JP2004266460A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus capable of preventing leakage of stored image data. <P>SOLUTION: In the image forming apparatus which forms an image based on the inputted image data, it is provided with a ciphering/decoding means for always ciphering the inputted image data by using a ciphering key to the image data in the case of storing the inputted image data in an image storage means and for decoding the ciphered image data in the case of reading the ciphered image data which is stored in the image storage means. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an image forming apparatus, and can be applied to an image forming apparatus having storage means for storing input data.
[0002]
[Prior art]
For example, a copying machine or the like stores the input data in a large-capacity storage device (HDD) in the copying machine, takes out the stored data from the storage unit, copies the data to a paper or the like based on the stored data, and outputs it.
[0003]
Therefore, the input data itself is stored in the storage means, and there is a security problem that, for example, after the storage means is stolen, the stored data can be maliciously extracted by using other devices or the like. . In particular, leakage of confidential documents is a problem.
[0004]
Conventionally, in order to solve such a problem, the following measures have been taken to prevent leakage of a confidential document.
[0005]
First, the first confidential document leakage prevention means has prevented leakage of a confidential document by, for example, prohibiting copying of a specific confidential document by a copying machine.
[0006]
Next, for example, when copying a document by a copying machine, when copying a document by a copying machine, a password or the like is given only to a user who is permitted to copy, and user authentication is performed based on the password or the like. In addition, image information stored in the copying machine cannot be accessed by copying by a person other than the authorized user, thereby preventing information leakage.
[0007]
[Patent Document 1]
JP-A-2002-50956
[0008]
[Patent Document 2]
JP 2001-325153 A
[0009]
[Problems to be solved by the invention]
However, according to the above-described confidential document leakage prevention means, there are the following problems.
[0010]
In the case of the first confidential document leakage prevention method described above, by prohibiting the copying of certain confidential documents, it is possible to prevent a copy of the confidential document by humans in the company from leaking outside the company, but to use it internally. In this case, the original function of the copying machine is restricted, and the convenience is impaired.
[0011]
Also, the following confidential document leakage prevention means can prevent unauthorized access for user authentication using a password or the like while the copying machine is energized, since the user authentication program is operating. If only the internal storage device (HDD) is removed and the HDD is connected to another device (for example, a personal computer) and the internal information is analyzed, the authentication program does not work and the internal information is easily Could be deciphered.
[0012]
By the way, for example, in the field of information communication using a network such as a facsimile, when performing information communication, in order to prevent information leakage on a transmission path, information is encrypted and transmitted.
[0013]
A common encryption method used at this time is that a common encryption key is determined in advance on the transmission side and the reception side, and information on transmission is encrypted on the transmission side based on the encryption key and the transmission path is encrypted. And the receiving side restores the received signal based on the encryption key. By doing so, the encryption key is not transmitted on the transmission path, and even if the encryption information leaks illegally, it cannot be decrypted.
[0014]
Therefore, the present invention provides an image forming apparatus capable of preventing leakage of a document by storing image data encrypted by using an encryption key with respect to input image data.
[0015]
[Means for Solving the Problems]
In order to solve such a problem, an image forming apparatus according to the present invention, in an image forming apparatus that forms an image based on input image data, always stores the input image data in an image storage unit when the image data is stored in an image storage unit. Encryption / decompression means for encrypting image data using an encryption key and for restoring the encrypted image data when reading the encrypted image data stored in the image storage means; It is characterized by having.
[0016]
BEST MODE FOR CARRYING OUT THE INVENTION
(A) First embodiment
Hereinafter, a first embodiment of the image forming apparatus of the present invention will be described with reference to the drawings.
[0017]
In the present embodiment, a digital copying apparatus (DPPC) will be described as an example of an image forming apparatus. However, an image forming apparatus (for example, a printer, a facsimile, Machine).
[0018]
(A-1) Configuration of First Embodiment
FIG. 1 schematically shows the configuration blocks of a digital copying apparatus according to the present embodiment.
[0019]
The image forming and storage apparatus according to the present embodiment includes a system control unit 1 that controls the entire apparatus, a scanner subsystem 2 that converts a document into a digital signal and outputs digital signal image data, and a digital signal image data. A printer subsystem 4 for printing an image on paper based on the output and a control panel 7 for displaying the status of the image forming apparatus such as a paper jam and for inputting various parameters and operation modes when the user performs copying. It is provided with.
[0020]
The scanner subsystem 2, the printer subsystem 4, and the control panel 7 are equipped with CPUs 203, 43, and 74, respectively. These CPUs 203, 43, and 74 are serially connected to the system CPU 10 of the system control unit 1 that performs overall control. Control information is transmitted and received via the IF to control each block.
