When it is judged at Step S 24  that the security level fails to conform to the level A (No at S 24 ), the procedure goes to Step S 30  where it is examined whether or not the security level is satisfied with the level B. When the security level is satisfied with the level B (Yes at S 30 ), the image data in the printing data is saved in the HDD  112  but not subjected to the printing action (Step S 26 ). When the password is entered (Yes at S 27 ), the image data is read out from the HDD  112  and transferred to the image forming section  107  where it is subjected to the printing action (Step S 28 ). This is followed by writing a zeroes or random data over the image data saved in the HDD  112  for invalidation of the image data (S 29 ).  
      When it is judged at S 30  that the security level fails to conform to the level B (No at S 30 ), the procedure goes to S 31  where it is examined whether or not the security level is satisfied with the level C. When the security level satisfied with the level C (Yes at S 31 ), the image data in the printing data is temporarily saved in the HDD  112  and subjected to the printing action (Step S 28 ). This is followed by writing a zeroes or random data over the image data saved in the HDD  112  for invalidation of the image data (S 29 ).  
      When it is judged at Step S 31  that the security level fails to conform to the level C (No at S 31 ) or the security level is satisfied with the level D, the procedure goes to Step S 32  where the image data in the printing data is directly subjected to the printing action without temporarily saved in the HDD  112 .  
       FIGS. 11A and 11B  are explanatory diagrams explaining examples for calculating the security levels. In the printing job shown in  FIG. 11A , the user authentication information is specified by “Taro OO” and the document information is of “confidential mode”. Also, the printing job indicates that the hold print information is “general print” and the additional image information is “confidential” while the printing data is encrypted. As calculated with the security level calculating table  104   a  shown in  FIGS. 6A  to  6 E, the security level of the image defined by the printing job is  31 . It is then apparent that the security level is satisfied with the level A in the table shown in  FIG. 9 . As a result, the image data is encrypted and held but not subjected to the printing action and after the printing action, is invalidated.  
      In the printing job shown in  FIG. 11B , the user authentication information is specified by “Jiro ((” and the document information is of “other mode”. Also, the hold print information is “general print” and the additional image information is “non” while the printing data is not encrypted. As calculated with the security level calculating table  104   a  shown in  FIGS. 6A  to  6 E, the security level of the image defined by the printing job is  14 . It is then apparent that the security level is satisfied with the level C in the table shown in  FIG. 9 . As a result, the image data is not encrypted and held but directly subjected to the printing action and after the printing action, is invalidated.  
      In this embodiment, the user authentication device  201  is used for providing the data processing terminal  200  with the user authentication information. The entry of the user authentication information is not limited to the user authentication device  201  but may be carried out by the data processing terminal  200  which displays a blank for entering the user authentication information on the print setting screen  20  during the setting of the printing job and allows the entry of the user authentication information from its operating panel. It would also be understood that the recording medium for carrying the user authentication information is not limited to an IC card or a card memory. Alternatively, the user authentication information may be received over a radio communications system, an infrared ray communications system, or a Blue-tooth system using mobile telephones, personal data assistants (PDAs), and wireless tag devices.  
      As this invention may be embodied in several forms without departing from the spirit of essential characteristics thereof, the present embodiment is therefore illustrative and not restrictive, since the scope of the invention is defined by the appended claims rather than by the description preceding them, and all changes that fall within metes and bounds of the claims, or equivalence of such metes and bounds thereof are therefore intended to be embraced by the claims.