JPH11143658A - Network system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent printing data being a security object from being referred to by the other person and from leaking to outside and to improve the security of printing data. SOLUTION: In a client device, printing data of the security object which becomes unnecessary after transfer completes is electronically shredded (128) and printing data which becomes unnecessary after ciphering and which is in the state of pre-ciphering (120). Thus, secret is kept on printing data after transfer completes and printing data in the state of pre-ciphering. At the same time, a printing server and a printer electronically shred printing data being the security object, which becomes unnecessary after transfer and printing complete and decoded printing data which remains when transfer and printing abnormally terminate so as to keep secret.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a network system, and more particularly, to a network system for transferring print data from a client device or a terminal device to a printer via a network, and printing the print data on the printer. About.

[0002]

2. Description of the Related Art Conventionally, as a security system in a print system, a client device which is a print data transmission source attaches password information permitting retrieval of the print data to the print data and transfers the print data to a printer or a print server. After the printer or print server temporarily holds and stores the received print job, the print data is stored in the memory when a regular password (= password matching the password information assigned to the print data) is input by the operator. A technique for extracting print data and referring to print data and executing printing is known (Japanese Patent Laid-Open No. Hei 8-31).
No. 4659).

[0003] However, in the above-described technology, the retrieval of print data in a printer or a print server is performed.
It is only suppressed until a formal password is input, and it is insufficient as a security protection method in that print data not subjected to any encryption or the like flows on a transmission path.

In order to improve this, a client device as a transmission source encrypts print data, transfers the encrypted print data to a printer or a print server, and the printer or print server that receives the data decrypts the print data. Techniques for referencing print data and realizing printing have been proposed. In this method, leakage and interpretation of the print data on the transmission path are prevented by flowing the encrypted print data on the transmission path.

[0005] Such an encryption technique and the above-mentioned Japanese Patent Laid-Open Publication No. Hei 8-3
It can be said that confidentiality has been considerably improved by using the technique described in Japanese Patent No. 14659 together.

However, these security methods do not consider the security of print data that is no longer needed after encryption or decryption, and the unnecessary print data is stored in the client device, Printer,
A storage device built in each of the print servers (for example,
(Eg, a magnetic disk device) in a readable state.

That is, a commonly used OS (Real Time Mo
In the file system provided by the Operating System including the nitor, etc., deleting data is merely an apparent deletion by changing the data management information such as turning on the deletion bit in the file control block. Processing such as clearing of data to be deleted with NULL data (X'00 ') is not performed.

Therefore, the contents of the print data before encryption and the print data after decryption remain unchanged until the storage area is overwritten with other data by a save process such as new creation or update of another file. Will continue to exist on the storage device in the same state.

For this reason, there has been a problem that if a commonly used file recovery tool, disk dump tool, or the like is used, even print data to be protected can be referred to.

[0010]

SUMMARY OF THE INVENTION The present invention has been made in order to solve the above-mentioned problems, and it is intended to prevent print data to be protected from being leaked to the outside by being referred to by another person, It is an object of the present invention to provide a network system capable of improving the security of a network.

[0011]

To achieve the above object, a network system according to the present invention includes a client device, a print server, and a printer connected to each other via a network. A network system in which transferred print data is once received by the print server and then transferred to a printer, or print data from the client device is directly transferred to the printer and prints the print data received by the printer. The client device may further include a security designating unit for designating print data to be secured, and confidential attribute information indicating the security subject may be included in the print data designated as security by the security designating unit. And an attribute information adding unit. First processing means for processing the print data to which the confidential attribute information has been added into unreadable data when the print data is no longer needed, wherein each of the printer and the print server receives Determining means for determining whether confidential attribute information has been added to the print data, and determining whether the print data to which confidential attribute information has been added by the determining means is determined when the print data becomes unnecessary. And second processing means for processing the data into unreadable data.

A network system according to the present invention includes a client device, a printer, and a print server connected to each other via a network. The print data transferred from the client device is once received by the print server and then transferred to the printer, or transferred directly to the printer and printed by the printer.

In such a network system, when the user of the client device specifies the print data to be secured by the security designating means, the information adding means adds the security data to the print data designated as the security subject. Add confidential attribute information indicating the protection target. As the confidential attribute information, for example, a flag made up of 1 bit (“1” for a security target, “0” for a non-security target, etc.) can be used.

