JP2005258784A - Resource management device, information processor, resource management program, resource display program and recording medium - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a resource management device, an information processor, a resource management program, a resource display program and a recording medium, capable of improving security related to use of a resource. <P>SOLUTION: This resource management device providing the resource via a network has: a first decision means deciding whether first authority information showing that browsing to the resource is possible to a browsing request to the resource is present or not; a second decision means deciding whether second authority information showing that output of the resource to the outside is forbidden is present or not; and a control means providing encryption data obtained by encrypting the resource when it is decided that the first authority information is present by the first decision means and when the second authority information is present by the second decision means. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a resource management apparatus, an information processing apparatus, a resource management program, a resource display program, and a recording medium, and more particularly, to a resource management apparatus, a resource management program and a recording medium that provide resources via a network, and the resource management apparatus The present invention relates to an information processing apparatus, a resource display program, and a recording medium that use provided resources.

  In computer systems, access rights are generally defined for each resource in order to prevent unauthorized use of the resource. Data in which access rights to resources are defined is generally called ACL (Access Control List). For example, in a document management system, an ACL is defined for each document, and viewing authority, writing (editing) authority, etc. of each user are set for each document. Here, the browsing authority often includes an authority for displaying a document file by viewer software or the like, and an authority for printing, copying (downloading) the document file, or the like.

  Further, in Patent Document 1, security information for each output form such as display, printing, transmission, and storage is provided for each document, and the output form is referred to when the logged-in user outputs the document by referring to the security information. Describes an invention relating to a document management system that determines whether or not output is possible by determining whether or not a document is accepted.

Further, Patent Document 2 describes an invention relating to a security method for protecting a document by allowing a classified user to deny access or set permission for each document and document field. Has been.
JP 2002-328843 A JP-A-7-191975

  However, it is problematic in terms of security to permit copying of a document file only when viewing authority is permitted. In other words, with the development of network technology, it is very difficult to limit the subsequent distribution of downloaded document files, but important confidential information is leaked as document files freely circulate on the network. This is because there is a risk of doing so.

  As for printing and browsing, after all, a document file is downloaded to the client side and held as a temporary file. Therefore, if a temporary file is accessed, the same adverse effects as when a document file is copied can be considered.

  The present invention has been made in view of the above points, and it is an object of the present invention to provide a resource management device, an information processing device, a resource management program, a resource display program, and a recording medium that can improve security related to resource use. And

  Accordingly, in order to solve the above-described problem, the present invention provides a resource management apparatus that provides a resource via a network, as described in claim 1, and is configured to supply the resource to a request for browsing the resource. First determination means for determining presence / absence of first authority information indicating that browsing is possible, and determination of presence / absence of second authority information indicating that output to the outside of the resource is prohibited When it is determined by the second determination means and the first determination means that the first authority information is present, and the second determination means determines that the second authority information is present, And control means for providing encrypted data obtained by encrypting the resource.

  In such a resource management device, since the encrypted data is provided as browsing data for a user who is prohibited from taking out resources from the resource management device, it is downloaded as browsing data by the user. Illegal use of the data thus obtained can be prevented.

  Moreover, in order to solve the said subject, this invention is the information which has a display means to display the resource provided by the resource management apparatus as described in any one of Claims 1 thru | or 4 as described in Claim 5. A processing device, wherein the display means decrypts the encrypted data of the resource based on the decryption information provided from the resource management device.

  In such an information processing apparatus, the encrypted data downloaded from the resource management apparatus can be displayed.

  In order to solve the above-mentioned problem, as described in claim 7, the present invention provides a resource acquisition unit that acquires a resource from a resource management device, and a display unit that displays the resource acquired by the resource acquisition unit. The resource acquisition unit requests the resource management device to provide encrypted data obtained by encrypting the resource when the output of the resource to the outside is prohibited. The display means decrypts the encrypted data when the encrypted data is obtained by the resource obtaining means.

  In such an information processing apparatus, for the user who is prohibited from taking out resources from the resource management apparatus, the encrypted data is downloaded together with the browsing data, and therefore downloaded as browsing data by the user. Illegal use of the data thus obtained can be prevented.

  In order to solve the above problems, the present invention may be a resource management program for causing a computer to execute the functions of the resource management apparatus, or a recording medium on which the resource management program is recorded.

