JP2001270198A - Printing data distribution system and printer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a printing data distribution system capable of distributing printing data in a form incapable of performing copying or processing and capable of performing only printing. SOLUTION: The printing data distribution system includes a printer 10 having a function for outputting the open key corresponding to a secret key held itself and a function for decoding and printing encoded printing data being distribution printing data, which is encoded using the open key, using the secret key and a data distribution center 50 wherein the printer 10 forms the encoded printing data, which can be decoded by the secret key, using the open key when the data distribution center receives a data delivery demand including the open key outputted by the printer 10 from a host computer 40.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a print data distribution system and a printing apparatus.

[0002]

2. Description of the Related Art As is well known, a general computer is configured to transmit and receive various electronic data via a portable recording medium such as a floppy disk, an MO, or the Internet. At that time, the electronic data is also encrypted for confidentiality.

[0003]

If electronic data is transmitted and received using an encryption technique, the electronic data created by one computer is intercepted before being read by another computer. Can be prevented. However, even if the electronic data is encrypted and transferred,
It is impossible to prevent the recipient of the encrypted data from copying or processing the decrypted electronic data.

That is, a conventional system for transmitting and receiving electronic data using an encryption technique cannot guarantee that copying or processing of electronic data is not performed on the receiver side. As a result, it has been difficult to prove that the print result of the electronic data has not been altered.

An object of the present invention is to provide a print data distribution system capable of distributing print data (electronic data for printing) in a form that cannot be copied or processed, and to constitute such a print data distribution system. A printing device that can be used is provided.

[0006]

According to the present invention, there is provided a communication apparatus for communicating a print data distribution system with a device connected via a first communication medium. Printing means for printing on paper in accordance with the supplied data in a predetermined format, information storage means for storing a public key and a secret key for decrypting information encrypted using the public key; Request responding means for returning the public key stored in the information storage means to the transmission source of the public key provision request using the communication means when the public key provision request is received by the communication means; When the data is received by the communication means, the encrypted print data is decrypted using the secret key stored in the information storage means, and data in a predetermined format is generated and printed based on the decryption result. A printing apparatus that includes a print data processing unit that generates data in a predetermined format based on the print data and supplies the generated data to the printing unit, when the print data is supplied to the unit and the unencrypted print data is received by the communication unit; Generating encrypted print data that allows print data processing means of the printing apparatus to generate data in a predetermined format based on print data to be printed by the printing apparatus using a given public key; And a print data supply device comprising the means.

In this print data distribution system, the printing of the encrypted print data generated by the print data supply device can be performed only by the public key used to generate the encrypted print data and the secret key corresponding to the public key. The key is limited to the printing device storing the key in the information storage means. Therefore,
With this print data distribution system, print data can be
It can be distributed in a form that only printing can be performed without copying or processing. In addition, the printed matter output from the printing apparatus as a result of processing the encrypted print data can guarantee that the contents have not been altered. Therefore,
If the print data distribution system is used to deliver print data related to a certificate or the like, an extremely reliable certificate or the like can be printed.

In configuring the print data distribution system of the present invention, data transmission and reception between the printing apparatus and the print data apparatus may be performed by any means. For example, the transmission and reception of data between the printing apparatus and the print data supply apparatus may be directly performed via some communication medium (the communication means in the printing apparatus may be directly connected to the print data supply apparatus). May be communicated with). Further, the printing device exchanges information with a host computer connected by the communication unit,
The information exchange between the host computer and the print data supply device may be performed using a portable recording medium such as a floppy disk.

[0009] It is also possible that the transfer of data between the printing apparatus and the print data supply apparatus is performed indirectly via a host computer connected to the printing apparatus and the second communication medium. That is, the print data delivery system includes a host computer connected to a printing apparatus, and the public key is transmitted from the host computer via a second communication medium as encrypted print data generation means of the print data supply apparatus. May be used to generate encrypted print data when the received print data is received, and to transmit the generated encrypted print data to the host computer via the second communication medium. If the print data distribution system is configured as described above, print data can be distributed at high speed. In configuring the print data distribution system as described above, the second communication medium may be the same as or different from the first communication medium.
In other words, the printing device may function as a local printer of the host computer, and the printing device may be a network printer connected to a network to which the host computer and the print data distribution device are connected. .