As described above, the print data to which the confidential attribute information is added is once received by the print server and then transferred to the printer or directly to the printer, but the print data becomes unnecessary. (For example, after the transfer of the print data is completed, or when the user instructs to delete the print data by canceling the print or canceling the transfer of the print data, etc.), the first processing unit converts the data into an unreadable data. Processed.

As a method for processing the data into unreadable data, clearing with NULL data, scrambling with random numbers, various types of encryption, and the like can be employed.

Thus, in the client device,
It is possible to prevent the unnecessary print data to be security-protected from remaining in the memory in the client device in a readable state, being referred to by an unintended person, and being leaked outside.

The print server receives the print data to which the confidential attribute information is added once, and then transfers the print data to the printer. In the print server, the determination unit determines whether the confidential attribute information is added to the received print data. Determine whether or not. Then, the second processing means removes the need for the print data for which the confidential attribute information has been determined to be added as a result of the determination (that is, the print data designated as a security target). At this point (for example, after the transfer of the print data to the printer is completed, or when the user instructs to delete the print data by canceling the print or canceling the transfer of the print data), the data is processed into unreadable data.

As a result, in the print server, the unnecessary security-protected print data remains in a readable state in the memory of the print server, is referred to by an unintended person, and leaks to the outside. Can be prevented beforehand.

The printer receives the print data added with the confidential attribute information from the client device via the print server or directly receives the print data from the client device,
The print data is printed. In this printer,
The determining unit determines whether the confidential attribute information is added to the received print data. Then, the second processing means removes the need for the print data for which the confidential attribute information has been determined to be added as a result of the determination (that is, the print data designated as a security target). At this point (for example, after the printing of the print data is completed, or when the user instructs to delete the print data due to print cancellation, print data transfer cancellation, or the like), the data is processed into unreadable data.

Thus, in the printer, the unnecessary security-protected print data remains in the memory of the printer in a readable state, is referred to by an unintended third party, and leaks to the outside. It can be prevented beforehand.

Incidentally, the print data transferred from the client device to the print server or the printer may be encrypted before the transfer to prevent the print data being transferred from being referred to or leaked from another person.

That is, in the client device, the print data is encrypted by the encryption means, and the encrypted print data (encrypted data) is transferred to the print server or the printer via the network. Then, decryption means provided in at least one of the printer and the print server decrypts the encrypted data. The decoded print data is printed by the printer.

In this case, in the client device, after the encryption of the print data to be protected by the encryption means is performed by the encryption means, the first processing means performs the encryption of the print data remaining in the state before encryption by the first processing means. It is desirable to process the print data into unreadable data.

Further, in the print server or the printer, after the transfer or the printing of the security target print data decrypted by the decryption means of the apparatus is completed, the decryption of the decrypted security data is performed by the second processing means. It is desirable to process the target print data into unreadable data.

As a result, the contents of the print data to be protected before encryption and the contents of the print data to be protected after decryption remain in a readable state in the memory of the apparatus, and are referred to by unintended others. Thus, leakage to the outside can be prevented beforehand.

The present invention can be applied to a network system including a terminal device for requesting print processing of print data and a printer for printing print data transferred from the terminal device. Thus, a similar effect can be obtained.

That is, when the user of the terminal device specifies the print data to be protected by the security specifying means, the information adding means adds the security attribute information indicating the security target to the specified print data. Then, the first processing means processes the print data to which the confidential attribute information is added (print data to be protected) into unreadable data when the print data becomes unnecessary.

As a result, in the terminal device, the unnecessary security-protected print data remains in a readable state in the memory in the terminal device, is referred to by an unintended person, and leaks to the outside. Can be prevented beforehand.

On the other hand, in the printer, the judging means judges whether or not confidential attribute information has been added to the print data transferred from the terminal device. Here, the print data determined to have the confidential attribute information added thereto (that is, the print data to be protected) is unreadable when the second processing unit no longer needs the print data. Process into data.

Thus, in the printer, it is possible to prevent unnecessary print data to be protected from remaining in the memory of the printer in a readable state, being referred to by an unintended third party, and leaking to the outside. It can be prevented beforehand.

[0031]

Embodiments of the present invention will be described below.

[Configuration of Network System] FIG. 1 is a schematic configuration diagram of a network system 50 according to the present embodiment. As shown in FIG. 1, the network system 50 includes a client device 10 that generates print data and requests printing of the print data, a printer 30 that receives and accumulates print data, and prints the print data on paper,
And a print server 20 that manages the operation of the printer 30 and receives and accumulates print data from the client device 10 and transfers the print data to the printer 30.
1 are connected to each other.