[0021]
As shown in FIG. 1, the system control unit 1 has two board configurations including a system control circuit 5 and an HDD block 80 capable of storing a plurality of image data. That is, each unit is composed of different units.
[0022]
The system control circuit 5 includes a system CPU 10, a main memory 12, a ROM 11, an NVRAM 14, a page memory control circuit 30, and a LAN controller 60.
[0023]
The system CPU 10, the main memory 12, the ROM 11, and the NVRAM 14 are connected via a local bus 15. Further, the system CPU 10, the HDD block 80, the page memory control circuit 30, and the LAN controller 60 are connected via the system bus 9.
[0024]
Hereinafter, each of the internal configurations of the system control circuit 5 will be described.
[0025]
The system CPU 10 controls the entire apparatus. The detailed internal configuration of the system CPU 10 will be described later.
[0026]
The ROM 11 stores a control program for controlling the entire apparatus. The control program stored by the system CPU 10 is read from the ROM 11 according to a predetermined rule when the power is turned on, and the boot process is performed by the control program.
[0027]
The main memory 12 is configured by a volatile DRAM, and stores a control program loaded from the ROM 11 by the system CPU 10 in a predetermined area when the power is turned on. The main memory 12 operates the stored control program while the power is on. When performing encryption processing of an encryption key used for encrypting or restoring image data (the encryption key encryption processing will be described later), the main memory 12 generates a random number generated according to a predetermined random number generation function. Is stored as an encryption key.
[0028]
The NVRAM 14 backs up with a battery that stores a set value for each machine. The NVRAM 14 stores a random number temporarily stored in the main memory 12 in a specific area.
[0029]
The page memory control circuit 30 temporarily stores image data (digital signals) in page units. The page memory control circuit 30 includes a page memory 300 that temporarily stores image data for each page, and a page memory control unit 301 that controls the page memory 300. The page memory control circuit 30 performs a compression process of image data and a decompression process of the compressed image data, which will be described later, in response to a request. The internal configuration of the page memory 301 will be described later.
[0030]
The LAN controller 60 interfaces transmission and reception of image data between a terminal (for example, a personal computer or the like) connected to a network (not shown) and the image forming storage device.
[0031]
Next, the internal configuration of the HDD block 80 will be described.
[0032]
The HDD block 80 includes a large-capacity storage device (hereinafter referred to as HDD) 830, an encryption / decompression circuit 810, an encryption key memory 820, and an IDE controller 800.
[0033]
The HDD 830 stores a plurality of image data encrypted by the encryption circuit 810.
[0034]
The encryption / decompression circuit 810 receives the image data subjected to the compression processing by the page memory control circuit 30 via the IDE controller 800, encrypts the compressed image data based on the encryption key, and performs encryption. The image data is stored in the HDD 830. Further, the encryption / decompression circuit 810 reads the encrypted image data stored in the HDD 830, restores the encrypted image data based on the encryption key, and restores the restored image data (ie, the original image data). Is given to the IDE controller.
[0035]
Here, the encryption method performed by the encryption / decryption circuit 810 can be widely applied as long as the encryption / decryption method is performed using an encryption key.
[0036]
The encryption key memory 820 is a volatile memory that stores an encryption key used for encrypting and restoring image data. At the time of encrypting and restoring image data by the encryption / decompression circuit 810, the encryption key stored in the encryption key memory 820 is read by the encryption / decompression circuit 810.
[0037]
The IDE controller 800 is an interface between the system bus 9, the HDD 830, the encryption circuit 810, the encryption key memory 820, and the system bus 9. The IDE controller 800 receives the compressed image data from the page memory control circuit 30 via the system bus 9 and supplies it to the encryption / decompression circuit 810. Further, the IDE controller 800 supplies the image data restored by the encryption / decryption circuit 810 to the page control circuit 30 via the system bus 9.
[0038]
Next, the internal configuration of the system CPU 10 of the above-described system control circuit 5 will be described. FIG. 2 is a block diagram showing the internal configuration of the system CPU 10.
[0039]
As shown in FIG. 2, the system CPU 10 includes a CPU core 100 that executes a control program of the ROM 11, a DRAM controller 101 that controls the main memory 12 (SDRAM) on the local bus 15, and a ROM 11 on the local bus 15. And a local bus I / F 103 for interfacing the local bus 15, the SDRAM controller 101 and the ROM controller 102, and inputting an interrupt from each block on the device, and based on a predetermined priority order. An interrupt controller 104 for notifying the CPU core 100 of only one interrupt, and a three-channel interface for communication between the scanner CPU 203, the printer CPU 43, the control panel CPU 74, and the CPU core 100. Serial I / O (SIO) 105, a system bus controller 106 for interfacing each block on the system bus 9 with each block on the system control unit 1, a timer 107, a CPU core 100, and each of these system CPUs 10. It has an internal bus 108 for connecting blocks (DRAM controller 101, ROM controller 102, interrupt controller 104, 3-channel serial I / O (SIO) 105, system bus controller 106, timer 107).