  Moreover, in order to solve the said subject, it is good also as a recording medium which recorded the resource display program for making a computer perform the function in this invention, the said information processing apparatus, or the said resource display program.

  According to the present invention, it is possible to provide a resource management device, an information processing device, a resource management program, a resource display program, and a recording medium that can improve security related to resource use.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the present embodiment, a document managed in the document management system will be described as a specific example of a resource. FIG. 1 is a diagram showing a configuration example of a document management system according to an embodiment of the present invention. As shown in FIG. 1, the document management system 1 according to the present embodiment includes a document management server 10 and one or more terminals such as terminals 20a, 20b, and 20c (hereinafter, collectively referred to as “terminal 20”). Are connected via a network 30 such as a LAN (Local Area Network) or the Internet.

  The document management server 10 is a computer in which a management function of document information (document file and document bibliographic information) is implemented. For example, the document management server 10 executes a search for document information in response to a request from the terminal 20 and transmits the searched document information to the terminal 20. The terminal 20 is a device such as a PC (Personal Computer), a PDA (Personal Digital (Data) Assistants), or a mobile phone used by an end user of the document management system 1. The terminal 20 transmits a request according to an instruction from the user (for example, a document search request) to the document management server 10 and displays information (for example, a search result) returned as a response to the request.

  FIG. 2 is a diagram illustrating a functional configuration example of the document management system according to the embodiment of the present invention. As shown in FIG. 2, the document management server 10 includes a server processing control unit 11, an encryption processing unit 12, a document management DB 13, and the like.

  The server process control unit 11 is a function that controls the entire process in response to a request from the terminal 20. The encryption processing unit 12 is a function for encrypting a document file (original file 132) managed in the document management DB 13. That is, when the original file 13 is transmitted to the terminal 20, the encryption processing unit 12 is used when the original file 13 needs to be encrypted. The document management DB 13 is a database that manages an original file 13 and an ACL (Access Control List) 131 in which each user's access authority for each document is set.

  In the ACL 131 according to the present embodiment, it is possible to set a viewing authority, an editing authority, etc. for each document and for each user, and to set a take-out prohibiting authority. Here, “taking out” means taking out (downloading) the original file 132 of the document to the outside of the document management server 10. Accordingly, if “take-out prohibition authority” is set for a certain document for a certain document, it means that the user is prohibited from downloading the document.

  On the other hand, the terminal 20 includes a UI providing unit 21, a client processing control unit 22, a decoding processing unit 23, a display application 24, a temporary area 25, and the like. The UI providing unit 21 is a function for providing an operation unit of the document management system 1 to a user through a GUI (Graphical User Interface). The client process control unit 22 is a function for controlling the entire process according to a user input on the screen displayed by the UI providing unit 21. The decryption processing unit 23 is a function for decrypting the original file 132 when the encrypted original file 132 is downloaded from the document management server 10. The display application 24 is an application for displaying a document when browsing of the document is instructed. The temporary area 25 is a storage area for temporarily storing an original file 132 of a document downloaded for display or the like as a file.

  Next, details of the document management server 10 will be described. FIG. 3 is a diagram illustrating a hardware configuration example of the document management server 10 according to the embodiment of the present invention. The document management server 10 shown in FIG. 3 includes a drive device 100, an auxiliary storage device 102, a memory device 103, an arithmetic processing device 104, and an interface device 105 that are connected to each other via a bus B. Is done.

  A program for realizing processing in the document management server 10 is provided by a recording medium 101 such as a CD-ROM. When the recording medium 101 on which the program is recorded is set in the drive device 100, the program is installed from the recording medium 101 to the auxiliary storage device 102 via the drive device 100. The auxiliary storage device 102 stores the installed program and also stores necessary files and data.

  The memory device 103 reads the program from the auxiliary storage device 102 and stores it when there is an instruction to start the program. The arithmetic processing unit 104 executes a function related to the document management server 10 in accordance with a program stored in the memory device 103. The interface device 105 includes, for example, a modem, a router, etc., and is used to connect to the network 30 in FIG.

  The terminal 20 can also be realized by the same configuration as the document management server 10 shown in FIG. However, it is necessary to include an input device such as a keyboard and a mouse for receiving input from the user and a display device such as a display for presenting information to the user.