A printing apparatus according to a first aspect of the present invention includes a communication unit for performing communication with a device connected via a communication medium, and a printing unit in accordance with the supplied data in a predetermined format. Means for printing on a sheet, an information storage means for storing a public key and a secret key for decrypting information encrypted using the public key, and a public key provision request received by the communication means. When the request is received, the request means for returning the public key stored in the information storage means to the transmission source of the request for providing the public key using the communication means, and the encrypted print data is received by the communication means. In this case, the encrypted print data is decrypted using the secret key stored in the information storage unit, and data in a predetermined format is generated based on the decryption result and supplied to the printing unit, and the encrypted print data is decrypted. hand If there is no print data is received by the communication means, and a print data processing means for supplying the product to printing means data of a predetermined format based on the print data that is not encrypted.

If this printing apparatus is combined with the above-described printing data supply apparatus, the printing data can be distributed in a form that allows only printing without copying or processing.
It is possible to configure a system that can obtain a printed matter that can guarantee that the contents have not been modified.

A printing apparatus according to a second aspect of the present invention includes:
Communication means for performing communication with a device connected via a communication medium, printing means for performing printing in accordance with the supplied data in a predetermined format on paper, and information storage for storing information Means, when a key issuance request is received by the communication means, generate a public key and a secret key for decrypting information encrypted using the public key, and then generate the generated public key. A request responding unit that returns the key issuance request to the transmission source of the key issuing request using the communication unit, and stores the generated secret key in the information storage unit, and when the encrypted print data is received by the communication unit. Decrypts the encrypted print data using the secret key stored in the information storage means, generates data in a predetermined format based on the decryption result, supplies the data to the print means, and outputs When the printing data is received by the communication means, and a print data processing means for supplying the product to printing means data of a predetermined format based on the print data that is not encrypted.

That is, the printing apparatus according to the second aspect of the present invention has substantially the same configuration as the first printing apparatus according to the present invention, except that a function of generating a public key and a secret key is added. Therefore, according to the printing apparatus of the second aspect of the present invention, a system in which the confidentiality of the secret key is higher can be configured.

In realizing the printing apparatus according to the first and second aspects of the present invention, means attached to a replaceable consumable part, which forms a part of the printing means, is used as information storage means. Can be

[0015]

Embodiments of the present invention will be specifically described below with reference to the drawings.

<First Embodiment> FIG. 1 shows the configuration of a print data distribution system according to a first embodiment of the present invention.

As shown in the figure, the print data distribution system according to the first embodiment includes a printing apparatus 10 and a host computer 4 connected to the printing apparatus 10 and having a data distribution request program 45 installed.
0, and a data distribution center 50 (print data supply device) connected to the host computer 40 via the Internet. Although only one printing device 10 is shown in FIG. 1, the present print data distribution system generally includes a plurality of printing devices 10 and a plurality of host computers 40 connected thereto. It is operated by.

This print data distribution system transmits distribution print data (image data) prepared in the data distribution center 50 to the purchaser of each printing apparatus 10.
This is a system for distributing in a form that can be used only for printing on the printing apparatus 10 as a privilege for purchase.

The printing apparatus 10 included in the print data distribution system includes a control panel 18, a printing mechanism 19, and a control unit 20. The control panel 18 is an interface between the user and the printer 10, and includes a plurality of buttons for operating the printer 10,
It is composed of several LEDs and a liquid crystal panel for displaying the operating state of the device. The printing mechanism 19 is a mechanism that functions as a printing unit, and actually performs printing on paper. The printing apparatus 10 is a so-called laser beam printer, and the printing mechanism 19 includes a paper feeder, a paper transport mechanism, a toner cassette, a print engine, and the like.