[0040]
Next, an internal configuration of the page memory control unit 301 of the page memory control circuit 30 described above will be described. FIG. 3 shows the internal configuration of the page memory control unit 301.
[0041]
As shown in FIG. 3, the page memory control unit 301 includes a system bus interface (system bus IF) 32 for interfacing each internal block with the system bus 9, an LCD controller 33, an LED controller 34, and a page memory. 300, and between the page memory 300 and a printer sub-unit 4 connected via a scanner image IF 92 to a scanner sub-unit 2 connected via a scanner image IF 92 to a device described later on the system bus 9 Has a PM-CON 35 for controlling the transfer of image data.
[0042]
The PM-CON 35 arbitrates an access request from a device accessing the page memory 300 in a predetermined priority order, and accesses the page memory 300 based on the sequential access request.
[0043]
A device that accesses the page memory 300 includes a scanner image processing unit 202 that writes image data to the page memory 300 via the scanner image IF 92 and a printer image processing unit that reads image data on the page memory 300 via the printer image IF 91 41, a system CPU 10, an LCD controller 33, and an IDE controller 800 for storing image data in the page memory 300 in the HDD 830 or returning image data stored in the HDD 830 to the page memory 300.
[0044]
The page memory 300 is provided with a display data area for storing display data to be displayed on the LCD 70 in addition to an area for temporarily storing image data, and the LCD controller 33 periodically displays the display data. The display data stored in the area is read out, and the display data is output to the LCD 70 in synchronization with a synchronization signal output from the LCD 70 on the control panel 7. The LCD 70 sequentially displays the display data.
[0045]
Next, the internal configuration of the PM-COM 35 of the page memory 300 will be described. FIG. 4 is a configuration diagram showing the internal configuration of the PM-COM 35.
[0046]
The PM-COM 35 includes a transfer channel that interfaces data transfer between the page memory 300 and another processing block, a data processing block (compression processing 3530 and decompression processing 3531), a rotation processing 3532, and a page memory for each transfer channel. It has an address generator for generating 30 addresses and a PDRAM controller 36.
[0047]
The transfer channels are the scanner IF 3501, the printer IF 3509, the HDD transfer (ch0) 3504, the HDD (ch1) 3506, the compression (input) 3502, the compression (output) 3503, the decompression (input) 3507, and the decompression (input). Output) 3508, a memory clear 3510, a CPU IF 3511, and an LCD IF 3512.
[0048]
Also, the address generation unit includes AGC (ch0) 3520, AGC (ch1) 3521, AGC (ch2) 3522, AGC (ch3) 3523, AGC (ch4) 3524, AGC (ch5) 3525, and FIFO. It has (ch1-A) 3526, FIFO (ch1-B) 3527, FIFO (ch0-A) 3528, and FIFO (ch0-B) 3529.
[0049]
The function of each component of the PM-COM 35 in FIG. 4 will be described in detail in the following description of operation.
[0050]
Returning to FIG. 1, the scanner subsystem 2 at least scans the original optically in line units and converts it into an electric signal in synchronization with the original transport, and a document transport unit (not shown) which transports the original at a predetermined timing. After converting the CCD 201 and the electric signal output from the CCD 201 into predetermined pixels (for example, 8 bits / pixel), and performing image processing suitable for a designated image mode such as a character mode, a character photograph mode, and a photograph mode, 1 bit / It has a scanner image processing unit 202 that performs gradation processing on pixel data and outputs image data to the page memory control unit 3 via the scanner image IF 92 at a predetermined timing, a scanner CPU 203 that controls the scanner subunit 2, and the like. Things.
[0051]
The printer subsystem 4 reads at least image data temporarily stored in the page memory 300 at a predetermined timing via the printer image IF 91 and performs image processing in a specified mode. A laser drive circuit 42 that converts image data from the printer image processing unit 41 into an optical signal; and an image is formed by an electrostatic recording method based on the optical signal of the laser drive circuit 42 and transferred to a predetermined sheet. It has an image forming unit (not shown) for outputting, a printer CPU 43 for controlling the printer subsystem 4, and the like.
[0052]
The control panel 7 includes an LCD 70 that displays the state of the machine or information on various parameters, a touch panel 71 disposed on the LCD 70, a numeric keypad (Key) 72, a plurality of LED units 73, And a panel CPU 74 for controlling the respective components of FIG.
[0053]
In the present embodiment, the touch panel 71 and the Key 72 are provided as input means. However, the present invention can be widely applied as long as the input operation is performed by the user.