The client device 10 includes a transmission interface 11 that is a physical interface with the transmission medium 41 and a transmission control unit that transmits print data to the outside via the transmission interface 11 by a network driver, a transmission application, or the like. 12, an application program operating unit 13 for generating print data,
A printer driver 14 that converts the generated print data into various printer control languages, an operation control unit 16 that receives various operation requests from the operator of the client device 10 and notifies the operator of the processing result, and encrypts the print data. And a storage device 18 that stores an application program, a control program to be described later, and the like, and is configured by a magnetic disk device or the like for storing print data, and accumulates print data in the storage device 18. And a spooling control unit 15 having a queue control mechanism for controlling the order in which the print data is taken out of the storage device 18, and prints information with security designation when the user designates security of print data by the operation control unit 16. A data processing unit 19 for adding print data and electronically shredding print data at a predetermined timing There, are provided.

The electronic shredding process according to the present embodiment corresponds to the process of converting print data into unreadable data according to the present invention, and means scrambling all target print data in a meaningless manner. doing. As the electronic shredding process, for example, clearing with NULL data, scrambling with random numbers, various types of encryption, and the like can be adopted. In the present embodiment, all of the target print data is simply padded with NULL data. Shall exhaust.

The print server 20 has a transmission interface 21 which is a physical interface with the transmission medium 41 and a transmission interface 2 for transmitting print data to the outside by a network driver or a transmission application.
1, a transmission control unit 22 that receives various operation requests from the operator of the print server 20, and notifies the operator of the processing result, and a decryption unit that decrypts the encrypted print data. Control unit 25, and a storage device 2 including a magnetic disk device or the like for storing a control program and the like to be described later and for storing print data
6, the storage of print data in the storage device 26 and the storage device 2
And a spooling control unit 24 having a queuing control mechanism for controlling the order in which the print data is extracted from the print data. A data processing unit 28 for electronically shredding print data to be protected at a predetermined timing,
A printer management unit 29 that manages the operation status of the printer 30 and the function / characteristic information of the printer 30 is provided.

The printer 30 has a transmission interface 3 which is a physical interface with the transmission medium 41.
1, a transmission control unit 32 for transmitting print data to the outside via a transmission interface 31 by a network driver, a transmission application, or the like, and receiving various operation requests from an operator of the printer 30 and notifying the operator of a processing result. An operation control unit 33, a decryption control unit 34 for decrypting the encrypted print data, a rasterizer 36 for performing a rasterization process of the print data, a transfer unit 38 for transferring the rasterized data to paper, and a transfer unit 3
8, a storage device 39 including a magnetic disk device or the like for storing a control program to be described later and storing print data, and storing print data in the storage device 39. And a spooling control unit 35 having a queuing control mechanism for controlling the order in which the print data is taken out of the storage device 39. Judgment unit 3A for judging whether or not it is a security target
And a data processing unit 3B for electronically shredding print data to be protected at a predetermined timing.

[Operation of this Embodiment] Next, as an operation of this embodiment, the client device 10 and the print server 2
A control routine relating to the printing process executed in each of the printer 0 and the printer 30 will be described.

In the client device 10, a control routine shown in FIG. 2 is executed. In step 102 of FIG. 2, print data is generated by the application program operating unit 13, and in the next step 104, it is determined whether or not the user has designated the print data as a security target.

If the user has designated the print data as a security target, the process proceeds to step 106, where the printer driver 14 converts the print data into a PDL (Page Description Language) interpretable by the printer 30.
age)), and the data processing unit 19 adds attribute information indicating that security is designated to the converted print data. here,
For example, a flag indicating the security attribute may be turned on (set to “1”).

On the other hand, if the user has not designated the print data as a security target in step 104, the process proceeds to step 108, where the printer driver 14 converts the print data into a printer such as a PDL that can be interpreted by the printer 30. The data is converted into print data including a control language, and attribute information indicating that security is not specified is given by the data processing unit 19 to the converted print data. Here, for example, the flag indicating the security attribute may be turned off (reset to “0”).

In the next step 110, the print data after conversion is stored in the storage device 18 by the spooling control unit 15.

Thereafter, in the next step 112, the print data (print data with attribute information) stored in the storage device 18 is extracted from the storage device 18 in accordance with the queuing control of the spooling control unit 15. Then, it is determined whether or not the print data is designated as security.
The determination is made based on the attribute information (for example, a flag indicating the security attribute) given to the print data.