The control unit 20 includes a host interface circuit 21, a CPU 22, a RAM 23, an EEPROM (electri
A callable erasable and programmable ROM) 24, a memory control unit 25, a ROM 26, and an interface circuit unit 27 are provided.

The host interface circuit 21 is a circuit functioning as a communication means. The host interface circuit 21 receives print data, a key issuance request, encrypted print data, and the like transmitted from the host computer 40 under the control (management) of the CPU 22, and sends the public key To the host computer 40. Although details of each information will be described later, the encrypted print data is data generated in the data distribution center 50, and the host computer 40 uses the Internet to
The encrypted print data is received from the data distribution center 50.

The ROM 26 is a memory in which programs and fonts are stored. The CPU 22 is a control circuit that controls each unit in the control unit 20, and functions as a request response unit and a print data processing unit in cooperation with other units. The CPU 22 reads a program stored in the ROM 26 onto the RAM 23 and operates according to the read program. At that time, the CPU 22
Is used to temporarily store data received by the host interface circuit 21 and data generated by itself based on the data. EEPROM2
Reference numeral 4 denotes a non-volatile memory used to store data defining default operating conditions of the printing apparatus 10 and a public key and a secret key of the RSA public key system. That is, E
The EPROM 24 is a memory functioning as information storage means, and the printing apparatus 10 is shipped without the public key and the private key stored in the EEPROM 24.
The procedure for storing the public key and the private key in the EEPROM 24 will be described later.

The memory control unit 25 sends a command from the host interface circuit 21 to the RAM 23 in accordance with an instruction from the CPU 22.
To transfer the data to the printing mechanism 1
9 to transfer data to the print engine. The interface circuit unit 27 includes several interface circuits for the CPU 22 to exchange information with the control panel 18 and the transport mechanism in the printing mechanism 19. That is, the CPU 22 recognizes the state of each button in the control panel 18 (whether or not each button is pressed) through the interface circuit unit 27 and controls the LEDs and the liquid crystal panel in the control panel 18. . Further, the CPU 22 controls the states of various mechanisms in the printing mechanism 19 (the amount of remaining toner in the toner cassette, the presence or absence of paper jam, etc.) via the interface circuit unit 27.
Recognize and control them.

As schematically shown in FIG. 2, each of the data distribution centers 50 holds a plurality of types of print data for distribution, which are print data to be distributed to purchasers of the printing apparatus 10. This data distribution center 50
Web-based file server (WWW server and FT
When a request for introduction information of predetermined content is received from the host computer 40, introduction information indicating what kind of print data for distribution is prepared is included in the request. Return to sender.

When the data distribution center 50 receives a data distribution request including a data ID, which is identification information of distribution print data, and a public key from each host computer 40, the data distribution center 50 uses the public key to transmit the data distribution request. It generates encrypted print data of the print data for distribution specified by the ID and returns it to the source of the data delivery request. In the data distribution center 50, encrypted print data is generated according to the following procedure. First, DES (data encryption sta
ndard), a key (hereinafter, referred to as a DES key) for encryption is arbitrarily generated. Then, DES encrypted data of the print data for distribution specified by the data ID included in the data distribution request is generated using the DES key. Next, at the beginning of the generated DES encrypted data, data type information indicating that the data is encrypted print data, a public key included in the data distribution request, and a cipher which is obtained by encrypting the DES key with the public key. By adding the encrypted key data, encrypted print data is created.

The data distribution request program 45 installed in the host computer 40 is a program (HTML data and an applet) executed on a Web browser. This data distribution request program 45
Is executed, the host computer 40 executes the following processing according to the user's instruction.

When an operation to output a key issuance request is performed, the host computer 40 transmits a key issuance request having predetermined contents to the printing apparatus 10. Then, the host computer 40 stores therein the data returned by the printing apparatus 10 as a response to the key issuance request as a public key to be incorporated in the data delivery request.