[0054]
(A-2) Operation of the first embodiment
Hereinafter, the operation of the image forming apparatus according to the first embodiment will be described with reference to the drawings.
[0055]
First, a copy sequence will be described with reference to FIG.
[0056]
The scanner IF 3501 fetches image data (for example, image data in units of 8 pixels) from the scanner subsystem 2 in synchronization with a synchronization signal output from the scanner subsystem 2 and transfers the image data to the page memory 300 (for example, At the time when the data of 32 pixels) is taken in, a transfer request is output to the PDRAM control unit 36.
[0057]
The scanner IF 3501 sends the image data and the address generated by the address generation channel AGC (ch0) 3520 corresponding to the scanner transfer channel to the PDRAM control unit 36 in synchronization with the data transfer permission signal output from the PDRAM control unit 36. Output.
[0058]
The PDRAM control unit 36 arbitrates transfer requests of each transfer channel, and determines a transfer-permitted channel according to a priority such as round robin.
[0059]
In the case of a write process from the transfer channel to the page memory 300, the PDRAM control unit 36 first outputs a transfer permission signal to the transfer channel that has permitted the transfer, and outputs the image data from the transfer channel in synchronization with this signal. And address.
[0060]
Next, the PDRAM control unit 36 converts the received address into an address corresponding to the SDRAM constituting the page memory 300, generates a control signal also corresponding to the SDRAM, and places the received signal in an area corresponding to the address. Write the image data.
[0061]
The address generation units (AGC (ch0) 3520, AGC (ch1) 3521, AGC (ch2) 3522, AGC (ch3) 3523, AGC (ch4) 3524, and AGC (ch5) 3525) are two-dimensional corresponding to a document or paper. , And is composed of two counters, a main scanning address counter and a sub-scanning address counter.
[0062]
The main scanning address counter counts up each time access to the corresponding transfer channel is permitted to the PDRAM control unit 36 and the access is completed. When the main scanning address counter reaches a predetermined set value of a document or a sheet, the sub-scanning address counter is counted up and the main scanning address counter is cleared.
[0063]
By repeating such processing, when both the sub-scanning address counter and the main scanning address counter reach a predetermined set value of the original or paper, one page transfer is completed, and the sub-scanning address counter and the The main scanning address counter is cleared, and at the same time, the completion of one page access is notified to the system CPU 10 via the page memory end interrupt 1201.
[0064]
As a result, the image data read by the scan subsystem 2 is stored on the page memory 300.
[0065]
Next, compression processing of image data stored on the page memory 300 will be described.
[0066]
When a request is output from the compression (input) channel 3502 to the PDRAM control unit 36 in response to an input request from the compression processing unit 3530, the image data on the page memory 300 is read, and the image data is subjected to the compression processing. Section 3530.
[0067]
At this time, the setting of the address generation unit AGC (ch1) 3521 used is the same as the setting of the address generation unit AGC (ch0) 3520 used when receiving the image data from the scanner subsystem 2. Image data transferred from the system 2 and stored in the page memory 300 is compressed by the compression processing unit 3530.
[0068]
If the image data (hereinafter also referred to as compressed data) compressed by the compression processing unit 3530 can be output to the page memory 300 (that is, if there is compressed data of a unit (for example, 32 bits) to be written to the page memory 300), A data output request is output from the compression processing unit 3530 to the compression (output) channel 3503, and the compression output channel 3503 writes the compressed data to the page memory 300 in the same manner as the scanner channel 3501.
[0069]
The address generation units (FIFO (ch1-A) 3528, FIFO (ch1-B) 3529, FIFO (ch0-A) 3526, and FIFO (ch0-B) 3527) are one-dimensional address generation channels, each of which has an initial address and an initial address. A register (not shown) for setting the last address, and a loop counter (not shown) for counting up the address for each access from the initial address, loading the initial address when reaching the final address, and counting up again from the initial address No).
[0070]
Also, the FIFO (ch1-A) 3528 and the FIFO (ch1-B) 3529, and the FIFO (ch0-A) 3526 and the FIFO (chO-B) 3527 form one pair, respectively, for two channels (ch0, ch1). Execute the FIFO counter operation.
[0071]
Here, the FIFO counter operation is an operation for adjusting the read operation of the page memory 300 so as not to overtake the write operation of the page memory 300. For example, the FIFO counter operation in ch0 will be described as an example. , FIFO (ch0-A) 3526 performs a write operation to the page memory 300 and a FIFO (ch0-B) 3527 performs a read operation, the FIFO (ch0-B) 3527 reads the page memory 300 from the FIFO (ch0-B) 3527. When the counter value of the FIFO (ch0-B) 3527 becomes equal to the counter value of the FIFO (ch0-A) 3526, the FIFO (ch0-B) 3527 does not overtake the writing by the ch0-A) 3526. An operation for waiting for read access is performed.