Here, if the print data has not been designated for security, the process proceeds to step 122 described later. If the print data has been designated for security, the process proceeds to step 116. In step 116, the print data is encrypted by the encryption control unit 17, and in step 118, the encrypted print data is stored in the storage device 18 by the spooling control unit 15. Further, the next step 12
In the case of 0, the print data before encryption, which becomes unnecessary by encryption, is electronically shredded and then deleted.

In the next step 122, under the control of the transmission control unit 12, the encrypted print data or the print data for which security is not designated is transferred to the print server 20 via the transmission I / F 11. .

If the transfer is not completed normally for some reason, the print data is held in the storage device 18 by the spooling control unit 15. Then, the process returns to step 112, and the processing of steps 112 to 122 is executed again.

On the other hand, if the transfer in step 122 has been completed normally, the flow advances to step 126 to determine whether or not the transferred print data that has become unnecessary is designated as security. Judge based on information.

If the print data is not designated for security protection, only the print data is deleted (step 130). On the other hand, if the security of the print data is designated, the print data is electronically shredded by the data processing section 19 (step 128) and then deleted (step 130).

As described above, the client device 10 electronically shreds the print data to be protected after the transfer is completed, which is unnecessary (step 12 in FIG. 2).
8) Therefore, confidentiality is maintained for the print data after the transfer is completed. In addition, since the print data in the state before encryption that is no longer needed after encryption is shredded electronically (step 120 in FIG. 2), the confidentiality of the print data in the state before encryption is maintained.

In the print server 20, the control routine of FIG. 3 is executed. In step 202 of FIG. 3, the client device 10 is controlled based on the control of the transmission control unit 22.
, And print data with attribute information (i.e., encrypted print data or print data for which security is not designated) from the storage device 26 in the next step 204. To be stored.

In the next step 206, the printer management section 29 determines whether or not the target printer 30 is ready to accept data. here,
When it is determined that the printer 30 is ready to accept the data, the process proceeds to step 208, and the print data with the attribute information is extracted from the storage device 26 according to the queue control of the spooling control unit 24.

In the next step 210, it is determined whether or not the print data is designated as security based on the attribute information given to the print data. Here, if the print data has not been designated as security, step 2 described later
The process proceeds to step S <b> 16, and if the print data is designated as security, the process proceeds to step 212. In step 212, the printer management unit 29 determines whether or not the printer 30 has a decryption function. Only when the printer 30 does not have a decryption function, the process proceeds to step 214. Is performed on the print data, and the decrypted print data (decrypted print data) is stored in the storage device 26.

In the next step 216, step 214
The decrypted print data or the print data for which security is not designated obtained in step (1) is transferred to the printer device 30 via the transmission I / F 21 under the control of the transmission control unit 22.

If the transfer is not completed normally for some reason, the print data is held in the storage device 26 by the spooling control unit 24, but is stored in the storage unit 26.
In step 20, the determination unit 27 determines whether or not the print data is designated for security. Only when security is designated, the process proceeds to step 222, where the print data (here, the decrypted print data) is output. The data is electronically shredded and deleted by the data processing unit 28.

Thereafter, the flow returns to step 208, and the processing of steps 208 to 216 is executed again.

On the other hand, if the transfer in step 216 has been completed normally, the process proceeds to step 224, where the determination unit 27 determines whether or not the transferred print data that has become unnecessary is designated as security.

If the security of the print data has not been designated, only the print data is deleted (step 228). On the other hand, if the security of the print data is designated, the print data is electronically shredded by the data processing unit 28 (step 226) and then deleted (step 228).

As described above, the print server 20 electronically shreds the print data to be protected after the transfer is completed, which is no longer necessary (step 22 in FIG. 3).
6) Therefore, confidentiality is maintained for the print data after the transfer is completed. If the transfer is not completed normally, the decrypted print data to be protected is electronically shredded (step 222 in FIG. 3), so that the security of the decrypted print data is maintained.

In the printer 30, the control routine of FIG. 4 is executed. In step 302 of FIG. 4, the transmission control unit 32 causes the print data with the attribute information from the print server 20 (that is, the encrypted print data, the decrypted print data, In step 304, the received print data is stored in the storage device 39 based on the control of the spooling control unit 35.

Then, in the next step 306, it is determined whether or not the transfer section 38 is ready for transfer. At this point, when the transfer unit 38 becomes ready for transfer, the process proceeds to step 308, and print data with attribute information is extracted from the storage device 39 according to the queue control of the spooling control unit 35.