  Hereinafter, the processing procedure of the document management system 1 in FIG. 2 will be described. FIG. 4 is a flowchart for explaining the processing when setting the take-out prohibition authority for a document.

  In step S101, the administrator of the document management system 1 selects an arbitrary document (referred to as document B) managed in the document management DB 13 on the administrator screen displayed by the UI providing unit 21. A take-out prohibition authority is set for the user (user A). Progressing to step S102 following step S101, the UI providing unit 21 transmits the setting content by the administrator to the document management server 10 via the client processing control unit 22. Progressing to step S103 following step S102, the server processing control unit 11 of the document management server 10 sets the user A's take-out prohibition authority for the ACL 131 of the document B based on the setting content received from the terminal 20. .

  FIG. 5 is a conceptual diagram of ACL for document B. As shown in FIG. 5, in the ACL 131b, the presence / absence of various access authorities for each user is registered for the document B. For example, it can be seen that the user A is authorized to view and edit. Further, it can be seen that the carry-out prohibition authority is set by the processing shown in FIG.

  Next, a case will be described in which user A who has been set with a take-out prohibition authority for document B attempts to print document B. FIG. 6 is a flowchart for explaining processing when printing is requested for a document. In the initial state of FIG. 6, the terminal 20 displays a list of documents searched from the document management DB 21 on a screen (hereinafter referred to as “document list screen”) displayed by the UI providing unit 21. It is assumed that

  When the user A selects the document B on the document list screen and instructs printing (S201), the client processing control unit 22 is notified of the printing instruction via the UI providing unit 21. Upon receiving the print instruction, the client process control unit 22 transmits a message indicating that “user A has instructed printing of document B” to the server process control unit 11 of the document management server 10 (S202). The server processing control unit 11 recognizes the subject (user A) and the target (document B) of the print instruction based on the received message, and acquires the access authority of the user A from the ACL 131b (FIG. 5) for the document B. (S203).

  The server processing control unit 11 determines whether or not the document A can be taken out by the user A by referring to the take-out prohibiting authority in the access authority of the user A (S204). As shown in FIG. 5, the user A is set to have a take-out prohibition authority. That is, since the user A is prohibited from taking out the document B, the server process control unit 11 prints to the client process control unit 22. Send an error message indicating that is not possible. The client process control unit 22 that has received the error message displays an error message indicating that printing is impossible via the UI providing unit 21 (S205). Here, it is determined that printing is impossible based on the take-out prohibition authority. In order to print a document, the original file 132 of the document is taken out of the document management server 10 (the terminal 20 downloads it). Because it is necessary.

  Note that if the take-out prohibition authority is not set, the server processing control unit 11 acquires the original file 132 of the document B from the document management DB 13 and sends the original file 132 to the terminal 20. When transmitted, the document B is printed on the terminal 20 (S206).

  As described above, according to the document management system 1 in the present embodiment, it is possible to prohibit copying, printing, and the like that need to take out the original file 132 of the document with the take-out prohibition authority. Can be improved.

  Next, a case where an arbitrary user tries to browse an arbitrary document will be described. FIG. 7 is a flowchart for explaining an outline of processing in the document management system when browsing is requested for a document. Even in the initial state of FIG. 7, it is assumed that the document list screen is displayed on the terminal 20.

  When the current user selects an arbitrary document (hereinafter referred to as “current document”) on the document list screen and instructs browsing (S301), the access right to the current document is acquired from the ACL 131 based on the browsing instruction. (S302) It is determined whether or not the current user can take out the current document, that is, whether or not the carry-out prohibition authority for the current user is set for the current document (S303). If the export prohibiting authority is not set for the current user (Yes in S303), the current user is allowed to take out the current document, and the original file 132 of the current document is transferred from the document management server to the terminal 20. (S304). The terminal 20 displays the transferred original file 132 (S305).