[0072]
In this case, the FIFO (ch0-A) 3526 performing the write operation monitors the difference between the counter values of the two, and if the difference between the counter values is equal to “final address−initial address”, the read operation is performed. Before the FIFO (ch0-B) 3527 reads the data, the FIFO (ch0-A) 3526 overwrites the data and the data is lost. To avoid this, the FIFO (ch0-B) 3526 is used. -A) An operation of waiting for the request of 3526 is performed.
[0073]
Thus, the FIFO (ch0-B) 3527 on the reading side can read only the compressed data that has been compressed by the compression processing unit 3530 from the page memory 300.
[0074]
The HDD transfer channels 3504 and 3506 interface data transfer between the HDD 830 and the page memory 300. The HDD (ch0) 3504 outputs a transfer request to the PDRAM control unit 36 if compressed data can be input. Fetches the compressed data from the page memory 300.
[0075]
When the compressed data is taken into the HDD (ch0) 3504, the IDE controller 800 acquires the control right of the system bus 9, and the compressed data in the HDD (ch0) 3504 is transmitted to the encryption circuit 810 via the system bus 9. Is output.
[0076]
In the encryption circuit 810, the compressed data from the HDD (ch 0) 3504 is subjected to an encryption process based on an encryption key stored in the encryption key memory 820 before power-on.
[0077]
Here, the encryption method uses DES (Data Encryption Standard) generally used in data communication. The encryption method is not limited to this, and can be widely applied as long as the encryption method is a reversible encryption method that can recover encrypted data.
[0078]
The encrypted code (encrypted image data) is written to the HDD 830 by the encryption circuit 810.
[0079]
By repeating such processing, the compression processing of one page is completed, and the compression processing operation ends.
[0080]
Next, the operation of decompressing and printing the encrypted code written in the HDD 830 will be described. The decompressed printing operation of the encryption code operates in the reverse order of the above-described compression processing operation.
[0081]
First, the corresponding compressed and encrypted image data (encryption code) is read out from the HDD 830 by the encryption circuit 810, and based on the encryption key stored in the encryption key memory 820, The encryption code is decrypted, restored to the original compressed data, and the restored compressed data is provided to the IDE controller 800.
[0082]
The IDE controller 800 outputs a transfer request to the system CPU 10 to acquire the system bus 9, and during the transfer permission period, the compressed data from the encryption circuit 810 is transmitted via the system bus 9 to the HDD (ch 1) in the PM-CON 35. Is transferred to 3506)
Here, the system bus controller 106 in the system CPU 10 arbitrates transfer requests from the devices on the system bus 9 and permits the IDE controller 800 to transfer when the order of the IDE controller 800 is reached.
[0083]
If data can be input, the HDD (ch1) 3506 fetches compressed data from the HDD 830 in response to a transfer request from the IDE controller 800. If the data input in the above process exists in the HDD (ch1) 3506, a transfer request is output to the PDRAM control unit 36, and the compressed data is written to the page memory 300.
[0084]
If data can be taken into the channel, the decompression (input) channel 3507 outputs a request to the PDRAM control unit 36, and compresses the compressed data from the HDD 830 taken into the page memory 300 by the HDD (ch1) 3506. The compressed data is read from the page memory 300 and transferred to the decompression processing unit 3531.
[0085]
The decompression processing unit 3531 decompresses the compressed data using a predetermined algorithm.
[0086]
If the decompressed data after the decompression process can be output, the decompression processing unit 3531 outputs a request to the decompression (output) 3508 and provides the decompression data to the decompression (output) 3508.
[0087]
The decompression (output) 3508 outputs a request to the PDRAM control unit 36 and writes the received decompression data to the page memory 300.
[0088]
By repeating such processing, the decompression processing operation is completed when the decompression processing of one page is completed.
[0089]
If there is no rotation printing instruction, the printer IF 3509 reads out the image data stored in the print area on the page memory 300 using the AGC (ch2) 3522. If there is a rotation printing request, the printer IF 3509 rotates. After the rotation processing in the unit 3532, the image data is output to the printer subsystem 4 in synchronization with the synchronization signal output from the printer subsystem 4.
[0090]
Next, a boot sequence of the image forming apparatus according to the present embodiment will be described with reference to FIGS.
[0091]
FIG. 6 shows a memory map of the system CPU 10 and the contents of the memory inside the boot ROM 11. FIG. 7 shows a processing sequence of the boot program.
[0092]
When the power is turned on, the system CPU 10 starts access from the address I where the boot program is stored on the memory map in FIG.
[0093]
First, the system CPU 10 initializes each block inside the system CPU 10 shown in FIG. 2 (S21).