Further, when a predetermined operation is performed, the host computer 40 acquires the introduction information from the data distribution center 50 and displays a screen (Web page) on which the distribution print data can be selected based on the acquired introduction information. To be displayed. When the distribution print data on the screen is selected by the user, the host computer 40 transmits the data ID of the selected distribution print data.
And a data delivery request including the stored public key to the data distribution center 50. Then, as a response to the data delivery request, the data distribution center 50
And saves the encrypted print data transmitted from the server as a file. When another predetermined operation is performed, the host computer 40 supplies the encrypted print data stored in a file to the printing apparatus 10 (when the printing apparatus 10 connects the encrypted print data file to the printing apparatus 10). (Copying to the specified print port).

Hereinafter, the operation of the printing apparatus 10 will be described in relation to the operation of the host computer 40 with reference to FIG.

The user of the printing apparatus 10 first causes the host computer 40 to execute the data distribution request program 45, and instructs the host computer 40 (data distribution request program 45) to output a key issuance request.
The host computer 40 that has received this instruction transmits a key issuance request to the printing device 10 as described above.

On the other hand, when the printing apparatus 10 (CPU 22) is started, as shown in FIG. 3, it waits for data to be received by the host interface circuit 21 (step S101; NO). Then, the data is received (step S101; YES), and when the data is a key issue request (step S102; YE).
S), the CPU 22 starts the function as the request response means, and first determines whether the public key and the secret key are stored in the EEPROM 24 (step S111).

When the public key and the private key are not stored in the EEPROM 24 (step S111; YE
S), In other words, when the printing apparatus 10 is in the state at the time of shipment, the CPU 22 generates a secret key and a public key of the RSA public key system (step S112). The procedure for generating the secret key and the public key in step S112 is as follows.
This is the same as that generally performed when using the RSA public key system. That is, in this step, two large prime numbers are randomly generated, and a public key and a secret key are generated from those prime numbers.

Next, the CPU 22 stores the generated public key and secret key in the EEPROM 24 (step S11).
3) Then, control is performed to return the public key (in this case, the public key generated in the previous step) stored in the EEPROM 24 to the host computer 40 (step S114). Then, the CPU 22 determines in step S1
01, and waits for data to be received by the host interface circuit 21.

If the public key and the private key are stored in the EEPROM 24 (step S111; YES), the C
The PU 22 generates the public key and the private key without newly generating the public key stored in the EEPROM 24 (in this case, the public key generated in response to the key generation request received in the past) in step S114. The control for returning to the host computer 40 is performed. And CPU
22 returns to step S101.

Under the control of step S114, the printing apparatus 1
The data (public key) transmitted from 0 is stored as a public key to be included in the data delivery request by the host computer 40 that has issued the key issuance request.

After the public key is prepared in the host computer 40 by instructing the output of the key issuance request, the user performs a predetermined operation on the host computer 40 to select the distribution print data. Is displayed on the display of the host computer 40, and the distribution print data to be downloaded is selected. By selecting the distribution print data, a data delivery request including the data ID of the distribution print data and the stored public key is transmitted to the data distribution center 50, and the file holding the encrypted print data is transmitted. , Host computer 40
Generated within. Then, the user causes the host computer 40 to supply the encrypted print data in the file to the printing apparatus 10 by performing a predetermined operation.

The CPU 22 in the printing apparatus 10 determines that the data received by the host interface circuit 21 is not a key issuance request (step S102;
NO), that is, if it is normal print data or encrypted print data, the operation as print data processing means is started. Then, the CPU 22 determines whether the received data is normal print data or encrypted print data based on the data included at the beginning of the data that has been received by the host interface circuit 21 (step S103). When the received data is normal print data (step S103; N
O), the CPU 22 performs a process according to the content of the print data, and supplies the print data to the printing mechanism 19 (print engine) (step S104). That is, when the print data is described in a high-level language, a process of interpreting the contents of the print data to generate an intermediate code, expanding the generated intermediate code into image data, and supplying the image data to the printing mechanism 19 is performed. . If the print data is image data,
The process of supplying the printing mechanism 19 almost as it is is performed. Then, the CPU 22 returns to Step S101 and waits for data to be received by the host interface circuit 21.