  On the other hand, when the take-out prohibition authority is set for the current user (No in S303), it is further determined based on the ACL 131 whether the current user has the authority to view the current document (S306). ). If the current user has browsing authority (Yes in S306), this is a case where browsing is permitted but taking out is prohibited. Therefore, the original file 132 of the current document cannot be transferred from the document management server 10 to the terminal 20 as it is. Therefore, first, the original file 132 of the current document is encrypted in the document management server 10 (S307), and the encrypted original file 132 (hereinafter referred to as “encrypted file”) and the encrypted file are decrypted. Required for the transfer (hereinafter referred to as “decoding information”) is transferred to the terminal 20 (S308). Note that the decryption information is transferred not as a file on the hard disk of the terminal 20 but as a file on the memory so that it cannot be misused by a malicious user. In the terminal 20 that has received the encrypted file and the decryption information, the encrypted file is decrypted based on the decryption information or the like (S309) and displayed (S310).

  If the current user has no viewing authority (No in S306), an error message indicating that browsing is not possible is displayed on the terminal 20 (S311).

  Next, the process outlined in FIG. 7 will be described more specifically and in detail by taking as an example the case where the user A tries to browse the document B. FIG. 8 is a sequence diagram for explaining processing when user A attempts to view document B. FIG. 8 shows an example in which the original file 132 of the document is PDF data.

  When the current user selects document B on the document list screen and instructs browsing, the UI providing unit 21 that has detected the notification notifies the client processing control unit 22 of the browsing instruction (S401). Proceeding to step S402 following step S401, the client processing control unit 22 transmits a message indicating that “user A has instructed browsing of document B” to the server processing control unit 11 of the document management server 10. The server processing control unit 11 acquires the access authority of the user A from the ACL 131b (FIG. 5) for the document B by identifying the subject (user A) and the target (document B) of the browsing instruction based on the received message. Then, it is determined whether or not the take-out prohibition authority is set for the user A (S403, S404). As shown in FIG. 5, the user A has the right to prohibit taking out. Therefore, the server processing control unit 11 transmits a message notifying that the user A is not allowed to take out the document B to the client processing control unit 22 (S405).

  Proceeding to step S406 following step S405, the client process control unit 22 that has received the error notification transmits a message to the server process control unit 11 inquiring whether the user A has the viewing authority for the document B. The server processing control unit 11 acquires the access authority of the user A from the ACL 131b for the document B, and determines whether or not the viewing authority is set for the user A (S407, S408). As shown in FIG. 5, since user A is authorized to view document B, server processing control unit 11 sends a message indicating that user A has viewing authority to document B to the client process control unit. (S409).

  From the above, it is clear that user A is not allowed to take out document B but is allowed to view it. Therefore, the client processing control unit 22 determines that it is necessary to download the encrypted file (encrypted PDF) from the document management server 10 instead of the original file 132 itself.

  Progressing to step S410 following step S409, the client process control unit 22 generates public information B. Here, the public information is information used to generate a document password for encrypting the original file 132 of the document B, as will be described later. The public information B may be loaded that has been generated and stored in advance.

  Proceeding to step S411 following step S410, the client process control unit 22 transmits a message requesting provision of the encrypted PDF to the server process control unit 11 together with the public information B. In step S412, following step S411, the server processing control unit 11 requests the encryption processing unit 12 to encrypt the original file 132 of the document B.

  Progressing to step S413 following step S412, the cryptographic processing unit 12 generates public information A. As for the public information A, similarly to the public information B, information generated and stored in advance may be loaded. Proceeding to step S414 following step S413, the encryption processing unit 12 generates a common key based on the public information A and the public information B, and further generates a document password based on the common key. Here, the document password is information (password) for encrypting PDF data.

  Progressing to step S416 following step S415, the cryptographic processing unit 12 acquires the original file 132 of the document B from the document management DB 13 (S417). Progressing to step S418 following step S417, the encryption processing unit 12 encrypts the original file 132 using the document password, and outputs the encrypted file (encrypted PDF) to the server processing control unit 11. In step S420 following step S419, when the server processing control unit 11 transmits the encrypted PDF and the public information A to the client processing control unit 22, the client control unit 22 stores the encrypted PDF in the temporary area 25. The public information A is stored in the memory area.

  In step S421 following step S420, the client process control unit 22 requests the decryption processing unit 23 to generate a document password with the encrypted PDF and the public information A. Progressing to step 422 following step S421, the decryption processing unit 23 generates a common key based on the public information A and B and with the same logic as the encryption processing unit 12, and further generates a document based on the common key. Generate a password. That is, the document password generated here is generated with the same logic based on the same information (public information A and public information B) as the document password used when encrypting the original file 132. is there. Therefore, both document passwords are the same.