[0094]
The OS unit, the application unit, and the display data are sequentially read from the ROM 11 and are copied to a predetermined area on the main memory 12 (S22 to S24).
[0095]
The system CPU 10 starts the main task from the application program copied on the main memory 12 and completes the boot process (S25).
[0096]
Next, a software configuration related to the operation of the image forming apparatus according to the present embodiment will be described with reference to FIG. FIG. 5 shows a software configuration related to the operation of the image forming apparatus. Note that the library layer and the driver layer shown in FIG. 5 belong to the OS section of the ROM 11 in FIG.
[0097]
The main task started by the boot process described above starts an application task.
[0098]
An application task started by the main task includes a copy application for controlling a copy process, a LAN printer print application for controlling a print operation in response to a print request from a terminal (for example, a personal computer) connected to a network, and a control application. There are various user interfaces (UI) for controlling an interface with a user via the panel 7, and a self-diagnosis app that operates when the machine is started in the adjustment mode.
[0099]
As a user interface (UI), there is a machine UI for notifying a user via the LCD of a machine state such as displaying a jam location on an LCD when a jam occurs.
[0100]
The copy UI and the Printer UI provide an interface for the user to set parameters and the like for the copy operation and the LAN-Printer operation, and control for notifying the user of each operation state of the copy operation and the LAN-Printer operation. Do.
[0101]
The Windows (registered trademark) System performs multi-window control of display information from each UI, and performs display management on the LCD.
[0102]
The self-diagnosis application that operates when started in the self-diagnosis mode is for setting an adjustment value unique to a machine. A typical example is a shading correction value of a scanner.
[0103]
In the present embodiment, the process of inputting the encryption key and generating and encrypting a random number with respect to the encryption key, and storing the encryption key and the random number in one area of the NVRAM 14 are executed as one function of the self-diagnosis mode.
[0104]
Next, the encryption key is encrypted in the self-diagnosis mode, the encrypted encryption key and the random number are stored in the NVRAM 14, the encryption key is read out from the NVRAM 14 in the normal operation mode, and the encryption key is stored in the encryption key memory 820. The storing process will be described with reference to FIG. FIG. 8 is a schematic flow of the control program of the machine.
[0105]
When the power of the machine is turned on, the above-described boot processing is performed (S1).
[0106]
During the boot process, initial settings inside the system control unit 1 and the control panel 7 shown in FIG. 1 are performed (S2).
[0107]
After the boot process, when the control program starts operating on the main memory 12, it is confirmed whether or not there is a key input in the main task (S3).
[0108]
At this time, if no key is pressed when the power is turned on, the operation shifts to the normal operation mode. If the key is pressed, the operation shifts to the self-diagnosis mode (S4). ).
[0109]
For example, a specific key to be pressed to shift to the self-diagnosis mode is predetermined. For example, when the specific key is a simultaneous press of “1” and “9”, when the power is turned on, the user If the numeric keys “1” and “9” of the Key 72 are pressed simultaneously, the mode shifts to the self-diagnosis mode (S5).
[0110]
In the self-diagnosis mode, a screen display of the self-diagnosis mode is displayed on the LCD 70, and a display for inputting the number of the self-diagnosis function is made, and the apparatus enters a standby state.
[0111]
When a function number other than the encryption key encryption processing is input, a self-diagnosis function determined based on the input function number is executed (S10).
[0112]
For example, when the number of the encryption key encryption processing is “123”, and when the user inputs “123”, the process proceeds to the encryption key encryption processing (S6).
[0113]
First, an encryption key is displayed on the LCD 70 so as to be input from the Key 72. When the user inputs the encryption key, the encryption key code is temporarily stored in the main memory 12, a random number is generated by a random number generation function prepared as software, and the random number is also stored in the main memory 12 once ( S7).
[0114]
Next, the encryption key code is encrypted using the random number as an encryption key (S8).
[0115]
The encryption method at this time uses the above-mentioned DES, and is executed by the system CPU 10 as software.
[0116]
Next, the encrypted encryption key and the random number are stored in a predetermined specific area of the NVRAM 14, which is a nonvolatile memory (S9).
[0117]
Finally, the completion of the storage of the encryption key code is displayed on the LCD 70 to notify the user, and at the same time, the same is displayed on the LCD 70 to notify the user to turn off the power (S11).
[0118]
This processing is completed when the power is turned off by the user based on this instruction (S12).
[0119]
When the power is turned on, if the user has not pressed any key of the KEY 72, the mode shifts to the normal mode after the boot process (return to S4).
[0120]
First, in the normal mode, the system CPU 10 issues a command to initialize the scanner subunit 2 and the printer subunit 4 (S13).
[0121]
Next, the system CPU 10 reads the encrypted encryption key and the random number stored in the NVRAM 14 (S14), and decrypts the encryption key using the random number as a key (S15).