On the other hand, if the data received by the host interface circuit 21 is the encrypted print data (step S103; YES), the CPU 22
The public key included in the encrypted print data is EEPR
It is determined whether or not it is stored in the OM 24 (step S105). When the public key and the private key are not stored in the EEPROM 24, or when the EEPROM 2
4 does not match the public key in the encrypted print data (step S105; N
O), the CPU 22 includes the host interface circuit 21
Nothing is performed on the data received by (the data is discarded and the data reception is interrupted), and the process returns to step S101.

If the public key stored in the EEPROM 24 matches the public key in the encrypted print data (step S105; YES), the CPU 22
The encrypted print data is decrypted by using the secret key stored in the storage device 24, the necessary processing is performed on the ordinary print data obtained by the decryption, and the processed data is supplied to the printing mechanism 19 (step S).
105). That is, the CPU 22 decrypts the encryption key data (the DES key is encrypted with the public key) subsequent to the public key in the encrypted print data with the secret key, and thereby obtains the DES key. obtain. Next, the CPU 22
Uses the DES key to generate D following the encryption key data.
The encrypted ES data (the print data for distribution encrypted with the DES key) is decrypted. Then, the CPU 22 causes the printing mechanism 19 to print the content represented by the distribution print data by performing a process according to the content of the decryption result (normal print data).

After processing the encrypted print data in such a procedure, the CPU 22 returns to step S101 and returns to a state of waiting for data to be received by the host interface circuit 21.

As described in detail above, the printing apparatus 10 included in the print data distribution system according to the present embodiment
Has a function of outputting a public key corresponding to a private key held by itself, but does not have a function of outputting a private key. Then, the data distribution center 50 has a function of generating, based on the given public key, encrypted print data that can be decrypted only by the printing apparatus 10 having a secret key corresponding to the public key. Therefore, according to the print data distribution system, the data distribution center 50 can distribute the distribution print data, which is the print data, to each host computer 40 in a form in which copying and processing cannot be performed.

<Second Embodiment> FIG. 4 shows the configuration of a printing apparatus 10 'according to a second embodiment of the present invention. As illustrated, the printing device 10 'according to the second embodiment has the same hardware configuration as the printing device 10 according to the first embodiment. However, the program stored in the ROM 26 'in the printing apparatus 10' is provided to the CPU 22 by an EEPROM.
Instead of the M24, the EEPROM 32 attached to the toner cassette 30 (which is originally provided for storing the usage state of the toner cassette, etc.) is not subjected to S105, S113, and S114 shown in FIG. Processing (processing related to key storage and reading) is executed.

The data distribution center 50 ', which provides the printing apparatus 10' with the encrypted print data via the host computer 40, manages the number of responses to the data delivery request for each public key, and the number of responses reaches the specified value. In response to the data delivery request including the public key, the information indicating the fact is returned instead of the encrypted print data.

That is, the print data distribution system described in the first embodiment is a system for distributing, to the purchaser of the printing apparatus 10, data that permits unlimited printing on the printing apparatus 10. However, the present print data distribution system provides the purchaser of the toner cassette 30 with the print data for distribution as a privilege for purchase.
It is a system for distributing in such a way that printing can be performed only within the usable period. Because if no toner remains in the toner cassette 30, the EE storing the key
The printing apparatus 1 includes the toner cassette 30 including the PROM 32.
This is because printing is not performed even if it is set to 0.