  Progressing to step S424 following step S423, when the decryption processing unit 23 requests the display application 24 to display the encrypted PDF with the document password and the encrypted PDF, the display application uses the document password. The encrypted PDF is decrypted on the memory, and the document B is displayed based on the decrypted information. (S425). Here, the display application prevents operations other than display, such as printing, saving as a file, and editing, as operations for the document. Specifically, a user interface (such as a menu) corresponding to these operations may be invalidated.

  As described above, according to the document management system 1 in the present embodiment, even when browsing is permitted, when browsing is instructed by a user who is prohibited from taking out, the original file 132 itself is not encrypted. Since the encrypted file is transferred to the terminal 20, even if the user intentionally takes out the encrypted file downloaded to the temporary area 25, the encrypted file cannot be opened. Also, the information for decrypting the encrypted file (public information A) is not stored as an easily accessible file but in a memory area, so that it is difficult for the user to obtain it intentionally. Therefore, it is possible to substantially prohibit taking-out while permitting browsing, and higher security can be ensured.

  Further, in the present embodiment, a common key is obtained by exchanging information (public information B) held on the client side and information (public information A) held on the server side with each other. Therefore, it is not necessary to transfer the common key or the document password itself between the server and the client. Even if the encrypted file and the public information A are illegally obtained on the network by a malicious user, The user cannot open the encrypted file with the public information A alone.

  Note that higher security can be ensured by dynamically generating the public information A and the public information B. That is, since the public information A and B are distributed on the network (steps S411 and S420), the possibility that both are obtained illegally at each timing cannot be denied. Therefore, when the logic for generating the public information A and B is static, or when the public information A and B is generated and stored in advance, the public information takes a fixed value. In this case, the risk of the encrypted PDF being decrypted increases due to the two public information being stolen. Therefore, for example, if the public information A as the encrypted SEED is generated based on a random value in the document management server 10 (S413), the value of the public information A can be made random. Higher security can be ensured. The random value may be, for example, a combination of a time when a document is instructed to browse and a random number.

  Incidentally, in FIG. 8, it is determined by the terminal 20 that the encrypted file should be downloaded. That is, the terminal 20 recognizes that the take-out prohibition authority is set for the user A in step S405, and recognizes that the user A has the viewing authority in step S409, and based on the recognition, the original file 132 is recognized. Instead, it is determined that the encrypted file should be downloaded, and the document management server 10 is requested to provide the encrypted file (S411).

  However, the document management server 10 may determine whether or not encryption is required when the original file 132 is transferred. The processing procedure in this case can be as shown in FIG. 9, for example. FIG. 9 is a sequence diagram for explaining processing when the server side determines whether encryption is necessary. 9, since there are many common parts with FIG. 8, these parts will be described in a simplified manner.

  When the current user selects document B on the document list screen and instructs browsing, the UI providing unit 21 that has detected the notification notifies the client processing control unit 22 of the browsing instruction (S501). The client processing control unit 22 generates public information B (S502), and sends a message indicating that “user A has instructed browsing of the document B” together with the public information B to the server processing control unit 11 of the document management server 10. It transmits to (S503).

  The server processing control unit 11 acquires the access authority of the user A from the ACL 131b (FIG. 5) for the document B, and whether or not the take-out prohibition authority is set for the user A. Then, it is determined whether or not the user A has browsing authority (S506). As shown in FIG. 5, the user A has a take-out prohibition authority and a browsing authority. Accordingly, the server processing control unit 11 determines that the original file 132 needs to be encrypted, and requests the encryption processing unit 12 to encrypt the original file 132 of the document B (S507).

  The subsequent steps are the same as those after step S413 in FIG. That is, the original file of the document B is encrypted (S508 to S513), and an encrypted PDF or the like is transmitted to the terminal 20 (S515). In the terminal 20, the encrypted PDF is decrypted and displayed (S516 to S520).

  In this way, the same function can be realized as the entire document management system 1 also by server initiative.

  The preferred embodiments of the present invention have been described in detail above, but the present invention is not limited to such specific embodiments, and various modifications can be made within the scope of the gist of the present invention described in the claims.・ Change is possible.