In the next step 310, it is determined whether or not the print data is designated as security based on the attribute information given to the print data. Here, if the print data has not been designated for security, step 3 described later
Proceeding to step S16, if the print data has been designated as security, the procedure proceeds to step 312. In step 312, it is determined whether the print data is encrypted print data (that is, encrypted print data), and if the print data is encrypted print data, Only in step 314, the decryption control unit 34 executes a decryption process corresponding to various types of encryption on the print data, and stores the decrypted print data (decrypted print data) in the storage device 39.

In the next step 316, the rasterized processing is performed by the rasterizer 36 on the decrypted print data, the print data already decrypted by the print server 20, and the print data not designated for security. Expanded to image. Then, in the next step 318, printing processing is performed by transferring the raster image to the transfer unit 38 under the control of the print control unit 37 and transferring it to paper.

If the printing process does not end normally for some reason, the print data is held in the storage device 39 under the control of the spooling control unit 35.
In step 322, the determination unit 3A determines whether or not the print data is designated for security. Only when security is designated, the process proceeds to step 324, where the print data (here, the decrypted print data) is determined. To the data processing unit 3
B electronically shreds and deletes.

Thereafter, the flow returns to step 308, and the processing of steps 308 to 318 is executed again.

On the other hand, if the printing process in step 318 has been completed normally, the flow advances to step 326, where the determining unit 3A determines whether or not the unnecessary printed data is designated for security protection.

Here, if the security of the print data has not been designated, only the print data is deleted (step 330). On the other hand, if the security of the print data is designated, the print data is electronically shredded by the data processing unit 3B (step 328) and then deleted (step 330).

As described above, in the printer 30,
Since the print data that is no longer needed after the printing is completed is shredded electronically (step 328 in FIG. 4), the confidentiality of the print data after the printing is completed is maintained. If the printing is not completed normally, the decrypted print data to be protected is electronically shredded (step 324 in FIG. 4), so that the security of the decrypted print data is maintained.

By the way, the user of the client device 10 can be arbitrarily processed at any time in the control routine of FIG.
It is possible to instruct the client device 10 through the operation control unit 16 to instruct the client device 10 to delete the print data, such as canceling the print processing or canceling the transfer. That is, when the user of the client device 10 issues a print data deletion instruction, the processing routine of FIG. First, upon receiving the print data deletion instruction, the spooling control unit 15 checks whether or not the print data is designated for security (step 402). If the security is not designated, the spooling control unit 15 deletes the print data. Only (Step 406). On the other hand, if the print data is designated as security, the print data is electronically shredded by the data processing section 19 (step 404) and deleted (step 406).

As described above, when the deletion instruction is given to the print data designated as security (the cancellation of the print or the cancellation of the transfer is instructed), the print data is immediately electronically shredded. In addition, it is possible to prevent the unnecessary print data to be security-protected from remaining in the storage device 18 in a readable state, being referred to by an unintended third party, and being leaked to the outside.

The interruption process (FIG. 5) at the time of instructing the deletion of the print data designated with security as described above is executed not only in the client device 10 but also in the print server 20 and the printer 30. That is, if the user of the print server 20 issues a print data deletion instruction such as cancellation of print processing or cancellation of transfer through the operation control unit 23, the processing routine of FIG.
For the print data to be protected, the data processing unit 28
Is immediately shredded electronically. Further, if the user of the printer 30 issues a print data deletion instruction such as cancellation of print processing or cancellation of transfer through the operation control unit 33, the processing routine of FIG. It is immediately electronically shredded by the processing part 3B.

In this way, in the print server 20 and the printer 30 as well, the unnecessary print data to be protected remains in the storage device in a readable state, is referred to by an unintended third party, and leaks to the outside. Can be prevented from occurring.

According to the above-described embodiment, the client device 1 involved in a series of printing processes from the time when the application 13 of the client device 10 generates print data to the time when the printer 30 completes printing the print data.
0, in each of the print server 20 and the printer 30, the print data designated as security is shredded electronically immediately when it is no longer needed, so that there is no possibility that the print data is referred to by an unintended person. As a printing system, you can keep consistent security.

In this embodiment, the print server 20 is provided with the decryption control unit 25. However, the decryption control unit 25 does not include a decryption mechanism as in the case of the conventional printer. It is only needed in some cases. When the encrypted print data is decrypted by the decryption control unit 25 of the print server 20 and the decrypted print data is transferred to the printer 30 via the transmission medium 41, the readable print data is transmitted to the transmission medium 41. This is undesirable in terms of security. However, in an actual use site, it is assumed that various printers having various specifications are often mixedly used. Therefore, in the above embodiment, the print server 20 is provided with the decryption control unit 25 and the decryption mechanism is provided. An example of a configuration that can be used even when printing print data from a printer that is not provided has been described.