[0122]
Next, the system CPU 10 sets the decrypted encryption key in the volatile encryption key memory 820 via the system bus 9 (S16).
[0123]
Next, the system CPU 10 waits for completion of the initialization (end) from the scanner subunit 2 and the printer subunit 4, and confirms that the completion (end) notification has been received and that the other blocks are in the ready state. Then, the LCD 70 displays the "ready" state, and stands by in a request waiting state (S17 and S18).
[0124]
When the user presses the copy start key of the key 72, the system CPU 10 executes the above-described copy sequence assuming that there is a copy request, and enters a standby state when the processing is completed (19).
[0125]
When the power is turned off in the request waiting state (S20), the power of the machine is turned off by executing a power-off process (S11).
[0126]
Key input from the control panel 7 is performed by the panel CPU 74 periodically checking the touch panel 71 and the Key 72. If a key is pressed at the time of checking, the panel CPU 74 generates a code corresponding to the pressed key. Is transmitted to the system CPU 10 via the serial IF 1100.
[0127]
The serial I / O (SIO) 105 in the system CPU 10 receives the transmitted code data and notifies the CPU core 100 via the interrupt controller 104 that the received code is present.
[0128]
The CPU core 100 recognizes the pressed key by reading the received data from the SI 0105.
[0129]
(A-3) Effects of the first embodiment
As described above, according to the present embodiment, by providing the encryption / decryption circuit 810, the image data encrypted based on the encryption key is stored in the HDD 830, so that even if the HDD 830 is stolen, the encrypted data is restored. Since it is necessary to decrypt the data, simple data leakage can be prevented.
[0130]
In addition, an NVRAM 14 which is a non-volatile memory on a circuit board different from the HDD and its peripheral control circuit board is provided, and by storing the encryption key used for encryption in the NVRAM 14, only the HDD and its peripheral control circuit are provided. Even if it is stolen, the encryption key itself can be prevented from being stolen, so that it is difficult to decrypt the encrypted data.
[0131]
Further, the encryption key code stored in the NVRAM 14 which is a non-volatile memory is encrypted based on a random number code which is stored in another area of the same NVRAM 14 and previously generated by random number generation at the time of machine shipment. Therefore, the NVRAM 14 is stolen at the same time as the HDD, and it is difficult to decrypt the encryption key from the data stored in the NVRAM 14.
[0132]
(B) Second embodiment
The second embodiment is different from the first embodiment in that an encryption key used for encrypting image data is subjected to a predetermined compression process, and the encrypted encryption key (compressed encryption key) is stored in NVRAM. Different from the embodiment.
[0133]
Therefore, in the following, the system control circuit 5 will be described in detail, and detailed description of the other components will be omitted. Further, in the second embodiment, the description will be made by using the configuration requirements and reference numerals in FIG. 1 as they are.
[0134]
(B-1) Configuration and operation of the second embodiment
FIG. 9 is a flowchart illustrating the operation of the second embodiment.
[0135]
In FIG. 9, the operation from power-on (S1) to determination (S4) of whether the mode is the normal mode or the self-diagnosis mode based on the Key input confirmation is the same as that of the first embodiment (S1). ~ S4). In this embodiment, the encryption key compression process is executed as one function of the self-diagnosis mode.
[0136]
When the mode is shifted to the self-diagnosis mode and the user inputs the function number of the encryption key compression process, the mode shifts to the compression mode (S91).
[0137]
First, an encryption key is input by the user via the Key 72, and the input encryption key temporarily stores the encryption key (S92).
[0138]
Next, the encryption key is given to the compression processing unit 3530 of the page memory control unit 35, and the encryption key is compressed by the compression processing unit 3530 (S93).
[0139]
Here, the compression processing method of the encryption key is performed, for example, as follows.
[0140]
When the encryption key is given to the compression processing unit 3530, the number of bits of the encryption key is adjusted to be equal to the number of unit bits of an area where compression processing can be performed. For example, when the number of bits of the encryption key is smaller than the unit number of bits of the area where the compression processing can be performed, the encryption key is positioned at the head of the compression processing area and “all 0 (or all 1)” is set in the remaining area. Is inserted, the encryption key is adjusted in units of the compression processing area.
[0141]
When the adjustment is performed in units of the compression processing area, the compression processing is performed by the compression processing unit 3530. The encryption key compression processing method of the present embodiment will be described assuming that the method used for image data compression processing is used as it is. However, if compression processing and decompression processing are reversible, any method is used. There may be.
[0142]
The encryption key (compressed encryption key) thus compressed by the compression processing unit 3530 is provided to the NVRAM 14 and stored in a predetermined area of the NVRAM 14 (S94).