It is a figure which shows the structural example of the document management system in embodiment of this invention. It is a figure which shows the function structural example of the document management system in embodiment of this invention. It is a figure which shows the hardware structural example of the document management server in embodiment of this invention. 6 is a flowchart for explaining a process when setting out prohibition authority for a document. 4 is a conceptual diagram of ACL for document B. FIG. 6 is a flowchart for explaining processing when printing is requested for a document. It is a flowchart for demonstrating the process outline | summary in a document management system when browsing with respect to a document is requested | required. FIG. 6 is a sequence diagram for explaining processing when user A attempts to view document B. It is a sequence diagram for demonstrating the process in the case of determining the necessity of encryption on the server side.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Document management system 10 Document management server 11 Server processing control part 12 Encryption processing part 13 Document management DB
20, 20a, 20b, 20c Terminal 21 UI providing unit 22 Client processing control unit 23 Decoding processing unit 23
24 Display Application 25 Temporary Area 100 Drive Device 101 Recording Medium 102 Auxiliary Storage Device 103 Memory Device 104 Arithmetic Processing Device 105 Interface Devices 131 and 131b ACL
132 Original File B Bus

Claims (13)

A resource management device that provides resources via a network,
In response to the resource browsing request, first determination means for determining the presence or absence of first authority information indicating that browsing to the resource is possible;
Second determination means for determining the presence or absence of second authority information indicating that output of the resource to the outside is prohibited;
If it is determined by the first determination means that the first authority information is present, and the second determination means determines that the second authority information is present, an encryption that encrypts the resource A resource management apparatus comprising: control means for providing the digitized data. When the control means determines that the first authority information is present by the first determination means and the second determination means determines that the second authority information is not present, the control means The resource management apparatus according to claim 1, wherein the original data is provided. The control means further includes encryption processing means for generating encrypted data of the resource and generating decryption information for decrypting the encrypted data based on a request for encryption of the resource. The resource management apparatus according to claim 1 or 2. 4. The resource management apparatus according to claim 3, wherein the control unit provides the decryption information generated by the encryption processing unit by memory transfer. An information processing apparatus having display means for displaying a resource provided by the resource management apparatus according to claim 1,
The information processing apparatus, wherein the display unit decrypts the encrypted data of the resource based on the decryption information provided from the resource management apparatus. The information processing apparatus according to claim 5, wherein the display unit prohibits an operation other than displaying the resource when the resource provided by the resource management apparatus includes the second authority information. . An information processing apparatus having resource acquisition means for acquiring resources from a resource management apparatus, and display means for displaying the resources acquired by the resource acquisition means,
The resource acquisition means requests the resource management device to provide encrypted data obtained by encrypting the resource when output of the resource to the outside is prohibited,
The information processing apparatus, wherein the display unit decrypts the encrypted data when the encrypted data is acquired by the resource acquisition unit. For resource management devices that provide resources over the network,
In response to the resource browsing request, a first determination procedure for determining whether there is first authority information indicating that browsing to the resource is possible;
A second determination procedure for determining whether there is second authority information indicating that output of the resource to the outside is prohibited;
When it is determined in the first determination procedure that the first authority information is present, and in the second determination procedure, it is determined that the second authority information is present, an encryption that encrypts the resource Management program for executing an encryption providing procedure for providing encrypted data. A computer-readable recording medium on which the resource management program according to claim 8 is recorded. On the computer,
A data reception procedure for receiving encrypted data of resources provided by the resource management device according to any one of claims 1 to 4 and decryption information for decrypting the encrypted data;
A data decryption procedure for decrypting the encrypted data of the resource based on the decryption information;
A resource display program for executing a display procedure for displaying the decoded resource. The computer-readable recording medium which recorded the resource display program of Claim 10. On the computer that displays the resources provided by the resource management device,
An inquiry procedure for inquiring of the resource management device whether or not the resource requested to be browsed can be output to the outside;
An encrypted data request procedure for requesting transmission of encrypted data of the resource when the resource management device returns that the output of the resource to the outside is prohibited;
A resource display program for executing a decryption procedure for decrypting the encrypted data returned from the resource management apparatus. A computer-readable recording medium on which the resource display program according to claim 12 is recorded.

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