In the above-described embodiment, an example is shown in which the present invention is applied to a processing mode in which print data generated by the client device 10 is transferred to the printer 30 via the print server 20 and printed. The device 10 issues only a print request to the print server 20, and print data is sent from the client device 10 to the printer 3.
The present invention is also applicable to a processing mode in which the data is directly transferred to 0 and printed. Of course, it goes without saying that the present invention is also applicable to a network system 90 in which a terminal device 70 and a printer 80 are locally connected as shown in FIG.

Even if the print data is not transferred between the devices in an encrypted state, the client device or the print server can electronically shred the unnecessary print data after the transfer is completed, and the printer can shred unnecessary print data after the print is completed. Thus, the confidentiality of the print data can be improved. Also, when the user issues a print data deletion instruction, the print data is immediately shredded electronically, thereby improving the confidentiality of the print data.

[0075]

As described above, according to the present invention,
The print data designated as a security target is processed into unreadable data in each of the client device, the server, and the printer when the print data becomes unnecessary. It is possible to prevent the print data from remaining in the memory of the apparatus in a readable state, being referred to by an unintended person, and being leaked outside.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a network system according to an embodiment of the present invention.

FIG. 2 is a flowchart showing a control routine executed in the client device.

FIG. 3 is a flowchart illustrating a control routine executed in the print server.

FIG. 4 is a flowchart showing a control routine executed in the printer.

FIG. 5 is a flowchart illustrating an interrupt processing routine executed in response to a print data deletion instruction.

FIG. 6 is a schematic configuration diagram of another network system to which the present invention can be applied.

[Explanation of symbols]

Reference Signs List 10 Client device 15, 24, 35 Spooling control unit 16 Operation control unit (security designating unit) 17 Encryption control unit (encryption unit) 18, 26, 39 Storage device 19 Data processing unit (first processing unit, Information adding means) 20 print server 25, 34 decoding control section (decoding means) 27, 3A determining section (determining means) 28, 3B data processing section (second processing means) 30 printer 41 transmission medium 50 network system

Claims (5)

[Claims] A print server configured to include a client device, a print server, and a printer connected to each other via a network, wherein print data transferred from the client device is temporarily received by the print server and then transferred to a printer; Or a network system in which print data from the client device is directly transferred to the printer and prints the print data received by the printer, wherein the client device has a security function for designating print data to be secured. A protection designating unit; an information adding unit that adds confidential attribute information indicating the security target to the print data designated as the security target by the security designating unit; and the confidential attribute information is added by the attribute information adding unit. The print data that has been printed when it is no longer needed. A first processing unit for processing into unprintable data, wherein the printer and the print server each determine whether or not confidential attribute information is added to the received print data; A second processing unit configured to process the print data, to which the confidential attribute information is determined to be added by the determination unit, into unreadable data when the print data becomes unnecessary. 2. The method according to claim 1, wherein at least one of the first processing unit and the second processing unit is configured to read the print data to which the confidential attribute information is added after the completion of the transfer or the completion of the printing. The network system according to claim 1, wherein the network system is processed. 3. The client device further includes an encryption unit that encrypts the print data, and the first processing unit encrypts the print data after the encryption of the print data is performed by the encryption unit. Processing the print data remaining in the state before the encryption into unreadable data, and at least one of the printer and the print server further includes a decryption unit for decrypting the print data encrypted by the encryption unit. The second processing unit processes the decrypted print data into unreadable data after transfer of the print data decrypted by the decryption unit or after completion of printing. 2. The network system according to 1. 4. When at least one of the first processing unit and the second processing unit is instructed to delete the print data to which the confidential attribute information has been added, the print data is unreadable data. The network system according to claim 1, wherein the network system is processed. 5. A network system comprising a terminal device and a printer for printing print data transferred from the terminal device, wherein the terminal device specifies print data to be secured. Security specifying means, information adding means for adding confidential attribute information indicating the security target to the print data designated as the security target by the security specifying means, and confidential attribute information by the attribute information adding means. First processing means for processing the added print data into unreadable data when the print data is no longer needed, wherein the printer adds confidential attribute information to the received print data. Determining means for determining whether or not the print data has been added with the confidential attribute information by the determining means; Network system having a second processing means for processing the unreadable data at the time point when needed, the.