<Modifications> The print data distribution system according to each embodiment can perform various modifications. For example, it is possible to guarantee that the printed materials output by the printing apparatuses 10 and 10 ′ in the print data distribution system according to each embodiment based on the encrypted print data have not been altered. Therefore, a system for outputting a certificate or the like may be constructed based on the technology used in the print data distribution system according to each embodiment.

In the print data distribution system according to each embodiment, data is exchanged between the host computer 40 and the data distribution center 50 by communication. May be performed using a floppy disk or the like.

The printing apparatus 10 according to the first embodiment
Is added to the function of generating a secret key and a public key, which increases the confidentiality of the secret key (if the configuration of the first embodiment is adopted, the manufacturer of the printing apparatus Because there is no way to know). Therefore, without providing this function, the EEPROM 24 or the R
The secret key and the public key may be written and stored in the OM 26. Further, the printing apparatus 10 is configured so that the private key and the public key are not regenerated (step S1).
The processing is branched depending on the presence / absence of a key at 11). The print data for distribution distributed by the print data distribution system according to the first embodiment is distributed as a privilege to the purchaser of the printing apparatus 10. This is because there is no particular need to regenerate the private key and the public key because the data permits printing in the apparatus 10 without restriction.

Therefore, for example, the number of distribution print data that can be downloaded by one user is determined by the data distribution center 5.
0, the secret key and the public key can be generated up to N times in the case of management and restriction based on the number of public keys transmitted from the user.
4, the printing apparatus 10 is modified so that a secret key corresponding to the public key included in the received encrypted print data is selected and decrypted. You may. In the printing apparatuses 10 and 10 ′ according to the first and second embodiments, the keys are the EEPROMs 24, 3 and
The reason why the public key is returned when the data is stored in the data distribution center 2 is that all the computers connected to the printing apparatuses 10 and 10 ′ execute the data distribution request program 45 to transmit the data to the data distribution center 50. This is because the delivery request can be sent (a plurality of computers can use the encrypted print data printing function of the printing apparatus 10).

In order to determine the period during which the encrypted print data can be printed, the public key and the private key are automatically generated in the EEPROM 24 or the EEPROM 24 within a certain period after the generation.
The function to delete from the printing device 10 or the printing device 1
It can be added to 0 '. Also, the printing device 1
It goes without saying that a device corresponding to 0 'may be realized by an ink jet printer or the like. That is, the toner cassette 3
0, not EE attached to consumable parts such as ink cassette
By storing the public key and the secret key in the PROM, a device corresponding to the printing device 10 'may be configured.

The printing apparatuses 10 and 10 ′ may be configured so that a public key and a secret key are generated and the public key is printed by operating the control panel 18. However, since the public key becomes large-sized data, it is desirable that the input of the public key to the host computer 40 be performed by communication as in each embodiment.

Further, in the print data distribution system according to each embodiment, the print data for distribution is not directly encrypted with the public key.
This is because encryption by ES can be performed at higher speed. Therefore, when the processing speed may be reduced, the print data for distribution may be directly encrypted with the public key, and the encrypted print data may be directly decrypted with the private key. Further, encrypted print data is generated in which only a part (for example, a leading part) of the print data for one page is encrypted with the public key, and the remaining part is the normal print data. Like the data distribution center 5
0, and the printing apparatus 10 may be configured to be able to decrypt such encrypted print data. However, in such a configuration, printing cannot be performed by another printing apparatus, but some data in the encrypted print data remains as data that can be processed. In addition, it is desirable to configure the system so that the entire distribution print data is encrypted in some way.

[0052]

According to the print data distribution system of the present invention, it is possible to distribute print data in a form in which copying and processing cannot be performed and only printing can be performed, and it is possible to guarantee a printed matter in which the contents are not altered. , Will be obtained. Further, according to the printing apparatus of the present invention, a system that can obtain a printed material that can distribute print data in a form that can not be copied or processed but can be printed only, and can guarantee that the contents are not altered, It can be built.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a print data distribution system according to a first embodiment of the present invention.