[0143]
Subsequent operations are the same as in the first embodiment, and a description thereof will be omitted.
[0144]
Next, if it is determined that the operation mode is the normal operation mode based on the confirmation of the Key input at the time of power-on, the compression encryption key stored in the NVRAM 14 is expanded as described below.
[0145]
A command is given to shift to the normal mode and proceed with initialization of the scanner subsystem 2 and the printer subsystem 4 (S13).
[0146]
Next, in response to a command from the system CPU 10, the compressed encryption key stored in the NVRAM 14 is provided to the page memory control unit 301, and the decompression processing unit 3531 performs the decompression processing of the compressed encryption key (S95).
[0147]
This decompression process is performed in the same manner as the decompression process of the image data in the first embodiment. If the decompression (input) channel 3507 can take in data in the channel, a request is made to the PDRAM control unit 36. Then, the data of the compression encryption key is provided from the page memory 300 to the decompression processing unit 3561.
[0148]
Subsequent operations are the same as in the first embodiment, and a description thereof will be omitted.
[0149]
(B-2) Effects of the second embodiment
As described above, according to the second embodiment, the same effects as those of the first embodiment can be obtained.
[0150]
Further, according to the second embodiment, since the NVRAM 14 stores a result of performing a compression process on the encryption key, even if the NVRAM 14 is stolen and the stored compressed encryption key is read, Since it is necessary to expand the compressed encryption key, decryption of the encryption key becomes difficult, and data leakage can be prevented.
[0151]
(C) Other embodiments
(C-1) In the above-described first embodiment, as for the encryption key, the generated random number and the encrypted encryption key are described as being stored in the NVRAM 14. However, even if the NVRAM 14 is stolen, the encryption key is stored. It is only necessary that the NVRAM 14 be able to store a format that is not easily understood.
[0152]
For example, for an encryption key for encrypting image data, the NVRAM stores an encryption key that has been encrypted using a different encryption key, and stores the encryption key used for encrypting this encryption key in another storage device. You may make it memorize | store in a means (nonvolatile).
[0153]
【The invention's effect】
As described above, according to the image forming apparatus of the present invention, in an image forming apparatus that forms an image based on input image data, when the input image data is stored in an image storage unit, the image data is always encrypted. When the encrypted image data stored in the image storage unit is read out while being encrypted using the key, the encryption / decompression unit for restoring the encrypted image data is provided. Leakage of image data can be prevented.
[Brief description of the drawings]
FIG. 1 is a block diagram illustrating an internal configuration of an image forming apparatus according to a first embodiment.
FIG. 2 is a block diagram illustrating an internal configuration of a system CPU 10 according to the first embodiment.
FIG. 3 is a block diagram illustrating an internal configuration of a page memory control unit 301 according to the first embodiment.
FIG. 4 is a block diagram illustrating an internal configuration of a PM-COM 35 according to the first embodiment.
FIG. 5 is an explanatory diagram illustrating a software configuration of the image forming apparatus according to the first embodiment.
FIG. 6 is an explanatory diagram showing a memory map of a system CPU 10 and contents of an internal memory of a ROM 11 according to the first embodiment.
FIG. 7 is a processing sequence of a boot program according to the first embodiment.
FIG. 8 is a flowchart of a control program of the image forming apparatus according to the first embodiment.
FIG. 9 is a flowchart of a control program of the image forming apparatus according to the second embodiment.
[Explanation of symbols]
1 ... System control unit, 80 ... HDD block, 810 ... Encryption / decryption circuit.

Claims (6)

In an image forming apparatus that forms an image based on input image data,
When the input image data is stored in the image storage unit, the image data is always encrypted using an encryption key, and the encrypted image data stored in the image storage unit is encrypted. An image forming apparatus comprising: an encryption / restoration unit for restoring the encrypted image data when reading. A nonvolatile storage unit for storing the encryption key,
The encryption / decompression unit stores the image data in the image storage unit and / or reads the image data from the image storage unit, and temporarily stores the encryption key from the nonvolatile storage unit. The image forming apparatus according to claim 1, wherein the image is taken into a unit. The image forming apparatus according to claim 2, wherein the encryption / decompression unit and the non-volatile storage unit are provided in separate units. The image forming apparatus according to claim 1, further comprising an encryption key forming unit configured to generate a random number and form an encryption key including at least a part of the generated random number. An encryption key compression / expansion processing means for compressing or expanding the encryption key by a predetermined compression / expansion processing method,
The image forming apparatus according to any one of claims 1 to 4, wherein the non-volatile storage means stores a compressed encryption key and reads out the compressed encryption key when using the encryption key. . 6. The image forming apparatus according to claim 5, wherein said encryption key compression / expansion processing means applies image compression / expansion processing means for performing image data compression / expansion processing.

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