FIG. 2 is a diagram for explaining an overall operation of the print data distribution system according to the first embodiment.

FIG. 3 is a flowchart illustrating an operation of a printing apparatus included in the print data distribution system according to the first embodiment.

FIG. 4 is a configuration diagram of a print data distribution system according to a second embodiment of the present invention.

[Explanation of symbols]

 10, 10 'printing device 18 control panel 19 printing mechanism 20 control unit 21 host interface circuit 22 CPU 23 RAM 24, 32 EEPROM 25 memory control unit 26, 26' ROM 27 interface circuit unit 30 toner cassette 40 host computer 45 data distribution request Program 50 Data distribution center

Continued on the front page F term (reference) 2C061 AP01 AQ06 CL10 HJ06 HK03 HN05 HN15 HQ12 2C087 AB06 AB08 AC08 BA03 BA06 BD00 BD01 DA13 5B017 AA06 BA07 BB02 CA08 CA12 CA16 5B021 AA01 BB04 CC05 CC06 EE04 9A001 BB 03 BB03 BB03 LL09

Claims (5)

[Claims] 1. A print data distribution system including a printing device and a print data supply device, wherein the printing device communicates with a device connected via a first communication medium. Printing means for performing printing in accordance with supplied data of a predetermined format on paper, and information storage means for storing a public key and a secret key for decrypting information encrypted using the public key. Request responding means for returning the public key stored in the information storage means to a transmission source of the public key provision request using the communication means when a public key provision request is received by the communication means; And when the encrypted print data is received by the communication means, decrypts the encrypted print data using the secret key stored in the information storage means,
The data of the predetermined format is generated based on the decryption result and supplied to the printing unit, and when the unencrypted print data is received by the communication unit, the data of the predetermined format is generated based on the print data. A print data processing unit that generates and supplies the print data to the printing unit, wherein the print data supply device uses the given public key based on print data to be printed by the printing device, A print data distribution system comprising: an encrypted print data generating unit that generates the encrypted print data by which the print data processing unit can generate the data of the predetermined format. 2. The apparatus further comprising a host computer connected to the printing device, wherein the encrypted print data generating unit of the print data supply device receives the public key from the host computer via a second communication medium. 2. The print data distribution system according to claim 1, wherein the encrypted print data is generated, and the generated encrypted print data is transmitted to the host computer via the second communication medium. 3. A communication unit for performing communication with a device connected via a communication medium, a printing unit for performing printing on paper in accordance with a supplied data of a predetermined format, and a public key. An information storage unit storing a secret key for decrypting information encrypted using the public key, and using the communication unit when a request for providing a public key is received by the communication unit. Request response means for returning the public key stored in the information storage means to the source of the public key provision request, and, if the encrypted print data is received by the communication means, The decrypted print data is decrypted using the secret key stored in the information storage unit, and the data in the predetermined format is generated and supplied to the printing unit based on the decryption result. And print data processing means for generating data in the predetermined format based on the unencrypted print data and supplying the data to the printing means when the print data is received by the communication means. Printing device. 4. A communication unit for communicating with a device connected via a communication medium, a printing unit for performing printing on paper in accordance with a supplied data of a predetermined format, and storing information. Information storage means for performing, when a key issuance request is received by the communication means,
After generating a public key and a secret key for decrypting information encrypted using the public key, the generated public key is returned to the transmission source of the key issuance request using the communication unit. Request response means for storing the generated secret key in the information storage means, and when the encrypted print data is received by the communication means, the encrypted print data is stored in the information storage means. The decryption is performed using the secret key stored in the storage unit, and the data in the predetermined format is generated and supplied to the printing unit based on the decryption result, and the unencrypted print data is received by the communication unit. A print data processing unit that generates the data in the predetermined format based on the unencrypted print data and supplies the data to the printing unit. Printing device. 5. The printing apparatus according to claim 3, wherein the information storage unit is attached to a replaceable consumable part forming a part of the printing unit.